2739.     Correlation of Tissue Proteomic Profiles with MR Measures in a Rat Brain

Tuhin K. Sinha¹, Zhengyu K. Yang², Erin H. Seeley³, Mary Loveless⁴, Daniel C. Colvin⁴, Richard M. Caprioli³, John C. Gore¹

¹Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, USA; ²Chemical and Physical Biology, Vanderbilt University, Nashville, TN, USA; ³Mass Spectrometry Research Center, Vanderbilt University, Nashville, TN, USA; ⁴Biomedical Engineering, Vanderbilt University, Nashville, TN, USA

We demonstrate a method to interrogate and correlate proteomic information from matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI IMS) in light of corresponding in vivo MR measures. MALDI IMS is capable of generating an image where each pixel represents a spectrum of constituent tissue proteins. We examine these spectra, in a co-registered, voxel-by-voxel basis to investigate contrast variations in MR. We hypothesize that the intrinsic variation in MR that is related to heterogeneous macromolecular distribution in tissues can be elucidated using MALDI IMS. We demonstrate quantitative correlation of MALDI IMS data in a rat brain with T1 measures, and show the varying proteomic profiles which correspond with these correlations.

                  2740.     T2 Estimation for Small Lesions Using a Model-Based Reconstruction with Sparsifying Penalty Functions and Highly Under-Sampled Radial FSE Data

Chuan Huang¹, Ali Bilgin², Christian Graff³, Maria I. Altbach⁴

¹Dept of Mathematics, University of Arizona, Tucson, AZ, USA; ²Department of Electrical and Computer Engineering, University of Arizona; ³Program in Applied Mathematics, University of Arizona; ⁴Dept of Radiology, University of Arizona

T2 weighted MRI is used clinically for characterization of various pathologies. It has been demonstrated that quantitative methods for measuring T2 values are superior to visual evaluation. However, many of the proposed methods to measure T2 values suffer from long acquisition times, motion-induced errors, low spatial resolution and/or low number of measured points on the T2 relaxation curve, etc. To overcome the problems we proposed a model-based approach with sparsifying penalty functions for estimating T2’s from radial FSE data which yields accurate T2 estimates of small lesions from highly undersampled data. This novel method has great potential for characterization of small neoplasms in the body where the acquisition time is restricted to a breath hold.

                  2741.     Optimisation of the Combined Gradient Echo/spin Echo (GESE) Sequence for the Measurement of T₂ at 7.0 T

Eleanor F. Cox¹, Penny A. Gowland¹

¹SPMMRC, School of Physics & Astronomy, University of Nottingham, Nottingham, Nottinghamshire, UK

The GESE sequence can be used to simultaneously measure T2 and T2�Œ in the brain and is particularly useful in conditions of B1 inhomogeneity such as ultrahigh field. In order to maximize the potential of GESE for tissue characterization, it is necessary to optimize the sequence. Here we have investigated two different fitting algorithms for this sequence to identify which one gives the lowest error in fitted values of T2 and optimized sequence timings in terms of the number and spacing of gradient echoes and echo times used for measuring T2 and T2�Œ in the brain at 7T.

                  2742.     Non-Regularized Multivoxel NNLS Is a Robust Analysis Approach to Quantitative T₂

Thorarin A. Bjarnason¹, Cheryl R. McCreary¹, Jeff F. Dunn¹, J Ross Mitchell¹

¹University of Calgary, Calgary, AB, Canada

Quantitative T₂ (qT₂) enables scientists to discern tissue microcompartments by measuring multiple T₂ decays using a multiecho acquisition. qT₂ is sensitive to myelin content. We show that traditional qT₂ analysis underestimates the myelin water fraction (MWF) with decreasing SNR. We present a robust approach to qT₂ analysis that does not underestimate the MWF with decreasing SNR, provides variance estimates for a single ROI, and has confidence intervals on the T₂ distribution.

                  2743.     Localized In Vivo Fast Field-Cycling Relaxometry

Kerrin J. Pine¹, Gareth R. Davies¹, David J. Lurie¹

¹Bio-Medical Physics and Bio-Engineering, University of Aberdeen, Aberdeen, Scotland, UK

Fast field-cycling (FFC) can provide access to endogenous information not available from conventional fixed-field imagers. One example is the T₁ dispersion plot, where T₁ is measured over a range of evolution field strengths. We present a new pulse sequence using field-cycling saturation-recovery/inversion-recovery with an implementation of point-resolved spectroscopy (PRESS), allowing dispersion plots to be produced for a voxel selected from a pilot image. On a whole-body FFC-MRI system consisting of a 59 mT permanent magnet and coaxial resistive magnet, the sensitivity of the experiment is sufficient to obtain distinctive “quadrupole dips” in dispersion plots of protein-rich human tissue in vivo.

                  2744.     Voxel-Based Relaxometry for Cases of an Unresolved Epilepsy Diagnosis

Robert Karl Kosior^1,2, Rachel Sharkey^2,3, Paolo Federico^2,4, Richard Frayne^2,4

¹Biomedical Engineering, University of Calgary, Calgary, Alberta, Canada; ²Seaman Family MR Centre, Foothills Medical Centre, Calgary Health Region, Calgary, Alberta, Canada; ³Radiology and Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada; ⁴Radiology and Clinical Neurosciences, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada

A patient may be diagnosed with epilepsy, but without a firm understanding of the seizure focus, or without confidence in the diagnosis. Voxel-based relaxometry (VBR) is a T2 relaxometry technique that may provide information to corroborate, or refute indeterminate information from the other sources. Our objective was to assess the performance of single-subject VBR at 3 T for cases of uncertain epilepsy diagnoses. We found that more VBR abnormalities occur in patients with a suspected focus. Our results show that single subject VBR can help identify seizure foci in patients in whom conventional investigations have failed to yield a diagnosis.

                  2745.     Comparison of Analysis of Brain Relaxation Times in Standard Space with Analysis in Individuals’ Real Space

Benjamin Segun Aribisala¹, Andrew M. Blamire¹

¹Newcastle Magnetic Resonance Centre, Newcastle University, Newcastle upon Tyne, Tyne and Wear, UK

One commonly used image analysis technique is registration of images to a standard space. This has the major benefit that target regions are defined only once in standard space and can then be applied to any dataset. We hypothesize that the re-sampling and spatial smoothing used in the registration processes introduces partial volume effects (PVE) into the data under analysis biasing results. Here we compare this standard approach with an alternative method which transforms standard space target ROIs into real space where quantitative analysis is performed. We show that real space analysis suffers from less PVE than standard space analysis

                  2746.     Detection of Changes in T₁ Values in Normal Brain During Normobaric Hyperoxia

Samantha Jane Mills¹, Gerard Thompson¹, Giovanni Alessandro Buonaccorsi¹, Geoff J. Parker¹, Alan Jackson¹

¹Imaging Science and Biomedical Engineering, School of Cancer and Imaging Sciences, University of Manchester, Manchester, UK

Molecular oxygen is paramagnetic and can therefore reduce observed T₁ values when dissolved in blood and in tissue. Presented here are novel data from a pilot study at 3Tesla in four healthy human volunteers showing a significant decrease in the T₁ values in cortical grey matter(CGM), deep white matter(DWM), thalamus(BG), and skeletal muscle(SkM) during administration of 100% oxygen versus air. Baseline mean T₁ values were 832+/-53ms, 1175+/-120ms, 1553+/-57ms, and 962+/-82ms for DWM, CGM, BG, and SkM respectively. Following correction for baseline drift , mean hyperoxic δT₁ was -8.5+/-2.3ms, -33.8+/-4.1ms, -16.4+/-6.5ms, and -10.1+/-3.3 in DWM, CGM, BG, and SkM respectively (p<0.05).

                  2747.     Off-Resonance Magnetisation Transfer Contrast MRI Using Fast Field-Cycling Technique

Chang-Hoon Choi¹, Gareth R. Davies¹, David J. Lurie¹

¹Bio-Medical Physics and Bio-Engineering, University of Aberdeen, Aberdeen, Scotland, UK

Magnetisation transfer contrast (MTC) imaging normally employs off-resonant irradiation with varying RF offset frequency but maintaining a desired constant RF field strength (B₁). This presents the main technical difficulty of MTC at low field, because the larger offset frequencies are likely to be outside the bandwidth of the RF transmit system, causing B₁ to vary with the frequency offset. In this work, we demonstrate a novel off-resonance irradiation method using the fast field-cycling technique which permits to counter this problem. The results obtained by the new technique agreed well with those obtained by the conventional technique.

                  2748.     Optimization and Validation of a Constrained Reconstruction Algorithm for Rapid Whole-Brain Cross-Relaxation Imaging at 3.0 Tesla

Hunter R. Underhill¹, Chun Yuan¹, Vasily L. Yarnykh¹

¹University of Washington, Seattle, WA, USA

Cross-relaxation imaging quantitatively maps the parameters describing magnetization transfer between free and bound protons in tissues. Whole-brain parametric maps of the fraction of macromolecular protons (f) and the rate constant (k) have been enabled at 1.5T by constraining the transverse relaxation time of both the free (T₂^F) and bound (T₂^B ) pools. We determine the optimized constraints for T₂^F and T₂^B to enable rapid, whole-brain parametric maps of f and k at 3.0T. In addition, we report the average values of f and k across various gray and white matter structures from a group of volunteers imaged at 3.0T.

                  2749.     Direct Quantitative Comparison Between Cross-Relaxation Imaging and Diffusion Tensor Imaging of the Human Brain

Hunter R. Underhill¹, Chun Yuan¹, Vasily L. Yarnykh¹

¹University of Washington, Seattle, WA, USA

Diffusion tensor imaging (DTI) has been proven to be an effective tool for the visualization of white matter fiber tracts in the human brain based on the anisotropic diffusion effect. Parameters acquired during cross-relaxation imaging (CRI) that describe magnetization transfer have also been shown to have a close association with major fiber tracts in the human brain. In this 3.0T study, we report the results of quantitative comparisons between the CRI parameters that describe the fraction of macromolecular protons and the magnetization transfer rate constant and the principle scalar metric of DTI, fractional anisotropy, in the human brain in vivo.

                  2750.     19F Signal Amplification by Heteronuclear Polarization Transfer

Florian Schmid¹, Manuel Tsotsalas², Michael Kuhlmann³, Carsten Höltke¹, Christoph Bremer¹, Walter Heindel¹, Andres Guerrero-Martinez², Jochen Keupp⁴, Michael Schäfers³, Luisa De Cola², Cornelius Faber¹

¹Institute for Clinical Radiology, University Hospital Münster, Münster, Germany; ²Physikalisches Institut and NRW Graduate School of Chemistry, Westfälische Wilhelms-Universität Münster, Münster, Germany; ³European Institute for Molecular Imaging, Westfälische Wilhelms-Universität Münster, Münster, Germany; ⁴Philips Research Europe, Hamburg, Germany

Signal enhancement by NOE was investigated in 19F-MRI using 2-Fluoro-2-deoxy-D-glucose (FDG) and 2,2,2-Trifluoroethanol (TFE). The 19F signal was considerably increased by steady-state NOE preparation in spectroscopy and imaging sequences. TFE was loaded in novel potential carriers of contrast agents, zeolite L crystal nanocontainers. FDG was applied to mice and 19F images of the fixed mouse heart could be aquired at a clinical MRI scanner at 3T.

                  2751.     Incorporation of ADC Information Into SMM-Based MREIT for Small Animal Conductivity Imaging

Mark Jason Hamamura¹, Orhan Nalcioglu¹, Lufti Tugan Muftuler¹

¹Tu & Yuen Center for Functional Onco-Imaging, University of California, Irvine, CA, USA

In this study, we investigated the incorporation of apparent diffusion coefficient (ADC) data into the sensitivity matrix method (SMM) for magnetic resonance electrical impedance tomography (MREIT) of a tumor-bearing rat. The results indicate that such an incorporation allows us to reconstruct sensible conductivity images, something which has remained problematic for in vivo MREIT.

                  2752.     SENSE Accelerated MREIT with Optimized RF Coil Design

Lutfi Tugan Muftuler¹, Gang Chen¹, Mark J. Hamamura¹, Orhan Nalcioglu¹

¹Center for Functional Onco-Imaging, University of California, Irvine, CA, USA

SENSE imaging technique is adapted to MR Electrical Impedance Tomography (MREIT) to shorten acquisition times. A phased array coil was designed and optimized for this application and MREIT data was reconstructed from the SENSE accelerated images. A quasi-intrinsic decoupling scheme was used to minimize couplings between coil elements and the geometry was optimized to achieve high and uniform SNR. Data was acquired with and without SENSE acceleration and the results were compared. Phantom studies demonstrated that conductivity maps could be reconstructed from MREIT data acquired with 2.7 times SENSE acceleration with no discernible artifacts.

                  2753.     Bright-Iron Imaging Applying an Off-Resonance Modulating Pre-Pulse (OMPP)

Volker Rasche¹, Vinzenz Hombach¹, Sonu Sharma¹, Gerlinde Schmidtke-Schrezenmeier², Axel Bornstedt¹

¹Internal Medicine II, University Ulm, Ulm, Germany; ²Transfusion Medicine, University Ulm, Ulm, Germany

A new off-resonance sensitive pre-pulse is presented. The pre-pulse enables direct visualization of off-resonant spins. The pre-pulse was applied to imaging of local iron oxide particle distributions at different concentrations and to direct visualization of stents.

                  2754.     Positive Iron Contrast by Flow Enhanced Off-Resonance-Saturation for Remote Detection of Iron Based Contrast Agents

Philipp Krämer¹, Xavier Helluy¹, Esra Lang¹, Peter Michael Jakob¹

¹Department of Experimental Physics V, University of Würzburg, Würzburg, Bavaria, Germany

Hypointense contrast originating from iron-loaded atherosclerotic plaques within a vessel wall have been observed in contrast-enhanced gradient echo based MRA images of vessel lumen, allowing a fast remote detection of iron-loaded plaques. We demonstrate here on a flow phantom how a more specific positive iron contrast mechanism - flow enhanced off-resonance saturation (feORS) -, combined with MRA might facilitate the detection of iron based contrast agents confined within a small vessel wall volume.

                  2755.     Switching of MRI Contrast Agents with Ultrasound

Nouri Elmiladi¹, Christian Hoehl¹, Karl Maier¹

¹Helmholtz-Institut für Strahlen- und Kernphysik (HISKP), Rheinische Friedrich-Wilhelms-Universität, Bonn, Germany

A method involving the application of ultrasound (US) while performing proton nuclear magnetic resonance (¹HNMR) spectroscopy in the presence of antibody coated magnetic nanoparticles has been developed. Especially prepared magnetic nanoparticles act as an US driven radio frequency antenna, emitting photons of US frequency. Influence of resonant US on ¹HNMR using the asymmetric magnetic nanoparticles is examined through the determination of the relaxation rate by an inversion recovery sequence. Measurements are obtained for two different sizes of magnetic particles. A significant increase of the relaxation rate is observed when using smaller sized particles.

                  2756.     Numerical Study of the Distant Dipolar Field

Stefan Kirsch¹, Peter Bachert²

¹Computer Assisted Clinical Medicine, Faculty of Medicine Mannheim, University of Heidelberg, Mannheim, Germany; ²Dept. of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany

In this numerical study we present 2D presentations of the distant dipolar field (DDF) for various sample geometries and different experimental conditions (e.g., gradient settings). The calculations show that the DDF depends on the geometry and/or spatial distribution of the magnetization within the sample. The spatial structure of the DDF shows the known dependence on distance (“correlation distance” d). The simulations suggest that d should be considered as an average value rather than an exact distance. Our results are consistent with previously published 1D representations of the DDF and can be used to find optimized spatial magnetization distributions which result in an enhanced DDF.

                  2757.     CRAZED Signal Dependence on Correlation Distance and Sample Orientation in Rat Sciatic Nerve

Arman S. Kussainov¹, Mark D. Does², Nellie E. Byun³, John C. Gore^1,3, Daniel F. Gochberg^1,3

¹Physics, Vanderbilt, Nashville, TN, USA; ²Biomedical Engineering, Vanderbilt, Nashville, TN, USA; ³Radiology, Vanderbilt, Nashville, TN, USA

We measured the CRAZED signal from ex vivo rat sciatic nerve while varying the sample orientation and the gradient induced correlation distance, and we compared these results to a doped water cylindrical sample of the same size but lacking any internal structure. The results for the sciatic nerve have characteristics indicative of cylinders at both the ten and hundreds of micrometers distance scales, re&#64258;ecting both axon and the tibial/peroneal fascicle structures that compose the nerve. These results support the view that CRAZED methods are able to probe a range of distance scales not available in other magnetic resonance methods.

                  2758.     Observation of Signal Dips in IMQC Study

Zhong Chen¹, Shengchun Zhang¹, Shuhui Cai¹

¹Physics, Xiamen University, Xiamen, Fujian, China

The CRAZED-like sequences were qualitatively investigated with the strength of coherence selection gradients (CSGs) varying from a very small value to a large value. Obvious signal dip was observed at a specific CSG value, even when the influence of the inhomogeneous fields was eliminated. A detailed study shows that the position of the dip is directly related to the size of sample tube. Results demonstrate the appearance of the dip is a complex effect of CSG, inhomogeneous field and sample geometry£¬which can be utilized to explore the structural feature of the sample in MRI applications.

                  2759.     T1 Contrast in the Human Brain at 7 Tesla

Michael Wyss¹, David Otto Brunner¹, Anne Morel², Klaas Paul Pruessmann¹

¹Institute for Biomedical Engineering, University and ETH Zürich, Zurich, Switzerland; ²Laboratory for Functional Neurosurgery, University Hospital Zurich, Zurich, Switzerland

MRI in humans at 7Tesla offers not only high baseline sensitivity but also interesting contrast behavior. In the present work we report sequence considerations for robust T1-weighted brain imaging at 7T. An inversion recovery (IR) approach with an adiabatic inversion pulse was chosen. The inversion pulse was optimized between the competing goals of robustness against B1 inhomogeneity, bandwidth and SAR. It was found that the high field yielded not only high SNR and resolution but also surprisingly strong contrast throughout the brain. It permitted the distinction of anatomical structures which have been hard to recognize at lower field strengths.

                  2760.     Magnetization Prepared 3D FLAIR Imaging at 7.0 Tesla

Fredy Visser^1,2, Jaco Zwanenburg³, Hans Hoogduin³, Peter Luijten³

¹University Medical Centre Utrecht, Utrecht, Netherlands; ²Philips Healthcare, Best, Netherlands; ³UMC

This study shows that with dedicated magnetization preparation pre-pulses it is possible to make High Resolution 3D TSE FLAIR images at 7Tesla. As FLAIR imaging should be routinely included in many clinical studies, this finding will have a positive impact on the applicability of 7T MRI in clinical studies.

                  2761.     3D FLAIR at 7 Tesla Highlights Peripheral Layers of the Cortex

Jaco J.M. Zwanenburg^1,2, Fredy Visser^1,3, Taro Takahara¹, Wim G.M. Spliet⁴, Peter R. Luijten¹

¹Dept. of Radiology, University Medical Center Utrecht, Utrecht, Netherlands; ²Image Sciences Institute, University Medical Center Utrecht; ³Philips Healthcare, Best, Netherlands; ⁴Dept. of Pathology, University Medical Center Utrecht

We observed that 3D FLAIR at 7T yields high signal in a layer different from the line of Gennari. This bright line is visible at the periphery of the cortex, and also around the ventricles, and is therefore consistent with the demyelinated layers I and II in the cortex and with the ependyma around the ventricles. The purpose of this work to describe this contrast in the FLAIR images and explore its anatomical origin.

                  2762.     Reconstruction of Multi-Channel MR Magnitude and Phase Images Using Dual-Echo Sequence at 7 Tesla

Chan Hong Moon¹, Kyongtae Ty Bae^1,2

¹Radiology, University of Pittsburgh, Pittsburgh, PA, USA; ²Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA

MR magnitude and phase images were reconstructed with improved intensity homogeneity and phase SNR by the highly efficient algorithm combined with dual-echo acquisition.

                  2763.     Phase Contrast in the Human Brain and Its Field Dependence

Ana Maria Oros-Peusquens¹, Miriam Rabea Kubach¹, N. Jon Shah¹

¹Institute of Neurosciences and Biophysics, Research Centre Juelich, Juelich, Germany

Phase information, though not fully understood, is intrinsically contained in MR data and is being increasingly used to enhance data quality. In addition to specific ROIs, in this study we have investigated the field dependence of the phase contrast of the entire brain at three fields (1.5T, 3T and 4T). We have used field maps and not single-TE phase images which are more difficult to compare between fields. The field dependence of the phase shift of the individual ROIs is approximately linear, suggesting a dominant susceptibility effect. However, the changes observed in the whole-brain distribution of the phase require further investigation.

                  2764.     Triple-Layer Appearance of Human Cerebral Cortices on Phase-Difference Enhanced Imaging Using 3D Principle of Echo Shifting with a Train of Observations (PRESTO) Sequence

Tetsuya Yoneda¹, Toshinori Hirai², Yasuhiro Hiai¹, Hiroki Arimura¹, Yoko Kitajima³, Tomoyo Ideta⁴, Mika Kitajima², Yasuyuki Yamashita²

¹School of Health Sciences, Kumamoto University, Kumamoto, Japan; ²Department of Diagnostic Radiology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan; ³Kumamoto Neurosurgery Hospital, Kumamoto, Japan; ⁴Saiseikai Kumamoto Hospital, Kumamoto, Japan

The laminar patterns in the human cerebral cortices have not been investigated at 3T MRI in living humans. We developed a novel technique of phase-difference enhanced (PADRE) imaging to enhance a phase difference of tissue structures. We evaluated axial 1-mm-thick PADRE images obtained using a 3T MR scanner in 6 healthy volunteers. We adjusted parameters of PADRE imaging using high-pass filter and phase enhancement techniques in order to enhance the laminar patterns of the cortices. In all 6 cases a triple-layer appearance was frequently seen in all bilateral primary motor, sensory, and visual cortices.

                  2765.     Robust Fast Clinical Neurological Examination Using Golden Angle Ordered Radial IR-TrueFISP

Stephen R. Yutzy^1,2, Nicole Seiberlich², Vikas Gulani², Jeffrey L. Duerk^1,2, Mark A. Griswold^1,2

¹Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA; ²Radiology, University Hospitals of Cleveland and Case Western Reserve University, Cleveland, OH, USA

A rapid steady state radial method is presented which allows estimation of “synthetic” images with multiple contrasts in an acquisition time of <5s per slice. A golden angle echo sharing reconstruction is used to reconstruct images with high temporal resolution which are used to fit tissue relaxation parameters and proton density. Perfectly registered synthetic images can be calculated with any arbitrary contrast retrospectively after the acquisition. This technique has the potential to dramatically decrease examination time per patient, thereby increasing patient comfort and compliance, decreasing interscan motion, and increasing patient throughput.

                  2766.     The Effect of B₀ Inhomogeneity on the SSFP Dixon Technique: A Comaprison of Variants

Yin-Cheng Kris Huang^1,2, Teng-Yi Huang³, Hing-Chiu Chang⁴, Hsiao-Wen Chung^1,2

¹Department of Electrical Engineering, National Taiwan University, Taipei City, Taiwan; ²Department of Radiology, Tri-Service General Hospital, Taipei City, Taiwan; ³Department of Electrical Engineering, National Taiwan University of Scienece and Technology, Taipei City, Taiwan; ⁴Applied Science Laboratory, GE Healthcare Taiwan, Taipei City, Taiwan

Images of fat-water separation can be obtained by combining the Dixon method and the balanced steady-state free precession (bSSFP) sequence, which is termed as SSFP Dixon method. The application of this method was successful at regions of relatively homogeneous B₀. Another variant of this method was the dual-TR method, which was anticipated to have a better immunity to the shimming condition. In this study, we validated this concept with experiments of both methods at regions with significant B₀ inhomogeneity.

                  2767.     Chimera Steady State Free Precession (Chimera SSFP)

Oliver Bieri¹, Markus Klarhöfer¹, Klaus Scheffler¹

¹Division of Radiological Physics, University of Basel Hospital, Basel, Switzerland

A new type of steady-state free precession (SSFP) sequence is introduced, termed chimera SSFP. The sequence consists of two alternating SSFP kernels (heads): odd TR-intervals feature a balanced SSFP (bSSFP) type of protocol, whereas even TR-intervals undergo gradient dephasing (unbalanced SSFP) and hence the name. Chimera SSFP features a peculiar frequency response profile with respect to the bSSFP interval of triangular shape. Potential applications of this new type of SSFP sequence are, among others, functional MRI (fMRI) and temperature mapping.

                  2768.     Multiple Acquisition Fat-Saturated Balanced Steady State Free Precession Imaging

Marcus T. Alley¹, Shreyas S. Vasanawala¹, Robert J. Herfkens¹, Brian A. Hargreaves¹

¹Radiology, Stanford University, Stanford, CA, USA

While bSSFP imaging is advantageous in its ability to produce high SNR in short imaging times, its clinical application has been limited. The fat signal is typically unwanted, and the short TRs required to avoid banding artifacts lead to resolution limitations. This is especially true at higher field strengths where SAR considerations begin to force longer TRs. Previous methods have combined multiple bSSFP acquisitions with different linearly-increasing excitation phases to either reduce signal variations with frequency or suppress fat. We propose the addition of fat suppression to a multiple phase-cycled, 3D bSSFP acquisition to address both issues simultaneously.

                  2769.     Investigation of  SPIO T₁-Signature: Positive Contrast Using Ultrashort TE Imaging

Olivier Maciej Girard¹, Jiang Du¹, Robert Frederick Mattrey¹

¹Department of Radiology, University of California, San Diego, CA, USA

Superparamagnetic iron oxide (SPIO) nanoparticles are efficient contrast agents for molecular and cellular MR imaging. They are usually considered to be negative contrast agents due to their strong T2* effect, but they also have intrinsic T1 shortening properties that can produce positive contrast using appropriate MR pulse sequences. In the present study Utrashort TE (UTE) sequences were used to demonstrate the positive contrast even at high iron concentrations. Saturation Recovery prepared UTE sequences revealed an efficient contrast pattern. In addition to the usual T2* contrast it is possible to use the T1-signature of SPIO agents to improve detection specificity and localization.

                  2770.     Imaging of Short T2 and Ultra-Short T2 Tissues Using R2* Map

Weitian Chen¹, Huanzhou Yu¹, Atsushi Takahashi¹, Anja Brau¹, Jeffrey Stainsby², Ann Shimakawa¹, Brian A. Hargreaves³, Garry E. Gold³

¹Applied Science Laboratory, GE Healthcare, Menlo Park, CA, USA; ²Applied Science Laboratory, GE Healthcare, Toronto, Canada; ³Radiology, Stanford University, Stanford, CA, USA

Ultrashort echo time (UTE) imaging techniques have potential clinical applications for imaging of short T2 species. To increase contrast of short T2 species, it is usually necessary to suppress signal from long T2 tissues. Two common methods used to suppress long T2 tissues are RF pulse preparation and image subtraction. In this work, we investigated imaging of short T2 species using a R2* map, which creates image contrast between long and short T2 species different to that provided by current long T2 suppression methods. We demonstrated our methods with both Cartesian and radial acquisition.

                  2771.     Application of 3Dcones Sequence for Ultra-Short Echo Time Imaging

Jian-Xiong Wang¹, Brian K. Rutt², Jeffrey A. Stainsby³

¹Applied Science Laboratory, GE HEALTHCARE, London, Ontario, Canada; ²Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada; ³Applied Science Laboratory, GE HEALTHCARE, Toronto, Ontario, Canada

3D Cones sequence utilizes a central-out k-space trajectory that does not require field gradients prior to the sampling. As well, the ultra-short TE (<0.1ms) capability of the 3D Cones provides an approach for measurement of ultra-short T2 images. This work presents a preliminary application work of 3D Cones sequence in human brain short T2 imaging.

                  2772.     MP-SWIFT with Adiabatic Inversion Preparation for Quiet, B₁ Insensitive T₁ Weighted Imaging.

Curtis Andrew Corum¹, Djaudat Idiyatullin¹, Steen Moeller¹, Michael Garwood¹

¹CMRR, University of Minnesota, Minneapolis, MN, USA

In this work we add a magnetization preparation (MP) segment interleaved

                  2773.     Enhancing Lipid Signals with SWIFT

Lauri Juhani Lehto^1,2, Curt Corum², Djaudat Idiyatullin², Michael Garwood², Olli Gröhn¹

¹A. I. Virtanen Institute for Molecular Sciences, University of Kuopio, Kuopio, Pohjois-Savo, Finland; ²Center for Magnetic Resonance Research, Minneapolis, MN, USA

We show in a proof of principle experiment that the imaging sequence SWIFT is able to enhance lipid signals (having very short T1 and T2) due to its extremely short dead time. Images of a lipid phantom taken with SWIFT and FLASH are compared qualitatively and quantitatively. With increasing flip angle the lipid signals imaged with SWIFT increase considerably, whereas for FLASH the difference is small. This shows promise that SWIFT could image short T2 signals from low concentration lipid signals in pathological cells.

                  2774.     Estimation of Attenuation Maps from UTE Derived R₂ Images

Vincent Keereman¹, Yves De Deene^1,2, Tom Broux³, Ignace Lemahieu¹, Stefaan Vandenberghe¹

¹MEDISIP, Ghent University - IBBT - IBiTech, Ghent, Belgium; ²Laboratory for Quantitative Nuclear Magnetic Resonance in Medicine and Biology, ECNURAD, Ghent University, Ghent, Belgium; ³Radiology/BEFY, UZ Brussel, Brussels, Belgium

The very low signal intensity of cortical bone in conventional MRI sequences makes it difficult to distinguish this tissue type from air and derive a PET attenuation map from MR images. We investigate the use of a quantitative parameter (R2) that correlates well with the density images obtained with CT. This parameter is derived from UTE images acquired at different echo times. We demonstrate the feasibility of using the R2-map derived from MR UTE images for making the distinction between bone and soft tissue. Segmentation of human MR images into bone, soft tissue and air is also shown.

                  2775.     Multi-Echo IDEAL Cardiac Water-Fat Imaging

Karl Kristopher Vigen¹, Christopher J. Francois¹, Huanzhou Yu², Ann Shimakawa², Jean H. Brittain³, Scott B. Reeder¹

¹Radiology, University of Wisconsin-Madison, Madison, WI, USA; ²Applied Science Laboratory, GE Healthcare, Menlo Park, CA, USA; ³Applied Science Laboratory, GE Healthcare, Madison, WI, USA

Separation of water and fat signals is of great importance in cardiac imaging, both to improve visualization of pathology through fat suppression and for direct visualization of fat-containing pathology. Separation of fat and water was achieved using a cardiac gated segmented k-space multi-echo chemical shift based water fat separation method (IDEAL). The use of a multi-echo sequence and the ability to add an inversion recovery pulse and/or T2-preparation allows rapid acquisition of separated fat and water images for important clinical applications, including morphological imaging, delayed enhancement imaging, and black-blood imaging.

                  2776.     Spatially Variable Fat-Water Separation Using Short 2DRF Pulses for Fast Imaging

Jing Yuan¹, Bruno Madore¹, Lawrence P. Panych¹

¹Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA

Conventional spatial-spectral pulses can only produce uniform fat-water contrast in the whole FOV. Their usefulness may be limited by the relatively long duration, especially for short TR sequences like SSFP. In this study, we demonstrate that more flexible spatially varying fat-water contrast can be achieved within the FOV with a novel-designed shorter 2DRF pulse. Up to 3.7X reduction factors in pulse duration has be achieved. The proposed approach may also lend itself to reduced-FOV imaging and accelerated acquisitions. The proposed shorter pulses should benefit applications in MR-guided therapy where ROIs for separation may be pre-specified.

                  2777.     Coil Combination Method for Multiple-Echo Sequences and PSF Mapping

Kun Zhou^1,2, Shanglian Bao¹, Juergen Hennig², Maxim Zaitsev²

¹Beijing Key Lab of Medical Physics and Engineering, Peking University, Beijing, China; ²Department of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany

In this work a new method for coil combination is proposed, which is particularly suited for multi-echo, multi-reference or spectroscopic acquisitions, which intrinsically contain information on the temporal phase evolution. In this method, receiver coil phase can be estimated for each pixel and coil. Thereafter, data from individual coils are divided by the resulting phase correction maps and can be added to generate a composite complex-valued data set. The method has been tested using point spread function mapping data and it can be extended to other multi-echo MRI sequences and spectroscopic applications.

                  2778.     Iterative Tuning of System Delay and Phase Correction for Echo-Planar Imaging

Holger Eggers¹

¹Philips Research Europe, Hamburg, Germany

Different phase corrections are commonly applied in echo-planar imaging to reduce ghosting artifacts arising from differences in the sample positions for echoes acquired with positive and negative readout gradient polarity. In this work, it is demonstrated that especially the nonlinear phase corrections are susceptible to a badly adjusted system delay. A new, iterative procedure for a joint tuning of the system delay and the phase correction is proposed to improve tolerance in this respect and is shown to substantially reduce ghosting artifacts in adverse conditions.

                  2779.     Self-Correction of Image Distortion in High-Field EPI Using EPI Phase

Kathryn E. Hammond^1,2, Duan Xu¹, Doug AC Kelley³, Sarah J. Nelson^1,2

¹Radiology and Biomedical Imaging, University of California, San Francisco (UCSF), CA, USA; ²UCSF/UCB Joint Graduate Group in Bioengineering; ³GE Global Healthcare

At high fields echo-planar imaging (EPI) becomes increasingly distorted due to imperfections in the magnetic field. This study implemented a technique for using the phase of the EPI to self-correct image distortion and demonstrated its application to phantom and in-vivo human data acquired at 3T and 7T.

                  2780.     Fieldmap-Free Retrospective Registration and Distortion Correction for EPI-Based Diffusion-Weighted Imaging

Clare Poynton¹, Mark Jenkinson², Carlo Pierpaoli³, William Wells III⁴

¹MIT, Boston, MA, USA; ²Oxford; ³NIH; ⁴Harvard, BWH

We evaluate a recent method for EPI B0 distortion correction in a test framework that was previously developed for evaluating B0 distortion correction methods for DWI. The correction method uses structural MRI, segmentation, registration, and physics-based estimation of a fieldmap, and accounts for unknown shim parameters. The predicted fieldmap is subsequently used to unwarp the EPI. The test framework uses a specially collected set of DWI data and associated methodology that analyzes the variability in FA and trace following correction. The distortion correction method produces results that agree well with current fieldmap-based methodology.

                  2781.     Noise Considerations in Slice Encoding for Metal Artifact Correction

Wenmiao Lu¹, Kim Butts Pauly², Garry Evan Gold², John Mark Pauly³, Brian Andrew Hargreaves²

¹Electrical & Electronic Engr., Nanyang Technological University, Singapore, Singapore; ²Radiology, Stanford University, Stanford, CA, USA; ³Electrical Engineering, Stanford University, Stanford, CA, USA

Slice encoding for metal artifact correction (SEMAC) is recently proposed to obtain artifact-free MR images near metallic implants. SEMAC corrects through-plane distortions by summing the resolved signals from multiple slices. This can lead to the degradation in SNR without careful noise considerations. This work describes two approaches to avoid the SNR degradation, namely eliminating the relative phases between the slices and excluding the slices containing only background noise. Maintaining high SNR of the correction results is particularly important for incorporating SEMAC with various acceleration techniques.

                  2782.     Phase Angle Tilting (PAT) for Distortion Correction Caused by Susceptibility in EPI

Lirong Yan¹, Deheng Weng^1,2, Rong Xue¹, Jiongjiong Wang³, Yan Zhuo¹

¹State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, CAS, Beijing, China; ²Siemens Mindit Magnetic Resonance Ltd., Shenzhen, China; ³Radiology, University of Pennsylvania, Philadelphia, PA, USA

A modified EPI sequence using Phase Angle Tilting (PAT) to correct distortion caused by susceptibility effects was introduced. Using this method, the local distortions were well corrected on both phantom and human. Compared with other correction methods, our method does not cost additional scanning time, and can easily be implemented in EPI sequences.

                  2783.     Parallel MRI Near Metallic Implants

Weitian Chen¹, Philip Beatty¹, Kevin Koch², Anja Brau¹

¹Applied Science Laboratory, GE Healthcare, Menlo Park, CA, USA; ²Applied Science Laboratory, GE Healthcare, Waukesha, WI, USA

MRI has potential advantages for diagnostic imaging near metallic implants compared to other modalities, but can suffer from severe artifacts caused by implant-induced inhomogeneities. MAVRIC is one of the recently developed MRI techniques for this application. A main challenge to MAVRIC, however, is prolonged scan time. In this work, we investigated the performance of parallel imaging methods in the presence of significant off-resonance and signal distortion caused by metal implants. We demonstrate that parallel imaging can effectively be combined with MAVRIC for imaging near metallic implants in reduced scan times.

                  2784.     A Novel Algorithm for the Correction of Eddy Current Distortion in Diffusion Weighted Imaging Data

Wei Liu^1,2, Guang Yang¹, Zhenyu Zhou², Yongdi Zhou¹, Gengying Li¹, Bradley S. Peterson², Dongrong Xu^1,2

¹Physics, FMRI Unit, East China Normal University, Shanghai, China; ²Psychiatry, MRI Unit, Columbia University, New York, USA

A novel approach is proposed for the correction of eddy-current distortion in diffusion-weighted imaging (DWI) data acquired using an echo-planar imaging sequence. Our method offers improvement over the commonly used Iterative Cross-Correlation (ICC) algorithm, in that our method excludes computational biases caused by variations of signal contrast in the cerebral ventricles, and it incorporates a mutual information-based coregistration procedure into ICC. Moreover, our method does not need to collect an additional imaging dataset, nor does it work well only with DWI data that are acquired at low b-values, which are the major disadvantages of conventional ICC. The effectiveness of the proposed method is demonstrated in two experiments using both simulated and real-world DWI data.

                  2785.     Correcting Phase Errors from B₀ Eddy Currents in Non-Cartesian Imaging

Ethan K. Brodsky^1,2, Jessica L. Klaers², Walter F. Block^2,3

¹Radiology, University of Wisconsin, Madison, WI, USA; ²Medical Physics, University of Wisconsin, Madison, WI, USA; ³Biomedical Engineering, University of Wisconsin, Madison, WI, USA

Overall consistency in image quality from non-Cartesian sequences is typically still not equivalent to that possible with Cartesian methods. One cause for this is phase errors from B₀ eddy currents. While scanners actively maintain a stable field, this compensation is limited to longer time constants, so variation is still seen during gradient activity. We enhance our per-scan gradient calibration to additionally measure phase errors due to B₀ eddy currents and measure and correct the phase errors for several multi-echo 3DPR acquisition. Phase variations of up to 45° are seen across a readout, but the resulting effects are typically negligible.

                  2786.     Quantifying Changes in Geometric Distortion Across a Gradient Coil Replacement

Jonathan Samuel Jackson¹, Daniel Tozer¹, Mark Symms², Claudia A. M. Wheeler-Kingshott¹

¹Department of Neuroinflammation, UCL Institute of Neurology, London, UK; ²Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, UK

To quantify the potential impact of a scheduled gradient coil replacement on longitudinal quantitative neuro-imaging studies, a 3D phantom with high spatial definition was scanned before and after the event. The change in geometric distortion was shown to be less than 0.3% over 98.5% of a typical brain volume and the impact on gray and white matter volumes less than 0.2%. This generic method uses a detailed 3D phantom and off-the-shelf non-linear registration.

                  2787.     A Generic Method of Quantifying Geometric Distortion Using Non-Linear Registration and a 3D Phantom

Jonathan Samuel Jackson¹, Daniel Tozer¹, Jerome M. Goffin², John S. Thornton³, Paul S. Tofts⁴, Claudia A. M. Wheeler-Kingshott¹, Mark Symms⁵

¹Department of Neuroinflammation, UCL Institute of Neurology, London, UK; ²University of Edinburgh, Edinburgh, UK; ³National Hospital for Neurology and Neurosurgery, London, UK; ⁴Brighton and Sussex Medical School, Brighton, UK; ⁵Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, UK

Measuring geometric distortion due to gradient non-uniformity has previously required image processing tools specific to the phantom design. Here we demonstrate geometric distortion measurement achieving a precision of 0.3mm over 95% of the useful volume (6.2 litres) of a phantom using off-the-shelf non-linear registration. This method can be used with any sufficiently detailed phantom. Geometric distortion is measured in a short-bore interventional MRI system, finding residual errors of 2mm at a distance of 9cm from the isocenter after the built-in gradient non-uniformity correction.

                  2788.     Sample-Specific Passive Shimming Using Optimization Algorithm

Sejung Yang¹, Hahnsung Kim², Sang-Young Zho², Byung-Uk Lee¹, Dong-Hyun Kim^2,3

¹Electronics Engineering, Ewha W. University, Seoul, Korea; ²School of Electrical & Electronic Engineering, Yonsei University, Seoul, Korea; ³Radiology, Yonsei University, Seoul, Korea

Shimming using passive shims can enhance the homogeneity. The position of the passive shims have been typically placed at fixed regions or manually adjusted. Further improvements are possible if the positions can be optimized for individual subjects. We present a sample-specific passive shimming method. A shim structure capable of adjusting the position of the passive shims is built and optimal shim positions are computed using an optimization algorithm. Compared to previous in-vivo passive shim approaches, the proposed method avoids trial and error when finding the best shim position and can be a robust method for improving B0 homogeneity in vivo.

                  2789.     Dynamic Magnetic Field Corrections Improve Phase-Only FMRI Activations

Andrew David Hahn¹, Andrew S. Nencka¹, Daniel B. Rowe¹

¹Biophysics, Medical College of Wisconsin, Milwaukee, WI, USA

The contribution of various “not-of-interest” global physiologic phenomena to phase time series in MRI is well documented and poses experimental challenges for complex data analysis techniques. Recently published results demonstrated that correction of global temporal variations in the main magnetic field, which directly impact phase, significantly reduces temporal phase variability, ultimately restoring statistical power of local phenomena in complex-valued functional MRI (fMRI) regression analysis. When this correction is applied in conjunction with an fMRI analysis of phase-only activation, local task related phase changes that are statistically invisible in the raw signal, become detectable with high levels of significance.

                  2790.     Application of K-Space Energy Spectrum Analysis for Inherent and Dynamic B₀ Mapping and Deblurring in Spiral Imaging

Trong-Kha Truong¹, Nan-kuei Chen¹, Allen W. Song¹

¹Brain Imaging and Analysis Center, Duke University, Durham, NC, USA

Spiral imaging is vulnerable to susceptibility-induced B₀ inhomogeneities as well as temporal B₀ variations due to subject motion, physiological noise, and system instabilities, resulting in image blurring. Here, we further develop and combine 1) a novel method termed k-space energy spectrum analysis, which can inherently and dynamically generate a full-resolution B₀ map from the k-space data at each time point without requiring any additional data acquisition, and 2) a multi-channel modulation deblurring method, to effectively and efficiently correct for these artifacts and achieve a high spatial fidelity and temporal stability in spiral imaging.

                  2791.     B₀ Field Monitoring by Air-Matched Phantoms

Frederik Testud¹, Maxim Zaitsev¹

¹Dept. of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany

Fast magnetic resonance imaging sequences such as GRE EPI are sensitive to spatial and temporal changes of B₀ arising from susceptibility effects, temperature changes of the shims and motion of the object. This leads to time variant common image artefacts such as distortions and intensity losses. A field map is typically acquired at the beginning of the scan whereas neither temporal nor spatial changes of B₀ are monitored during the experiment. As a possible remedy, we propose to use phantoms susceptibility-matched to air which are used to monitor the B₀ evolution and determine the changes of the shim coefficients.

                  2792.     On Dephasing Effects in Complex Projection Data: Implications for Rapid B0 Estimation

Daniel Nicolas Splitthoff¹, Maxim Zaitsev¹

¹Dept. of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, BW, Germany

Often complex projection data is used for fast assessment of B0 field inhomogeneities. We here present considerations concerning dephasing effects to be taken into account when dealing with such complex projection data, and present a possible solution for the example of an Echo Planar Imaging sequence, comparing field inhomogeneities detected by projections with values from field maps.

                  2793.     The Impact of Finite RF Excitation on Steady State Free Precession

Oliver Bieri¹, Klaus Scheffler¹

¹Division of Radiological Physics, University of Basel Hospital, Basel, Switzerland

For quantitative imaging a detailed understanding of the pulse sequence’s signal behavior is of fundamental importance. Although SSFP signal theory is based on the concept of instantaneous radio-frequency (RF) rotation, and thus being in contradiction to any real sequence implementation, SSFP theory is generally well-accepted and unquestioned. To clear things up, SSFP signal behavior for finite RF pulses is analyzed.

                  2794.     Evaluation of a Template-Based B1 Field Correction Approach for 3T MRI Brain Images

Marcelo Adrian Castro¹, Jianhua Yao¹, Christabel Lee¹, Yuxi Pang^1,2, Eva Baker¹, John Butman¹, David Thomasson¹

¹Radiology and Imaging Sciences, National Institutes of Health, Bethesda, MD, USA; ²Philips Healthcare, Cleveland, OH, USA

A method to correct B1 field inhomogeneity in brain MRI images from a template B1 map is presented and applied to five volunteers. T1 maps are computed from T1-weighted images without B1 correction, with the proper B1 correction (reference T1 map), and using B1 maps from other subjects. The quality of a given correction is characterized by the percentage of voxels having a difference less than 10% with respect to the reference map. The T1 maps significantly improved when compared to the non-corrected ones. For each case the best correction was comparable to the reference T1 map.

                  2795.     Inherent Insensitivity to B1 Field Inhomogeneity Using Regularized Nonlinear Inversion Reconstruction

Aiming Lu¹, Keith R. Thulborn¹

¹Center for MR Research, Univ. of Illinois at Chicago, Chicago, IL, USA

Signal intensity variation that arises from inhomogeneous transmit and receive fields not only complicates the qualitative appearance of MR images but also presents the major source of error in quantitative MRI/S. To date no approach can correct for both fields in vivo effectively. An iterative nonlinear image reconstruction method was proposed recently for parallel imaging, which can jointly reconstruct the images and estimate the coil sensitivity. Here we show that this algorithm may inherently compensate for both field effects, therefore it may play a vital role in MRI/S beyond its application for parallel imaging.

                  2796.     Optimization and Group Comparison of RF (B1) Mapping Methods at 3T

Antoine Lutti¹, Chloe Hutton¹, Gunther Helms², Jurgen Finsterbusch³, Nikolaus Weiskopf¹

¹Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, London, UK; ²MR-Research in Neurology and Psychiatry, Faculty of Medicine, University of Göttingen, Göttingen, Germany; ³Department of Systems Neuroscience, University Medical Center Hamburg–Eppendorf, Hamburg, Germany

Inhomogeneities in the RF field (B1) lead to bias in quantitative imaging. We optimize three B1 mapping methods (dual-TR FLASH/AFI, SE/STE 3D EPI, 2D STEAM) in order to reduce the level of artefacts arising from inhomogeneities of the main static field (B0) and physiology in the resulting B1 maps. Our group study shows that flip angle maps obtained using the AFI and EPI methods are within 5% agreement and their stability is ~2% over repetitions across subjects. These optimized methods are therefore ideally suited for correction of B1 inhomogeneities in quantitative imaging at 3T.

                  2797.     Optimization of 3D EPI Technique for Radio Frequency (B1) Field Mapping at 3T

Antoine Lutti¹, Chloe Hutton¹, Nikolaus Weiskopf¹

¹Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, London, UK

Spatial inhomogeneities in the radio-frequency field (B1) pose various problems such as spurious signal and contrast changes in MRI, leading to bias in quantitative imaging and difficulties in tissue segmentation. We optimize a 3D EPI B1 mapping method using carefully chosen RF pulses and a post-processing procedure that corrects biased flip angles and image distortions along the phase direction. We obtain reliable flip angle maps at 3T over the entire brain volume with a sufficient resolution and in an achievable experimental time.

                  2798.     UTE Excitation Pulses Followed by Spin Lock to Preserve Magnetization

Michael Carl¹, Mark Bydder², Atsushi Takahashi¹, Eric Han¹, Graeme Bydder²

¹GE Healthcare, Applied Science Lab, Milwaukee, WI, USA; ²Radiology, University of California, San Diego, CA, USA

UTE excitation usually operates near the maximum gradient slew-rates and can cause transient short-term eddy currents and gradient amplifier non-linearities that can last from tens to hundreds of microseconds and thus may produce image artifacts. We propose a sequence in which the original UTE excitation pulse is immediately followed by a spin lock pulse, applied 90° out of phase with the excitation pulse to allow the transients to decay away. We have investigated this approach by studying the results of Bloch simulations.

                  2799.     Characterizing and Correcting Gradient Errors in Non-Cartesian Imaging: Are Gradient Errors Linear Time-Invariant?

Ethan Brodsky^1,2, Walter F. Block^2,3

¹Radiology, University of Wisconsin - Madison, Madison, WI, USA; ²Medical Physics, University of Wisconsin, Madison, WI, USA; ³Biomedical Engineering, University of Wisconsin, Madison, WI, USA

Non-Cartesian sequences are sensitive to gradient delays and eddy currents, imperfections that vary between scanners and over time. Uncorrected trajectory errors lead to misregistration of k-space data and reductions in image quality. We apply a per-scan rapid gradient calibration and correction to multi-echo 3DPR acquisitions. Trajectories for oblique projections are synthesized by linearly combining measurements made on the three orthogonal gradient axes. This rapid calibration depends on the assumption that gradient errors are linear (with respect to gradient amplitude) and time-invariant (within a scan). We show that the assumption of linearity is reasonable, but that gradient errors can change rapidly over time, highlighting the importance of per-scan calibration.

                  2800.     k-Space Water-Fat Decomposition with Chemical Shift Correction and T₂* Decay Compensation for Ultrashort TE Imaging

Kang Wang¹, Jiang Du², Huanzhou Yu³, Jean H. Brittain⁴, Scott B. Reeder^1,5

¹Medical Physics, University of Wisconsin-Madison, Madison, WI, USA; ²Radiology, University of California, San Diego, San Diego, CA, USA; ³Applied Science Laboratory, GE Healthcare, Menlo Park, CA, USA; ⁴Applied Science Laboratory, GE Healthcare, Madison, WI, USA; ⁵Radiology, University of Wisconsin-Madison, Madison, WI, USA

Tissues with very short T₂*, such as bone and tendon, can be imaged with ultrashort TE (UTE) techniques. However, like all radial methods, UTE methods can be degraded by chemical shift artifacts and T₂* decay. Here we proposed a k-space decomposition method that incorporates chemical shift correction and accounts for the T₂* decay between echo images. More importantly, it also compensates for the blurring artifacts caused by the intrinsic T₂* decay during readout, which can be pronounced for tissue with very short T₂*.

                  2801.     Computer Simulation for Evaluating MR Image Artifacts Caused by Magnetic Field Fluctuations Induced by Gradient Pulses

Yo Taniguchi¹, Suguru Yokosawa¹, Yoshitaka Bito¹

¹Hitachi, Ltd., Central Research Laboratory, Kokubunji-shi, Tokyo, Japan

A computer simulator for evaluating MR image quality is extended for easily evaluating MR image quality in the presence of temporal fluctuations of the magnetic field caused by gradient switching. The temporal fluctuations are defined by feature parameters, which are inputs to the simulator. The feature parameters of the fluctuations are spatial distributions of amplitude, decay time constant, frequency, and phase. We confirmed that geometrical distortions in the images obtained by DWEPI (diffusion weighted echo-planar imaging) simulations are correspond well with those from the experiments with intentionally increased eddy currents.

                  2802.     Reduction of FSE Cusp Artifact Using Slice Tilting

Novena Rangwala^1,2, Xiaohong Joe Zhou^1,3

¹Center for Magnetic Resonance Research, University of Illinois Medical Center, Chicago, IL, USA; ²Dept. of Bioengineering, University of Illinois at Chicago, Chicago, IL, USA; ³Depts. of Radiology, Neurosurgery and Bioengineering, University of Illinois Medical Center, Chicago, IL, USA

In fast spin echo (FSE) imaging, a “feather-like” artifact, termed as cusp artifact, is commonly seen along the phase-encoding direction in sagittal and coronal images. This artifact occurs due to specific combinations of B₀-field, B₁-field, and gradient non-linearity at regions beyond the field of view. To reduce this artifact, an FSE pulse sequence was modified to slightly tilt the slice selected by the RF excitation pulse. This modification, followed by simple post-processing, has been shown to noticeably decrease the cusp artifact by more than 80% in both phantom and human subjects.

                  2803.     A Method to Measure Gradient Delay Due to Gradient Coupling

Ajit Devaraj¹, James G. Pipe¹

¹Keller Center for Imaging Innovation, Barrow Neurological Institute, Phoenix, AZ, USA

Gradient delays can potentially be considerably influenced by gradient interactions. This work presents a simple approach to measure changes in gradient delays due to gradient coupling for spiral waveforms.

                  2804.     Navigator-Stabilized GRASE Imaging for High Magnetic Fields

Daniel Gembris¹, Anita Siebert¹, Franzisek Hennel¹

¹Bruker BioSpin MRI GmbH, Ettlingen, Germany

The GRASE imaging technique allows a flexible combination of gradient- and spin echoes to gather a maximum of spatial information within a single T2 decay. A source of ghosting in this technique is the combined modulation of the k-space data by the relaxation decay and resonance offsets. The original interleaved scheme of Feinberg and Oshio that converts resonance offsets to minimal pixel shifts is the most promising at high fields. We demonstrate that the ghosting due to the T2 decay (the main drawback of interleaved GRASE) can be alleviated using navigator signals.

                  2805.     k-Space Trajectory Mapping for Ultra-Short, Single-Shot, Non-Cartesian Imaging

Florian Wiesinger¹, Pekka Tapani Sipilae^1,2, Yi-Fen Yen³, Dirk Mayer⁴, Eric Fiveland⁵, Sebastian A. Greding¹, Daniel M. Spielman⁴, Adolf Pfefferbaum⁴, Rolf F. Schulte¹

¹Imaging Technologies, GE Global Research, Munich, Germany; ²Institute for Physics of Electrotechnology, Technical University Munich, Munich, Germany; ³Global Applied Science Laboratory, GE Healthcare, Menlo Park, CA, USA; ⁴Department of Radiology, Stanford University School of Medicine, Stanford, CA, USA; ⁵MRI Laboratory, GE Global Research, Niskayuna, NY, USA

In-vivo MR image encoding speed is physiologically limited by gradient-induced peripheral nerve stimulations. This makes high performance gradient insert coils an attractive choice for performing small-animal MR imaging and microscopy studies in a whole-body, clinical MR scanner. Such enhanced performance also amplifies gradient imperfections due to Eddy currents, coupling effects, mechanical vibrations, etc. Recently, magnetic field sensors in the form of small NMR probes have been described as a highly accurate tool for spatiotemporal magnetic field mapping. In this work such magnetic field sensors were used in combination with a high-performance gradient insert coil for ultra-fast, single-shot, high-resolution, non-Cartesian imaging.

                  2806.     Robust Compensation of Magnetic Field Perturbations for Localized Spectroscopy Applications

caixia Fu¹, GuoBin Li¹

¹Siemens Mindit Magnetic Resonance Ltd, ShenZhen, GuangDong, China

In this abstract, factors affecting the results of the sideband cancellation in opposite-gradient acquisition scheme are analyzed. Based on this scheme, a robust and simple compensation method is presented, in which optimized cancellation is achieved by carrying out eddy-current phase correction for positive-gradient and negative-gradient acquisitions respectively.

                  2807.     Robust Volume Segmentation Using Noise Statistics of Phase and Magnitude

Yiping P. Du¹, Zhaoyang Jin^2,3, Yuzheng Hu⁴

¹Psychiatry, Radiology, University of Colorado Denver, Aurora, CO, USA; ²Institute of Information and Control, Hangzhou Dianzi University, Hangzhou, Zhejiang, China; ³Biomedical Engineering, Zhejiang University, Hangzhou, Zhejiang, China; ⁴Physics, Zhejiang University, Hangzhou, Zhejiang, China

A robust volume segmentation algorithm using the noise statistics of both phase and magnitude is proposed. First-order phase difference is used to calculate local phase distribution to circumvent the need for phase unwrapping. A correction scheme is presented to correct the effect of linear background phase introduced by local field gradient in regions with severe field inhomogeneity. Robust volume segmentation is obtained in 3D susceptibility weighted images acquired with a TE=16ms at 3T. By applying the segmented brain volume, veins in the peripheral regions of the brain are well depicted in the minimum-intensity projection of the 3D data.

                  2808.     Removing Phase Artifacts Using Fourier Transform Based Field Estimation Can Lead to Significant Improvement in Phase Unwrapping Based SWI Processing

Jaladhar Neelavalli^1,2, Yu-Chung Norman Cheng³, Jing Jiang², Ewart Mark Haacke³

¹Biomedical Engineering, Wayne State University, Detroit, MI, USA; ²The MRI Institute for Biomedical Engineering, Detroit, MI, USA; ³Academic Radiology, Wayne State University, Detroit, MI, USA

Recently an novel method for removing background field effects from SWI phase images was proposed which was based on predicting the air-tissue geometry induced phase and removing its contribution form the collected phase. The resultant images are referred to as Geometry Dependent Artifact Corrected phase images (GDAC phase). In this abstract, results of using GDAC phase versus original phase for the conventional SWI processing steps of, (1) phase unwrapping and (2) subsequent high pass filtering, were compared and it is shown that using GDAC phase improves the results of this conventional SWI processing.

                  2809.     A Multi-Mask Multi-Seed Free Growing Field Map Estimation Algorithm for Iterative Multi-Point Water-Fat Decomposition

Chuan Huang¹, Maria I. Altbach²

¹Dept of Mathematics, University of Arizona, Tucson, AZ, USA; ²Dept of Radiology, University of Arizona

In MRI, fat/water separation in the presence of B0 field inhomogeneity is an important research area. In this work, we introduce a new method called Multi-mask Multi-seed Free Growing as an alternative to the Region Growing (RG) algorithm to provide the initial field map estimate for IDEAL fat water separation. Our results show that this algorithm is more robust than RG algorithm, especially when a large region of low signal intensity is present or strong field inhomogeneity occurs.

                  2810.     Challenges for MR-Based Attenuation Correction in PET Imaging of the Head

Andre Jan Willem van der Kouwe^1,2, Ciprian Catana^1,2, Thomas Benner^1,2, Christian J. Michel³, Michael Hamm⁴, Sonia Nielles-Vallespin⁵, Stephan Kannengiesser⁵, Matthias Fenchel⁵, Bruce R. Rosen^1,2, A. Gregory Sorensen^1,2

¹Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA; ²Department of Radiology, Harvard Medical School, Brookline, MA, USA; ³Siemens Medical Solutions USA Inc., Knoxville, TN, USA; ⁴Siemens Medical Solutions USA Inc., Charlestown, MA, USA; ⁵Siemens Healthcare, Erlangen, Germany

Attenuation correction (AC) is essential for accurate reconstruction of PET images. With combined MR-PET scanners such as the prototype Siemens BrainPET/3T TIM Trio combination, CT and transmission source data are unavailable for AC purposes. We demonstrate that with this head imaging system, the skull and the location of the MR RF coil can be detected with radially encoded ultrashort TE imaging and that inclusion of the RF coil in the AC map is critical for precise PET image reconstruction.

                  2811.     Gradient Echo Assisted 3D Look-Locker  - A Method for Improved Volume T1-Quantification Accuracy Applied to DGEMRIC

Carl Siversson¹, Carl-Johan Tiderius², Leif Dahlberg², Jonas Svensson¹

¹Department of Radiation Physics, Lund University, Malmo, Sweden; ²Department of Orthopaedics, Lund University, Malmo, Sweden

3D Look-Locker (LL) can be used for various T1 quantification applications, such as delayed Gadolinium enhanced MRI of cartilage (dGEMRIC). The LL method is however usually dependent on both the excitation- and inversion pulse performing well in order to generate reliable T1 values. By introducing an additional very quick (45 seconds) spoiled Gradient Echo sequence it is however possible to map both the B1 field and the inversion quality and compensate for any fluctuations. With this method T1 is measured very accurately, throughout all slices, both in gel phantoms and in in vivo dGEMRIC measurements.

                  2812.     Accelerated MR Parameter Mapping Using Compressed Sensing with Model-Based Sparsifying Transform

Mariya Doneva¹, Julien Sénégas², Peter Börnert², Holger Eggers², Alfred Mertins¹

¹University of Luebeck, Luebeck, Germany; ²Philips Research Europe, Hamburg, Germany

The estimation of MR parameters, such as the relaxation times T1, T2 and diffusion coefficients D, requires the acquisition of multiple images at different sequence parameters, which is often associated with long acquisition times. These data show a high temporal correlation, which could be described by a model facilitating accelerated image acquisition by data undersampling. In this work we show that the prior knowledge about the data could be used to define a model-based sparsity transform for improved compressed sensing reconstruction for MR parameter estimation.

                  2813.     A Combination of Nonconvex Compressed Sensing and GRAPPA (CS-GRAPPA)

Andre Fischer^1,2, Nicole Seiberlich³, Martin Blaimer¹, Peter Jakob^1,2, Felix Breuer¹, Mark Griswold³

¹Research Center Magnetic Resonance Bavaria e.V., Würzburg, Germany; ²Department for Experimental Physics 5, University of Würzburg, Würzburg, Germany; ³Department of Radiology, Case Western Reserve University, Cleveland, OH, USA

An extension of the nonconvex Compressed Sensing (CS) algorithm is presented. We propose to add a GRAPPA reconstruction step to take advantage of the inherent coil sensitivity profiles of multi-coil datasets. This parallel imaging step introduces a new constraint to the CS algorithm which ensures that the reconstructed data are in accordance with the inherent coil sensitivity profiles. By adding the GRAPPA step, one can reach higher acceleration factors with the CS-GRAPPA algorithm than with each individual technique due to synergy effects of both methods. We were able to recover high quality reconstructions of the sparse dynamic differences between a temporal average and a single timeframe from only 16 interleaved radial projections out of 224 of a dynamic cardiac radial dataset. The results show a significantly improved reconstruction quality compared to nonconvex CS reconstructions without the GRAPPA step. Thus, the proposed method shows potential for all applications where high spatial and high temporal resolution is required.

                  2814.     Compressed Sensing Using Dual-Tree Complex Wavelet Transform

Yookyung Kim¹, Maria I. Altbach², Theodore P. Trouard^2,3, Ali Bilgin^1,2

¹Electrical and Computer Engineering, University of Arizona, Tucson, AZ, USA; ²Radiology, University of Arizona, Tucson, AZ, USA; ³Biomedical Engineering, University of Arizona, Tucson, AZ, USA

Compressed Sensing (CS) holds great promise in accelerating magnetic resonance imaging (MRI). In this work, we explore the use of dual-tree complex wavelet transform (DT-CWT) as a sparsifying transform in CS MRI. Our results indicate that DT-CWT can alleviate some of the shortcomings of traditional discrete wavelet transform.

                  2815.     Compressed Sensing in Parallel Imaging: Towards Optimal Sampling

Panu Tapani Vesanen^1,2, Fa-Hsuan Lin², Risto Juhani Ilmoniemi¹

¹Department of Biomedical Engineering and Computational Science, Helsinki University of Technology, Espoo, Finland; ²Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan

Compressed sensing (CS) is a method to measure and reconstruct signals from highly incomplete information. CS can be applied to parallel MRI to achieve great reductions in the scanning time. The performance of CS reconstruction depends on the randomness of k-space sampling. Here we consider a true random 2D under-sampling of k-space. By simulations based on real brain MRI data using 2-12 fold imaging time reduction, we show an 8-12% reduction in the reconstruction error compared to the constricted sampling patterns suggested earlier. In practice, the method can be implemented with 3D sequences by randomizing the phase encoding gradients.

                  2816.     Region of Interest Compressed Sensing

Samir D. Sharma¹, Krishna S. Nayak¹

¹Electrical Engineering, University of Southern California, Los Angeles, CA, USA

Compressed sensing (CS) MRI has been shown to provide satisfactory image reconstruction from fewer k-space samples than in traditional methods. CS assumes transform sparsity of the image. However, the use of this assumption may introduce image artifacts that could lead to misdiagnoses in clinical applications. In this work, we exploit the benefits of CS by only imposing the sparsity constraint outside of a region of primary clinical interest (ROI), where small errors are tolerable. With this approach, we are able to increase the ROI reconstruction quality without sacrificing the acceleration gain.

                  2817.     Compressed Sensing with Vascular Phase Contrast Acquisition

Kevin F. King¹, Wei Sun²

¹Applied Science Lab, GE Healthcare, Waukesha, WI, USA; ²MR Science and Technology, GE Healthcare, Waukesha, WI, USA

Vascular phase contrast imaging has recently become more popular due to the emergence of nephrogenic systemic fibrosis. Several echoes with different flow moments are processed to give flow velocity weighted images. Since the images are sparse, compressed sensing can be combined with parallel imaging to accelerate phase contrast acquisition with better results than if parallel imaging were used alone. Most of the benefit is obtained by applying compressed sensing to each echo separately. A small additional improvement results from using a sparsifying transform of the final flow image as well. This produces a jointly optimized solution for all echoes.

                  2818.     Case-PDM Optimized Random Acquisition in High Quality Compressed Sensing MR Image Reconstruction

Jun Miao¹, Feng Huang², David L. Wilson^1,3

¹Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA; ²Invivo Corporation, Gainesville, FL, USA; ³Radiology, University Hospitals of Cleveland, Cleveland, OH, USA

Case-PDM is applied to optimize acquisition trajectory of compressed sensing (CS). Based on the experimental results, it can be concluded 1) CS can generate significantly better images with the optimized trajectory than the experience-based trajectory when all other parameters are same; 2) The optimized trajectory trained with one data set can be successfully applied to other data sets of different objects acquired by different MR systems, different coil, and different pulse sequences if only the anatomical structure is similar.

                  2819.     Accelerated High-Resolution Imaging of Trabecular Bone Using Total Variation Constrained Reconstruction

Michael J. Wald¹, Ganesh Adluru¹, Hee Kwon Song¹, Felix W. Wehrli¹

¹Laboratory for Structural NMR Imaging, University of Pennsylvania Medical Center, Philadelphia, PA, USA

High-resolution micro-MR imaging of trabecular bone is hampered by long scan times. Parallel imaging techniques offer a means to reduce scan times but the associated losses in SNR limit the achievable acceleration rates as structural parameters are sensitive to noise. Compressed sensing techniques take advantage of image sparsity to reconstruct alias-free images from undersampled data. Here we explore the application of Total Variation Constrained Reconstruction (TVCR) to trabecular bone imaging and compare the method in terms the derived topological parameters with a generalized partially-parallel acquisition-based reconstruction.

                  2820.     Nullspace Compressed Sensing for Accelerated Imaging

Leo J. Grady¹, Jonathan R. Polimeni²

¹Imaging and Visualization, Siemens Corporate Research, Princeton, NJ, USA; ²NMR Center, Radiology Department, Massachusetts General Hospital, Charlestown, MA, USA

Compressed sensing techniques have recently become very popular for image reconstruction given sparsely sampled data. However, previous methods only approximately enforce the constraint that the reconstructed image has Fourier coefficients at the sampled locations, which require manual parameter tuning and result in slower speeds for convergence. We present a fast, parallelizable method that it is capable of quickly reconstructing a sparsely sampled image that exactly satisfies the acquisition. We demonstrate that our technique is able to produce an exact reconstruction of the Shepp-Logan phantom with very sparsely sampled k-space data for realizable accelerated acquisitions using two common sampling trajectories.

                  2821.     Accelerated Free Breathing MRI with Continously Moving Table Using Compressed Sensing

Matthias Honal¹, Jochen Leupold¹, Ute Ludwig¹

¹Dept. of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany

Breathing motion is an important issue in MRI with continuously moving table (CMT). In this study the compressed sensing method is applied to an axial multi-slice CMT technique to acquire artifact free snapshots of the breathing motion. For a reduction factor of R = 2 images without significant motion or reconstruction artifacts are obtained.

                  2822.     Adaptive Regularization in Compressed Sensing Using the Discrepancy Principle

Kevin F. King¹, Luca Marinelli², Christopher J. Hardy²

¹Applied Science Lab, GE Healthcare, Waukesha, WI, USA; ²GE Global Research, Niskayuna, NY, USA

Compressed sensing images are usually reconstructed by finding the minimum of an objective function with two terms: one that measures the difference between the k-space data of the reconstructed image and the measured k-space data (discrepancy term), and a term that measures the L1-norm of the image in a sparsifying transform domain. A weighting factor (regularization parameter) that must be properly chosen for good image quality, balances the contribution of the two terms. A method called the discrepancy principle automatically chooses the regularization parameter based on the size of the discrepancy term and the measured noise in the k-space data.

                  2823.     Compressed Sensing with Phase Constrained Partial Radial K-Space

Ali Bilgin^1,2, Yookyung Kim¹, Vineeth Abraham³, Theodore P. Trouard^2,4, Maria I. Altbach²

¹Electrical and Computer Engineering, University of Arizona, Tucson, AZ, USA; ²Dept. of Radiology, University of Arizona, Tucson, AZ, USA; ³Optical Sciences Center, University of Arizona, Tucson, AZ, USA; ⁴Biomedical Engineering, University of Arizona, Tucson, AZ, USA

Compressed sensing has been successfully used with radial k-space trajectories. In this work, we illustrate that partial Fourier

                  2824.     Sequential Application of Parallel Imaging and Compressed Sensing

Philip James Beatty¹, Kevin F. King², Luca Marinelli³, Chris J. Hardy³, Michael Lustig⁴

¹Applied Science Laboratory, GE Healthcare, Menlo Park, CA, USA; ²Applied Science Laboratory, GE Healthcare, Waukesha, WI, USA; ³Global Research Center, General Electric, Niskayuna, NY, USA; ⁴Electrical Engineering, Stanford University, Stanford, CA, USA

An alternative approach to combining parallel imaging (PI) and compressed sensing (CS) is proposed. The k-space sampling pattern is modified to allow parallel image and compressed sensing to be applied in separate sequential stages during image reconstruction. The proposed approach allows compressed sensing to be used with many proven and pre-existing parallel imaging techniques and has the potential to reduce the amount of computation required for PI+CS reconstructions.

                  2825.     Reconstruction of Undersampled MR Data Using Lp (0<p<1) Spatial Constraints

Ganesh Adluru¹, Mark Rosen¹, Hee Kwon Song¹

¹Radiology, University of Pennsylvania, Philadelphia, PA, USA

Compressed sensing reconstruction using an L1 norm constraint offers high quality reconstructions from undersampled k-space data. The method is based on exploiting the implicit sparsity of the image. More recently it has been shown mathematically and using simulated numerical experiments that faithful reconstructions can be obtained from even fewer Fourier samples when an Lp constraint, where 0<p<1, is used. Here we test the feasibility of using the Lp spatial constrained reconstruction on in-vivo Cartesian MR images. Even though the cost function to be minimized is non-convex when p<1, results demonstrate that improved reconstructions can be consistently obtained.

                  2826.     Catheter Visualization for Endovascular MR Using Compressive Sampling: Comparison Against POCS

Jerome Yerly^1,2, M Louis Lauzon^2,3, Henry S. Chen^2,4, Richard Frayne^2,3

¹Electrical and Computer Engineering, University of Calgary, Calgary, AB, Canada; ²Seaman Family MR Research Centre, Foothills Medical Centre, Calgary Health Region, Calgary, AB, Canada; ³Radiology and Clinical Neurosciences, University of Calgary, Calgary, AB, Canada; ⁴Physics and Astronomy, University of Calgary, Calgary, AB, Canada

Passive catheter MR imaging is a promising visualization technique applicable to endovascular procedures. It provides several clinical advantages compared to the current x-ray fluoroscopy gold standard. Regrettably, conventional MR fluoroscopy offers limited refresh rates at moderate-to-high spatial resolution, so k-space undersampling is usually required. Compressive sampling (CS) and projection-onto-convex sets (POCS) are two nonlinear reconstruction algorithms that can accurately reconstruct undersampled k-space datasets. We demonstrate that passive catheter tracking using multi-cycle projection dephasers (a background suppression technique) coupled with CS generates higher quality images compared to POCS, and is fast enough to permit real-time monitoring.

                  2827.     Accelerated 2D Fourier-Velocity Encoded MRI Using Compressed Sensing

Luca Marinelli¹, Kedar Khare¹, Kevin F. King², Robert Darrow¹, Christopher J. Hardy¹

¹Global Research Center, General Electric, Niskayuna, NY, USA; ²GE Healthcare, Waukesha, WI, USA

We develop a new pulse sequence for accelerated 2D Fourier-velocity-encoded (FVE) MRI to measure blood-velocity in disturbed flows. 2D Fourier-velocity-encoded M-mode MRI provides a non-invasive probe of 2D velocity distributions that cannot be measured by other modalities such as Doppler ultrasound but can be exceedingly time consuming. Unlike conventional imaging, parallel imaging cannot be utilized to reduce number of velocity encoding steps. We apply compressed sensing to this newly developed pulse sequence to increase velocity resolution without a scan time penalty and show that an accurate reconstruction with reduction factors up to 5 is possible.

                  2828.     Auto-Calibration Method for K-T-SENSE: Using TGRAPPA to Calculate the Training Data

Paola Irene Ponce¹, Martin Blaimer², Felix A. Breuer², Peter M. Jakob¹, Mark A. Griswold³, Peter Kellman⁴

¹Department of Experimental Physics 5, University of Würzburg, Würzburg, Bavaria, Germany; ²Research Center Magnetic Resonance Bavaria (MRB), Würzburg, Bavaria, Germany; ³Department of Radiology, University Hospitals of Cleveland and Case Western Reserve University, Cleveland, OH, USA; ⁴Laboratory of Cardiac Energetics, National Institutes of Health, National Heart, Lung and Blood Institute, Bethesda, MD, USA

In accelerated dynamic MRI, several methods have been proposed to reconstruct missing data based on prior knowledge about the motion. The k-t SENSE method utilizes coil sensitivity variations and correlations in k-space and time to reconstruct missing data. However, k-t SENSE requires additional training data as prior information about the dynamics of the object. This work removes the requirement of an additional training data acquisition by employing additional TGRAPPA reconstructions on the undersampled dataset. TGRAPPA produces images with high spatial and temporal resolution without temporal filtering effects and is therefore fully applicable for producing high-quality training data for k-t SENSE.

                  2829.     Optimal Method for Obtaining Dynamic Phase Images from Multi-Channel EPI Data

Erik B. Beall¹, Ken E. Sakaie¹, Kecheng Liu², Pallab K. Bhattacharyya¹, Mark J. Lowe¹

¹Imaging Institute, Cleveland Clinic, Cleveland, OH, USA; ²Siemens Medical Solutions, USA Inc.

Dynamic MR phase information is important for many applications, and current multi-channel methods are not optimal. Optimal combination and phase referencing are two separable steps that can be used to improve results. The implementation of an improved method for obtaining MR phase information over time in rapid acquisitions was used to obtain phase images and the benefits are demonstrated.

                  2830.     Constrained Reconstruction of Dynamic Contrast Enhanced Tumor MR Data with Respiratory Self-Gating

Ganesh Adluru¹, Wei Lin¹, Mark Rosen¹, Hee Kwon Song¹

¹Radiology, University of Pennsylvania, Philadelphia, PA, USA

Compressed sensing/constrained reconstruction methods have recently been proposed and applied to accelerate MR acquisitions. Here we apply the spatio-temporal constrained reconstruction method in conjunction with the recently proposed respiratory self-gated DCE-MRI strategy to improve the reconstructions of radially undersampled DCE tumor data. Respiratory gating effectively reduces the temporal signal variations due to breathing and leads to enhanced sparsity in the temporal gradient. Improved image quality is clearly demonstrated in undersampled lung and liver tumor DCE-MRI datasets. The approach offers a promising framework to accelerate DCE-MRI of lesions located in regions severely affected by respiratory motion.

                  2831.     Fast and Motion Robust R2* Reconstruction for Functional MRI

Valur Olafsson¹, Jeffrey A. Fessler¹, Douglas C. Noll²

¹EECS, The University of Michigan, Ann Arbor, MI, USA; ²BME, The University of Michigan, Ann Arbor, MI, USA

Quantitative images such as R2* maps are beneficial in understanding the BOLD contrast commonly used for functional MRI. However, due to its non-linear relationship to the MR signal equation it is problematic to efficiently estimate it directly from k-space data. We propose a new fast reconstruction that uses a linear approximation facilitated by a reference image to reconstruct R2* along with field map and M0 to make it robust to motion. Results from an fMRI experiment shows increased functional sensitivity for the R2* images compared to conventional T2*-weighted images and a reconstruction time just under a minute per slice.

                  2832.     Analytical Analysis of the Accuracy of HYPR LR in CE MRA

Huimin Wu¹, Alexey A. Samsonov², Julia Velikina², Walter F. Block³

¹Medical Physics, University of Wisconsin-Madison, Madison, WI, USA; ²Radiology, University of Wisconsin-Madison, USA; ³Biomedical Engineering, University of Wisconsin-Madison, USA

Image acceleration methods have recently been of significant interest due to their capabilities for capturing dynamic events with MRI. However, few accuracy characterizations with analytical methods have been developed for these non-linear methods. An analytical prediction of the temporal and spatial accuracy for HYPR Local Reconstruction (HYPR LR) is presented with a model for CE-MRA including arterial and venous vessels and enhancing background signal. We demonstrate the theory with a digital phantom whose results agree with the prediction of the analytical expression.

                  2833.     Motion Compensated Reconstruction for Free Breathing Dynamic Constrast-Enhanced MRI

Marina Filipovic^1,2, Pierre-André Vuissoz^1,2, Michel Claudon^1,3, Jacques Felblinger^1,2

¹IADI, Nancy-Université, Nancy, France; ²INSERM-U947, Nancy, France; ³CHU-Nancy, Nancy, France

The presented method generalizes GRICS, a motion compensated reconstruction algorithm, in order to apply it to contrast-enhanced MRI. The mathematical representation of the true image has been replaced by a new model taking into account possible contrast changes induced by contrast agent concentration. Tested in a two-step contrast-enhancing experiment on healthy subjects, the method both corrects for motion artefacts and performs a good detection of local contrast change. This first step opens a path to auto-registered motion compensated reconstruction for DCE-MRI and for substraction imaging.

                  2834.     Time-Resolved Imaging with Multiplicative Algebraic Reconstruction Technique (MART): An Application of HYPR Principles for Variable Density Cartesian Acquisitions

Reed F. Busse¹, Angel R. Pineda², Kang Wang³, James H. Holmes¹, Jean H. Brittain¹, Frank R. Korosec⁴

¹Applied Science Laboratory, GE Healthcare, Madison, WI, USA; ²Mathematics, California State University, Fullerton, CA, USA; ³Medical Physics, University of Wisconsin, Madison, WI, USA; ⁴Radiology, University of Wisconsin, Madison, WI, USA

MART reconstruction is applied to time-resolved MRI with an interleaved variable k-t density Cartesian acquisition. As introduced by HYPR, a time-averaged image is used as an initial estimate, conditioning the problem. Several multiplicative update iterations enforce consistency with the data. Additionally, a median filter in the time dimension is applied to suppress artifacts not consistent with physiological assumptions. Modeling experiments, simulating instantaneous contrast arrival in vessels of various sizes, are used to compare the proposed technique to conventional view sharing. MART was found to reproduce the enhancing objects more faithfully with less blurring in the spatial and temporal dimensions.

                  2835.     Iterative Soft-Thresholding Reconstruction for Time-Of-Flight MR Angiography

Kedar Khare¹, Luca Marinelli¹, Christopher J. Hardy¹, Kevin F. King²

¹Global Research Center, General Electric, Niskayuna, NY, USA; ²GE Healthcare, Waukesha, WI, USA

The implementation of Compressed Sensing strategies for accelerated MRI applications typically involve iterative methods to minimize nonlinear functionals consisting of terms representing L1-norm, total variation, etc. Iterative approaches (e.g. conjugate gradient) involve computation of complex cost functions and the solution is also sensitive to the choice of free parameters associated with the various non-linear priors. In this paper we present an iterative soft-thresholding method with slowly decreasing thresholding parameter and apply it to reconstruction and analysis of Time-of-Flight MRA. This method is not sensitive to the choice of free parameters and the computations involve only Fourier and wavelet transforms, both of which can be implemented efficiently. This method may be used either for reducing the scan time or for improving the spatial resolution of TOF-MRA images for fixed scan time.

                  2836.     Improved Temporal Resolution in Radial K-Space Sampling Using an Hourglass Filter

Maria Magnusson^1,2, Olof Dahlqvist Leinhard^2,3, Patrik Brynolfsson^2,4, Peter Lundberg^2,3

¹Department of Electrical Engineering, Linköping University, Linköping, Sweden; ²Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden; ³Department of Medical and Health sciences, Linköpings University, Linköping, Sweden; ⁴Radiation Sciences, Umeå Universitet, Umeå, Sweden

Using a radial sampling of k-space where consecutive profiles are separated by an angle δγ as close as possible to 180°/(golden ratio), dynamic scans with high temporal resolution can be achieved. By using N profiles where N is a prime number, all profiles are updated before any profile is revisited, ensuring a completely filled k-space before any profile is re-sampled. Using a modified hourglass-shaped sliding window filter during reconstruction, oversampling near the origin can be used to significantly increase temporal resolution without compromising image quality.

                  2837.     2D Graphical Assessment for Fast Imaging Strategies

Tzu-Cheng Chao^1,2, Hsiao-Wen Chung², William Scott Hoge³, Jing Yuan⁴, Bruno Madore⁴

¹Department of Radiology, Brigham and Women's Hospital, Harvard Medical School,, Boston, MA, USA; ²Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan; ³Department of Radiology,, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA; ⁴Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA

As the number and complexity of partially sampled dynamic imaging methods continues to increase, a reliable method to evaluate performance would be important. In the present work, an analytical formulation to evaluate the reconstruction efficiency of given fast imaging strategies was proposed. Assessments in terms of MTF, signal to artifact ratio and noise enhancement are visualized graphically, for all combinations of temporal and spatial frequencies. Three fast imaging strategies, kt-SENSE, UNFOLD-SENSE and a combination of the two (hybrid SENSE) were tested to illustrate their respective abilities, using in-vivo datasets.

                  2838.     Real-Time Elimination of Undersampling Artifacts Using 3D Total Variation on Graphics Hardware

Florian Knoll¹, Markus Unger², Franz Ebner³, Rudolf Stollberger¹

¹Institute of Medical Engineering, TU Graz, Graz, Austria; ²Institute for Computer Graphics and Vision, TU Graz, Graz, Austria; ³Department of Radiology, Medical University Graz, Graz, Austria

Undersampled radial acquisition strategies have great potential to acquire CE MRA data sets with high spatial and temporal resolution. It has been shown recently that image reconstruction with a total variation constraint efficiently eliminates undersampling artifacts. We show that 3D TV optimization problems can be solved on modern graphic processing units (GPUs), with computation times that allow real-time image reconstruction. Our results show excellent removal of streaking artifacts for highly undersampled CE MRA data sets. With the GPU implementation we achieve a reconstruction time of 0.24s for the whole 3D data set.

                  2839.     Online Real-Time Reconstruction of Adaptive TSENSE with Commodity CPU / GPU Hardware

Sébastien Roujol¹, Baudouin Dennis De Senneville¹, Erkki Vahala², Thomas Sangild Sørensen³, Chrit Moonen¹, Mario Ries¹

¹UMR 5231, CNRS/Université Bordeaux 2, Laboratory for Molecular and Functional Imaging, Bordeaux, France; ²Philips Medical Systems, Vantaa, Finland; ³University of Aarhus, Department of Computer Science and Institute of Clinical Medicine, Aarhus, Denmark

A real-time reconstruction for adaptive TSENSE is presented that is optimized for MR-guidance of interventional procedures. The proposed method allows high frame-rate imaging with low image latencies, even when large coil arrays are employed and can be implemented on affordable commodity hardware.

                  2840.     Segmentation of Multiple Sclerosis Lesions Using Quantitative MRI

Dagmar R. Lang¹, Veronika Ermer¹, N. Jon Shah^1,2, Heiko Neeb³

¹Institute of Neurosciences and Biophysics, Research Centre Juelich, Juelich, Germany; ²Faculty of Medicine, Department of Neurology, RWTH Aachen University, JARA, Aachen, Germany; ³RheinAhrCampus Remagen, University of Applied Sciences Koblenz, Remagen, Germany

Quantitative MRI provides the possibility to accurately monitor the course of neurological diseases, such as multiple sclerosis. Quantitative maps of the absolute water content of the brain of MS patients exhibit an approximately 8 % higher water content in lesions compared to that of the normal appearing white matter (WM). In order to investigate different characteristics of lesions in pure WM or close to the ventricles, different automatic segmentation algorithms were developed. Based on an improved tissue segmentation approach, lesions were segmented using the combination of a quantitative water content brain atlas and typical lesion characteristics such as the quantitative MR parameter distribution or the spatial localisation.

                  2841.     Artifact-Free and Multi-Contrast SSFP Imaging Achieved in a Single Acquisition

Ming-Long Wu¹, Nan-Kuei Chen¹

¹Brain Imaging and Analysis Center, Duke University, Durham, NC, USA

Balanced SSFP (bSSFP) is a pulse sequence with great clinical potential because of its short scan time, high SNR and lower SAR (specific absorption rate). However, due to its sensitivity to field inhomogeneities, SSFP imaging is always degraded by banding artifacts. Recently, partially-dephased SSFP (PD-SSFP) was developed to reduce banding artifact. Here we report novel echo separation and multi-scheme reconstruction methods to significantly improve PD-SSFP, enabling artifact-free, higher-SNR, and multi-contrast imaging with a single PD-SSFP acquisition.

                  2842.     Improved Image Reconstruction for Multi-Shot Multi-Coil Diffusion Imaging

Martin Uecker¹, Alexander Karaus¹, Jens Frahm¹

¹Biomedizinische NMR Forschungs GmbH, Max-Planck-Institut fuer biophysikalische Chemie, Goettingen, Germany

In multi-shot diffusion imaging each segment is affected differently by phase variations caused by brain pulsation during the diffusion gradients. For this reason image reconstruction requires phase maps for each segment. Since the resolution of the maps obtained with navigator based approaches is limited by its size, images reconstructed from strongly disturbed data suffer from residual phase cancellation. Reconstructing each segment independently with parallel imaging allows to calculate phase maps with high resolution avoiding phase cancellation problems during the reconstruction. The proposed technique was applied to data from a segmented STEAM sequence where large 2D-navigators are not feasible.

                  2843.     Tradeoffs in Supersampling of DTI Metrics

Jadrian Miles¹, Ron A. Cohen², David H. Laidlaw¹

¹Dept. of Computer Science, Brown University, Providence, RI, USA; ²Dept. of Psychiatry, Brown Medical School, Providence, RI, USA

Values derived from diffusion tensors (such as FA and eigenvectors) are often needed at higher spatial resolution than provided by a DW-MRI scan. One may magnify, or "supersample", the DWIs, DTI, and fields of derived values in turn, but what are the tradeoffs? In this work we examine the 15 different combinations of power-of-two supersamplings that achieve 16x magnification of the derived value fields. We find that interpolating derived values is as good as interpolating diffusion tensors, provided the DWIs have been sufficiently supersampled.

                  2844.     Fast Concomitant Gradient Field Correction for Spiral Scans

Joseph Yitan Cheng¹, Juan M. Santos¹, John M. Pauly¹

¹Department of Electrical Engineering, Stanford University, Stanford, CA, USA

For non-Cartesian scans, the off-resonance distortion greatly degrades the image quality. In this work, two post-gridding correction algorithms are presented: one performed in the frequency domain and the other in the image domain. Both of these computationally fast methods yield noticeable improvements. However, the image domain approach is preferred due to its flexibility in increasing accuracy with little cost. These phase correction algorithms can be applied prior to the correction for B0 inhomogeneities and gradient nonlinearities with accurate results.

                  2845.     Improved Gradient Field Distortion Correction in Continously Moving Table Acquisitions Using GIRAFFE

Rita Gouveia Nunes¹, Joseph V. Hajnal¹, David J. Larkman¹

¹Robert Steiner MRI Unit, Imaging Sciences Department, MRC Clinical Sciences Centre, Hammersmith Hospital, Imperial College London, London, UK

Continuously-Moving table allows efficient acquisition of whole-body images. Unfortunately, B0, gradient and B1 field imperfections result in data inconsistency leading to artifacts. Commonly, to reduce these, smaller excitation volumes are used and linear k-space traversal imposed, limiting the range of contrasts attainable. Polzin et al. developed a reconstruction method which incorporates distortion correction due to gradient non-linearities. We show that although this approach is reasonably accurate for linear schemes, its performance is poorer for segmented acquisitions. Improved reconstructions can be obtained for all schemes using the Generalised Image Reconstruction Accounting For Field Effects method, increasing design flexibility and scanning efficiency.

                  2846.     Water-Fat Decomposition with MR Data Based Regularized Estimation in MRI

Won Seok Huh¹, Jeffrey A. Fessler¹

¹EE:system, University of Michigan, Ann Arbor, MI, USA

The ability of MRI to separate chemical components is important in clinical use. We describe a new regularized iterative algorithm, termed k-space method, which reconstructs water and fat and field map. The k-space method has been implemented with MR data to consider different data acquisition time. In the method, the cost function includes a regularized term due to prior knowledge that off-resonance is usually smooth. We use iterative approach with field map estimation, and water and fat estimation. By providing readout information to the cost function, the method yields improved estimates of the chemical components.

                  2847.     Independent Estimation of T2* for Water and Fat for Improved Accuracy of Fat Quantification

Venkata Veerendranadh Chebrolu¹, Catherine D G Hines¹, Huanzhou Yu², Angel R. Pineda³, Ann Shimakawa², Charles McKenzie⁴, Jean H. Brittain⁵, Scott B. Reeder^1,6

¹Biomedical Engineering, University of Wisconsin Madison, Madison, WI, USA; ²Applied Science Laboratory, GE Healthcare, Menlo Park, CA, USA; ³Mathematics, California State University, Fullerton, Fullerton, CA, USA; ⁴Medical Biophysics, The University of Western Ontario, London, London, Ontario, Canada; ⁵MR Global Applied Science Lab, GE Healthcare, Madison, WI, USA; ⁶Radiology, University of Wisconsin Madison, Madison, WI, USA

Non-invasive quantification of intracellular fatty accumulation of the liver (steatosis) is needed for early detection and grading of fatty liver disease, the leading cause of chronic liver disease. T2* values of water and fat are independently estimated using a modified Gauss-Newton method for multiple variables, relaxing the assumptions made by single exponential T2* correction methods, that assume a common value of T2* for both water and fat. Accurate quantification of fat is demonstrated with independent estimation of T2* values for water and fat, in phantom experiments.

                  2848.     Robust Multicoil Reconstruction for Phase-Sensitive Fat-Water Separation

Tolga Çukur¹, Brain A. Hargreaves², Dwight G. Nishimura¹

¹Electrical Engineering, Stanford University, Stanford, CA, USA; ²Radiology, Stanford University, Stanford, CA, USA

Phase-sensitive (PS) SSFP efficiently separates the fat and water resonances by exploiting the 180^o phase-difference between adjacent pass-bands in balanced SSFP. This difference can be detected if all other sources introduce slow phase variations in space. However, for surface coils, the abrupt variations at the edge of the sensitivity regions can lead to fat-water misclassification in multicoil reconstructions. In this work, we propose to first obtain a reliable phase estimate by combining individual coil images. The PS-reconstruction is then performed for successful fat-water separation.

                  2849.     Water-Fat Imaging by Direct Phase Encoding with Solution Along Isophasic Lines (SAIL)

Qing-San Xiang¹

¹Department of Radiology, University of British Columbia, Vancouver, BC, Canada

Direct Phase Encoding (DPE) is a simple and efficient technique for water-fat imaging, allowing even pixel level analytical water-fat separation and identification. However, for pixels containing only a single chemical component, the relative phase relationship between water and fat is unavailable. As a result, region growing is often needed to extract phase information from neighboring pixels. This work describes a novel approach to address the single-peak issue. Pixels along isophasic lines should experience the same magnetic field inhomogeneity, and thus satisfy the same equations. Water and fat can then be found by DPE with Solutions Along Isophasic Lines (SAIL).

                  2850.     Phase Optimized Sensitivity Estimation Method for SENSE

Zhaolin Chen^1,2, Leigh Johnston^1,2, Zang-Hee Cho³, Gary Egan^1,4

¹Howard Florey Institute, Carlton South, VIC, Australia; ²Department of Electrical and Electronic Engineering, University of Melbourne, Melbourne, VIC, Australia; ³Neuroscience Research Institute, Incheon, Korea; ⁴Centre for Neuroscience, University of Melbourne, Australia

MR phase images provide additional information beyond magnitude images. It has been noted that the SENSE reconstruction using traditional square-root-sum-of-squares sensitivity estimation approach cannot provide accurate phase reconstruction for single echo although it can preserve dynamic phase updates among echoes. This paper presents a phase optimized sensitivity estimation method for the self-calibrated SENSE methods. The new method can provide improved phase contrasts in structural imaging applications. Demonstrated in both the 3T and the 7T datasets, the proposed method produces dramatically improved phase image contrasts when compared with the current sensitivity estimation method. The new method is potentially useful for both structural and dynamic phase sensitive imaging applications.

                  2851.     Accelerating Sparse Object Imaging by Simplified Skipped Phase Encoding and Edge Deghosting with Array Coil Enhancement (SPEED-ACE)

Zheng Chang¹, Qing-San Xiang^2,3, Fang-Fang Yin¹

¹Department of Radiation Oncology, Duke University, Durham, NC, USA; ²Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada; ³Department of Radiology, University of British Columbia, Vancouver, BC, Canada

The parallel imaging method of Skipped Phase Encoding and Edge Deghosting with Array Coil Enhancement (SPEED-ACE) is simplified with enhanced acceleration for imaging sparse objects; the method is termed S-SPEED-ACE that partially samples k-space with multiple coils in parallel and yields a deghosted image based on a least-square-error solution. Without differential filtering and full central k-space sampling, S-SPEED-ACE uses more straightforward reconstruction and achieves further scan time reduction as compared with SPEED-ACE. As demonstrated by a simulated scan using experimental head PC-MRA data, S-SPEED-ACE can achieve 8 times acceleration using 4 coils with reasonable image quality.

                  2852.     Performance of Three Parallel MRI Reconstruction Methods in the Presence of Coil Sensitivity Map Errors

Lotfi Chaâri^1,2, Philippe Ciuciu², Amel Benazza-Benyahia³, Jean-Christophe Pesquet¹

¹IGM Lab. Info., Université Paris Est, Marne-la-Vallée, France; ²NeuroSpin, CEA, Saclay, France; ³URISA, SUP'COM, Tunis, Tunisia

A study of parallel MRI reconstruction techniques performance in the presence of coil sensitivity map errors, using artificially simulated parallel MRI images.

                  2853.     Boosting Image Quality by Automatic Low SNR Channel Detection and Its Removal in K-Space

Christian Ros¹, Jan Sedlacik², Najat C. Daw³, Ralf Loeffler², Juergen R. Reichenbach¹, Claudia M. Hillenbrand²

¹Medical Physics Group, Institute for Diagnostic and Interventional Radiology, Friedrich Schiller University, Jena, Germany; ²Department of Radiological Sciences, St. Jude Children's Research Hospital, Memphis, TN, USA; ³Department of Oncology, St. Jude Children's Research Hospital, Memphis, TN, USA

Phased array coils with a large number of elements are used for peripheral and/or body MRI. Activated coil elements that are located far from the measurement volume detect almost no signal and cause the automated system adjustment to improperly increase the gain factor of the respective receiver channels. If such low signal channels are incorporated in the final combination of coil elements, their artificially elevated noise is added to the reconstructed image and may result in degenerated image quality. We propose a novel k-space based algorithm which identifies such channels and discards them from the reconstruction process.

                  2854.     Fast Phase Unwrapping Using Fourier Transform

Amir M. Abduljalil¹, Seongjin Choi¹, Michael Vincent Knopp¹, Petra Schmalbrock¹

¹Radiology, The Ohio State University, Columbus, OH, USA

Phase image extraction and unwrapping is explored using discrete Fourier transforms. The slow varying phase changes are filtered out using a convolution algorithm to reveal the phase changes due to the anatomy. The applied method is robust and an improvement in the contrast to noise ratio is observed when the noise in the images is masked out prior to starting the calculations.

                  2855.     Coil Array Compression in Coronary MRA

Johannes Frieder Schmidt¹, Martin Buehrer¹, Peter Boesiger¹, Sebastian Kozerke¹

¹Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland

SNR limits the spatial resolution necessary for coronary MRA. Higher SNR is provided by large coil arrays, but at the expense of increased data sizes for image reconstruction. This work demonstrates the applicability of coil array compression for coronary imaging which uses a linear combination of channels to compress the data to a reduced set of virtual coils. In 10 healthy volunteers, it is shown for various compression factors that the visible image quality remains comparable. For a compression factor of 8, the relative loss in SNR on the coronaries is 5%.

                  2856.     Hybrid Roemer Reconstruction for Multi-Element TX/RX Body Coil at 3T

Kay Nehrke¹, Klaus Michael Uhr², Peter Börnert¹

¹Philips Research Europe, Hamburg, Germany; ²Technische Universität, Hamburg-Harburg, Germany

For a TX/RX coil array, the transmit field inhomogeneity at higher field strengths (>3T) is an important problem. However, as a result of the principle of reciprocity, the receive fields are affected by wave propagation effects at high fields as well. Hence, appropriate combination of the data from the individual receive channels has to be performed by image reconstruction. In the present work, a hybrid Roemer reconstruction based on pre-calibrated sensitivity data is proposed. It has been implemented, and its performance has been compared with simple data combination approaches based on sum-of-squares or complex superposition.

                  2857.     Kaczmarz Iterative Reconstruction for Arbitrary Hybrid Encoding Functions

Jason Peter Stockmann¹, Robert Todd Constable²

¹Biomedical Engineering, Yale University, New Haven, CT, USA; ²Diagnostic Radiology & Neurosurgery, Yale School of Medicine, and Biomedical Engineering, Yale University, New Haven, CT, USA

The Kaczmarz iterative algorithm (also known as Algebraic Reconstruction Technique, or ART) is applied to the problem of reconstructing images using arbitrary combinations of coil and gradient encoding. Methods have recently been proposed to form images using higher-order gradient encoding functions such as spherical harmonics. Since these encoding functions do not project the object into k-space, we propose to solve the MR signal equation directly without Fourier Transforming the echoes. Kaczmarz is used to reconstruct simulated data produced by linear and non-linear gradients, and spatially-varying point spread functions are illustrated.

                  2858.     A Phase Constrained Graph Cut Algorithm for Reconstruction of MR Parallel Imaging Under 3D Spatial Priors

Ashish Raj¹, Ramin Zabih²

¹Radiology, Weill Medical College of Cornell University, New York, NY, USA; ²Computer Science, Cornell U, Ithaca, NY

Current parallel imaging methods like SENSE and GRAPPA are seriously limited by SNR and g-factors associated with coil geometry. Most MR images have sharp edges and are piecewise smooth. A new edge preserving Markov Random Field (MRF) prior model was proposed in to address this issue, and a new graph cut-based algorithm was developed to solve the computationally challenging non-convex optimization problem. Here we propose two important extensions of the EPIGRAM method by (a) incorporating 3-D spatial priors and by jointly reconstructing multi-slice images, and (b) using low-frequency phase as a constraint during the reconstruction process. Recent reports indicate that phase-constrained reconstruction improves image quality. The proposed method performs better than the conventional SENSE method applied slice-by-slice.

                  2859.     Extended Anti-Aliasing Reconstruction for Phase-Scrambled MRI with Quadratic Phase Modulation

Maxim Zaitsev¹, Gerrit Schultz¹, Jürgen Hennig¹

¹Dept. of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany

As shown recently, phase-scrambled MRI is capable of a scalable anti-aliasing image reconstruction. The purpose of the present work is to extend the concept via a transparent mathematical framework capable of handling scalable alias-suppressing image reconstruction of the phase-modulated data. Our results show that translation of the Fresnel transform concept to k-space representation allows to define limits and boundary conditions for practical implementations and to understand signal behaviour and potential artefacts.

                  2860.     Generalized Reconstruction of Multi-Spectral MR Acquisitions for Imaging Near Metal Implants

Diego Hernando¹, Kevin M. Koch², Kevin F. King², Zhi-Pei Liang¹

¹Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA; ²Applied Science Laboratory, General Electric Healthcare, Waukesha, WI, USA

Several techniques have been recently proposed for imaging near metal implants (i.e., in the presence of extreme B0 field inhomogeneity), by effectively dividing the large spectral range into smaller bins. However, conventional sum-of-squares reconstructions result in localized image intensity distortions in regions of rapid field variation. This abstract presents a novel method for generalized reconstruction of multi-spectral acquisitions, where the reconstruction is posed as a regularized least squares problem. The proposed method overcomes some of the main limitations of current techniques, and provides increased flexibility for the selection of imaging parameters.

                  2861.     Bayesian Reconstruction of DW-PROPELLER Images Using Joint Entropy

Jinhua Sheng¹, Dong Liang¹, Jing Tang², Donglai Huo³, Leslie Ying¹

¹Dept. of Electrical Engineering and Computer Science, Univ. of Wisconsin-Milwaukee, Milwaukee, WI, USA; ²Dept. of Radiology, the Johns Hopkins University, Baltimore, MD, USA; ³Keller Center for Imaging Inno,Barrow Neurological Institute, St. Joseph Hospital and Medical Center, Phoenix, AZ, USA

Turboprop has shown to reduce the artifacts of single-shot EPI for Diffusion-weighted imaging (DWI) but at the cost of longer acquisition. In this abstract, we propose a novel Bayesian reconstruction method to reduce the number of acquisitions without compromising the SNR. The method incorporates the information from high quality non-weighted images into the DWI reconstruction, with the joint entropy between the weighted and non-weighted image features as the prior. The method is shown to improve the DW image quality with a set of DW-PROPELLER brain data.

                  2862.     Resolution and Noise Properties of Linear Phase-Constrained Partial Fourier Reconstruction

Justin P. Haldar¹, Kenneth Sakaie², Zhi-Pei Liang¹

¹Beckman Institute, Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA; ²Cleveland Clinic, Cleveland, OH, USA

Phase-constrained partial Fourier (PF) reconstruction is a classical technique that leverages prior knowledge of the image phase to reduce k-space sampling requirements. While the technique has seen wide use, the characteristics of PF reconstructions are usually only evaluated empirically. In this work, we show that resolution and noise properties of the class of linear PF reconstruction methods (including homodyne, projection onto convex sets with linear projections, and matrix inversion methods) can be characterized theoretically in terms of spatial response functions and interference response functions. We demonstrate an application of these theoretical characterizations in the context of regularized PF reconstruction.

                  2863.     Data Interpolation in Phase-Scrambling Fourier Transform Technique for Alias-Free Image Reconstruction by Iterative Signal Restoration Algorithm

Yoshifumi Yamada¹, Satoshi Ito¹

¹Department of Information Systems Science, Utsunomiya University, Utsunomiya, Tochigi, Japan

The phase scrambling Fourier transform (PSFT) signal can be converted into the Fresnel transform signal by multiplying by a quadratic phase term. In this paper, a new alias-free image reconstruction technique in the PSFT imaging technique is presented in which the signal is converted into the Fresnel transform signal and residual alias in the image is removed by increasing the data interpolation accuracy with using iterative signal restoration algorithm. Numerical simulation using MR images showed that almost alias-free images can be reconstructed using this technique.

                  2864.     Iterative Reconstruction for Off-Resonance Effects in SWIFT Imaging

Steen Moeller¹, Djaudat Idiyatullin¹, Curt Corum¹, Rong Zhou², Michael Garwood¹

¹Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, USA; ²Departments of Radiology, University of Pennsylvania, PA, USA

: We demonstrate the feasibility for off-resonance correction with SWIFT applications where field mapping is not possible. Myocardium injected with SPIO-labeled stem cells is imaged ex-vivo, and the locally dephased signal is reconstructed.

                  2865.     Including Prior Knowledge in the Reconstruction of ASL Perfusion Images to Reduce Noise and Improve Spatial Resolution

Philip M. Robson¹, David C. Alsop¹

¹Radiology, Beth Israel Deaconess Medical Center, Boston, MA, USA

ASL perfusion images are often acquired at low spatial resolution to attain sufficient SNR in the perfusion signal. However, ASL studies often include acquisition of high resolution anatomical reference images. ASL perfusion imaging is, therefore, a good candidate to benefit from the combined functional and anatomical information available from MRI. We explore the use of constrained image reconstructions and inclusion of prior knowledge from anatomical reference images to enhance SNR in perfusion images and improve spatial resolution.

                  2866.     Estimation of Tissue at Risk of Infarction Using a Support Vector Machine on Multimodal Stroke MRI Data

Susanne Schnell¹, Irina Mader², Dorothee Saur³, Kim Mouridsen⁴, Roza Umarova³, Dorothee Kümmerer³, Hans Burkhardt⁵, Valerij G. Kiselev¹

¹Dept. of Diagnostic Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany; ²Dept. of Neuroradiology, University Medical Center Freiburg, Freiburg, Germany; ³Dept. of Neurology, University Medical Center Freiburg, Freiburg, Germany; ⁴Dept. of Neuroradiology, Center for Functionally Integrative Neuroscience, Aarhus University Hospital, Aarhus, Denmark; ⁵Dept. of Computer Science, Chair in Pattern Recognition and Image Processing, Albert-Ludwigs University Freiburg, Freiburg, Germany

Acute ischemic stroke is a frequent cause of neurological disability. A clinical tool for the differentiation of reversable from irreversable damaged tissue would be of valuable use. This requires accurate prediction of the extent of the infarction. Typically, the estimation relies on models derived from perfusion and diffusion data (e.g. perfusion-diffusion mismatch, CBF, CBV). In this successfully performed trial study we introduce a data-driven method using Support Vector Machine (SVM) classification. The input data for the SVM consists of acute diffusion and perfusion information. A labelled training dataset is created using the patient’s follow-up scan in the chronic stage.

                  2867.     Direction of Plaque Progression Is a Significant Predictor in Plaque Vulnerability: An Evaluation by MRI

Dongxiang Xu¹, Chun Yuan¹

¹Radiology, University of Washington, Seattle, WA, USA

This study explores the relationship between the direction of plaque progression and plaque vulnerability. Projection length along the axial and longitudinal directions were analyzed and correlated with subjects’ symptom status. The statistical results show that plaque progression in the axial direction is a better predictor for patient’s symptom than longitudinal progression. This means that the plaque’s morphology change, in addition to plaque size which has been widely used in atherosclerosis research, can potentially be another significant factor to carotid artery disease evaluation and patient’s symptom prediction.

                  2868.     The Optimised Projection Image Method for Targeted Tissue Contrast Enhancement.

Amanda Ching Lih Ng^1,2, Nathan Faggian^2,3, Zhaolin Chen^2,4, Jingxin Zhang¹, Gary F. Egan^2,3, Leigh A. Johnston^2,4

¹Department of Electrical and Computer Systems Engineering, Monash University, Melbourne, Vic, Australia; ²Howard Florey Institute, University of Melbourne, Melbourne, Vic, Australia; ³Centre for Neuroscience, University of Melbourne, Melbourne, Vic, Australia; ⁴Department of Electrical and Electronic Engineering, University of Melbourne, Melbourne, Vic, Australia

In recent years there has been an increased interest in combining phase and magnitude MRI data. We propose an Optimised Projection Image (OPI) technique which removes heuristics involved in combining phase and magnitude to enhance contrast in MRI for a target tissue class. This method fits a bivariate Gaussian mixture model to the magnitude and phase data, and projects the data onto an intensity axis optimised for the model. This algorithm is shown to combine the detail in both magnitude and phase images to create an image with enhanced edge definition and structural detail in comparison to the original images.

                  2869.     Enhancement of Venous Vasculature in the Brain with Multi-Scale Filtering

Zhaoyang Jin^1,2, Ling Xia², Yiping Peter Du³

¹Institute of Information and Control, Hangzhou Dianzi University, Hangzhou, Zhejiang, China; ²Biomedical Engineering, Zhejiang University, Hangzhou, Zhejiang, China; ³Psychiatry,Radiology, University of Colorado Denver School of Medicine, Denver, CO, USA

In susceptibility weighted imaging, off-resonance artifacts can appear in regions with severe field inhomogeneity. The use of minimum-intensity projection can also cause signal loss in the peripheral regions of the brain. In this study, we present a multi-scale filter to enhance venous vasculature using magnitude images. Venography with positive venous contrast can be obtained. The maximum-intensity projection display of the filtered venography does not suffer from signal loss. Excellent venous contrast was obtained with a relatively short TE acquisition (TE=16.3ms) at 3T, making it feasible to reduce the scan time while preserving good visibility of small veins.

                  2870.     Semi-Automated Volume Segmentation of the Brain Based on a Level Set Approach

Zhaoyang Jin¹, Ling Xia², Yiping Peter Du³

¹Institute of Information and Control, Hangzhou Dianzi University, Hangzhou, Zhejiang, China; ²Biomedical Engineering, Zhejiang University, Hangzhou, Zhejiang, China; ³Psychiatry,Radiology, University of Colorado Denver School of Medicine, Denver, CO, USA

The minimum-intensity projection (mIP) display of 3D susceptibility weighted images can introduce signal loss in peripheral regions of the brain because of the low intensity in air or bone along the path of projection. In this study, we present the results of semi-automated volume segmentation using a level set approach to obtain a brain mask using magnitude images. Signal loss in the mIP display of 3D susceptibility weighted images in the peripheral regions of the brain can be effectively avoided using the brain mask.

                  2871.     Segmentation of Amyloid Plaques in MR Images of the APP Transgenic Mouse Brain Using SVM

George Iordanescu¹, Palamadai Venkatasubramanian¹, Alice Wyrwicz¹

¹Northwestern University, Evanston, IL, USA

We present an automated method for the selection of the segmentation parameters used for the quantification of amyloid plaques in APP transgenic mice that are models for Alzheimer’s disease (AD). For this we use support vector machines (SVM) in an unsupervised way. The usual approach for classification is to use the “ground truth”, in our case real examples of amyloid deposits in MR images. Obtaining such examples is however very difficult, due to the reduced size and low contrast of plaques. To address this, we employ a “learning by counter-example” approach, by training one class SVM classifier on control datasets.

                  2872.     Determination of Whole Body Fat and Visceral Adipose Tissue, Combining Three Volume Estimation Methods

Tania Buehler¹, Daniel GQ Chong¹, Chris Boesch¹

¹Dept. of Clinical Research, University Bern, Bern, Switzerland

Whole body fat (WBF) and particularly visceral adipose tissue (VAT) are of paramount importance as cardiovascular risk factors related to the metabolic syndrome. At 3 Tesla MR systems an inherent inhomogeneity of the radiofrequency field in the abdominal region jeopardizes the estimation of VAT and WBF and make it necessary to find a more robust and accurate method to measure these volumes. This study suggests and tests a method that combines the strengths of three volume determination methods (threshold, planimetry, and point counting), which makes the determination of the fragmented VAT compartment feasible and quick.

                  2873.     Establishment of a Novel Automated Approach for Quantification of Subcutaneous and Visceral Adipose Tissues: Correlates with Other Anthropometric Measurements and Cardiometabolic Risk Factors

Sarayu Annamalai Parimal¹, Karren Hui Min Chen¹, Suresh Anand Sadananthan², Sam Sim¹, Vitali Zagorodnov², Michael WL Chee¹

¹Cognitive Neuroscience Laboratory, Duke-NUS Graduate Medical School, Singapore, Singapore; ²Computer Engineering, Nanyang Technological University, Singapore, Singapore

We developed a novel automated algorithm for estimation of visceral and subcutaneous adipose tissues. Using it on abdominal MR scans obtained from 119 healthy elderly volunteers showed that women have more subcutaneous abdominal fat while men have more visceral abdominal fat [6], which was consistent with previous studies. Visceral, and not subcutaneous abdominal fat, is associated with the various risk factors for cardiometabolic diseases [7]. We conclude that this automated method of abdominal adiposity quantification and analysis is a sensitive and valid tool to be utilized in future epidemiological studies of abdominal adiposity and cardiovascular and metabolic health.

                  2874.     Automatic Liver Segmentation of  3D Abdominal MR Images of Rodents

Way Cherng Chen¹, Ying Min Wang¹, Kai-hsiang Chuang¹, Xavier Golay², Anqi Qiu³

¹Singapore Bioimaging Consortium, A*STAR, Singapore, Singapore; ²University College London, UK; ³National University of Singapore, Singapore

An automatic segmentation approach that integrates both a probabilistic model and an atlas-based method for utilizing both image intensity and liver shape information was developed for fast and accurate liver segmentation. An average volume difference of 20% and overlap ratio of 70.3% between the automatic segmentation and manual segmentation was obtained from 5 mice images. These variabilities are due to the limited contrast between the liver and surrounding tissues. More subjects are needed to test the robustness of the algorithm. The segmentation accuracy should be further improved by using a probabilistic atlas based on a large number of subjects.

                  2875.     Influence of a Partial Volume Effect in the Segmentation of Brain Tissue Based on Diffusion Tensor Imaging (DTI) Data: A Digital DTI Phantom Study

Seiji Kumazawa¹, Takashi Yoshiura², Hiroshi Honda², Fukai Toyofuku¹, Yoshiharu Higashida¹

¹Department of Health Sciences, Faculty of Medical Sciences, Kyushu University, Fukuoka, Japan; ²Department of Clinical Radiology, Kyushu University, Fukuoka, Japan

The performance of the brain segmentation based on diffusion tensor imaging (DTI) data has not been evaluated by using the digital DTI phantoms. We extended the previous DTI phantom model to the partial volume description of diffusion measurements, and investigated the performance of segmentation using the conventional method on the DTI phantom with a partial volume effect (PVE) model. The values of overlap measure between segmentation and the ground truth in the data with a PVE are lower than those without a PVE. These results indicate that a method taking a PVE into account can improve the segmentation performance on DTI data.

                  2876.     MR ONCO-TREAT:  a New Tool for Volumetric and Functional Analysis of Hepatic Tumors Monitored with Multi-Modal MRI

Mehmet Akif Gulsun¹, Clifford Raabe Weiss^2,3, Ralph Strecker³, Glenn Meredith¹, Ihab R. Kamel²

¹Imaging and Visualization, Siemens Corporate Research, Princeton, NJ, USA; ²The Russell H. Morgan Department of Radiology and Radiologic Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA; ³MR Oncology, Siemens Healthcare, Erlangen, Germany

Multi-parametric MRI is becoming the gold standard for assessing hepatic tumor response to intra-arterial therapy. We present the MR-ONCO-TREAT software package for 3D evaluation of multi-parametric MR studies. The software includes: deformable image registration, interactive segmentation, and volumetric and functional analysis. In six patients with hepatocellular carcinoma, this software was able to register pre and post intra-arterial treatment MRI scans, segment tumor from surrounding liver, and provide volumetric and functional data analysis. On average, percent arterial enhancement decreased by 35.7, and the ADC increased by 9.5%. The MR-ONCO-TREAT software can automate the evaluation of hepatic tumors, possibly decreasing interpretive errors.

                  2877.     Comparison of Brain Segmentation Results Using Automated FSL-FAST with DTI Channel Inputs

Elizabeth Zakszewski^1,2, Deok Han¹, Jee Eun Lee¹, Vikas Singh¹, Andrew L. Alexander^1,2

¹Waisman Laboratory for Brain Imaging and Behavior, University of Wisconsin, Madison, WI, USA; ²Dept. of Medical Physics, University of Wisconsin, Madison, WI, USA

The performance of the FSL-FAST algorithm for segmenting brain tissue from DTI data is evaluated in comparison with hand-drawn white matter segmentations. Various ways of combining different DTI parameter maps with FSL's built-in option are compared and evaluated.

                  2878.     Optimizing N3 Parameters Leads to Better Segmentation Accuracy on 3T Scanners

Weili Zheng¹, Michael WL Chee², Vitali Zagorodnov¹

¹Computer Engineering, Nanyang Technological University, Singapore, Singapore; ²Cognitive Neuroscience Laboratory, Duke-NUS Graduate Medical School, Singapore, Singapore

A recent study by Boyes at al. have found that performance of non-parametric nonuniformity correction approach N3 on 3T scanners could be improved by reducing the value of the parameter that controls the smoothness of the estimated bias field. The present study not only confirms this finding but also demonstrates the benefits of using smaller smoothing distances (30-50mm compared with default 200mm) on the quality of white matter surface estimation and reliability of cortical thickness and subcortical structures volumes, which is promising to increase the feasibility of longitudinal neurological studies.

                  2879.     Use of Lesion Walker Classification in Patients with Multiple Sclerosis

David Scott Wack^1,2, Michael G. Dwyer, Jackie Durfee, Sara Hussein, Deepa P. Ramasamy, Niels Bergsland, Robert Zivadinov¹

¹ Buffalo Neuroimaging Analysis Center, Jacobs Neurological Institute, Dept. of Neurology, State University of New York at Buffalo, Buffalo, NY, USA; ²Dept. of Nuclear Medicine, State University of New York at Buffalo, Buffalo, NY, USA

Software for the analysis and serial classification of multiple sclerosis lesions was developed and tested. The system is based on the definition of a lesion complex (LC) which maintains a one to one correspondence between scans. A grammatically consistent labeling system was used to classify LCs in a chronological progression. The software forces a quality control check to ensure that the operator has not missed ROIs prior to the classification stage. The analysis time is significantly reduced for an operator; while the result has a higher credence by virtue of the forced quality control and grammatical consistency of the labels.

                  2880.     Validation of Fat Volume Quantification with IDEAL MRI

Abdullah Alabousi¹, Salam Al-Attar², Tisha R. Joy^1,3, Robert A. Hegele^1,3, Charles A. McKenzie^3,4

¹Schulich School of Medicine and Dentistry, London, Ontario, Canada; ²University of Ottawa School of Medicine, Ottawa, Ontario; ³The Robarts Research Institute, London, Ontario; ⁴Department of Medical Biophysics, Schulich School of Medicine and Dentistry , University of Western Ontario

We will be validating IDEAL (Iterative Decomposition of water and fat with Echo Asymmetry and Least-squares estimation), an MRI technique that allows images to be produced only from fat containing tissues. Four normal controls were recruited to validate IDEAL for fat volume measurements. IDEAL correlates strongly with our gold standard (1.5T imaging) except for visceral abdomi-nal fat measurements. The lower value of visceral fat volume given by IDEAL may reflect an improved ability to differentiate be-tween true visceral fat and other tissues, however, this will require evaluation of a larger number of subjects with a range of visceral fat mass.

                  2881.     Three-Dimensional (3-D) Segmentation of Knee Cartilage from 3.0 T MR Images Using a Graph-Cuts Technique

Hackjoon Shim^1,2, Samuel Chang³, Cheng Tao¹, Jinhong Wang¹, Kyongtae Ty Bae¹

¹Department of Radiology, University of Pittsburgh, Pittsburgh, PA, USA; ²School of Electrical Engineering, Seoul National University, Seoul, Korea; ³Department of Radiology, Washington University, St. Louise, MO, USA

In this study, a 3-D semi-automated segmentation method of knee cartilages from MR images was proposed. The segmentation process is based on a graph-cuts algorithm and was evaluated with experiments on MR images from osteoarthritis initiative (OAI) database. It was significantly more efficient and reproducible than the manual delineation method.

                  2882.     Deterministic Automatic Segmentation in MRI, CT and CTA: A Robust Method Based on Anatomical Structures Modelling and Local Recursive Intensity Analysis

Manfredo Atzori^1,2, Gianluca Rambaldelli¹, Paolo Brambilla³, Alessandra Bertoldo²

¹Medicine and Public Health, Università di Verona, Verona, Italy; ²Information Engineering, Università di Padova, Padova, Italy; ³Pathology & Exp. Clin. Medicine, Università di Udine, Udine, Italy

At the state of the art some semiautomatic and automatic segmentation procedures have been described. Current methods don’t mind geometric and physical constitution of anatomical structures, not making a physically justified segmentation. This implies 8-9% volume errors, low methods concordance and low adaptability. We realized an automatic method for MRI, CT, CTA deterministic segmentation, based on mathematical modelling and analysis of anatomical structures physical and geometrical properties. It has been applied for several structures segmentation, as brain, grey-white matter, heart, kidneys, urinary tracts and bone. It is characterized by high precision (volume error 4.5%), non subjective parameters and high adaptability.

                  2883.     Towards Localization of Transcranial Magnetic Stimulation Inside the MRI Scanner

Aranee Techawiboonwong¹, Alvaro Pascual-Leone², Daeshik Kim¹, Itamar Ronen¹

¹Boston University School of Medicine, Boston, MA, USA; ²Beth Israel Deaconess Medical Center, Boston, MA, USA

Transcranial magnetic stimulation (TMS) has been used as a non-invasive tool in various neuroscience applications. One of the greatest challenges TMS faces is an exact coil positioning to deliver the pulse to the intended area. In this work, we propose a new method of localizing the TMS stimulation by exploiting the fact that interference of TMS field inside the MR magnet lead to intensity variation of MR images. Our phantom studies showed that origins of the TMS fields could be localized and mapping of the TMS fields can potentially lead to quantification of neurostimulations that the TMS produce.

                  2884.     Changes in in Vivo Tibiofemoral Cartilage-To-Cartilage Contact Area Under Acute Loading; Comparison of Two Sequences (3D-SPGR Vs. T2-Weighted FSE)

Choongsoo S. Shin¹, Richard B. Souza¹, Xiaojuan Li¹, Brad Wyman², Thomas M. Link¹, C Benjamin Ma³, Sharmila Majumdar¹

¹Department of Radiology and Biomedical Imaging, University of California at San Francisco, San Francisco, CA, USA; ²Pfizer Inc., New London, CT, USA; ³Department of Orthopaedic Surgery, University of California at San Francisco, San Francisco, CA, USA

The purpose of this study is 1) to compare human in vivo tibiofemoral cartilage-to-cartilage contact area using 3D-SPGR vs. T2-weighted FSE images; 2) to determine the influence of acute mechanical loading on tibiofemoral cartilage-to-cartilage contact area in the medial and lateral compartment. Cartilage contact area using both sequences showed strong positive correlation (Pearson Correlation coefficient =0.969). Acute loading significantly increases tibiofemoral cartilage contact area both at the medial and lateral compartments. Absolute changes as well as relative changes in cartilage contact under acute loading were more distinctive in the medial compartment.

                  2885.     Automated Segmentation of 3D Histological Mouse Brains Using a MRI-Based 3D Digital Atlas

Jessica Lebenberg¹, Anne-Sophie Hérard¹, Albertine Dubois², Marc Dhenain¹, Philippe Hantraye¹, Vincent Frouin³, Thierry Delzescaux¹

¹MIRCen, CEA, Fontenay-aux-Roses, France; ²NeuroSpin, CEA, Saclay, France; ³SCSR, CEA, Evry, France

We propose a method to register MRI-based 3D digital atlas on histological and autoradiographic mouse brain images to automatically segment those post mortem data. To co-register the atlas with these data, we first deformed the MRI volume to match with 3D-reconstructed post mortem volumes. We then applied the deformation parameters to warp the MRI-based 3D digital atlas. The reliability of this method was evaluated by qualitatively and quantitatively comparing the atlas-based with manual segmentations, considered as gold standard. Our results show that this approach is promising to investigate post mortem datasets in the mouse, and make group or strain comparisons.

                  2886.     Semi-Automatic Segmentation of Mouse Embryo MRIs

Leila Baghdadi¹, John G. Sled^1,2, Jurgen E. Schneider³, R Mark Henkelman^1,2, Jason P. Lerch^1,2

¹Mouse Imaging Center, Toronto, Ontario, Canada; ²University of Toronto, Toronto, Ontario, Canada; ³University of Oxford, Department of Cardiovascular Medicine, UK

A semi-automatic technique to segment individual embryos from the 32 stacked in the MRI dataset using a deformable model algorithm.

                  2887.     Automatic Identification and Segmentation of Infarct Lesions from Diffusion Weighted MR Images and ADC Maps

Suja Saraswathy¹, Saurabh Sharma², Dattesh Shanbhag¹, Uday Patil¹, Rakesh Mullick¹

¹Imaging Technologies Lab, GE Global Research, Bangalore, Karnataka, India; ²Dept of Computer Science, IIIT,Hyderabad, Hyderabad, A.P., India

Stroke is a major cause of death and disability in both the more developed and the less developed world. The core of the lesion that is dead shows up in dwi image as hyper intense region. Previous methods for infarct segmentation from DWI images had many false positives, as they did not use the complementary information from apparent diffusion coefficient (ADC) maps available with DWI images. In the present work, we have combined the contrast information provided by DWI and physiological information provided by the apparent diffusion coefficient (ADC) maps to segment the infarct core automatically.

                  2888.     A Multi-Strategy Method for MRI Segmentation

Miguel Martin-Landrove^1,2, Gabriel Padilla³, Giovanni Figueroa³, Marco Paluszny^3,4, Wuilian Torres^3,5

¹Center for Molecular and Medical Physics, Universidad Central de Venezuela, Caracas, Venezuela; ²Centro de Diagnóstico Docente, Las Mercedes, Caracas, Venezuela; ³Center of Geometry, Universidad Central de Venezuela, Caracas, Venezuela; ⁴Department of Mathematics, Universidad Nacional de Colombia, Medellín, Colombia; ⁵Fundación Instituto de Ingeniería, FII, Caracas, Venezuela

A method for T2-weighted MRI segmentation according to tissue transversal magnetization decay rates is presented. A log-convexity filter is applied first to regularize image intensity decay and control noise, followed by curve fitting with de Prony pseudo-interpolating and Montecarlo-Vandermonde robustness filters. Decay rate distributions and decay modes are obtained for tissue classification. Linear regression analysis is used for image segmentation assuming that pixel intensity decay is a linear superposition of decay modes. The proposed approach shows accuracy and computational speed compared to Inverse Laplace Transform or Vandermonde like methods. It can be extended to other images such as diffusion-weighted MRI.

                  2889.     Identification of Functional Subunits of the Human Cortex Using Resting State FMRI

Xilin Shen¹, Fuyuze S. Tokoglu¹, Jennifer K. Roth¹, Xenophon Papademetris¹, Robert Todd Constable¹

¹Diagnostic Radiology, Yale University, New Haven, CT, USA

Since the first lesion studies of Broca (1861) and Wernicke (1874) scientists

                  2890.     Improved Skull Stripping Using Graph Cuts

Suresh Anand Sadananthan¹, Weili Zheng¹, Michael WL Chee², Vitali Zagorodnov¹

¹Computer Engineering, Nanyang Technological University, Singapore, Singapore; ²Cognitive Neuroscience Laboratory, Duke-NUS Graduate Medical School, Singapore, Singapore

Many recent skull stripping approaches rely on iterative surface deformation to fit the brain boundary and tend to leave residual dura, which may cause cortical thickness overestimation. The approach proposed here is based on intensity thresholding followed by removal of narrow connections using graph theoretic image segmentation to position cuts that serve to isolate and remove dura. Relative to the Hybrid Watershed Algorithm (HWA), the novel approach achieved at least 10-30% reduction in dura mater without having to trade off for increased brain tissue erosion. However, the main value of the new approach is significant reduction in cortical thickness overestimation when combined with HWA.

                  2891.     Automatic Extraction of 3D Cortical Profiles as the Basis for Anatomically-Based Cortical Parcellation

Marcel Weiss¹, Gabriele Lohmann¹, Gerik Scheuermann², Robert Turner¹

¹Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Saxonia, Germany; ²Institute of Computer Science, University of Leipzig, Leipzig, Saxonia, Germany

We present a framework for the creation of three-dimensional cortical profiles based on cortical surface reconstruction.

                  2892.     The EMD-Test for Shape-Based Morphometry.

Nathan Faggian^1,2, India Bohanna², Leigh A. Johnston^2,3, Nellie Georgiou-Karistianis⁴, Gary Francis Egan^1,2

¹Center for Neuroscience, Melbourne University, Melbourne, Victoria, Australia; ²Neuroimaging, Howard Florey Institute, Melbourne, Victoria, Australia; ³Department of Electrical and Electronic Engineering, Melbourne University, Melbourne, Victoria, Australia; ⁴Centre for Developmental Psychiatry, Monash University, Melbourne, Victoria, Australia

Shape analyses commonly assume normality and apply an appropriate statistical test correction. However, non-parametric methods such as the KS-test are more suitable when normality is not assured. Parametric methods are inaccurate when applied to non-normally distributed data and require correction. Our aim was to use non-parametric shape analysis methods to investigate shape differences between Huntingtons Disease (HD) patients and controls. Non-parametric shape differences were examined using a novel statistical method based on Earth Movers Distance (EMD).

                  2893.     Quantitative Voxel-Based Analysis of T1-Weighted MRI Signal Intensity

David Fenton Abbott^1,2, Gaby S. Pell^1,2, Heath Pardoe^1,2, Graeme D. Jackson^1,3

¹Brain Research Institute, Florey Neuroscience Institutes (Austin), Melbourne, Victoria, Australia; ²Department of Medicine, The University of Melbourne, Melbourne, Victoria, Australia; ³Departments of Medicine and Radiology, The University of Melbourne, Melbourne, Victoria, Australia

Abnormalities in the brain generally manifest on MRI as changes in shape (morphometry) or changes in the nature of the tissue (signal intensity). Voxel Based Morphometry (VBM) is a well-known whole brain quantitative way of assessing morphometric changes. Here we demonstrate the effectiveness of a complementary method, Voxel-Based Iterative Sensitivity (VBIS) analysis, applied to directly assess signal intensity of T1-weighted MRI. In a group of patients with left hippocampal sclerosis, compared to healthy controls, VBIS-T1 was able to detect the major regions of tissue abnormality as well as more subtle pathology often not evident using conventional quantitative measures.

                  2894.     MR Brain 3D Contouring Using Atlas Matching and Snake Edge Detection Combined Approach

Robert Ambrosini¹, Walter O'Dell¹

¹University of Rochester, Rochester, NY, USA

Brain extraction is a critical pre-processing step for enabling automated lesion detection algorithms to achieve a minimal false positive rate at a low computational cost for MR datasets. We have developed a method that combines atlas-based techniques with image edge detection capabilities provided by snakes for the purpose of performing brain extraction while preserving the MR appearance of lesions. We were able to achieve a Jaccard Index value of 0.87 and a Dice Coefficient of 0.93. These preliminary results indicate our approach’s potential value as a method for extracting the MR brain prior to employing a lesion detection algorithm.

                  2895.     A Geo Cut Algorithm for Brain MRI Segmentation

Jie Zhu¹, Ashish Raj², Ramin Zabih³

¹Electrical Engineering, Cornell U, Ithaca, NY, USA; ²Radiology, Weill Medical College of Cornell University, New York, NY, USA; ³Computer Science, Cornell U, Ithaca, NY

Segmentation of MR brain images is an important step in many clinical applications, but is challenging due to the vast amount of fine structures. Conventional EMS algorithm fails in presence of noise, partial voluming or fine details and textures. Recent improvement were reported using graph cuts but standard inter-voxel edge weighting in graph cuts fails near small structures. We propose a graph-based combinatorial algorithm called geo-cuts, where image gradient magnitudes and gradient directions determine the weighting, to overcome this problem. Our results show that the overall percentage of correctly classified voxels is higher using the geo-cuts method except when noise is present. The Dice Similarity Measure indicates that both methods work well with geo-cuts generally outperforming standard graph cuts for white matter and CSF and vice versa for gray matter. Visually, geo-cuts gives better performance on both real and synthetic images with respect to fine structures of white matter and CSF.

                  2896.     Reliable Segmentation of Subcortical Gray Matter Structures Using Magnetization Transfer (MT) Maps

Nikolaus Weiskopf¹, Bogdan Draganski^1,2, Richard Frackowiak¹, John Ashburner¹, Gunther Helms³

¹Wellcome Trust Centre for Neuroimaging, University College London, London, UK; ²Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany; ³MR-Research in Neurology and Psychiatry, Goettingen University, Goettingen, Germany

Segmentation and voxel-based morphometry (VBM) of subcortical structures is partly limited by the reduced contrast of these structures in T1w images that it is based on. We have developed a novel approach based on magnetization transfer (MT) maps instead of T1w images. MT maps are not affected by T1 shortening due to iron accumulation that degrades T1 contrast. We have demonstrated, in a group of 49 subjects, that MT-based segmentation improves the delineation of subcortical structures significantly. Thus, this method promises to be a powerful novel approach to MRI based morphometric descriptions of subcortical structures.

                  2897.     A Rat Brain Template of Class Distribution Maps Based on Diffeomorphic Image Registration

lei zheng¹, Sarah Biedermann, Jürgen Hesser², Alexander Sartorius, Wolfgang Weber-Fahr

¹central institute of mental health, mannheim, mannheim, baden-württemberg, Germany; ²Medical Faculty of Mannheim, University of Heidelberg

Brain tissue segmentation is an important step to post-process MR images. From part of the data, the rat brain was extracted and segmented. The individual segmentation results were co-registered based on diffeomorphic image registration to generate a rat brain template of class distribution maps. With this template, later, the segmentation of rat brain can be achieved automatically.

                  2898.     Assessing the Impact of Image Registration on Texture Analysis of MR Images

Henry Tran^1,2, Roger Tam^1,3, Anthony Traboulsee^1,4, David Li^1,3

¹MS/MRI Research Group, Vancouver, BC, Canada; ²Faculty of Medicine, University of British Columbia (UBC), Vancouver, BC, Canada; ³Radiology, UBC; ⁴Neurology, UBC

The study looks at the impact of image registration on texture analysis of MR images. Texture analysis is a technique used to detect subtle changes in MR image to elucidate certain pathologies that are too subtle to detect visually. Using MR images of patients with definite MS, image resampling was performed using the linear, Blackman and B-spline interpolation methods. The polar Stockwell transform was then computed for the MS lesion regions of the original and resampled images. The study found that the differences in the texture analysis values after resampling was significant enough to affect the texture analysis results.

                  2899.     Integration of Model Information Into Model-Free Multivariate Analyses of Structural and Diffusion MRI Data

Stephen Smith¹, Achim Gass², Andreas U. Monsch³, Anil Rao⁴, Brandon Whitcher⁴, Paul M. Matthews⁴, Christian Beckmann^1,5

¹Oxford University FMRIB Centre, Oxford, Oxon, UK; ²Depts. Neurology and Neuroradiology, University Hospital Basel, Switzerland; ³Memory Clinic Basel, Switzerland; ⁴GlaxoSmithKline, Clinical Imaging Centre, London, UK; ⁵Clinical Neuroscience Department, Imperial College London, UK, UK

Model-based analysis methods are generally reliable in identifying expected responses, aiding interpretability of results. Conversely, model-free methods are able to find “surprising” effects in the data, or separate out structured confound processes from signals of interest. Little work has been carried out to combine the best aspects of the different approaches. We present initial results from inserting model information into a multivariate model-free approach and compare this approach to a GLM analysis as well as to PLS and CVA. We find that approaches containing both model-based and data-driven aspects are almost always more interpretable than rigidly enforcing model structure.

                  2900.     Establishing Probabilistic Chinese Human Brain Templates Using HAMMER Elastic Registration Algorithm

Zhentao Zuo¹, Xing Wang², Nan Chen², Jing Luo¹, Yan Zhuo¹, Dinggang Shen³, Kuncheng Li², Rong Xue¹

¹State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China; ²Department of Radiology, Xuan Wu Hospital, Capital Medical University, Beijing, China; ³Department of Radiology & BRIC, School of Medicine, University of North Carolina, Chapel Hill, NC, USA

We have successfully constructed Chinese human brain templates for male and female groups using the HAMMER automatic deformable registration algorithm. Sharp white matter and gray matter boundaries and brain ventricular edges of the templates were displayed compared with other normalization results. The average Chinese human brain templates had smaller brain volumes but wider brain shape than the MNI templates of the western society. In the future, we would further apply the HAMMER registration algorithm to a larger data set of Chinese people and generate the probabilistic Chinese brain templates, to promote the establishment of digitized standard brain (DSB) database for fMRI and disease-related neuroscience studies in China.

                  2901.     Fully Automated DTI Postprocessing Embedded in Scanner Control Software: Deghosting, Denoising, Smoothing, and Registration to a Standard Atlas

Kurt Hermann Bockhorst¹, Jaivijay Ramu¹, Venkata Kishore Mogatadakala¹, Cheukkai K. Hui¹, Ponnada A. Narayana¹

¹DII, University of Texas, Houston, TX, USA

Diffusion tensor imaging (DTI) produces large data sets and requires significant post-processing that includes minimization of image artifacts such as ghosting and geometric distortions. The post-processing generally requires significant user intervention that is tedious and could introduce bias and human errors. We implanted a fully automatic pipeline for processing the DTI data that is initiated from the scanner control program. The sole input by the user is the selection of the files to be processed. The automatic processing pipeline includes deghosting, extrameningial stripping, spatial normalization and calculation of DTI metrics. This pipeline allows processing multiple studies in a batch job.

                  2902.     Automated Registration of Sequential Breath-Hold DCE-MRI Images

Sivaramakrishnan Rajaraman¹, Jeffery J. Rodriguez¹, Christian Graff², Maria I. Altbach², Tomislav Dragovich³, Claude B. Sirlin⁴, Ronald L. Korn⁵, Natarajan Raghunand²

¹Electrical & Computer Engineering, The University of Arizona, Tucson, AZ, USA; ²Radiology, The University of Arizona, Tucson, AZ, USA; ³Cancer Center, The University of Arizona, Tucson, AZ, USA; ⁴Radiology, The University of California, San Diego, CA, USA; ⁵Scottsdale Medical Imaging Ltd., Scottsdale, AZ, USA

We introduce a novel technique for registration of DCE-MRI images, the sequential elastic registration (SER) scheme. The performance of SER is compared with two recently published schemes for DCE-MRI registration, progressive principal components registration (PPCR) and pharmacokinetic model-driven registration (PMDR). When tested on a novel DCE-MRI software phantom, all 3 registration schemes were found to be comparably accurate for registering relatively large regions of interest (ROIs) such as muscle, liver, and spleen. However, SER outperformed the other two schemes in registering smaller but significant ROIs such as tumor rim. Quantitative results and performance statistics from clinical DCE-MRI data are presented.

                  2903.     Automatic Scan Plane Planning Method for Brain MRI

Xiaodong Tao¹, Sandeep Narendra Gupta¹

¹Visualization and Computer Vision Lab, GE Global Research Center, Niskayuna, NY, USA

Consistent scan plane prescription for MRI is very important clinically for easy comparison of images across subjects and in serial evaluation of longitudinal exams. Typical workflow requires careful manual slice positioning and suffers from inter-operator variability. Existing automated methods use probabilistic atlases or segmentation of anatomic landmarks to align images. We present a novel scheme for registering brain images using an implicit symmetry axis determination. This algorithm is robust to asymmetry and large motion. We have incorporated this approach in a clinical MR system and demonstrated its usefulness in automatically obtaining consistent imaging planes across examinations irrespective of subject position.

                  2904.     Automatic Detection of Quiescent Cardiac Phases Using Navigator Echoes with Adjacent Complex Correlation Algorithm

Maggie M. Fung¹, Vincent B. Ho², Maureen N. Hood², Yuval Zur³, Ehud J. Schmidt⁴

¹Applied Science Lab, GE Healthcare, Waukesha, WI, USA; ²Radiology, Uniformed Services University, Bethesda, MD, USA; ³GE Healthcare, Tirat Carmel, Israel; ⁴Radiology, Brigham and Women’s Hospital, Boston, MA, USA

A novel automatic quiescent cardiac phase detection technique is presented. An adjacent complex correlation algorithm was used to analyse the cardiac navigator echoes acquired continously throughout the cardiac cycle. We have shown the feasibility of detecting the timing and duration of the quiescent phases using this technique. Respiratory motion can also be detected effectively. This technique could be applied to various cardiac pulse sequences for automatic and adaptive triggering, and therefore, increase the robustness of cardiac imaging.

                  2905.     Deformation Based Morphometry with Implicit Reference-Based Registration: Validation and Detection of Structural Changes in a Primate Model of Early-Life Stress

Xiujuan Geng¹, Thomas J. Ross¹, Svetlana Chefer¹, Hong Gu¹, Elliot Stein¹, Yihong Yang¹

¹Neuroimaging Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, USA

A framework of deformation-based morphometry (DBM) with implicit reference-based group (IRG) registration is proposed. Comparisons between the proposed DBM method and the commonly used approach were made and results demonstrated more accurate volume change detection. Validation of cross group volumetric comparison using DBM was performed by simulating known volume change and deformation fields. The DBM technique was applied to a study of monkey brain morphological change due to early life stress, and compared to manual segmentation results. DBM provided consistent but more localized structural changes.

                  2906.     Assessment of SPM5’s Brain Registration Performance Using Landmark Points

Joao Miguel Pereira¹, Guy B. Williams¹, Li Xiong^2,3, Julio Acosta-Cabronero¹, George Pengas², Peter J. Nestor²

¹Wolfson Brain Imaging Centre, University of Cambridge, Cambridge, UK; ²Clinical Neurosciences, University of Cambridge, Cambridge, UK; ³Neurology Department, Wuhan University, Wuhan, China

The performance of registration algorithms is known to be one of the limiting factors of automated morphology methods. One such technique is voxel based morphometry (VBM), which is used to detect structural changes in diseased cohorts by contrasting them with healthy subjects – this is highly dependent on the performance of the registration step. The goal of this study was to quantify the misregistration of well characterised landmark points using standard SPM5 tools in both normal and diseased cohorts. Results showed that the standard unified segmentation and more complex methods such as DARTEL yield comparable results.

                  2907.     Retrospective Evaluation of Brain PET-MR Registration

Zuyao Y. Shan¹, Sara J. Mateja², Wilburn E. Reddick³, John O. Glass³, Barry L. Shulkin⁴

¹Division of Translational Imaging Research, Department of Radiological Sciences  , St. Jude Children's Research Hospital , Memphis, TN, USA; ²Eckerd College, St. Petersburg, FL, USA; ³Division of Translational Imaging Research, Department of Radiological Sciences, St. Jude Children's Research Hospital, Memphis, TN, USA; ⁴Division of Nuclear Medicine, Department of Radiological Sciences, St. Jude Children's Research Hospital, Memphis, TN, USA

We retrospectively evaluated the accuracy of PET-MR atlas fusion of 5 well-accepted registration methods, using data acquired for purposes of clinic care. Both visual inspection and quantitative analysis showed that the affine registration based on ratio image uniformity is the most accurate for PET-MR atlas registration.

                  2908.     Scaling Methods for Registration of Pre- And Post-Androgen Ablation MR Prostate Images

Sophie Riches¹, Mike Partridge², Geoff S. Payne¹, Vonnie A. Morgan¹, Nandita M. deSouza¹

¹CRUK Clinical Magnetic Resonance Group, Institute of Cancer Research & Royal Marsden NHS Trust, Sutton, Surrey, UK; ²Department of Physics, Institute of Cancer Research & Royal Marsden NHS Trust, Sutton, Surrey, UK

Synposis: MR offers improved visualisation of the prostate gland over the standard CT imaging currently used for planning of radical radiotherapy for prostate cancer. Hormone therapy often prescribed prior to radiotherapy reduces the discrimination of tumor with functional MR techniques therefore necessitating registration of functional information acquired prior to androgen ablation to anatomical images acquired immediately prior to radiotherapy. Comparison of three scaling techniques to account for changes in prostate shape during hormone treatment found assuming bi-linear shrinkage of the prostate allowed pre-treatment tumor regions to be registered to post-treatment anatomical images.

                  2909.     Quantitative Comparison of Methods for Spatial Normalisation of CASL Perfusion MR Images

Stephen J. Wastling¹, Owen O'Daly², Fernando O. Zelaya², Matthew Howard², David C. Alsop³, Ruth L. O'Gorman^2,4

¹Medical Engineering and Physics, King's College Hospital, London, UK; ²Centre for Neuroimaging Sciences, Institute of Psychiatry, London, UK; ³Neuroradiology, Beth Israel Deaconess Medical Center, Boston, MA, USA; ⁴Neuroradiology, King's College Hospital, London, UK

This study quantitatively examined the accuracy and precision of various registration software methods, cost functions, and templates for the spatial normalisation of continuous ASL (CASL) perfusion MRI data. While the registration precision was broadly comparable across all methods, the registration accuracy varied considerably, although several methods yielded registrations accurate to 1 mm or less.

                  2910.     A MR Brain Template of Young Children

Zuyao Y. Shan¹

¹Division of Translational Imaging Research, Department of Radiological Sciences  , St. Jude Children's Research Hospital , Memphis, TN, USA

We developed a brain atlas of young children on the basis of MR images from 96 children aged from 6-8 yrs old and used it for spatial normalization of PET images. The spatial normalization results showed that a pediatric brain atlas is more appropriate for pediatric neuroimaging research than the adult brain atlas.

                  2911.     Image Registration of Whole-Body Mouse MRI

X Josette Chen¹, Satheesh Maheswaran², Daniel Rueckert², R Mark Henkelman¹

¹Mouse Imaging Centre, Hospital for Sick Children, Toronto, Ontario, Canada; ²Department of Computing, Imperial College London, London, UK

We registered together 13 whole-body MR images of perfusion-fixed mice.

                  2912.     Diffeomorphic Normalization Via Constant Acceleration Field

Yung-Chin Hsu¹, Ching-Han Hsu¹, Wen-Yih Isaac Tseng²

¹Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, Taiwan; ²Center for Optoelectronic Biomedicine and Department of Medical Imaging, National Taiwan University College of Medicine and Hospital, Taipei, Taiwan

Image registration plays an important role in neuroimaging research. Under diffeomorphic framework, it is possible to solve the large-deformation problem usually encountered in image registration. Both Beg¡¦s LDDMM and Ashburner¡¦s constant velocity filed methods are diffeomorphic. We extended Ashburner¡¦s method by using a constant acceleration filed. The result shows that LDDMM has shortest path length and lowest energy. Comparing our method and the constant velocity field method, the prior has lower energy and the later has shorter path length. The result suggests that these three methods might have their own strength and weakness in accuracy and computation cost.

                  2913.     Registration Methodology of Histology with in Vivo 3T MRI for Human Prostate

Hyunjin Park¹, Morand Piert¹, Bing Ma¹, Charles Meyer¹

¹University of Michigan, Ann Arbor, MI, USA

Registration of histology and in vivo MRI is an important problem as registered histology onto the in vivo MRI enables pixel by pixel comparison of in vivo MRI imaging features with ground truth of ex vivo histology. For human prostate, registration of histology and in vivo MRI is a difficult as the prostate undergoes a complex set of deformations. A methodology has been proposed to register various in vivo scans with histology for human prostate. Here we have refined and applied the methodology to in vivo 3T diffusion MRI for two cases.

                  2914.     3D Phase Unwrapping Based on Expansion in Chebyshev Polynomials

Jason Langley^1,2, Qun Zhao^1,2

¹Physics and Astronomy, The University of Georgia, Athens, GA, USA; ²Bioimaging Research Center, The University of Georgia, Athens, GA, USA

A three dimensional phase unwrapping algorithm is presented in this

                  2915.     Effects of Distortion and Inhomogeneity Correction on Brain Morphometry with 3T MRI

Osamu Abe¹, Hidemasa Takao¹, Hiroyuki Kabasawa², Hidenori Yamasue³, Masami Goto⁴, Wataru Gonoi¹, Harushi Mori¹, Akira Kunimatsu¹, Yoshitaka Masutani¹, Kiyoto Kasai³, Kuni Ohtomo¹

¹Department of Radiology, University of Tokyo, Tokyo, Japan; ²GE Yokogawa Medical Systems, Tokyo, Japan; ³Department of Neuropsychiatry, University of Tokyo, Tokyo, Japan; ⁴Radiological Technology, University of Tokyo Hospital, Tokyo, Japan

We investigate the effects of distortion and inhomogeneity correction on brain morphometry with 3T MRI. Significant group difference was observed in the brainstem, bilateral cerebral and cerebellar cortices between uncorrected and corrected images using SPM5 and FreeSurfer. Gradient-nonlinearity-induced spatial distortion and signal inhomogeneity correction allow accurate cross-platform or longitudinal comparisons of quantitative morphometry results.

                  2916.     New Thresholding Correction Methods on BOLD FMRI for Interpreting Brain Function

Han-Su Baek¹, Gwang-Woo Jeong^1,2, Tae-Hoon Kim¹, Hyeong-Jung Kim¹, Thirunavukkarasu Sundaram¹, Gwang-Won Kim¹, Tae-Jin Park³

¹Department of Biomedical Engineering, Chonnam National University Medical School, Gwangju, Korea; ²Department of Radiology, Chonnam National University Medical School, Gwangju, Korea; ³Department of Psychology, Chonnam National University, Gwangju, Korea

In order to reduce the type I and II errors and obtain more accurate brain activation map, fMR images were statistically analyzed with uncorrected t-test, false discovery rate(FDR) and family-wise error rate(FWE) in the general linear model (GLM) through statistic parameter mapping software(SPM). This study compared and evaluated the power of thresholding correction methods with uncorrected t-test, FDR and FWE, and further discussed about new thresholding correction method.

                  2917.     Evaluation of Methods for Removal for Background Field Inhomogenities in Susceptibility Weighted Phase Imaging

Ferdinand Schweser¹, Andreas Deistung¹, Berengar Wendel Lehr¹, Juergen R. Reichenbach¹

¹Medical Physics Group, IDIR, University Clinics Jena, Friedrich-Schiller-University, Jena, Thueringen, Germany

We quantitavely compare different methods for removing background field inhomogenities in susceptibility weighted phase imaging. We discovered that the commonly used homodyne-filter changes phase differences while other methods e.g. spherical mean value estimation keep phase differences and properly reduce background field inhomogenities.

                  2918.     Evaluating Reliability of Performance Metrics for Bias Field Correction in MR Brain Images

Vitali Zagorodnov¹, Zin Yan Chua¹, Weili Zheng¹

¹Computer Engineering, Nanyang Technological University, Singapore, Singapore

Performance evaluation of nonuniformity correction approaches is usually performed indirectly, on the basis of remaining tissue intensity variability. However, inconsistencies between indirect measures reported in recent studies suggest that indirect measure might be poor proxies for true correction performance. This was confirmed by reliability study reported here. Reliability can be improved by evaluating the same metrics over conservative brain tissue masks and by applying slight smoothing to suppress image noise. On real brain MR data, due to potential difficulty in obtaining a conservative GM mask, we recommend using coefficient of variation (CV) measured on smoothed conservative WM mask.

                  2919.     Distortion Correction for Echo Planar MR Imaging Using the Regularized Inverse Solution of the Point Spread Function (PSF) Map ©

Yu Cai¹, Qingwei Liu², Hongyu An¹, Weili Lin¹, Craig Hamilton³

¹Radiology, University of North Carolina-Chapel Hill, Chapel Hill, NC, USA; ²BME, University of North Carolina-Chapel Hill, Chapel Hill, NC, USA; ³BME, Wake Forest University, Winston Salem, NC, USA

The PSF mapping technique for distortion correction of EPI images is improved by solving for the inverse solution of the PSF map using Tikhonov regularization. the Tikhonov regularization-based method is robust for the correction of distortion caused by magnetic susceptibility. In particular, in light of the continuing increase of the magnetic field strength in both clinical and research arenas, the proposed Tikhonov method should further improve the image quality of high field MRI.

                  2920.     Fast and Automatic Quantification of Cardiac Perfusion MRI

Andreas Weng¹, Christian Oliver Ritter¹, Joachim Lotz², Meinrad Joachim Beer¹, Dietbert Hahn¹, Herbert Köstler¹

¹Institut für Röntgendiagnostik, Uniklinik Würzburg, Würzburg, Bayern, Germany; ²Institut für Radiologie, Medizinische Hochschule Hannover, Hannover, Niedersachsen, Germany

An automatic postprocessing workflow for cardiac perfusion MRI was evaluated with perfusion studies of 75 subjects. Motion correction and image segmentation was performed both completely automatically and manually. Additionally the interobserver variability was investigated by manually segmenting 10 datasets by two different observers.

                  2921.     Orientation Dependence of Grey/white Matter Contrast in Ultra High Fields

Andreas Schäfer¹, Richard Bowtell², Robert Turner¹

¹Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany; ²Sir Peter Mansfield Magnetic Resonance Centre, University of Nottingham, Nottingham, UK

Recently, it has been shown that high resolution T2*-weighted images acquired at ultra high field show much more T2* heterogeneity in white matter than at lower field, which alters with the orientation of fibre bundles with respect to the static field. Phase images show high contrast between different compartments. Since phase images reflect susceptibility variations more strongly than magnitude data, we have used phase images at 7 Tesla to address the orientation dependence of GM/WM contrast. Furthermore we compare measurements with simulations based on applying a field calculation to the HUGO body model.

                  2922.     Systematic Comparison of Quantitative T1 Mapping Methods at 7 T High Field

Thomas Trantzschel¹, Kai Zhong¹, Oliver Speck¹

¹Biomedical Magnetic Resonance, Otto-von-Guericke-University, Magdeburg, Germany

B1-inhomogenity leads to problems in quantitative T1-mapping case at high field. TESSA as a new rapid method has been presented. This study systematically studied the efficiency and accuracy of TESSA and other established methods. While most methods need an additional B1-map to determine T1 correctly, TESSA is able to estimate T1 and B1 from one measurement. The SNR and accuracy of TESSA can be increased by averaging without sacrificing scan time compared to IR. In addition The T1 fitting algorithm for TESSA is much faster and easy to implement.

                  2923.     Complex-Valued Voxel Thresholding Increases Image Contrast in SWI

Daniel B. Rowe¹, E. Mark Haacke²

¹Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI, USA; ²The MRI Institute for Biomedical Research, Detroit, MI

It is often desirable to threshold signal plus noise voxels from pure noise voxels. Generally thresholding utilizes only the magnitude of the images. More recently a method has used both the magnitude and phase. This work is an extension and uses the normality of the real and imaginary values with phase coupled means. A statistic is derived that is F-distributed in large samples. In small samples Monte-Carlo critical values can be used. We apply this method to SWI images and show increased image contrast while it is found to be more robust to phase variations from unwanted field inhomogeneity effects.

                  2924.     Connectivity in Controls and Epilepsy: Demonstration of a Metabolic Network by MRSI

Jullie W. Pan^1,2, Ruben Kuzniecky³, Susan Spencer⁴, Dennis Spencer¹, Hoby P. Hetherington^1,5

¹Neurosurgery, Yale University School of Medicine, New Haven, CT, USA; ²BME, Yale University School of Medicine, New Haven, CT, USA; ³Neurology, New York University School of Medicine, New York, NY, USA; ⁴Neurology, Yale University School of Medicine, New Haven, CT, USA; ⁵Radiology, Yale University School of Medicine, New Haven, CT, USA

While resting fMRI connectivity studies have linked the thalamus and hippocampus in humans, whether such connectivity maps are manifest metabolically is unknown. Our goal is to establish the presence of such a network through 1H spectroscopic imaging data. We use 1H MRSI data from a subcortical set of loci with a common factor analysis to assess for metabolic connectivity in controls and epilepsy patients. Not only is the subcortical network readily detected in resting connectivity studies, it is important to evaluate this system in epilepsy as it may be thought to participate in nearly all seizures and epilepsy types.

                  2925.     Cortical Surface Structure Analysis in Sharks Using Magnetic Resonance Imaging (MRI)

Kara E. Yopak¹, Greg T. Balls¹, Lawrence R. Frank¹

¹Radiology, UCSD - Center for Scientific Computation in Imaging, La Jolla, CA, USA

The shark cerebellum has morphologically diversified throughout vertebrate evolution. We have previously developed a qualitative visual grading index for cerebellar foliation (n=60). Here we provide a more robust method using MRI in conjunction with rigorous 3D shape analysis methods to quantify our previous scheme. Quantification was based upon the number of parameters necessary to accurately describe the cortical surface decomposed onto a spherical harmonic basis using the spherical harmonics decomposition (SHD). These methods, previously used to characterize global brain shape in humans, were preliminarily applied to a small number of representative shark species. More foliated shark brains required a more complex SHD to accurately fit its cortical surface.

                  2926.     Computer-Aided Detection (CAD) for Breast MRI at 3.0T: A Comparison Between Four Observers with Different Levels of Experience.

carla meeuwis¹, S M. van de Ven², G Stapper³, A M. Fernandez Gallardo³, M A. van den Bosch3, ³, W P. Mali³, W B. Veldhuis³

¹Radiology, Rijnstate Hospital, Arnhem, Netherlands; ²Radiological Sciences Laboratory Stanford, Lucas MRS Imaging Center; ³Department of Radiology, University Medical Center Utrecht

MRI of the breast is a promising diagnostic modality with a high sensitivity. The main drawback is its relatively low specificity. Computer-aided detection systems have been developed that automate processing and kinetic analysis. This study was performed to compare the accuracy of 3.0T breast MRI interpretation, between manual- and fully automated-kinetic analysis in 71 lesions for four observers with different levels of experience in reading breast MRI. Our study shows that CAD system significantly improved the specificity of interpretation compared with manual analysis of enhancement kinetics. Additionally there was no significant difference in diagnostic accuracy using CAD between the observers.

                  2927.     Prediction of Malignant Breast Lesions from MRI Features: A Comparison of Artificial Neural Network and Logistic Regression Techniques

Ke Nie¹, Christine E. McLaren², Wen-Pin Chen², Jeon-Hor Chen^1,3, Orhan Nalcioglu¹, Min-Ying Lydia Su¹

¹Tu & Yuen Center for Functional Onco-Imaging, University of California, Irvine, Irvine, CA, USA; ²Department of Epidemiology, University of California, Irvine, Irvine, CA, USA; ³Department of Radiology, China Medical University, Taichung, Taiwan

This study compared two different approaches using artificial neural network (ANN) and logistic regression analysis (LRA) for selecting diagnostic models to differentiate between malignant (N=43) and benign (N=28) lesions. For each case, 8 parameters were used to characterize morphology, 10 GCLM and 14 Laws features were used to characterize enhancement texture (homogeneity) within the lesion. The diagnostic performance of classifiers obtained by ANN or different LRA models was similar. While ANN is more robust and does not require a high level of operator judgment, LRA may be used complimentarily to understand the role of the selected predictors.

                  2928.     Comparison of Normalized DTI Analytical Methods: Detection Powers of Voxel-Based Analysis and Sub-Atlas Based Analysis

Koji Sakai^1,2, Susumu Mori², Kenichi Oishi², Andreia Faria²

¹Kyoto University, Kyoto, Japan; ²Johns Hopkins University, USA

The voxel-based group analysis (VBA) is one of the most effective examination methods of the entire white matter (WM) of brain. However, the VBA often suffers from low statistical power (high false discovery rate), which caused by embedded noise in voxels. We attempted to further extend the ABA to obtain statistically stronger detection power than the VBA. We propose a sub-atlas-based analysis (SBA), which uses 3D plane made from the fitting curves to the WM atlas. We compared detection power among the VBA and the SBA by using ICBM-152 normal brain artificially embedded abnormal values.

                  2929.     Selective Evaluation of Fast MRI Reconstruction Artifacts Using Case-PDM

Jun Miao¹, David L. Wilson^1,2

¹Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA; ²Radiology, University Hospitals of Cleveland, Cleveland, OH, USA

The perceptual difference model (Case-PDM) is being used to quantify image quality of fast, parallel MR acquisitions and reconstruction algorithms as compared to slower, full k-space, high quality reference images. To date, most perceptual difference models average image quality over a wide range of image degradation effects. Here, we develop and evaluate a modification, which allows one to selectively quantify noise, blur, and aliasing artifacts. Results from over 120 images indicate that the PDM compares favorably to human evaluation.

                  2930.     Comparison of Methods for the Measurement of Cardiac Function in Rats

Johannes Riegler^1,2, Anthony Niel Price¹, Kenneth King Cheung¹, Jon Orlando Cleary¹, Mark Francies Lythgoe¹

¹Centre for Advanced Biomedical Imaging (CABI), Department of Medicine and Institute of Child Health, University College London (UCL), London, UK; ²Centre for Mathematics and Physics in the Life Sciences and Experimental Biology (CoMPLEX), UCL, London, UK

Cardiac MRI is used for the assessment of animal models of heart failure. Manual image processing is frequently used to determine cardiac function. Since this is time consuming two different clinical cardiac analysis tools were compared against manual segmentation to establish the intra-observer variability and preclinical applicability for rats pre- and post-myocardial infarction (MI). Semi-automated methods offered faster analysis time, and showed similar intra-observer variability and acceptable limits of agreement compared to a manual method for rodent CMR. However, a different bias was found for the estimation of the ejection fraction for pre- and post-MI data.

                  2931.     Calculation of the Magnetic Susceptibility from Susceptibility Weighted Phase Images

Andreas Deistung¹, Berengar W. Lehr¹, Ferdinand Schweser¹, Jürgen R. Reichenbach¹

¹Medical Physics Group, Institute for Diagnostic and Interventional Radiology, University Clinics, Friedrich-Schiller-University, Jena, Germany

We present a modified method for quantifying the magnetic susceptibility for arbitrary shaped objects from high-resolution susceptibility weighted phase images. The inverse problem of going from the relative difference field (RDF) to the magnetic susceptibility was extended by a shutter and a possible offset of the RDF. The field inhomogeneity pattern seen in phase images was efficiently removed in the susceptibility maps.

                  2932.     Magnetic Resonance Elastography of Polymer Gel Dosimetry Phantoms

Yogesh Kannan Mariappan¹, Silvio L. Vieira², Julianna P. Fernandes², Antonio Adilton Carneiro², Mostafa Fatemi³, Richard L. Ehman¹

¹Department of Radiology, Mayo clinic, Rochester, MN, USA; ²Departamento de Fisica e Mathematica da FFCLRP, Universidade de Sao paulo, Ribeorao Preto, SP, Brazil; ³Department of Physiology and Biomedical Engineering, Mayo clinic, Rochester, MN, USA

Polymer gel dosimetry involves the estimation of radiation dose distribution based on radiation induced changes. Since these phantoms undergo polymerization of monomers, we hypothesized that it would affect the mechanical properties. We tested this hypothesis in a series of phantom experiments and investigated the stiffness of radiated phantoms as a function of absorbed radiation doses using Magnetic Resonance Elastography (MRE). The results show that the stiffness of a polymer gel dosimeter is directly correlated to the amount of the applied radiation dose and hence it would be feasible to estimate radiation dose distribution with MRE.

                  2933.     Model Regularization with Blind Deconvolution

Jacob U. Fluckiger¹, Matthias C. Schabel¹, Edward VR DiBella¹

¹University of Utah, Salt Lake City, UT, USA

We have developed an alternating minimization with model (AMM) algorithm for estimating the arterial input function directly from measured tissue activity curves. This method uses an analytic form for the AIF to regularize noise in measured DCE-MRI data. Simulations show the AMM method performs nearly as well as conventional deconvolution with a known AIF.