Tom Hilbert^1,2,3, Damien Nguyen^4,5, Jean-Philippe Thiran^2,3, Gunnar Krueger^2,3,6, Tobias Kober^1,2,3, and Oliver Bieri^4,5
1Advanced Clinical Imaging Technology (HC CMEA SUI DI BM PI), Siemens Healthcare AG, Lausanne, Switzerland, ²Department of Radiology, University Hospital (CHUV), Lausanne, Switzerland, ³LTS5, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, ⁴Radiological Physics, Department of Radiology, University of Basel Hospital, Basel, Switzerland, ⁵Department of Biomedical Engineering, University of Basel, Basel, Switzerland, ⁶Siemens Medical Solutions USA, Inc., Boston, MA, United States

Various methods have been published to quantify the longitudinal relaxation T1; amongst others, a variable-flip-angle fast low-angle shot acquisition can be used. Here, we suggest applying an 8-fold undersampling to such an acquisition, subsequently using a model-based iterative optimization to estimate T1 maps. This approach allows the acquisition of whole-brain 1.3mm isotropic T1 maps within 3:20min using 16 different flip angles. Aliasing artifacts due to the undersampling were successfully removed by the iterative reconstruction. However, the T1 maps show a slight overestimation of T1 values and require a B1-field correction as it is typical for variable-flip-angle approaches.

Tom Hilbert^1,2,3, Damien Nguyen^4,5, Jean-Philippe Thiran^2,3, Gunnar Krueger^2,3,6, Oliver Bieri^4,5, and Tobias Kober^1,2,3
1Advanced Clinical Imaging Technology (HC CMEA SUI DI BM PI), Siemens Healthcare AG, Lausanne, Switzerland, ²Department of Radiology, University Hospital (CHUV), Lausanne, Switzerland, ³LTS5, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, ⁴Radiological Physics, Department of Radiology, University of Basel Hospital, Basel, Switzerland, ⁵Department of Biomedical Engineering, University of Basel, Basel, Switzerland, ⁶Siemens Medical Solutions USA, Inc., Boston, MA, United States

Quantitative imaging promises to be a good biomarker of disease but requires long acquisition times, especially when 3D acquisition techniques are used. Here we propose to use a highly undersampled 3D phase-cycled balanced steady-state free-precession sequence in combination with the reconstruction methods MIRACLE and trueCISS, providing quantitative maps (T2,T1,M0). Additionally, synthetic contrasts can be generated using the previously calculated quantitative maps and signal models, exemplarily shown for bSSFP, T2- and T1-weighted contrast. In summary, the proposed method provides a set of quantitative maps and various conventional contrasts using a single 3:31min acquisition.

Yuchi Liu¹, Zheng Han¹, Kai Jiang², Yun Jiang¹, Yajuan Li¹, Zheng-Rong Lu¹, and Xin Yu^1,3,4,5
1Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States, ²Division of Nephrology and Hypertension, Mayo Clinic, Rochester, MN, United States, ³Radiology, Case Western Reserve University, Cleveland, OH, United States, ⁴Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, United States, ⁵Case Center for Imaging Research, Case Western Reserve University, Cleveland, OH, United States

In this study, a rapid multislice saturation-recovery Look-Locker (MSRLL) T₁ mapping method with spiral readout was developed for the application on tissues with long T₁ value, such as tumor. This method was validated in vitro and evaluated in a dynamic contrast-enhanced MRI (DCE-MRI) study on mouse tumor. The spiral MSRLL method showed a strong agreement with Cartesian method, and achieved temporal resolution of 2 min 40s with a voxel size of 0.23×0.23×1 mm³ in vivo.

Pradeep Kumar Gupta¹, Prativa Sahoo², Alok Kumar Singh³, Ravindra Kumar Garg³, Rupsa Bhattacharjee⁴, and Rakesh Kumar Gupta^1
1Radiology and Imaging, Fortis Memorial Research Institute, Gurgaon, India, ²Healthcare, Philips India ltd, Bangalore, India, ³Department of Neurology, KG Medical University, Lucknow, India,⁴Healthcare, Philips India ltd, Gurgaon, India

Gadolinium based contrast agents are necessary for MRI for disease detection and therapy. Studies reported gadolinium remains in brain for long time after injecting contrast particularly in follow up patients undergoing serial contrast applications. T1 signal intensity increases slowly due to contrast accumulation in brain. Our study quantifies T1 relaxation time as a measure for follow up contrast patients. Results show absolute T1 significantly decreases in Gray Matter regions, putamen, thalamus and globus pallidus. We conclude that absolute T1 quantification can efficiently pick up deposition of gadolinium much earlier than T1 signal intensity changes as observed in Gray matter regions.

Gabriel Ramos-Llordén¹, Arnold J. den Dekker^1,2, Marcus Björk³, Marleen Verhoye¹, and Jan Sijbers^1
1University of Antwerp, Antwerp, Belgium, ²Delft University of Technology, Delft, Netherlands, ³Uppsala University, Uppsala, Sweden

The longitudinal relaxation time T1 can be estimated from a set of spoiled gradient recalled echo (SPGR) magnetic resonance images acquired over a range of flip angles with constant repetition time (TR). While linear estimators are widely used because of their low computation time, they are less accurate than their slower nonlinear counterpart¹. In this work, we introduce a novel  NOn-linear VarIable Flip Angle data baSed T1 (NOVIFAST) estimator  that combines the best of both worlds: high accuracy and precision in a low computation time.

Mukund Balasubramanian^1,2 and Robert V. Mulkern^1,2
1Department of Radiology, Boston Children's Hospital, Boston, MA, United States, ²Harvard Medical School, Boston, MA, United States

We made slice profile measurements and acquired 2D multi-gradient-echo data on a phantom in the presence of various through-plane gradients. The sinc-term correction for R₂* mapping that is commonly used to compensate for the dephasing effects of these gradients was substantially outperformed by a correction based on the measured slice profiles. Our results highlight the importance of incorporating realistic slice profiles into the estimation of “intrinsic” R₂* values, which may contain information about tissue structure at microscopic-to-mesoscopic spatial scales.

Gregory J Wilson¹, Charles S Springer², Sarah Bastawrous^1,3, and Jeffrey H Maki^1
1University of Washington, Seattle, WA, United States, ²Oregon Health and Science University, Portland, OR, United States, ³Puget Sound VA HCS, Seattle, WA, United States

Previously reported T₂* values in oxygenated whole blood with gadolinium based contrast reagents are very small. This has important implications for optimization of contrast-enhanced MR angiography and quantification of arterial input functions. To investigate the molecular mechanism of these short T₂* values, we have performed Monte Carlo simulations of signal dephasing that predict the reported values remarkably well. Intracellular water signal experiences a frequency shift that is dependent on the orientation of the RBC in the magnetic field. The resulting frequency distribution in combination with trans-membrane water exchange results in rapid dephasing of water signal.

Sharon Portnoy¹, Mark Osmond², Meng Yuan Zhu³, Mike Seed⁴, John G. Sled^1,2,5, and Christopher K. Macgowan^1,4
1Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada, ²Department of Obstetrics and Gynaecology, University of Toronto, Toronto, ON, Canada, ³Institute of Medical Science, University of Toronto, Toronto, ON, Canada, ⁴Diagnostic Imaging, The Hospital for Sick Children, Toronto, ON, Canada, ⁵Mouse Imaging Centre, The Hospital for Sick Children, Toronto, ON, Canada

Relaxometry measurements were performed on umbilical cord blood samples (N=88) spanning a broad range of hematocrits (0.19<Hct<0.76) and oxygen saturations (4%<sO₂<100%).  Simple biophysical models were used to describe variations in T₁ and T₂ as a function of these blood properties.  The data and fitted model parameters presented here can be used for calibration of future MRI investigations of fetal and neonatal blood physiology.  

Dominik Weidlich¹, Hendrik Kooijman², Peter Börnert³, Jan S. Kirschke⁴, Ernst J. Rummeny¹, Axel Haase⁵, and Dimitrios C. Karampinos^1
1Department of Diagnostic and Interventional Radiology, Technische Universität München, Munich, Germany, ²Philips Healthcare, Hamburg, Germany, ³Philips Research Laboratory, Hamburg, Germany,⁴Section of Neuroradiology, Technische Universität München, Munich, Germany, ⁵Zentralinstitut für Medizintechnik, Technische Universität München, Garching, Germany

T2 mapping has been emerging as a tool to quantitatively assess tissue edema and inflammation. Sequences employing T2 preparation have been suggested for accurate and precise T2 quantification. The use of the modified BIR-4 pulse has been proposed to minimize the sensitivity of T2 mapping to B1 inhomogeneities. However, in the presence of large B0 offsets, part of the magnetization can experience both T1 and T2 relaxation during the BIR-4 pulse leading to T2 quantification errors. The present work proposes a novel methodology to make T2 quantification based on the modified BIR-4 robust to the presence of large B0 offsets.

Nicolas Chanet¹ and Ludovic De Rochefort^1
1IR4M (Imagerie par Résonance Magnétique Médicale et Multi-modalités), Univ. Paris-Sud, CNRS, UMR8081, Université Paris-Saclay, Orsay, France

Fast Field Cycling MRI offers the possibility to explore new contrasts generated from NMR dispersion (NMRD) profiles of tissue or contrast agents. Here, it is shown that dreMR contrast can be generated and optimized in fast low flip angle sequences extending the range of sequences that can be used with this new degree of freedom. The expression of a generalized Ernst angle maximizing signal with dreMR pulses is derived as well as the angle maximizing the dispersive contrast.

Aida Kiviniemi¹, Harri Merisaari¹, Marko Pesola¹, Timo Liimatainen², Hannu Juhani Aronen¹, and Ivan Jambor^1
1University of Turku, Turku, Finland, ²A.I. Virtanen Institute for Molecular Sciences, Kuopio, Finland

The adiabatic T_1ρ and RAFF measurements, RAFF2 and RAFF4, were performed in 28 healthy volunteers (24-69 years) and four of them had repeated MR scan within 4 weeks to evaluate short term repeatability. The relative differences on the voxel level were below 5% in gray and white matter for all of the relaxation parameters except of T_RAFF4 in gray matter which was 7.3%. No statistically significant age related changes in white and gray matter were present as evaluated by adiabatic T_1ρ, RAFF2 and RAFF4 imaging.

Ping Wang^1,2, Henry Zhu^1,2, Hakmook Kang³, Jake Block², and John C. Gore^1,2
1Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, United States, ²Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, United States, ³Department of Biostatistics, Vanderbilt University Medical Center, Nashville, TN, United States

T_1ρ imaging is sensitive to slow macromolecular interactions which may be generally characterized by a correlation time (τ_c) but also varies with the strength of the locking field used (ω₁).  At higher fields (3T and beyond) T_1ρ is also strongly influenced by chemical exchange processes and the dispersion of the relaxation rate R_1ρ (=1/T_1ρ) with locking field may be used to quantify exchange processes.  We imaged normal muscles from individuals of different ages and found that R_1ρ value is negatively correlated with age in normal muscle, and there is a small dispersion of R_1ρ that appears to increase with age.

CY Wang¹, R Zhang², L Jiang³, R Wang⁴, XD Zhang⁴, H Wang³, K Zhao⁴, LX Jin³, J Zhang^1,2, XY Wang^1,4, and J Fang^1,2
1Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China, People's Republic of, ²College of Engineering, Peking University, Beijing, China, People's Republic of, ³Philips Healthcare, Suzhou, China, People's Republic of, ⁴Department of Radiology, Peking University First Hospital, Beijing, China, People's Republic of

This study demonstrates the feasibility of dynamic renal R2, R2’ and R2* measurement with the proposed psMASE-ME method. High temporal resolution was achieved by combining psMASE sequence and moving estimation strategy. The superiorities of this method could potentially be used in the renal oxygenation evaluation.

Guan Wang^1,2, Yi Zhang², Shashank Sathyanarayana Hegde^2,3, and Paul A. Bottomley^2
1Dept. of Electrical & Computer Engineering, Johns Hopkins University, Baltimore, MD, United States, ²Russell H. Morgan Dept. of Radiology & Radiological Sciences, Johns Hopkins University, Baltimore, MD, United States, ³(currently) Philips Innovation Campus, Bangalore, India

Vessel wall MRI with intravascular (IV) detectors can produce superior local signal-to-noise ratios (SNR) and generate high-resolution T₁, T₂, and proton density (PD) maps that could be used to automatically classify atherosclerotic lesion stage. However, long acquisition times potentially limit multi-parametric mapping. Here, for the first time, spectroscopy with linear algebraic modeling (SLAM) is applied to yield accurate compartment-average T₁, T₂ and PD measures at least 10 times faster compared to a standard full k-space reconstructed MIX-TSE sequence at 3T. Simple phase and magnitude sensitivity corrections are incorporated into the SLAM reconstruction to compensate for IV detector non-uniformity. 

Weitian Chen¹, Queenie Chan², Min Deng¹, and Yixiang Wang^1
1Imaging and Interventional Radiology, the Chinese University of Hong Kong, New Territory, Hong Kong, ²Philips Healthcare, New Territory, Hong Kong

T1rho is a potential biomarker for  evaluation of liver fibrosis. However, the application of T1rho imaging for liver disease in human subjects remains challenging. We propose a pulse sequence based on single shot Turbo (Fast) Spin Echo (SSTSE or SSFSE) acquisitions to address the problems.

Eberhard Daniel Pracht¹ and Tony Stöcker^1,2
1German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany, ²University of Bonn, Department of Physics and Astronomy, Bonn, Germany

The longitudinal relaxation time in the rotating frame (T_1ρ) is a non-invasive biomarker, which is sensitive to slow macromolecular interactions. It might potentially be useful to detect pathological changes in neurodegenerative diseases such as Alzheimer’sDisease. However, long scan times and high SAR limit the application of this technique in a routine setting. Furthermore, high CSF signal modulates the image intensity at CSF/tissue boundaries leading to an overestimation of T1ρ in these regions. To overcome these issues we developed a fast and robust approach to assess T_1ρ in the human brain at high image resolution.

Akbar Alipour^1,2,3, Vijay Kumar Shamra^3,4, Zeliha Soran Erdem³, Zaliha Gamze Aykut⁵, and Hilmi Volkan Demir^2,3,4
1UMRAM-National Magnetic Resonance Research Center, Bilkent University, Ankara, Turkey, ²Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey, ³UNAM – Institute of Materials Science and Nanotechnology, Bilkent University, Ankara, Turkey, ⁴School of Mathematical and Physical Sciences, Nanyang Technological University, Singapore, Singapore, ⁵Department of Molecular Biology and Genetics, Bilkent University, Ankara, Turkey

Magnetic resonance imaging (MRI) contrast agents, employed as image contrast enhancement mechanism, are able to change either negative or positive signal intensity. T₂ contrast normally offers magnetic susceptibility artifacts and decreases the resolution. On the other hand, T₁ contrast provides high spatial resolution, but it suffers from the deficiency of high contrast-to-noise ratio, which limits their clinical applications. To overcome the aforementioned limitations, we offer cubic shape super-paramagnetic iron oxide nanoparticles (SPIONs) as dual-mode colloidal MRI contrast agents. The in vitro and in vivo T₁ and T₂ MR images promise the great potential clinical application of SPIO nanocubes as dual-mode MR contrast agent.

John Thomas Spear^1,2 and John Gore^1,2,3,4
1Physics and Astronomy, Vanderbilt University, Nashville, TN, United States, ²Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States, ³Radiology, Vanderbilt University, Nashville, TN, United States, ⁴Biomedical Engineering, Vanderbilt University, Nashville, TN, United States

R_1ρ dispersion provides insight into the rates of molecular processes that give rise to relaxation, and a technique called Exchange Rate Contrast (ERC) can differentiate proton pools based on chemical exchange rates. Double dispersion phenomena may occur when three exchanging proton pools are present, and parametric images may be calculated in which the image intensity scales with the concentration of the exchanging pools. A theoretical equation was derived for this contrast and shown to align well with Bloch-McConnell simulations. Various applications with exogenous contrast agents present a great deal of potential for utilizing this technique in practice.

Diego Hernando¹, Samir D Sharma¹, Debra E Horng², and Scott B Reeder^1,2,3,4,5
1Radiology, University of Wisconsin-Madison, Madison, WI, United States, ²Medical Physics, University of Wisconsin-Madison, Madison, WI, United States, ³Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States, ⁴Medicine, University of Wisconsin-Madison, Madison, WI, United States, ⁵Emergency Medicine, University of Wisconsin-Madison, Madison, WI, United States

In phantoms with large iron particles, as well as in patients with liver iron overload, a paradoxical relationship was observed where the linewidth measured from MRS was smaller than the linewidth obtained from multi-echo spoiled gradient echo MRI. Assuming a model of “apparent” R2 decay in the presence of iron where single-echo acquisitions are essentially diffusion-weighted by the iron-induced B0 heterogeneities, we speculate that different isochromats within the observed spectra undergo different diffusion weighting related to their location relative to nearby large iron particles. These observations may have implications for the characterization of iron deposition in tissue. 

Bo Zhao¹, Justin P. Haldar², Kawin Setsompop¹, and Lawrence L. Wald^1
1Martinos Center for Biomedical Imaging, Chalestown, MA, United States, ²Signal and Image Processing Institute, University of Southern California, Los Angeles, CA, United States

A principled framework is proposed to optimize the experiment design for magnetic resonance fingerprinting (MRF) based on the Cramer-Rao bound. Within this framework, we optimize the acquisition parameters (flip angle, TR, etc.)  to maximize the SNR efficiency of quantitative parameter estimation. Preliminary results indicate that the optimized experiments allow for substantially reducing the length of an MRF acquisition and substantially improving estimation performance for the T2 map, while maintaining similar accuracy level for the T1 map. The proposed framework should prove useful for fast quantitative MR imaging with MRF. 

Hongpyo Lee¹, Yoonho Nam², Min-Oh Kim¹, Dongyeob Han¹, Sung-Min Gho¹, and Dong-Hyun Kim^1
1School of Electrical and Electronic Engineering, Yonsei University, Soeul, Korea, Republic of, ²Department of Radiology, Seoul St. Mary Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea, Republic of

Recently, myelin water fraction was investigated using multi-echo GRE data. In case of complex model fitting for MWF, only a small fraction of the total signal is used, small artifacts caused by physiological motion can induce severe noise in MWF. To overcome this problem, radial trajectory which is known to have robustness against object motion can be used. Also, this trajectory has the additional advantage of acquiring the more center of k-space than Cartesian trajectory which is helpful for detecting accurate T2* decay curve, and it may provide higher SNR and improved quantification. In this abstract, we demonstrated that the radial acquisition can reduce artifacts and improve image quality in MWF.

Amy McDowell¹, Natalia Petrova¹, Irene Vavasour², David Thomas³, Daniele Carassiti¹, Marc Miquel⁴, Shannon Kolind², and Klaus Schmierer^1,5
1Neuroscience and Trauma, Queen Mary University of London, London, United Kingdom, ²University of British Columbia, Division of Neurology, Department of Medicine, Vancouver, BC, Canada,³Neuroimaging Analysis Centre, Department of Brain Repair and Rehabilitation, London, United Kingdom, ⁴Clinical Physics, Barts Health Trust, London, United Kingdom, ⁵Department of Neurology, Barts Health Trust, London, United Kingdom

Evidence obtained from post mortem multiple sclerosis (MS) brain suggest that ‘myelin water fraction’ (MWF) acquired using the CPMG sequence is strongly associated with myelin.  However, relaxation times differ significantly between brain and spinal cord (SC), a key area of the clinical manifestations of MS. We investigated the histological correlates of MWF in post mortem MSSC. Good separation of the short T₂ components, and correlation between MWF and myelin content detected using immunohistochemistry were observed.

Riccardo Metere¹ and Harald E. Möller^1
1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany

Quantitative MRI maps are believed to strongly correlate with myelin and and ferritin content. Recently, a model combining prior information from non-MRI quantitative techniques was proposed for the quantification of myelin and ferritin based on relaxometry information $$$R_1$$$ and $$$R_2^*$$$ in post mortem human brain samples. Here, we propose four different simple linear models for tentatively obtaining semi-quantitative information using simultaneous quantitative acquisitions under in vivo conditions. Three of the four model are relatively consistent, but do not agree with previously published measurements. A fourth model, although not validated, is compatible with previous works.  

 

Thanh D. Nguyen¹, Kofi Deh¹, Sneha Pandya¹, Yi Wang¹, and Susan A. Gauthier^1
1Weill Cornell Medical College, New York, NY, United States

The purpose of this study was to measure the inter-scanner reproducibility of fast myelin water fraction (MWF) mapping using a 4 min FAST-T2 sequence on three scanners from two vendors at 1.5T and 3T. Regional MWF measurements obtained in 7 healthy volunteers were highly reproducible with excellent inter-scanner correlation (R>0.95) and small MWF bias of less than 1%.

Thanh D. Nguyen¹, Pascal Spincemaille¹, Sneha Pandya¹, Susan A. Gauthier¹, and Yi Wang^1
1Weill Cornell Medical College, New York, NY, United States

The purpose of this study was to develop a clinically feasible method for quantifying myelin and iron distribution in white matter lesions by integrating absolute myelin water mapping using Fast Acquisition using Spiral Trajectory and T2prep (FAST-T2) sequence with Quantitative Susceptibility Mapping (QSM). Preliminary results from 8 healthy volunteers and 3 MS patients demonstrated the feasibility of the developed method.

Takuya Hinoda¹, Yasutaka Fushimi¹, Tomohisa Okada^1,2, Tsutomu Okada¹, Akira Yamamoto¹, and Togashi Kaori^1
1Radiology, Graduate school of Medicine, Kyoto University, Kyoto, Japan, ²Human Brain Research Center, Graduate school of Mediine, Kyoto University, Kyoto, Japan

Gadolinium-based contrast agents (GBCAs) have been widely used for contrast material-enhanced magnetic resonance (MR) imaging. However, gadolinium accumulation in the dentate nucleus (DN) has gained attention due to recent studies. In this study, we retrospectively evaluated the susceptibility values of DN, using quantitative susceptibility mapping. The susceptibility values of the patients with GBCA administration were significantly higher than those of normal controls.

Russell Dibb^1,2 and Chunlei Liu^3,4
1Center for In Vivo Microscopy, Duke University, Durham, NC, United States, ²Biomedical Engineering, Duke University, Durham, NC, United States, ³Brain Imaging & Analysis Center, Duke University, Durham, NC, United States, ⁴Radiology, Duke University, Durham, NC, United States

Susceptibility mapping is limited in part due to reconstruction artifacts spawning from errors in tissue frequency data. Through simulations of susceptibility tensor imaging (STI) data, we show that a lack of phase information in the image background (where there is typically no signal) engenders artifacts in reconstructed susceptibility property maps. These errors are most egregious in the boundary regions of the object and affect mean susceptibility, susceptibility anisotropy, and tissue structure orientation measurements. Greater understanding of susceptibility mapping artifacts will aid in developing the tools necessary for accurate and reliable susceptibility imaging techniques.

Carlos Milovic^1,2, Jose Miguel Pinto^1,2, Julio Acosta-Cabronero³, Petr Dusek^4,5, Vince Istvan Madai⁶, Till Huelnhagen⁷, Thoralf Niendorf⁷, Jens Wuerfel⁸, and Cristian Tejos^1,2
1Department of Electrical Engineering, Pontificia Universidad Catolica de Chile, Santiago, Chile, ²Biomedical Imaging Center, Pontificia Universidad Catolica de Chile, Santiago, Chile, ³German Center for Neurodegenerative Deceases (DZNE), Magdeburg, Germany, ⁴Institute of Neuroradiology, University Medicine Goettingen, Goettingen, Germany, ⁵Department of Neurology and Center of Clinical Neuroscience, Charles University in Prague, 1st Faculty of Medicine and General University Hospital in Prague, Praha, Czech Republic, ⁶Department of Neurology and Center for Stroke Research Berlin (CSB), Charité-Universitaetsmedizin, Berlin, Germany, ⁷Berlin Ultrahigh Field Facility (B.U.F.F.), Max-Delbrueck Center for Molecular Medicine, Berlin, Germany, ⁸Medical Image Analysis Center, Basel, Switzerland

We propose a new magnetic dipole kernel for QSM reconstructions based on the discrete cosine transform and discrete derivative operators. The method minimises aliasing artefacts, reduces noise and improves detection of small objects and tissue interfaces. This is demonstrated numerically with a synthetic phantom and qualitatively with an ultra-high resolution QSM of post-mortem brain tissue.

Patrick McDaniel¹, Berkin Bilgic², Audrey Fan³, Jeffrey Stout⁴, and Elfar Adalsteinsson^1,4
1Electrical Engineering and Computer Science, MIT, Cambridge, MA, United States, ²Athinoula A Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, ³Richard M Lucas Service Center for Imaging, Stanford University, Stanford, CA, United States, ⁴Health Sciences and Technology, Harvard/MIT, Cambridge, MA, United States

Accurate, quantitative determination of blood vessel oxygenation and caliber from GRE data would be useful for assessing local perfusion and oxygen consumption. However, partial-volume effects confound both measurements. Vessel edges are blurred and discretized, hampering assessment of vessel size.  Oxygenation can be measured from GRE phase, but partial-volume effects with other tissues often contaminate these measurements. In this work, we present a novel approach that simultaneously obtains accurate measurements of vessel caliber and oxygenation state for vessels nearly parallel to B₀. This approach is demonstrated in numerical and in vivo experiments.

Russell Dibb^1,2, Luke Xie^1,3, and Chunlei Liu^4,5
1Center for In Vivo Microscopy, Duke University, Durham, NC, United States, ²Biomedical Engineering, Duke University, Durham, NC, United States, ³Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, UT, United States, ⁴Brain Imaging & Analysis Center, Duke University, Durham, NC, United States, ⁵Radiology, Duke University, Durham, NC, United States

Conjoint relaxation and susceptibility tensor imaging (CRSTI) uses both magnitude- and phase-derived tensor data to compute susceptibility-based tractography in magnetically anisotropic tissues. CRSTI reduces image artifacts that appear in traditional susceptibility tensor imaging by taking advantage of mutual eigenvector data in relaxation and susceptibility tensors. We present an efficient conjoint tensor estimation algorithm and demonstrate improved susceptibility-based tractography in myofibers, renal tubules, and axon fiber bundles. As susceptibility imaging is sensitive to both microstructure and cellular content, CRSTI is a potential tool for studying disease in tissues throughout the body.

Pinar Senay Özbay^1,2, Cristina Rossi¹, Sonja Stieb³, Oliver Riesterer³, Andreas Boss¹, Klaas Paul Pruessmann², and Daniel Nanz^1
1Department of Radiology, University Hospital Zurich, Zurich, Switzerland, ²Institute of Biomedical Engineering, ETH Zurich, Zurich, Switzerland, ³Department of Radio-Oncology, University Hospital Zürich, Zurich, Switzerland

Glioblastoma multiforme and anaplastic astrocytoma are aggressive brain tumors which can form large heterogeneous lesions, parts of which respond with varying sensitivity to radiotherapy. The long-term goal of the current study is to characterize the oxygenation state of tumors or parts of heterogeneous large tumors by quantitative-susceptibility-mapping, under hyperoxic respiratory challenge, and yield valuable information, e.g., for an improved dose shaping, which may lead to an improved therapy outcome. The preliminary results suggest that QSM may indeed be capable of differentiating the response of well vascularized tumor-tissue volumes to respiratory-induced hypoxia from the response of likely necrotic and edematous volumes.

Hongjiang Wei¹, Luke Xie², Yuyao Zhang¹, and Chunlei Liu^1,3
1Brain Imaging and Analysis Center, Duke University, Durham, NC, United States, ²Utah Center for Advanced Imaging Research, Department of Radiology, University of Utah, Salt Lake City, UT, United States, ³Department of Radiology, School of Medicine, Duke University, Durham, NC, United States

In the pulmonary tissue, strong-susceptibility-induced field perturbation is mostly a source of artifact resulting in severe distortion. Breathing artifacts pose further challenges, especially in pediatric populations. These artifacts coupled with the intrinsic low proton SNR make it extremely difficult to perform quantitative susceptibility mapping in the lung.  State-of-the-art STAR-QSM method combined with the recently developed locally low rank parallel imaging method could further reduce motion artifacts and allow free-breathing high resolution QSM of the lung.

Pinar Senay Özbay^1,2, Andreas Deistung³, Xiang Feng^3,4, Daniel Nanz², Jürgen Reichenbach^3,5, and Ferdinand Schweser^4,6
1Institute of Biomedical Engineering, ETH Zurich, Zurich, Switzerland, ²Department of Radiology, University Hospital Zurich, Zurich, Switzerland, ³Medical Physics Group, Institute of Diagnostic and Interventional Radiology, Jena University Hospital - Friedrich Schiller University Jena, Jena, Germany, ⁴Buffalo Neuroimaging Analysis Center, Department of Neurology, Jacobs School of Medicine and Biomedical Sciences, The State University of New York at Buffalo, Buffalo, NY, United States, ⁵Friedrich Schiller University Jena, Michael Stifel Center for Data-driven and Simulation Science Jena, Jena, Germany, ⁶MRI Clinical and Translational Research Center, Jacobs School of Medicine and Biomedical Sciences, The State University of New York at Buffalo, Buffalo, NY, United States

Sophisticated Harmonic Artifact Reduction for Phase data (SHARP) is a method widely used for removal of background fields, which is one of the steps of Quantitative susceptibility mapping (QSM). In this work we analyzed SHARP using different radii between 1 and 15mm, with varying regularization parameters in mm^-1, determined optimum values and showed two cases that can arise due to wrong interpretation of the original parameters. A direct conversion of the old-parameters-scheme to the new one is presented. Best and extreme cases for parameters are demonstrated for simulated models and an in-vivo case, and the effects on images are discussed.

Berkin Bilgic¹, Jonathan R Polimeni¹, Lawrence L Wald¹, and Kawin Setsompop^1
1Martinos Center for Biomedical Imaging, Charlestown, MA, United States

An automated method for tissue phase and susceptibility estimation from multichannel data is proposed. Using ESPIRiT with virtual body coil calibration on multichannel data, phase-sensitive coil combination is achieved without an additional reference acquisition. This is shown to perform similarly to SNR-optimal Roemer combination that requires additional reference body and head coil acquisitions. Estimation of the tissue phase from the combined data is posed as a regularized inverse problem using the spherical mean value property. The extension of the technique to single-step Quantitative Susceptibility Mapping is also demonstrated on 2D, 3D and Simultaneous MultiSlice data. 

Daniel Nunes¹, Tomás Cruz¹, Sune Nørhøj Jespersen², and Noam Shemesh^1
1Champalimaud Neuroscience Program, Champalimaud Center for the Unknown, Lisbon, Portugal, ²CFIN/MindLab, Aarhus Universitet, Århus C, Denmark

Characterizing white matter (WM) microstructure in terms of axon size and volume fraction remains elusive and typically requires extremely strong gradients to resolve water diffusion in micron-sized axons. Here, we develop and apply a new approach for quantifying WM microstructure using a simple multi-gradient-echo (MGE) sequence. We use rat spinal cord as our experimental system, and show that, at long echo times, oscillations in the signal decay emerge, which can be used to robustly quantify the WM microstructure. The ensuing parameteric maps segment the SC into its underlying microstructures. The simplicity of the approach bodes well for many future applications.

Jean-Christophe Brisset¹, Pippa Storey¹, Saifeng Liu², E. Mark Haacke³, and Yulin Ge^1
1Radiology, New York University School of Medicine, New York, NY, United States, ²The MRI Institute for Biomedical Research, Waterloo, ON, Canada, ³Radiology, Wayne State University, Detroit, MI, United States

The magnetization of diamagnetic and paramagnetic materials is proportional to the strength of the applied magnetic field, with a constant of proportionality (χ) known as the magnetic susceptibility. While the magnetization of ferromagnetic and superparamagnetic materials is much higher than that of diamagnetic and paramagnetic materials, it becomes saturated in strong magnetic fields. We show that the magnetization of USPIO agents such as Ferumoxytol saturates at around 1.5T. This introduces a perceived inverse correlation between apparent susceptibility and field strength. By contrast, the magnetization of GdDTPA is proportional to field strength up to 7T, as expected for a paramagnetic material.

Emma Dixon¹, Anna Barnes², and Karin Shmueli^1
1Department of Medical Physics and Biomedical Engineering, University College London, London, United Kingdom, ²Institute of Nuclear Medicine, UCLH-NHS Foundation Trust, London, United Kingdom

Magnetic susceptibility mapping has the potential to facilitate segmentation of air and teeth in the head due to their different magnetic susceptibilities, though there is no phase signal in these regions. An iterative phase replacement method to improve the calculation of susceptibility distributions in regions with no phase signal is validated using a numerical phantom consisting of three classes: air, teeth and tissue with the phase image set to zero in the air and teeth to simulate the real case. Calculated susceptibility distributions in regions with no phase signal were not accurate and standard deviations were seen to increase in some regions, though the iterative technique improved a simple segmentation.

Young Joong Yang^1,2, Jong-Hyun Yoon¹, Jinho Park¹, Hyeon-Man Baek², and Chang-Beom Ahn^1
1Kwangwoon University, Seoul, Korea, Republic of, ²Korea Basic Science Institute, Ochang, Korea, Republic of

A tissue characterization with susceptibility e.g., susceptibility weighted imaging (SWI), quantitative susceptibility mapping (QSM), susceptibility tensor imaging (STI), gets more attention in high field MRI. Using a numerical phantom, various processing elements for QSM are analyzed. We propose a method to remove background phase using a discrete wavelet transform (DWT).  The proposed DWT method shows superb performances over exiting techniques including SHARP in the QSM experiments with volunteer subjects at 7.0T and 3.0T MRI, without distortions at the susceptibility maps.

Zahra Hosseini¹, Junmin Liu², and Maria Drangova^3
1Biomedical Engineering Graduate Program, Western University, London, ON, Canada, ²Imaging Research Laboratories, Robarts Research Institute, London, ON, Canada, ³Department of Medical Biophysics, Western University, London, ON, Canada

Local frequency shift (LFS) mapping from multi-channel acquisition is traditionally performed with channel-combined data set prior to background field removal. In this work we utilize inter-echo variance channel combination to evaluate the effect of pre-channel combination (pre-CC) phase image processing on the quality of LFS maps. We compare our results with post-channel combination (post-CC) LFS maps. The results illustrate superior performance in the contrast of LFS maps resulting from pre-CC processing compared to the post-CC LFS maps. Several examples where vessel conspicuity is lost through post–CC processing but preserved through pre-CC processing are presented.

Samir D. Sharma¹, Jens-Peter Kühn², Marie-Luise Kromrey², Scott B. Reeder^1,3, and Diego Hernando^1
1Radiology, University of Wisconsin - Madison, Madison, WI, United States, ²Experimental Radiology, Greifswald University, Greifswald, Germany, ³Medical Physics, University of Wisconsin-Madison, Madison, WI, United States

Magnetic susceptibility is a fundamental property of all tissues. The presence of biomaterials (e.g. iron, gadolinium) changes the susceptibility of the tissue in a direct and well-understood manner, allowing quantification of biomaterial concentration. Quantitative susceptibility mapping (QSM) techniques have been developed, largely to investigate iron and calcium deposits in the brain. The development and application of whole-body QSM may enable improved characterization and quantification of tissue pathophysiology based on a fundamental property of tissue. Thus, the purpose of this work was to develop and demonstrate the feasibility of whole-body QSM in healthy subjects and in patients with suspected iron overload.

Bing Wu¹, Dandan Zheng¹, and Zhenyu Zhou^1
1GE healthcare MR Research China, Beijing, China, People's Republic of

In this work, the stability of simultaneously obtained R2* and susceptibility are investigated and compared across 10 sites with identical experiment setup and post-processing hardware, as may be the case for a multi-center study.

 

 

Xiang Feng¹, Andreas Deistung¹, Marianne Cleve¹, Ferdinand Schweser^2,3, and Juergen Reichenbach^1
1Medical Physics Group, Institute of Diagnostic and Interventional Radiology, Jena University Hospital - Friedrich Schiller University Jena, Jena, Germany, ²Buffalo Neuroimaging Analysis Center, Department of Neurology, Jacobs School of Medicine and Biomedical Sciences, The State University of New York at Buffalo, Buffalo, NY, United States, ³MRI Molecular and Translational Research Center, Jacobs School of Medicine and Biomedical Sciences, The State University of New York at Buffalo, Buffalo, NY, United States

In the present work, we quatitatively assessed the reproducibility of Quantitative susceptibility mapping (QSM) and effective transverse relaxation rate (R2*) in healthy volunteers at 3T scanner during multiple scanning sessions. We also investigated the QSM normalization based on 2 reference structures, Cerebrospinal fluid (CSF) and frontal White Matter (fWM).Our results indicated that QSM using CSF as reference region reveals increased scan-rescan reliability than referencing with fWM.

Rui Pedro A. G. Teixeira^1,2, Christopher Kelly¹, Tomoki Arichi¹, Shaihan J. Malik², Serena Counsell¹, and Joseph V. Hajnal^1,2
1Perinatal Imaging and Health, King's College London, London, United Kingdom, ²Imaging Sciences and Biomedical Engineering, King's College London, London, United Kingdom

Susceptibility-weighted imaging (SWI) is sensitive to susceptibility changes associated with blood and and shows excellent performance in detecting hemorrhage. Infants born preterm and those with congenital heart disease are at risk of parenchymal, cerebellar or intraventricular/ germinal layer haemorrhage.As such, there is a clinical need for rapid, high resolution SWI to assess brain injury in these infants.In this work a dedicated neonatal SWI protocol is proposed that aims to maximize the obtainable signal while minimizing the expected WM/GM contrast to improve sensibility to local field variations.

Saifeng Liu¹, Chaoyue Wang², Xiaoqi Zhang³, Hongyan Ni³, Panli Zuo⁴, Jiani Hu⁵, and E. Mark Haacke^1,2,5
1The MRI Institute for Biomedical Research, Waterloo, ON, Canada, ²School of Biomedical Engineering, McMaster University, Hamilton, ON, Canada, ³Tianjin First Central Hospital, Tianjin, China, People's Republic of, ⁴Siemens Healthcare, MR Collaborations NE Asia, Beijing, China, People's Republic of, ⁵Department of radiology, Wayne State University, Detroit, MI, United States

Quantification of liver iron concentration (LIC) is critical for the diagnosis of patients with liver iron overload. LIC is conventionally measured using R₂/R₂* mapping methods which have limited accuracy and precision, partly due to the non-linear relation between relaxation rate and iron concentration. Quantitative susceptibility mapping (QSM) has been shown to be effective in quantifying cerebral iron deposition. For LIC quantification using QSM, the challenges include dealing with air-tissue interface in the abdomen in background field removal and solving the ill-posed inverse problem. Here we show a method which uses the apparent susceptibility of liver vessels for LIC quantification. 

Benjamin Tendler¹ and Richard Bowtell^1
1Sir Peter Mansfield Imaging Centre, University of Nottingham, Nottingham, United Kingdom

There has been longstanding interest in the anisotropic magnetic properties of muscle tissue, but to date there has been little examination of these properties using MRI. Here we describe an initial examination of muscle via field mapping measurements carried out at 7T on phantoms containing small pieces of muscle embedded in agar.  The results indicate that the susceptibility of this muscle is  diamagnetic (~-100ppb) with respect to agar and only weakly anisotropic (<5 ppb).  There was a significant uniform and orientation-independent positive frequency offset inside the muscle of 30 ppb most likely due to chemical exchange effects.

Diana Khabipova^1,2, Rita Gil², Marcel Zwiers², and José Pedro Marques^2
1CIBM-AIT, EPFL, Lausanne, Switzerland, ²Centre for Cognitive Neuroimaging, Donders Institute, Nijmegen, Netherlands

Quantitative susceptibility mapping (QSM) has been shown to provide quantitative measures of iron concentration in deep gray matter structures. In white matter, QSM is affected not only by local susceptibility but also by the local organized microstructure of axons and its myelin coating where reduced water signal exists. Recently, the anisotropic effect of myelin susceptibility was shown to be minor compared to the effect of its compartmentalization. In this work, the Lorentzian correction was, for the first time, implemented in a COSMOS like QSM reconstruction. The correction does not affect deep gray matter structure values, but creates QSM maps of isotropic susceptibility and maps of the susceptibility of cylindrically organized inclusion spaces.

Simon Daniel Robinson^1,2, Barbara Dymerska^1,2, Wolfgang Bogner^1,2, Markus Barth³, Zaric Olgica^1,2, Sigrun Goluch^1,4,5, Günther Grabner^1,2, Xeni Deligianni^6,7, Oliver Bieri^6,7, and Siegfried Trattnig^1,2
1High Field Magnetic Resonance Centre, Medical University of Vienna, Vienna, Austria, ²Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria,³Centre for Advanced Imaging, The University of Queensland, Brisbane, Australia, ⁴Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria, ⁵Division of Endocrinology and Metabolism, Department of Internal Medicine III, Medical University of Vienna, Vienna, Austria, ⁶Department of Radiology, Division of Radiological Physics, University of Basel Hospital, Basel, Switzerland, ⁷Department of Biomedical Engineering, University of Basel, Basel, Switzerland

A new method for combining phase images from multi-channel radio-frequency coils in the absence of a volume reference coil is presented and tested with calf, breast and head coils at 7 Tesla. This approach, called COMbining Phased array data using Offsets from a Short Echo-time Reference, or COMPOSER, is shown to yield phase matching between channels which is better than a rival, widely adopted reference-free method (MCPC-3D) and comparable with the reference-based Roemer method. COMPOSER can be used with all coil arrays, including the next generation of PTx coils where the transmit array may not be engineered to receive signal.

Hongjiang Wei¹, Yuyao Zhang¹, Yan Zhou², Yawen Sun², Jianrong Xu², Nian Wang¹, and Chunlei Liu^1,3
1Brain Imaging and Analysis Center, Duke University, Durham, NC, United States, ²Department of Radiology, Ren Ji Hospital, Shanghai Jiaotong University, Shanghai, China, People's Republic of,³Department of Radiology, School of Medicine, Duke University, Durham, NC, United States

Quantitative susceptibility mapping (QSM) based on GRE phase data can provide an accurate measurement of the hemorrhage volumes by removing blooming artifacts inherent in traditional T2* weighted imaging.  It is shown here that new developed STAR-QSM can effctively remove the streaking artifact and provide more reiable measure for hematoma volume and suceptibility quantification, e.g., for evaluating the patients per- and post-treatment. By taking the avantage of high quality susceptibility maps, susceptibility information can help to provide furhter classification of the hemorrhage stage.

Phaneendra Kumar Yalavarthy¹, Kasireddy Viswanatha Reddy¹, and Junki Lee^2
1Samsung R & D Institute, Bangalore, India, ²Medical System Lab, Samsung Electronics, Suwon, Korea, Republic of

The standard approaches for performing the deconvolution in post-processing of DSC-MRI data is  singular value decomposition (SVD) and Frequency-Domain Deconvolution (FDD), which are known to be relatively less accurate and requires a careful choice of threshold to obtain physiologically meaningful results. In this work, a method that utilizes QR decomposition to perform the deconvolution is proposed. The QR method is a well-known dimensionality reduction technique for solving ill-conditioned linear system of equations and known to have better numerical properties in obtaining a regularized solution. It is shown that the proposed method provides superior results compared to the standard deconvolution methods.

Anita Banerji¹, Derek Magee², Constantina Chrysochou³, Philip Kalra³, David Buckley¹, and Steven Sourbron^1
1Department of Biomedical Imaging, The University of Leeds, Leeds, United Kingdom, ²School of Computing, The University of Leeds, Leeds, United Kingdom, ³Department of Renal Medicine, Salford Royal hospital NHS foundation trust, Salford, United Kingdom

In this work we present an automated arterial input function voxel selection method for estimation of glomerular filtration rate (GFR) from renal DCE-MRI data. We assessed the agreement of GFR values estimated using the automated method with values estimated using semi-automatic expert selection and nuclear medicine techniques using 16 acquired data sets. The automated method successfully selected voxels within the aorta in all cases. The agreement between the expert and automated method was in some cases poor. However, the agreement of the automated method with the nuclear medicine results was similar to that of the expert method. 

lei hu¹, fei yun zha¹, dong xing¹, wei gong¹, jiao wang¹, yuan lin¹, hui lin², and xiao xu^2
1Renmin Hospital of Wuhan University, wuhan, China, People's Republic of, ²GE healthcare, wuhan, China, People's Republic of

To estimate the effect of diabetes on vertebral bone marrow, twelve young New Zealand White rabbits including alloxan-induced diabetic rabbits (n=6) and the controls (n=6) underwent sagittal magnetic resonance imaging (IDEAL-IQ, DCE-MRI) of lumbar at each time point. At the week of 16, all rabbits were killed. L7 sampling, HE staining and immunoperoxidase CD31 labeling were performed. According to statistical analysis, there were statistically significant differences of the vertebral DCE-MRI parameters and fat fraction (FF) between the diabetic groups and controls at each time point. The variety of vertebral microvascular permeability was strongly associated with the increasing vertebral fat deposition.

Kai Jiang¹, Hui Tang¹, Prassana K. Mishra², Slobodan I. Macura², and Lilach O. Lerman^1
1Division of Nephrology and Hypertension, Mayo Clinic, Rochester, MN, United States, ²Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN, United States

In this study, a saturation recovery fast spin echo method was developed for fast T₁ mapping of mouse kidney at a temporal resolution of ~3 min. The validity of this method was first demonstrated in vitro on a phantom with different concentrations of MnCl₂ by comparing to the conventional spin echo T₁ mapping method and a previously validated saturation recovery Look-Locker (SRLL) method and then in vivo on mouse kidneys at both pre- and post-MnCl₂ infusion by comparing to SRLL. 

Conny F. Waschkies^1,2, Fatma Kivrak Pfiffner³, Yinghua Tian¹, Maurizio Calcagni³, Pietro Giovanoli³, Markus Rudin², and Johanna Buschmann^3
1Division of Visceral and Transplantation Surgery, University Hospital Zurich, Zurich, Switzerland, ²Institute for Biomedical Engineering, ETH and University Zurich, Zurich, Switzerland, ³Plastic Surgery and Hand Surgery, University Hospital Zurich, Zurich, Switzerland

MRI has been presented as a nondestructive in vivo readout to report perfusion capacity in biomaterials planted on the CAM in the living chick embryo in ovo. Perfusion capacity was assessed through changes in T1 relaxation pre and post injection of a paramagnetic contrast agent, Gd-DOTA (Dotarem®, Guerbet S.A.). Hence local contrast agent concentration was dependent on perfusion, vascular permeability and extravascular compartment size. In the present study we explore intravascular SPIO particles of 30-40 nm size (FeraSpin series M, Viscover™, Miltenyi Biotec, Germany) that stay in the vasculature to deliver a more direct measure of vascularization.  

Nicole Wake¹, Hersh Chandarana¹, Koji Fujimoto¹, Daniel K Sodickson¹, and Sungheon Gene Kim^1
1Bernard and Irene Schwartz Center for Biomedical Imaging, Center for Advanced Imaging Innovation and Research, Department of Radiology, New York University School of Medicine, New York, NY, United States

The purpose of this study was to assess the effect of linear and non-linear signal-to-concentration conversion methods on the estimation of contrast kinetic parameters in T1-weighted dynamic contrast-enhanced MRI. A simulation study was conducted, using the Generalized Kinetic Model with a population-based arterial input function, to compare the two conversion methods in terms of the uncertainty in contrast kinetic parameter estimation, influence by the error in the pre-contrast T1 value, and the effect of flip angle, one of the important scan parameters. The results provide useful information on how to interpret the results with the linear conversion method.  

Feng Xu^1,2 and Qin Qin^1,2
1Radiology, Johns Hopkins University, Baltimore, MD, United States, ²F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States

Current MRI techniques for quantification of absolute cerebral blood volume (CBV) are all contrast-based. To reduce associated risks and cost, we proposed a non-contrast-enhanced (NCE) MRI method using a velocity-selective (VS) spin labeling approach for CBV measurement at 3T. Gray matter CBV values across 5 subjects are 2.4±0.2 mL/100g for blood flowing between the encoded cutoff velocities of 0.5cm/s and 3.1cm/s, with a GM/WM ratio of 1.9±0.3. 

Joshua S. Greer^1,2, Xinzeng Wang², Ivan Pedrosa^2,3, and Ananth J. Madhuranthakam^2,3
1Bioengineering, University of Texas at Dallas, Richardson, TX, United States, ²Radiology, UT Southwestern Medical Center, Dallas, TX, United States, ³Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, TX, United States

Cardiac triggering is regularly used in arterial spin labeled (ASL) pulmonary perfusion imaging to minimize pulsatile flow effects. A cardiac-triggered pseudo-continuous ASL (pCASL) sequence was previously implemented to improve the SNR of lung perfusion, but was found to be sensitive to variations in heart rate due to the prolonged TR, causing the data acquisition to occasionally occur during systole. The purpose of this study was to investigate methods to reduce this cardiac cycle sensitivity in pulmonary perfusion images using pCASL, including cardiac triggering the acquisition and alternative readouts such as a projection acquisition.

Audrey Fan¹, Praveen Gulaka¹, Mohammad Mehdi Khalighi², Bin Shen¹, Aileen Hoehne¹, Prachi Singh¹, Jun H Park¹, Dawn Holley¹, Frederick T Chin¹, and Greg Zaharchuk^1
1Radiology, Stanford University, Stanford, CA, United States, ²Applied Science Lab, GE Healthcare, Menlo Park, CA, United States

The ability to noninvasively image cerebral blood flow (CBF) would help with assessment of many cerebrovascular disorders including stroke. We compared simultaneous PET-MRI measurements of CBF by arterial spin labeling MRI and the [15O]-water PET reference standard in healthy volunteers. ASL and PET revealed similar spatial distributions of perfusion in the brain and reliably detected CBF augmentation due to Diamox administration. ASL MRI also demonstrated lower scan-rescan coefficient of variation across the gray matter relative to PET. Going forward, we will perform kinetic modeling of absolute CBF from [15O]-water PET and consider potentially different radiotracer arterial input functions (derived from the PET-MRI images themselves) that occur in different brain perfusion states.

Ze Wang^1
1Hangzhou Normal University, Hangzhou, China, People's Republic of

ASL perfusion fMRI has much less neurovascular effects than BOLD fMRI, but its application in time-series analysis is still depreciated due to the low signal-to-noise-ratio (SNR). Robust principal component analysis (RPCA) decomposing the original data into a smoothly varying low-rank component and a residual component with sparse signal. In this study, we used RPCA to denoise ASL MRI. Our results showed that RPCA can markedly increase the sensitivity of ASL MRI-based functional connectivity analysis. 

David L Thomas^1,2, Fabio Nery³, Isky Gordon³, Chris A Clark³, Sebastien Ourselin², Xavier Golay¹, David Atkinson⁴, and Enrico De Vita^1,5
1Department of Brain Repair and Rehabilitation, UCL Institute of Neurology, London, United Kingdom, ²Translational Imaging Group, UCL, London, United Kingdom, ³Developmental Imaging and Biophysics Section, UCL Institute of Child Health, London, United Kingdom, ⁴Centre for Medical Imaging, UCL, London, United Kingdom, ⁵Lysholm Department of Neuroradiology, National Hospital for Neurology and Neurosurgery, London, United Kingdom

Multi-shot 3D acquisition schemes offer an efficient method to obtain ASL data with good SNR and spatial resolution. However, multi-shot techniques are susceptible to motion-induced artefacts that can severely degrade image quality. In this work, we investigate the use of the autofocus algorithm to correct k-space phase inconsistencies caused by inter-shot motion, and demonstrate its effectiveness at improving image sharpness and removing artefacts in motion-corrupted 3-shot 3D GRASE data. As such, autofocus offers a retrospective approach to improve the quality of multi-shot ASL data, with the associated improvements in CBF quantification accuracy and reproducibility.

Jia Guo¹, Richard B. Buxton¹, and Eric C. Wong^1,2
1Radiology, UC San Diego, La Jolla, CA, United States, ²Psychiatry, UC San Diego, La Jolla, CA, United States

Pulsed arterial spin labeling (PASL) has the potential to achieve full labeling duty cycle with almost instant labeling. We explore here a new PASL-based fast labeling and imaging method for measuring blood flow (BF) and transit delay (TD) simultaneously, through a series of simulations. The results show that the BF and the TD can be accurately estimated. This new approach shows promise for substantially improved sensitivity and efficiency compared with conventional methods using PASL or pseudo-continuous ASL.

Bing Wu¹, Jianxun Qu¹, Ziyang Meng², and Zhenyu Zhou^1
1GE healthcare MR Research China, Beijing, China, People's Republic of, ²Department of Precision Instrument, Tsinghua University, Beijing, China, People's Republic of

CBF quantification in territorial arterial spin labeling (tASL) is difficult in practice due to unknown labeling efficiency as compared to non-selective ASL perfusion. It is also difficult to derive this labeling efficiency based on perfusion map due to the irregular cerebral region and potential multi-vessel supply. In this work, tASL MRA is used as a reference scan to derive the needed labeling efficiency for correct derivation of the CBF quantification.

Peiying Liu¹, Yue Li², Angelica Herrera³, Andreia Vasconcellos Faria¹, Can Ceritoglu⁴, Michael Miller⁴, Susumu Mori⁵, and Hanzhang Lu^1
1Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States, ²AnatomyWorks, LLC, Baltimore, MD, United States, ³Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, United States, ⁴Center for Imaging Science, Johns Hopkins University, Baltimore, MD, United States, ⁵Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States

There has been a surging interest in using arterial spin labeling (ASL) MRI to measure cerebral perfusion. Current downloadable ASL analysis toolboxes are still primitive compared those for fMRI and DTI, and involves issues of software compatibility and computational burden. Here we describe a cloud-computing-based tool for comprehensive analysis of ASL-MRI. With this tool, the user can obtain CBF maps and ROI-averaged CBF values without having to install any software on the local computer. The maintenance of software upgrades will be performed by the developer. This tool may prove valuable and timely in accommodating the recent surging interest in ASL-MRI.

Moss Y Zhao¹, Egill Rostrup^2,3, Otto Mølby Henriksen³, and Michael A Chappell^1
1Institute of Biomedical Engineering, University of Oxford, Oxford, United Kingdom, ²Functional Imaging Unit, Department of Clinical Physiology, Nuclear Medicine and PET, Copenhagen University Hospital Rigshospitalet Glostrup, Glostrup, Denmark, ³Department of Clinical Physiology, Nuclear Medicine and PET, Copenhagen University Hospital Rigshospitalet Blegdamsvej, Copenhagen, Denmark

The precise quantification of cerebral blood flow (CBF) using ASL MRI is affected by signal contaminations and partial volume (PV) effects. Among the numerous ASL techniques, QUASAR ASL exhibits unique characteristics of separating tissue and arterial blood components, allowing the bias from the arterial blood component being controlled. However, PV effects remain a critical issue that has not been fully addressed for QUASAR ASL. Here, we investigate a spatially regularised method to correct PV effects in QUASAR ASL using a three-component model. The results indicate that the proposed method preserves more spatial variations than the linear regression method.

Xiufeng Li¹, Dingxin Wang^1,2, Edward J. Auerbach¹, Steen Moeller¹, Gregory J. Metzger¹, and Kamil Ugurbil^1
1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States, ²Siemens Medical Solutions USA Inc., Minneapolis, MN, United States

        Recent studies have demonstrated the benefits of multi-band (MB) EPI for high-resolution whole brain PCASL imaging. However, the intrinsic nature of spatially interleaved simultaneous slice acquisition of MB-EPI requires a post-labeling delay larger than the longest arterial transit time in the brain, resulting in SNR efficiencies in the inferior or middle-inferior slices only comparable to or lower than those in SB-EPI PCASL imaging. To overcome the limitations of traditional MB-EPI and further improve SNR efficiencies of whole-brain high-resolution PCASL imaging, an alternative imaging acquisition strategy has been proposed and demonstrated: Time Efficient ASL Imaging with Segmented Multiband-acquisition (TEAISM).

Sudipto Dolui^1,2, David A. Wolk², and John A. Detre^1,2
1Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States, ²Department of Neurology, University of Pennsylvania, Philadelphia, PA, United States

We propose SCRUB, a data cleaning technique to improve cerebral blood flow (CBF) estimation based on arterial spin labeling (ASL) data. The method consists of (i) an outlier detection and removal stage and (ii) a subsequent voxel-wise empirical robust Bayesian estimation step. Compared to alternative options, SCRUB provided (i) better retest agreement between CBF values obtained from ASL scans of elderly Controls in ADNI database acquired 3 months apart, and (ii) better discrimination between Controls and patients with Alzheimer’s disease (AD) based on CBF values in several regions of interest which are sensitive to AD related changes.

Adam Bush¹, Yaqoing Chia², Julie Coloigner², Thomas Coates³, Natasha Lepore⁴, and John Wood^1
1Biomedical Engineering/ Cardiology, University of Southern California/ Children's Hospital Los Angeles, Los Angeles, CA, United States, ²Cardiology, Children's Hospital Los Angeles, Los Angeles, CA, United States, ³Hematology, Children's Hospital Los Angeles, Los Angeles, CA, United States, ⁴Children's Hospital Los Angeles, Los Angeles, CA, United States

In this study we propose a time varying correction technique for pseudo continuous arterial spin labeling efficiency.  We compare this correction method to other correction methods and phase contrast MRI. 

Joseph G Woods¹, Michael A Chappell², and Thomas W Okell^1
1FMRIB Centre, NDCN, University of Oxford, Oxford, United Kingdom, ²Institute of Biomedical Engineering, University of Oxford, Oxford, United Kingdom

This study aims to investigate the ideal labeling and delay parameters for single-delay, multi-delay and time-encoded pCASL and compare their theoretical performance in cerebral blood flow (CBF) and bolus arrival time (BAT) estimation under realistic noise levels over two BAT ranges: healthy (500ms-1500ms) and disease (500ms-3000ms).

Marta Vidorreta^1,2, Yulin V Chang², and John A Detre^1,2
1Neurology, University of Pennsylvania, Philadelphia, PA, United States, ²Radiology, University of Pennsylvania, Philadelphia, PA, United States

The effects of labeling location were assessed in pseudo-continuous ASL by performing kinetic modeling of data acquired at multiple post-labeling delays and by assessing the ratio of mean ASL intensity to M0.  Labeling location differences resulted in significant MT effects on raw ASL data, and produced nonlinear effects on bolus arrival time across vascular distributions.

Rashmi Reddy¹, Imam Shaik¹, Nithin N Vajuvalli¹, Dharmendra Kumar K C¹, and Sairam Geethanath^1
1Dayananda Sagar Institutions, Bangalore, India

The proposed method combines Compressed Sensing (CS) framework with view sharing to accelerate Dynamic Contrast Enhanced Magnetic Resonance Imaging (DCEMRI). A novel method to combine k-spaces of different regions (Temporal Region (TR) and Spatial Region (SR)) is carried out in this work. View sharing is adapted to combine the kspace, by mapping samples from SR region frames onto corresponding frames in TR region to improve the edge information, achieving better reconstruction with higher acceleration. It is shown that the proposed method provides better Pharmacokinetic(PK) maps at higher acceleration rates than existing methods with minimum error, as qualified by NRMSE values.

Nithin N Vajuvalli¹, Amaresh Konar¹, Shivaprasad Ashok Chikop¹, Darshan S Keelara¹, Ashwini Kumnoor¹, and Sairam Geethanath^1
1Medical Imaging Research Centre, Dayananda Sagar Institutions, Bangalore, India

DCE MRI technique is widely used in tissue characterization and tissue perfusion. Current work focuses on the design and development of a low cost in vivo DCE phantom for providing a reference standard for quantitative validation and the ability to generate Signal Intensity curves similar to arterial input functions. Poly vinyl Alcohol material was used in the phantom to mimic tissue perfusion characteristics and obtain signal intensity curves for different flow rates. We obtained similar curves compared to Arterial Input Function and were able to control flow rates through different tube and pore sizes.

Yunbin Chen ¹, Meng Liu², Dechun Zheng¹, Qiuyuan Yue¹, Xiaoxiao Zhang¹, Hao Lin¹, Weibo Chen ³, Queenie Chan⁴, Wang Ren¹, and Xiangyi Liu^1
1Fujian Provincial Cancer hospital, Fuzhou, China, People's Republic of, ²Fujian Provincial Cancer Hospital, Fuzhou, China, People's Republic of, ³Philips Healthcare, Shanghai, China, People's Republic of,⁴Philips Healthcare, Hong Kong, China, People's Republic of

We assessed correlations between DCE-MRI quantitative parameters with immunohistochemical labeling indices which reflect tumor hypoxia (HIF-1α), tumor angiogenesis (VEGF, MVD) and tumor proliferation (Ki67) in nasopharyngeal carcinoma(NPC). We found that HIF-1α positive group was significantly correlated with VEGF positive expression and MVD count respectively. K^trans and K_epwas positively associated with HIF-1α positive expression, VEGF positive expression and MVD respectively .There were significantly positive correlations between vp and the VEGF expression, MVD count respectively. However, there were no significant relationship between the Ki67 expression and any DCE-MRI quantitative parameters in our study.

SEOKHA JIN¹ and HyungJoon Cho^2
1UNIST, Ulsan, Korea, Republic of, ²Ulsan, Korea, Republic of

Dynamic susceptibility contrast MRI (DSC MRI) is widely used for cerebral blood flow (CBF) measurement for diseases, such as stroke and cancer.^1-2 Fundamental assumption of DSC-MRI based CBF measurement is that contrast agent is non-leaking with intact blood brain barrier (BBB).³ Here, we investigate the effect of BBB disruption on the CBF measurement, especially for stroke model utilizing serial dual acquisitions using DOTAREM and SPION. As SPION remains as intravascular agent, while DOTAREM becomes extravasating agent with BBB disruption, dual CBF acquisitions with both agents provide quantitative way to characterize the effect of BBB disruption on CBF measurements with DSC-MRI.

Huanling Liu^1,2, Wenbo Li^1,3, Yuguo Li^1,3, Dexiang Liu^1,2, Hanwei Chen^2,3, Peter C.M Van Zijl^1,3, and Guanshu Liu^1,3
1F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States, ²Department of Radiology, Guangzhou Panyu Central Hospital, Guangzhou, China, People's Republic of, ³The Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research, Johns Hopkins University School of Medicine, Baltimore, MD, United States

There is an urgent need for a quantitative imaging technique that can stage deep vein thrombosis (DVT) and guide thrombolysis treatment.  In the present study, we explored the ability of quantitative Magnetization transfer (qMT) technique as a non-invasive means to stage thrombi based on their macromolecular content. Thrombi in the inferior vena cava were formed using a Mouse Complete Stasis Model. A two-pool MT mathematical model was adapted to fit high-resolution MT data of excised thrombi samples. The results clearly showed that bound proton fraction (BPF) is a useful parameter for distinguishing aged blood clots from freshly formed ones. 

Kai Jiang¹, Christopher M. Ferguson¹, Behzad Ebrahimi¹, Hui Tang¹, Timothy L. Kline², Prassana K. Mishra³, Joseph P. Grande⁴, Slobodan I. Macura³, and Lilach O. Lerman^1
1Division of Nephrology and Hypertension, Mayo Clinic, Rochester, MN, United States, ²Department of Radiology, Mayo Clinic, Rochester, MN, United States, ³Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN, United States, ⁴Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, United States

In this study, magnetization transfer was used to measure renal fibrosis in a murine model of renal artery stenosis. A collagen phantom study was performed to optimize the irradiation-offset frequency of MT pulses. Renal fibrosis by in vivo MT and ex vivo histology or hydroxproline assay showed a good correlation, suggesting that MT could be used to assess renal fibrosis. In addition, MT successfully captured the physiological changes at different stages of renal fibrosis, indicating that MT was capable of monitoring the longitudinal development of functionally significant renal fibrosis.

Gopal Varma¹, Olivier M Girard², Valentin H Prevost², Guillaume Duhamel², and David C Alsop^1
1Radiology, Division of MR Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States, ²CRMBM-CEMEREM UMR 7339, CNRS-AMU, Aix Marseille Université, Marseille, France

High power, off-resonance irradiation as utilized in ihMT/MT can saturate pools of bound magnetization before they exchange in tissues. Observation of such saturation phenomena is limited by power constraints in-vivo and by attenuation of the free pool magnetization. A technique for studying and enhancing saturation effects using relatively short bursts of higher power irradiation is evaluated. The results provided 2-5 fold increases in ihMTR (depending on average power and offset frequency). Such short duration, high power pulses offer a new window to probe exchange kinetics and dipolar order effects, as well as enhancing the quality and feasibility of ihMT imaging.

Jiadi Xu^1,2, kannie W. Y. Chan^1,2, Xiang Xu², Nibhay Yadav^1,2, Guanshu Liu^1,2, and Peter C. M. van Zijl^1,2
1F. M. Kirby Center, Kennedy Kriger Institute, Baltimore, MD, United States, ²Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, United States

An on-resonance variable delay multi-pulse (onVDMP) scheme was developed for separation and quantification of magnetization transfer contrast (MTC) and total fast-exchanging protons (TFP) contributions. Phantom studies of glucose, bovine serum albumin (BSA) and hair conditioner show the capability of onVDMP to separate out exchangeable protons with different exchange rates by their unique signal buildup curves. Quantitative MTC and TFP maps acquired on healthy mouse brains showed strong gray/white matter contrast for the slowly transferring MTC protons while the TFP map was more uniform across the brain. 

Olivier M. Girard^1,2, Gopal Varma³, Samira Mchinda^1,2, Valentin Prevost^1,2, Arnaud Le Troter^1,2, Stanislas Rapacchi^1,2, Maxime Guye^1,2, Jean-Philippe Ranjeva^1,2, David C. Alsop³, and Guillaume Duhamel^1,2
1CRMBM, UMR 7339 CNRS, Aix-Marseille University, Marseille, France, ²Pôle d'Imagerie Médicale, CEMEREM, APHM, Marseille, France, ³Radiology, Division of MR Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States

Inhomogeneous Magnetization Transfer (ihMT) has shown improved specificity for myelinated tissue as compared to conventional MT. Recently, fundamental developments have led to theoretical modeling of the ihMT effect. In this study forward modeling of a steady-state ihMT gradient echo (GRE) sequence is used to guide experimental optimization for various TRs, power levels and ihMT pulse-train duration. An efficient RF-energy deposition scheme is demonstrated for relatively long TRs, leading to ihMTRs as high as 15-17% and 10-12% in WM at 1.5T and 3T, respectively. This opens new perspectives for patient studies at clinical field strength and ihMT implementation at higher field strength.

Phillip Zhe Sun¹, Yingkun Guo^1,2, Iris Yuwen Zhou¹, Suk-Tak Chan¹, Yu Wang³, Emiri Mandeville⁴, Eng H Lo⁴, and Xunming Ji^3
1Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, United States, ²Department of Radiology, Key Laboratory of Obstetric & Gynecologic and Pediatric Diseases and Birth Defects of Ministry of Education, West China Second University Hospital, Sichuan University, Chengdu, China, People's Republic of, ³Cerebrovascular Diseases Research Institute, Xuanwu Hospital of Capital Medical University, Beijing, China, People's Republic of, ⁴Neuroprotection Research Laboratory, Department of Radiology and Neurology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, United States

Amide proton transfer (APT) MRI probes amide protons from endogenous proteins/peptides, which has shown promising results in defining tissue acidosis. pH MRI complements perfusion and diffusion MRI for enhanced stratification of heterogeneous ischemic tissue injury. However, the endogenous APT effect depends not only on pH but also on tissue water content, MRI relaxation rates, and experimental conditions. There are also concomitant RF irradiation effects including direct RF saturation, magnetization transfer and nuclear overhauser effects (NOE). Our study evaluated magnetization transfer and relaxation-normalized APT (MRAPT) MRI in an animal model of acute ischemic stroke that enabled semiautomatic segmentation of graded ischemic tissue injury.

Shu Zhang¹, Stephen Seiler¹, Ananth Madhuranthakam^1,2, Jochen Keupp³, Ivan E Dimitrov^2,4, Robert E Lenkinski^1,2, and Elena Vinogradov^1,2
1Radiology, UT Southwestern Medical Center, Dallas, TX, United States, ²Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, TX, United States, ³Philips Research, Hamburg, Germany, ⁴Philips Medical Systems, Cleveland, OH, United States

In this work, the feasibility of mDixon-based CEST-MRI for breast lesions characterization at 3T was explored. The mDixon technique was used to acquire pure water CEST images without fat contamination. The B₀ maps derived from mDixon technique were used for field inhomogeneity correction. Human studies demonstrated marked differences in MTR_asym between malignant and healthy tissue in hydroxyl range (0.8-1.8 ppm) and amide range (3.1-4.1 ppm). In addition, the width of the Z-spectrum was reduced in malignant vs healthy breast tissue. The results suggest that the CEST-mDixon has the potential as a robust detection and characterization tool of breast malignancy.

Dong-Hoon Lee¹, Hye-Young Heo¹, Yi Zhang¹, Shanshan Jiang¹, and Jinyuan Zhou^1
1Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States

APT imaging can provide endogenous contrast related to the mobile amide proton concentration, amide proton exchange rate (depending on tissue pH), and other tissue and experimental parameters. Here, based on the correlations between quantified APT signals and combined parameter of water proton concentration and water T₁ (T_1w/[water proton]), we attempted to reveal the origin for APT imaging signals in multiple disease models. The results showed no significant correlations between APT signals and the T_1w/[water proton]. Our findings clearly indicated that the APT signals is primarily related to the mobile amide proton concentration and amide proton exchange rate.

Alessandro M Scotti^1,2,3, Rong-Wen Tain^1,3, Xiaohong Joe Zhou^1,2,3, and Kejia Cai^1,3
1Radiology, University of Illinois, Chicago, IL, United States, ²Bioengineering, University of Illinois, Chicago, IL, United States, ³Center for MR Research, University of Illinois, Chicago, IL, United States

Artifacts arising from tissue motion and static field inhomogeneities can heavily impact the measurement of metabolites concentration in CEST-MRI experiments in vivo. We present a correction strategy applied to CEST-MRI of creatine concentration during muscle exercise. Corrections consisted in image registration by means of a demons algorithm and signal calibration over static field offsets map at baseline, without the need of additional scanning. After correction, results are in accord with conventionally corrected data and published results. This method is shown to be effective in dynamic studies, where a high temporal resolution and coverage is required.

Neil Wilson¹, Kevin D'Aquilla¹, Catherine Debrosse¹, Hari Hariharan¹, and Ravinder Reddy^1
1Department of Radiology, Center for Magnetic Resonance and Optical Imaging (CMROI), University of Pennsylvania, Philadelphia, PA, United States

Ultrafast z-spectroscopy can be collected by saturating the nuclear spins with an RF pulse in the presence of a gradient, effectively encoding the offset frequency spatially across a voxel and allowing full z-spectra to be collected in a single shot. When asymmetry analysis is applied, frequencies on one physical side of the voxel are compared with those on the other physical side. This can be a problem if there is inhomogeneity or partial voluming. By acquiring an additional z-spectrum with the gradient polarity reversed, mixed z-spectra can be created in which the positive and negative offset frequencies come from the same side of the voxel. This method is more robust to inhomogeneity and partial voluming typically found in vivo as demonstrated here with studies on 7T in human brain.

Marilena Rega^1,2, James Fairney¹, Francisco Torrealdea^1,3, Blair Leavitt⁴, Rachel Schahill¹, Raymund Roos⁵, Bernhard Landwehrmeyer⁶, Beth Borowsky⁷, Sarah Tabrizi¹, and Xavier Golay^1
1Institute of Neurology, University College London, London, United Kingdom, ²Medical Physics, University College London Hospital, London, United Kingdom, ³Center of Medical Imaging, University College London, London, United Kingdom, ⁴Department of Medical Genetics, University of British Columbia, Vancouver, BC, Canada, ⁵Department of Neurology, University Medical Center, Leiden, United Kingdom, ⁶Department of Neurology, Ulm University, Ulm, Germany, ⁷HighQ foundation, CHDI, New York, NY, United States

Huntington’s is a hereditary disease caused by the HTT gene, resulting in the aggregation of mutant huntingtin in the cytoplasm. CEST, known to be affected by protein concentration and structure, was considered a potential biomarker for a clinical trial and comparison with MT, T1 and T2 relaxometry. Data were acquired in n=54 HD patients and n=46 healthy individuals. Comparison of CEST revealed significant differences (p<0.05) in the putamen and globus pallidus regions which did not correlate with any changes in relaxometry or MT, suggesting that CEST might be able to provide additional contrast to the already existing methods. 

Wei Hu¹, Zhuozhi Dai¹, Zhiwei Shen¹, Yuanyu Shen¹, Xiangyong Tang¹, Zhiyan Zhang¹, Gang Xiao², Phillip Zhe Sun³, and Renhua Wu^1
12nd Affilicated Hospital, Shantou University Medical College, Shantou, China, People's Republic of, ²Hanshan Normal University, Chao zhou, China, People's Republic of, ³Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, United States

The promising imaging technique of chemical exchange saturation transfer (CEST) MRI, which is sensitive to microenvironment properties including pH, metabolites, temperature, metal ions, and enzymatic activities, has been increasingly applied in vivo such as acute ischemia, infection and cancer. The aim of this work was to observe the differentiation between normal and acute kidney injury (AKI) using echo-planar imaging sequence (EPI) as well as the sensitive ratiometric methods under 7T magnetic field.

Vitaliy Khlebnikov¹, Nicolas Geades², Dennis WJ Klomp¹, Hans Hoogduin¹, Penny Gowland², and Olivier Mougin^2
1Radiology, University Medical Center Utrecht, Utrecht, Netherlands, ²Sir Peter Mansfield Imaging Centre, University of Nottingham, Nottingham, Nottinghamshire, United Kingdom, Nottingham, United Kingdom

Chemical Exchange Saturation Transfer (CEST) has gained much popularity due to its unmatched sensitivity to dilute labile protons when compared to other MRI techniques. Of particular interest are two CEST effects: Amide Proton Transfer (APT, CEST of amides) and Nuclear Overhauser Enhancement (NOE). Fast-paced developments for CEST resulted in the design of multiple CEST imaging sequences. This raises the obvious question as to which sequence to use and in what particular applications. Two pulsed volumetric CEST acquisition schemes are currently available in the literature. The first is based on the standard Magnetization Transfer imaging technique: a steady-state (SS) acquisition with alternating brief saturation and image acquisition. The second is based on the preparation of the magnetization before a long readout, where the prolonged saturation reaches a pseudo-steady state (PS) before the image acquisition. In this report, these two CEST acquisition schemes, optimized for maximum sensitivity to APT and NOE effects through Bloch-McConnell simulations, were systematically compared for the same spatial resolution, brain coverage and scan time.

Jérémy Pépin^1,2, Françoise Piguet^3,4,5,6, Hélène Puccio^3,4,5,6, and Julien Flament^1,7
1CEA/DSV/I2BM/MIRCen, Fontenay-aux-Roses, France, ²CNRS Université Paris-Saclay UMR 9199, Fontenay-aux-Roses, France, ³Department of Translational Medecine and Neurogenetics, Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France, ⁴INSERM U596, Illkirch, France, ⁵CNRS UMR7104, Illkirch, France, ⁶Université de Strasbourg, Strasbourg, France, ⁷INSERM UMS 27, Fontenay-aux-Roses, France

Friedreich Ataxia (FA) is the most common form of recessive inherited ataxia which induces severe neurological disabilities and reduced life expectancy. As glutamate has been shown to be a potential biomarker of neurodegenerative diseases, we used Chemical Exchange Saturation Transfer imaging of glutamate (gluCEST) in order to characterize our mouse model of FA and to monitor glutamate alterations in the spinal cord. GluCEST images revealed decrease of glutamate level in FA mouse model compared to control littermates, especially in the lumbar part. These results demonstrate the potential of gluCEST in providing innovative and relevant biomarkers of FA.

Iris Yuwen Zhou¹, Taylor Fuss^1,2, Gang Xiao³, Takahiro Igarashi¹, Lin Li¹, Leo L. Cheng^1,2, and Phillip Zhe Sun^1
1Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, United States, ²Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States, ³Department of Mathematics and Statistics, Hanshan Normal University, Chaozhou, China, People's Republic of

Z-spectrum is conventionally acquired through multiple experiments with selective saturation at different frequency offsets of interest, leading to extreme long acquisition time. Here, we employ gradient-encoding to substantially accelerate the acquisition of Z-spectrum. This speedup in combination with higher spectral resolution provided by high resolution magic angle spinning (HRMAS) allows rapid quantification of chemical exchange rates of CEST agents, monitoring dynamic processes and fast tissue characterization. The approach was validated in phantom and used for characterization of brain tissues after ischemic stroke. 

Jérémy Pépin^1,2, Laetitia Francelle^1,2, Maria-Angeles Carillo-de Sauvage^1,2, Huu Phuc Nguyen^3,4, Nicole El Massioui^5,6, Valérie Doyère^5,6, Emmanuel Brouillet^1,2, and Julien Flament^1,7
1CEA/DSV/I2BM/MIRCen, Fontenay-aux-Roses, France, ²CNRS Université Paris-Saclay UMR 9199, Fontenay-aux-Roses, France, ³Institute of Medical Genetics and Applied Genomics, University of Tuebingen, Tuebingen, Germany, ⁴Centre for Rare Diseases, University of Tuebingen, Tuebingen, Germany, ⁵Paris-Saclay Institute of Neuroscience, Université Paris-Sud, UMR 9197, Orsay, France, ⁶Centre National de la Recherche Scientifique, Orsay, France, ⁷INSERM UMS 27, Fontenay-aux-Roses, France

Huntington’s disease (HD) is an inherited neurodegenerative disease characterized by motor, cognitive and psychiatric symptoms. As glutamate has been shown to be a potential biomarker of neurodegenerative diseases, we used Chemical Exchange Saturation Transfer imaging of glutamate (gluCEST) to map cerebral glutamate distribution in mouse and rat models of HD. A decrease of [Glu] was measured in the striatum by MRS and gluCEST. In addition, good spatial resolution of gluCEST over MRS allowed identification of other afflicted brain regions such as corpus callosum. These results demonstrate the potential of gluCEST in providing relevant biomarkers of HD in the whole brain.

Huajun She¹, Bian Li¹, Robert Lenkinski¹, and Elena Vinogradov^1
1Radiology, Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, TX, United States

This work investigates accelerating CEST imaging. The original blind compressive sensing method assumes that a few functions are enough to represent the dynamic behavior, and the coefficient matrix should be sparse. In CEST imaging, z-spectrum shows group sparsity in the same compartment. So not only the coefficients matrix is sparse but also the transformation of the coefficients matrix is sparse, such as total variation and wavelets. The proposed method addresses this prior information and further improves the original BCS method, demonstrating a better estimation of the CEST effect at high reduction factors for both Cartesian and radial sampling patterns.

Giuseppe Ferrauto¹, Michel Sarraf², Enza Di Gregorio¹, Vincent Auboiroux³, Ulysse Gimenez², François Berger², Silvio Aime¹, and Hana Lahrech^2
1Dept of Molecular Biotechnologies & Health Sciences, University of TORINO (IT), Torino, Italy, ²CLINATEC-CEA-INSERM UA01 – CHU –UJF Grenoble (FR), Grenoble, France, ³CLINATEC-CEA Grenoble (FR), Grenoble, France

  MRI maps of extracellular/extravascular pH distribution in glioblastoma mouse model (U87 cells) have been obtained by administrating YbHPDO3A CEST probe. This molecule has potential in a clinical setting as it displays analogue properties (stability and in vivo pharmacokinetic) of its analogue clinically approved Gd-HPDO3A (ProHance). Furthermore, glioblastoma pH maps have been correlated with histology (H/E, Hif-1a and Ki-67 staining). The assessment of glioblastoma pHe could be used to monitor tumor development and to target acidic tumor regions using innovative responsive pH therapies.

Vladimir Mlynarik^1,2, Stefan Zbyn¹, Markus Schreiner³, Vladimir Juras¹, Pavol Szomolanyi¹, Didier Laurent⁴, and Siegfried Trattnig^1,2
1Department of Biomedical Imaging and Image-Guided Therapy, High Field MR Center, Medical University of Vienna, Vienna, Austria, ²CD Laboratory for Clinical Molecular MR Imaging, Vienna, Austria,³Department of Orthopedic Surgery, Medical University of Vienna, Vienna, Austria, ⁴Novartis Institutes for Biomedical Research, Basel, Switzerland

There are several methodological and data processing issues in gagCEST, which complicate the translation of this method into clinical practice. For assessing performance of the gagCEST protocol optimized in our laboratory, corrected signal intensities from sodium images were used as a reference. The results demonstrate a good correlation between both methods, although the small magnitude of the gagCEST effect and the low resolution in sodium images require carefully optimized methodology and long measurement times. It can be concluded that the gagCEST method can be useful in evaluating early degeneration of articular cartilage at 7 Tesla.

Jamal J. Derakhshan¹, Elizabeth S. McDonald², Evan S. Siegelman³, Mitchell D. Schnall³, and Felix W. Wehrli^4
1Radiology, Hospital of the University of Pennsylvania, Philadelphia, PA, United States, ²Radiology, Breast Imaging Division, Hospital of the University of Pennsylvania, Philadelphia, PA, United States,³Radiology, Abdominal Imaging Division, Hospital of the University of Pennsylvania, Philadelphia, PA, United States, ⁴Radiology, University of Pennsylvania, Philadelphia, PA, United States

A common subtraction band artifact in breast MRI was not understood, causing reduced confidence in clinical interpretation.  The source of the artifact is shown to be a subtle chemical shift effect between fat and water in the presence of contrast enhancement. The phenomenon is now generalized and characterized at all off-resonance angles. Strong echo-time and fat signal dependence may lead to enhancement errors as a function of scanner hardware, field strength and fat suppression limitations. A time and SNR-equivalent in-phase VIBE sequence eliminates the artifact; gradient-echo based contrast enhanced imaging can be performed in-phase to eliminate these important potential pitfalls.

Yi Wang¹, Yang Fan², Bing Wu², and Jia-Hong Gao^1
1School of Physics, Peking University, Beijing, China, People's Republic of, ²MR Research Group, GE Healthcare China, Beijing, China, People's Republic of

In CEST imaging, when saturation time is not sufficient long (empirically smaller than 0.8s), rotation effect would appear and contaminate with saturation effect, making the signal unavailable for further analysis. Considering the inhomogeneity of $$$B_{0}$$$ and $$$B_{1}$$$ in reality, we propose a novel Fixed Angle Single Rotation CEST(FASR-CEST) sequence to overcome the restriction, successfully reducing the saturation time to about 0.5s while keeping identical effect as CEST sequence with long saturation time, with the help of analytical calibration method in another abstract. Effect of the sequence is verified with vitro and in vivo data. 

Guillaume Duhamel¹, Valentin H Prevost¹, Gopal Varma², David C Alsop², and Olivier M Girard^1
1CRMBM / CNRS 7339, Aix Marseille University, Marseille, France, ²Radiology, Division of MR Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States

The inclusion of a dipolar reservoir in the existing two pool model for MT allowed interpreting the inhomogeneous MT (ihMT) signal as a dipolar order effect -characterized by a relaxation time T_1D - within motion restricted molecules.  In this study, we demonstrate that an ihMT signal can actually be evidenced in any component with non-trivial T_1D value. Adjustment of the dual frequency irradiation efficiency by increase of Δt, the repetition rate of consecutive saturation pulses, filters the signal of shorter T_1D components. This provides a means to realize T_1D-weighted imaging, a new source of MR contrast between tissues.

Ping-Huei Tsai^1,2,3, Hua-Shan Liu^4,5, Fei-Ting Hsu⁶, Yu-Chieh Kao³, Chia-Feng Lu³, Li-Chun Hsieh², Pen-Yuan Liao², Hsiao-Wen Chung⁷, and Cheng-Yu Chen^1,2,3
1Department of Radiology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan, ²Department of Medical Imaging, Taipei Medical University Hospital, Taipei Medical University, Taipei, Taiwan, ³Translational Imaging Research Center, Taipei Medical University, Taipei, Taiwan, ⁴Graduate Institute of Clinical Medicine, Taipei Medical University, Taipei, Taiwan,⁵Department of Medical Imaging, Taipei Medical University Hospital, Taipei, Taiwan, ⁶Taipei Medical University Hospital, Taipei Medical University, Taipei, Taiwan, ⁷Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan

GlucoCEST have been proposed to assess the discrepant concentrations of glucose in vitro. However, it is still a challenge to obtain accurate signals from glucose in vivo.  Our preliminary finding demonstrated that the proposed analytical scheme provides an alternative to extract glucose profile and could be more robust to the field inhomogeneity, which may be helpful in further implementation in disease models.

Jianpan Huang¹, Miao Zhang¹, Shuhui Cai¹, Congbo Cai², Lin Chen¹, and Ting Zhang^1
1Department of Electronic Science, Xiamen University, Xiamen, China, People's Republic of, ²Department of Communication Engineering, Xiamen University, Xiamen, China, People's Republic of

Chemical exchange saturation transfer (CEST) is widely exploited in magnetic resonance imaging (MRI) because of its special quantitative contrast mechanisms. To overcome the long acquisition time required by fast spin-echo multi-slice imaging and alleviate the sensitivity to field inhomogeneity and chemical shift effects appeared in echo planar imaging, we proposed a CEST imaging scheme based on spatiotemporally encoded magnetic resonance imaging (SPEN MRI). Experimental results validated the feasibility and capability of the new scheme.

Jingwei Sheng¹, Yuhui Chai¹, Bing Wu², Yang Fan², and Jia-Hong Gao^1
1Center for MRI Research, Peking University, Beijing, China, People's Republic of, ²GE Healthcare MR Research China, Beijing, China, People's Republic of

Traditional rotary saturation based methods requires triggered phases to create a robust signal change, which may not be satisfied in practical application. In this work, based on the analysis of magnetization in the double rotating frame, we proposed detecting the signal fluctuations of proposed SLOE method by manipulating TRs, which needs no triggering. Further, a spectral statistical test in the frequency domain was proposed and verified, which featured an enhanced detection sensitivity than that of deviation test. 

Samir D. Sharma¹, Timothy J. Colgan¹, Camilo A. Campo¹, Tilman Schubert¹, Utaroh Motosugi², Diego Hernando¹, and Scott B. Reeder^1,3
1Radiology, University of Wisconsin - Madison, Madison, WI, United States, ²Radiology, University of Yamanashi, Yamanashi, Japan, ³Medical Physics, University of Wisconsin-Madison, Madison, WI, United States

Ferumoxytol is an ultrasmall superparamagnetic iron oxide (USPIO) agent that is taken up by the reticuloendothelial system where it accumulates in organs such as the liver, spleen, and bone marrow. Given the superparamagnetic properties of ferumoxytol, it may be possible for quantitative susceptibility mapping (QSM) techniques to detect and quantify the concentration of ferumoxytol in these organs. Recent technical developments have demonstrated the feasibility of a QSM technique for magnetic susceptibility mapping of the abdomen. Thus, the purpose of this work was to test the feasibility of QSM to assess the longitudinal changes of ferumoxytol in the liver and spleen.

Shuohui Yang¹, Jiang Lin¹, Fang Lu², Yuanyuan Dai¹, Zhihong Han³, and Caixia Fu^4
1Radiology, Zhongshan Hospital, Shanghai Medical College, Fudan University, Shanghai, China, People's Republic of, ²Radiology, Shuguang Hosipital, Shanghai University of Traditional Chinese Medicine, Shanghai, China, People's Republic of, ³Pathology, Shuguang Hosipital, Shanghai University of Traditional Chinese Medicine, Shanghai, China, People's Republic of, ⁴Siemens Shenzhen Magnetic Resonance Ltd., Shenzhen, China, People's Republic of

Hepatocellular carcinoma (HCC) is a hyper-vascular tumor and knowledge of the intratumoral vascularity is essential. Susceptibility weighted imaging (SWI) uses magnitude and filtered-phase information to provide high sensitivity to susceptibility changes caused by hemorrhage, calcium, iron, and small veins. It has been used to visualize normal or pathologic vascular structures that are not visible on conventional MRI. Ultrasmall superparamagnetic iron oxide (USPIO) is an intravascular blood pool contrast medium. After intravenous administration, it can cause a greater effect on local magnetic field inhomogeneities and results in higher susceptibility differences between all intratumoral vessels and the tumor on SWI. This study showed that USPIO-enhanced SWI could further enhance the demonstration of tumor vascularity inside HCC when compared to unenhanced SWI in an orthotopic xenograft nude mice HCC model.  

Benjamin Tendler¹ and Richard Bowtell^1
1Sir Peter Mansfield Imaging Centre, University of Nottingham, Nottingham, United Kingdom

Frequency difference mapping (FDM) is a recently developed phase-based technique that takes advantage of the non-linear temporal evolution of the phase in GE sequences to produce images that are sensitive to white matter microstructure. Images can be produced simply from raw phase data, with minimal post-processing. In this study 10 subjects underwent six repeats of a single-slice, sagittal multi-echo GE scan on the mid-line.  Frequency difference maps reproducibly depicted white matter tracts oriented perpendicular to the applied field. Fitting the FD and magnitude data to a three-pool model provided insight into the variation of microstructure along the corpus callosum.  

Hongda Shao¹, Soorena Azam ZAnganeh¹, Rong Luo¹, Jun Chen¹, Graeme Bydder¹, and Jiang Du^1
1Radiology, University of California, San Diego, San Diego, CA, United States

Directly assessing the integrity of myelin in white matter is important for diagnosis and assessment of prognosis in multiple sclerosis (MS). However, the protons in myelin have extremely short T2s and cannot be directly imaged with conventional clinical MRI sequences. Adiabatic inversion recovery prepared ultrashort echo time (IR-UTE) sequences can detect signal from myelin protons and efficiently suppress the signal from water. In this study we aimed to further validate the IR-UTE technique in sheep brain using a D2O exchange model.

Hongfu Sun¹, M. Ethan MacDonald¹, and G. Bruce Pike^1
1University of Calgary, Calgary, AB, Canada

A method to remove phase offsets in bipolar gradient-echo readouts is proposed. Their effects on Quantitative Susceptibility Mapping (QSM) reconstruction are demonstrated by comparing QSM before and after phase offsets removal. 

Thomas Christen¹, Samantha Holdsworth¹, Samuel Cheshier², Michael Moseley¹, Greg Zaharchuk¹, and Kristen Yeom^1
1Radiology, Stanford University, Palo Alto, CA, United States, ²Neurosurgery, Stanford University, Stanford, CA, United States

In this study, we probed the potential of ultrasmall superparamagnetic iron oxide particles (USPIOs) to provide high-resolution angiographic images of the human brain using T2* and T1 contrasts. 10 paediatric patients suspected of arteriovenous malformations (AVM) were scanned pre and post intravenous USPIOs injection as part of their clinical exam. To test the influence of USPIOs concentration on both T2* and T1 images, a healthy volunteer was scanned before and after injections of 7 incremental doses of the contrast agent. The results suggest that both approaches can provide exquisite details of the neurovascular anatomy while offering complementary information.

Stefano Mandija¹, Alessandro Sbrizzi¹, Astrid L.H.M.W. van Lier¹, Peter R. Luijten¹, and Cornelis A.T. van den Berg^1
1Center For Image Sciences, UMC Utrecht, Utrecht, Netherlands

EPT conductivity reconstruction is affected by difficulties to reliably calculate spatial derivatives on voxelized MRI data. Here, we explore the impact of several numerical approximations. In particular: the different size of finite-difference kernels and the k-space truncation (always present in MR images). We also explore a Fourier-domain alternative, which does not require finite-difference approximation kernels.

Yicun Wang¹, Gregor Adriany², Jiaen Liu¹, Xiaotong Zhang¹, Pierre-Francois Van de Moortele², and Bin He^1,3
1Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, United States, ²Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States,³Institute for Engineering in Medicine, University of Minnesota, Minneapolis, MN, United States

Electrical Properties Tomography (EPT) is a promising technique to provide high specificity in breast cancer diagnosis. Previous studies have demonstrated that multi-transmit coils array enables reconstruction of the electrical properties free of transmit phase and local homogeneity assumptions. In this study, the strengths and drawbacks of a microstrip array and a loop array for EPT reconstruction in the breast at 3T were investigated based on numerical simulations. It has been discovered that with the same driving power, a loop array provides higher signal to noise ratio on the reconstructed image while a microstrip array performs better at delineating tissue boundaries.

Necip Gurler¹ and Yusuf Ziya Ider^1
1Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey

In this study, a new formulation for phase based electrical properties tomography (EPT) has been proposed to eliminate the boundary artifact issue and to provide robustness against noise. The feasibility of the proposed method, which is called "generalized phase based EPT", has been demonstrated using simulation, experimental phantom, and in vivo experiments. 

Ulrich Katscher¹, Jürgen Rahmer¹, Christian Stehning¹, Peter Vernickel¹, and Bernhard Gleich^1
1Philips Research Europe, Hamburg, Germany

MRI-based “Electric Properties Tomography” (MRI-EPT) determines electric conductivity measuring and post-processing the spatial distribution of the TX RF field. Obtained conductivity corresponds to Larmor frequency, reflecting biochemical content of tissue, but not its specific cellular structure. Cellular tissue structure is reflected by conductivity at low frequency (LF, 100-500 kHz), as used for “Magnetic Particle Imaging” (MPI). Similar to MRI, MPI is able to determine the spatial distribution of applied LF field, and thus, a reconstruction of LF conductivity should be possible (“MPI-EPT”) in analogy to MRI-EPT. This study investigated the principle feasibility of MPI-EPT and compared results with MRI-EPT.

Jose E.C. Serralles¹, Athanasios Polimeridis², Manushka V. Vaidya^3,4, Gillian Haemer^3,4, Jacob K. White¹, Daniel K. Sodickson^3,4, Luca Daniel¹, and Riccardo Lattanzi^3,4
1Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA, United States, ²Center for Computational and Data-Intensive Science and Engineering, Skolkovo Institute of Science and Technology, Moscow, Russian Federation, ³Center for Advanced Imaging Innovation and Research (CAI2R) and Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY, United States, ⁴The Sackler Institute of Graduate Biomedical Science, New York University School of Medicine, New York, NY, United States

We introduce Global Maxwell Tomography (GMT), a novel volume integral equation-based technique for the extraction of electric properties from MR data. GMT is framed as an unconstrained optimization problem in which the error between measured and simulated B1+ magnitude maps is minimized. Due to its global nature, GMT is not subjected to edge artifacts. By using exclusively B1+ magnitude, GMT does not rely on symmetry assumptions to estimate B1+ phase. In one numerical example, three tumors were inserted into a head model, and starting from a tumorless initial guess, GMT accurately inferred the electrical properties and locations of these tumors.

Necip Gurler¹, Omer Faruk Oran¹, Hava Donmez Keklikoglu², and Yusuf Ziya Ider^1
1Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey, ²Department of Neurology, Yildirim Beyazit University Atatürk Education and Research Hospital, Ankara, Turkey

In this study, clinical applicability of the recently proposed generalized phase based EPT method has been investigated for two patients with neurovascular diseases in the subacute phase, i.e. hemorrhagic and ischemic stroke. In the case of ischemia, conductivity was found to be increased in the lesion area. In the case of hematoma, although the conductivity of the surrounding edema region was found to be increased, the conductivity in the hematoma region itself was found to be similar to that of brain tissue.

Gokhan Ariturk¹, Necip Gurler¹, and Yusuf Ziya Ider^1
1Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey

Phase based MR-EPT methods mainly make use of the balanced SSFP since it is a fast MRI sequence. As SSFP sequence yields high magnitude contrast variations, Gibbs artifacts occur at tissue boundaries. This artifact manifests itself as phase spikes and oscillations at and near tissue boundaries respectively. The commonly used image enhancement methods, for reducing the ringing artifact, mainly focus on the magnitude images, leaving out the phase images. Throughout simulation and phantom experiment results, we investigate and propose a method for the reduction of the effect of ringing artifact on phase based MR-EPT studies.

Eric Michel¹ and Soo Yeol Lee^1
1Kyung Hee University, Suwon, Korea, Republic of

New MRI-based tissue electrical properties (EPs) mapping techniques had achieved higher accuracy and resolution increasing its chances to be used in several clinical applications. In this work, we describe a validation study for a technique called water-content-assisted electrical properties tomography (wEPT) based on in situ measurements of a brain-tissue-like phantom created by electrolytic protein solutions. The influence of inhomogeneous radiofrequency field distributions and its impact in wEPT reconstructions is also analyzed. Significant consistency between in vivo brain tissue estimations and phantom measurements was found, supporting the formalism and validity of wEPT for EPT studies.

Darryl Sneag¹, Mitsuharu Miyoshi², Maggie Fung³, Daniel Litwiller³, and Hollis Potter^1
1Hospital for Special Surgery, New York, NY, United States, ²GE Healthcare, Hino, Japan, ³GE Healthcare, New York, NY, United States

High-resolution MRI currently plays an important role in diagnostic management of peripheral nerve pathology. Peripheral nerves, however, pose particular imaging challenges that conventional sequences frequently cannot address. Their small size and oblique course between muscles and alongside vessels may inhibit reliable identification. We propose a 2-point Dixon fat/water separation 3D fast spin echo technique to achieve uniform fat suppression, combined with a flow-saturation prep pulse to suppress moving vascular spins to improve nerve visualization.  The objective of this study was to assess the technique’s feasibility and potential diagnostic utility in evaluating peripheral nerves throughout the body.

Anagha Deshmane¹, Debra F. McGivney², Yun Jiang¹, Dan Ma², and Mark A. Griswold^2
1Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States, ²Radiology, Case Western Reserve University, Cleveland, OH, United States

We present a method to compute fraction maps of tissue types using a subset of three dictionary entries chosen specifically for each individual, enforcing consistency with a physical tissue model.  This approach removes erroneous partial volumes in the fraction maps, and reduces noise and distortions in T1, T2, and M0 maps.

Kecheng Liu¹, Xiaodong Zhong¹, Dan Ma², Brian Dale¹, and Mark Griswold^2
1Siemens Healthcare USA Inc., Malvern, PA, United States, ²Case Western Reserve Univisity, Cleveland, OH, United States

Fat suppression or saturation (FatSat) is widely used in MRI applications, which reduces the fat signal and preserves water signal for clinical diagnosis, enhancing potential pathological changes. Different degree of FatSat yields different image contrast. However, when radiologists read FatSat images, they have different contrast preferences. To provide such variable preferences is not trivial because it typically costs more imaging time to re-acquire another contrast of FatSat image by adjusting imaging parameters. This work presents an alternative approach to provide continuously adjustable image contrast of FatSat images with only one acquisition.

Gigi Galiana^1
1Diagnostic Radiology, Yale University, New Haven, CT, United States

Recent work has highlighted the complicated and distinctive dynamics that shape the signal observed during an irregularly-spaced train of spin echoes.  Here, we use those signals as codes that allows us to identify mixtures of molecules that are too similar to distinguish by standard spectroscopy.  Extensions to water based systems, where relaxation mechanisms are the primary driver of signal dynamics, will also be presented.

Pelin Aksit Ciris¹, Cheng-Chieh Cheng², Chang-Sheng Mei³, Lawrence P. Panych², and Bruno Madore^2
1Department of Biomedical Engineering, Akdeniz University, Antalya, Turkey, ²Department of Radiology, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, United States,³Department of Physics, Soochow University, Taipei, Taiwan

Dual-pathway sequences have been proposed to improve the temperature-to-noise-ratio (TNR) in MR thermometry. The present work establishes how much improvement these sequences may bring for various tissue types. Simulation results were validated against analytical equations, phantom and in vivo human results. PSIF-FISP thermometry allowed TNR improvements for kidney, pelvis, spleen or gray matter, and up to 2-3 fold reductions in TR with 20% TNR gains were achievable. Further TNR benefits are expected for heated tissues, due to heating-related changes in relaxation rates. In other tissue types such as liver, muscle or pancreas improvements were observed only for short TR settings.  

Janusz Henryk Hankiewicz¹, Jason Nobles¹, Zbigniew Celinski¹, Karl Stupic², and Robert Camley^1
1UCCS Center for Biofrontiers Institute, University Colorado Colorado Springs, Colorado Springs, CO, United States, ²National Institute of Standards and Technology, Boulder, CO, United States

The aim of this study was to develop a novel temperature-sensitive MRI contrast agent based on temperature changes of the magnetic moment of magnetic particles. Gadolinium was used to test the hypothesis that magnetic particles will create a temperature-dependent local dipole magnetic field. This effect was locally visible as a temperature dependent darkening on gradient-echo MRI images. Shades of gray within the images can then be calibrated to map the local temperatures in specific areas of tissue during medical procedures. The estimated accuracy of temperature determination deep in the phantom using MR image intensity is ±1.8^oC, at 37^oC.

Hassaan Elsayed^1,2,3,4, Matti Hanni^2,3,4, Jari Rautiainen^2,3,5, Mikko Johannes Nissi^5,6, and Miika Nieminen^2,3,4
1Computer Science and Engineering, University of Oulu, Oulu, Finland, ²Research Unit of Medical Imaging, Physics and Technology, University of Oulu, Oulu, Finland, ³Medical Research Center, University of Oulu and Oulu University Hospital, Oulu, Finland, ⁴Department of Diagnostic Radiology, Oulu University Hospital, Oulu, Finland, ⁵Department of Applied Physics, University of Eastern Finland, Kuopio, Finland, ⁶Diagnostic Imaging Center, Kuopio University Hospital, Kuopio, Finland

Correlation time ($$$\tau_c$$$) maps were obtained by fitting $$$\tau_c$$$ from $$$T_{1\rho}$$$ dispersion measurements of human articular cartilage specimens and enzymatically digested bovine samples to develop a new MRI contrast which characterizes tissue properties at molecular level. $$$\tau_c$$$ revealed the laminar appearance in control and PG depleted bovine specimens, which was not observable in the collagen-digested specimens. The laminar appearance was also visible in the early OA human specimens, in contrast to the advanced OA group. The results demonstrated that $$$\tau_c$$$ mapping is a potential method for providing information about the articular cartilage structure and associated changes with degeneration.  

Ronald J Beyers¹, Meng Yu², Dean Schwartz³, Nouha Salibi^1,4, Christian Goldsmith⁵, and Thomas Denney^1
1MRI Research Center, Auburn University, Auburn University, AL, United States, ²Chemistry & Biochemistry, Auburn University, Auburn University, AL, United States, ³Anatomy, Physiology and Pharmacology, Auburn University, Auburn University, AL, United States, ⁴MR R&D, Siemens Healthcare, Malvern, PA, United States, ⁵Chemistry and Biochemistry, Auburn University, Auburn University, AL, United States

Pathological cardiac oxidative stress causes cardiac dysfunction and possible cardiac failure. We developed a novel reactive oxygen species sensing T1 agent (H4qpt2) and applied it with in vivo cardiac T1 mapping MRI at 7T in a doxorubicin-treated (Dox) rat model.  Cardiac T1 mapping with H4qpt2 specifically detected significantly shortened myocardial T1 in Dox rats while no change in T1 occurred in skeletal muscle or control rats with H4qpt2.  This new H4qpt2 agent combined with cardiac or non-cardiac T1 mapping may advance the early detection of oxidative stress in multiple pathologies and promote their early treatment.

Tim Klasen¹, Carsten Höltke¹, and Cornelius Faber^1
1Department of Clinical Radiology, University of Münster, Münster, Germany

Heteronuclear proton MRI is a recent method for MRI cell tracking and opens up the possibility for Multicolor MRI when using different Ln-DOTMA complexes. Here, we compare UTE and CSI as readout with regard to SNR efficiency, sensitivity towards temperature changes and performance in separating resonance lines from different Ln-DOTMA complexes at 9.4 T. UTE readout provides faster image acquisition and higher SNR efficiency than CSI. CSI on the other hand is insensitive to temperature changes. Multicolor MRI was possible with both readout schemes. Further studies will use these methods for in vivo cell tracking experiments.