Manoj Kumar Sarma¹, Zohaib Iqbal¹, Rajakumar Nagarajan¹, and M. Albert Thomas^1
1Radiological Sciences, UCLA School of Medicine, Los angeles, Los Angeles, CA, United States

Multi-echo based echo-planar correlated spectroscopic imaging (ME-EP-COSI) has been an innovative method to study muscle lipid content in T2D and a variety of other metabolic conditions. In this study we implemented accelerated ME-EP-COSI and validated in a corn oil phantom and in healthy human calf muscle. Both phantom and human calf muscle results show that 5D ME-EP-COSI has the potential to be a powerful tool for human calf muscle examination. Further studies will investigate various pathologies, including obesity and type 2 diabetes, using the 5D ME-EP-COSI method.

Judy Alper^1,2, Priti Balchandani¹, Francois Fay¹, and Hadrien Dyvorne^1
1Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States, ²Department of Biomedical Engineering, City College of New York, New York, NY, United States

MRI has long been used as a detection tool for cells labeled with superparamagnetic iron-oxide nanoparticles (SPIOs). Positive contrast imaging of off-resonance SPIO signal provides benefits over negative contrast methods and imaging the SPIOs at 7 Tesla (7T) allows for leveraging greater off-resonance sensitivity for quantitative imaging of smaller cell populations. In this study, we imaged a cell phantom containing SPIO labeled macrophages at 7T. We demonstrated the performance of frequency shift imaging (FSI), a new acquisition technique, for characterizing the magnetic signature of SPIOs, as compared to negative contrast methods.  

Nadine Luedicke Dispenza¹, Hemant Tagare^1,2, Gigi Galiana², and Robert Todd Constable^1
1Biomedical Engineering, Yale University, New Haven, CT, United States, ²Radiology and Biomedical Imaging, Yale University, New Haven, CT, United States

Accelerated imaging with nonlinear gradients can result in undersampling artifacts. A computationally efficient k-space point spread function metric that reflects the qualitative features of interest in the object is used to design a repeating nonlinear gradient trajectory that can be added to the linear trajectory.  The nonlinear gradient solution is found through optimization of the metric calculated for only a few time points in the linear trajectory over a subregion of k-space containing the linear encoding. Images reconstructed from data simulated with the optimized nonlinear trajectories result in less undersampling artifacts compared to linear trajectories. 

Martyn Paley¹, Steven Reynolds¹, Sarah Calvert², and Allan Pacey^2
1Immunity, Infection and Cardiovascular Disease, University of Sheffield, Sheffield, United Kingdom, ²Oncology and Metabolism, University of Sheffield, Sheffield, United Kingdom

A novel encoding method known as Continuously Ordered B0 Readout acquisition or COBRA is described. The method uses an additional B0 coil with a unique field at every point in space to perform Volume Frequency Encoding. The field increases as a monotonic function within the coil and can be sorted to the appropriate 3D location for reconstruction. 3D data sets have been acquired and reconstructed at 9.4T.

Jakob Assländer¹, Steffen Glaser², and Jürgen Hennig^1
1Dept. of Radiology - Medical Physics, University Medical Center Freiburg, Freiburg, Germany, ²Dept. of Chemistry, Technische Universität München, Munich, Germany

This paper proposes an inversion-recovery spin-echo SNAPSHOT-FLASH sequence for quantifying proton-density and T₁ of the lung. It is shown that T₁ is reduced compared to the standard gradient-echo sequence. Similar results have been previously reported for UTE sequences. In combination with an iterative algorithm that is similar to MR-fingerprinting reconstructions, the feasibility of acquiring quantitative maps of the entire lung with a resolution of 5 mm x 5 mm x 10 mm within 5.5 s is demonstrated.

Curtis Wiens¹, Nathan S. Artz^1,2, Hyungseok Jang¹, Alan McMillan¹, Kevin Koch³, and Scott B. Reeder^1,4,5,6,7
1Radiology, University of Wisconsin, Madison, WI, United States, ²Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, TN, United States, ³Biophysics and Radiology, Medical College of Wisconsin, Milwaukee, WI, United States, ⁴Medical Physics, University of Wisconsin, Madison, WI, United States, ⁵Biomedical Engineering, University of Wisconsin, Madison, WI, United States,⁶Medicine, University of Wisconsin, Madison, WI, United States, ⁷Emergency Medicine, University of Wisconsin, Madison, WI, United States

Large magnetic susceptibility differences between metallic implants and tissue generate severe B₀ inhomogeneities that present several challenges for MR: excitation of the entire off-resonance spectrum, distortion in the frequency encoding direction, and severe intra-voxel dephasing.  In this work we propose an ultra-short echo time acquisition with broadband excitation. Single point encoding was use to avoid in-plane distortions while 3D undersampling facilitated clinically feasible acquisition times.  The effects of RF pulse duration on signal loss near the implant and T₁ weighting were evaluated in a total hip replacement phantom and a volunteer with a total knee replacement.

Kosuke Ito¹, Atsushi Kuratani¹, Yukio Kaneko², and Masahiro Takizawa^1
1Healthcare Company, Hitachi Ltd., Chiba, Japan, ²Research and Development Group, Hitachi Ltd., Tokyo, Japan

A technique of ICA-selective 3D TOF imaging using asymmetrically RF-shimmed Pre-saturation pulse is presented. By using 4-channel RF transmit coil, spatially asymmetric RF transmission is achieved. Then apply RF shimming parameter to Pre-saturation pulse, the saturation effect becomes spatially asymmetric, and achieved selectively visualize blood flow from each ICA. This technique provides high contrast between blood and brain parenchyma because it does not make TR longer.

Hong Shang^1,2, Subramaniam Sukumar¹, Robert A. Bok¹, Irene Marco-Rius¹, Cornelius von Morze¹, Adam B. Kerr³, Galen Reed⁴, Michael Ohliger¹, John Kurhanewicz¹, Peder E. Z. Larson¹, John M. Pauly³, and Daniel B. Vigneron^1
1Radiology and Biomedical Imaging, UCSF, San Francisco, CA, United States, ²Bioengineering, UC Berkeley - UCSF, San Francisco / Berkeley, CA, United States, ³Electrical Engineering, Stanford University, Stanford, CA, United States, ⁴HeartVista, Menlo Park, CA, United States

Balanced SSFP sequences can provide superior SNR efficiency for hyperpolarized ¹³C imaging, by efficiently utilizing the non-recoverable magnetization. A spectrally selective bSSFP sequence was developed to enable fast mapping of hyperpolarized metabolites. A novel approach for bSSFP spectral selectivity was developed utilizing a combination of optimized multiband RF pulses and a bSSFP pulse train with a carefully chosen TR to avoid banding artifact. The sequence enabled 3D dynamic imaging of HP resonances generated in studies with co-polarized pyruvate and urea (with ~1% selectivity), attaining 2mm isotropic resolution and <1s temporal resolution.

Ke Jiang¹, Wen Song¹, Chao Zou¹, and Yiu Cho Chung^1
1Paul C. Lauterbur Research laboratory for Biomedical imaging, Shenzhen Institutes of Advanced Technology, ShenZhen, China, People's Republic of

We propose to acquire the different components in the steady state signal by interleaving. Using DESS as an example, we show that through appropriate gradient design, the two major components (S+ and S-) in the SSFP signal can be separately acquired in alternate TR and form images similar to those conventionally acquired by DESS. The new technique shortens TR and reduces motion and diffusion sensitivity.

Dan Ma¹, Jesse Hamilton², Yun Jiang², Nicole Seiberlich², and Mark Griswold^1
1Radiology, Case Western Reserve University, Cleveland, OH, United States, ²Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States

The purpose of this study is to accelerate the acquisition time of 3D MRF scans. A simple acquisition scheme was applied to allow a total factor of 144 acceleration as compared to the Nyquist rate, such that 3D T1, T2 and proton density maps can be acquired from a whole brain scan at clinical resolution in 2.6 minutes.

Alexander D. Cohen¹, Andrew S. Nencka^1,2, and Yang Wang^1,2
1Radiology, Medical College of Wisconsin, Milwaukee, WI, United States, ²Biophysics, Medical College of Wisconsin, Milwaukee, WI, United States

A multiband (MB) echo planar imaging (EPI) sequence with multishot autocalibration was developed and implemented at 7T. Slices were unaliased using the principles of Hadamard encoding, resulting in a fully-sampled calibration scan reconstructed without parallel imaging techniques. A Hadamard unaliasing procedure was demonstrated with an acceleration factor of lower rank than the Hadamard encoding matrix. Using this sequence, a functional MRI protocol at 7T was introduced to obtain a sufficient calibration volume, that was then utilized to unalias the remaining repetitions using a slice-GRAPPA technique. Preliminary resting state data acquired using this protocol has generated reliable connectivity networks.

Fan Lam¹, Qiang Ning^1,2, Chao Ma¹, Bryan Clifford^1,2, and Zhi-Pei Liang^1,2
1Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, United States, ²Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States

We present an integrative subspace-based sampling and reconstruction method for 3D high-resolution mapping of brain metabolites and neurotransmitters using MRSI. An echo-planar spectroscopic imaging sequence with J-resolved encoding capability has been developed to implement the proposed sparse sampling strategy for fast spatiospectral encoding. An explicit subspace model-based reconstruction scheme that incorporates J-resolved spectral prior to enable joint reconstruction of the metabolite and neurotransmitter signal components from the sparse data is described. Results from experimental data are used to demonstrate the capability of the proposed method in producing high-resolution and high-SNR spatiospectral distributions of both metabolites and neurotransmitters.

Mehdi Hedjazi Moghari^1,2, Martin Uecker^3,4, Sébastien Roujol⁵, Tal Geva^1,2, and Andrew J Powell^1,2
1Pediatrics, Harvard Medical School, Boston, MA, United States, ²Cardiology, Boston Children's Hospital, Boston, MA, United States, ³German Center for Cardiovascular Research (DZHK), Goettingen, Germany, ⁴Department of Diagnostic and Interventional Radiology, University Medical Center, Goettingen, Germany, ⁵Division of Imaging Sciences and Biomedical Engineering, King’s Health Partners, St. Thomas’ Hospital, King’s College London, London, United Kingdom

To accelerate whole-heart magnetic resonance angiography, we implemented a variable density Poisson disc undersampling pattern and compressed sensing parallel image reconstruction, and compared it to a standard parallel image (SENSE) acquisition in 15 patients. The compressed sensing technique was faster (mean 3.4±1.0 minutes vs 7.6±1.7 minutes) and had similar objectively measured sharpness in 4 designated regions (all p>0.05) but a lower subjective image quality scores (all p≤0.05). 

Chao Zou¹, Wensha Guo¹, Xin Liu¹, Hairong Zheng¹, and Yiu-Cho Chung^1
1Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, CAS, Shenzhen, China, People's Republic of

A novel SSFP sequence with interleaved acquisition for F0, F- and F+ was proposed and applied to T1/T2 relaxometry. The good agreement with analytical solution of SSFP implies that steady state is maintained at different TR. Compared to TESS, TEs of the three echoes can be identical to eliminate T2* effect. The reduced TR decreases susceptibility induced signal void and motion sensitivity. The crusher in slice select direction avoids the unwanted diffusion effect for high resolution imaging. The phantom study shows that the T1/T2 relaxometry results are consistent with the traditional IR-TSE and SE results.

Eric James Keller¹, Susanne Schnell¹, James C Carr¹, Michael Markl^1,2, and Jeremy Douglas Collins^1
1Radiology, Northwestern University, Chicago, IL, United States, ²Biomedical Engineering, Northwestern University, Evanston, IL, United States

Abdominal 4D flow MRI is currently limited by long acquisition times required to capture the wide range of velocities and flows present in the abdomen with separate low and high velocity encoding gradient (venc) acquisitions. By instead using a single 4D flow sequence with two different velocity encodings (dual-venc), we were able to quantify abdominal hemodynamics with similar accuracy in a total of 21% less time. Overall, this is encouraging as it directly addresses scan time, a major limitation of 4D flow MRI, increasing its clinical utility.

Pavan Poojar¹, Bikkemane Jayadev Nutandev², Ramesh Venkatesan³, and Sairam Geethanath^1
1Medical Imaging Research Centre, Dayananda Sagar College of Engineering, Bangalore, India, ²Bangalore, India, ³Wipro-GE Healthcare, Bangalore, India

K-space trajectories such as cartesian, radial, spiral are not optimal for traversing arbitrary k-space shapes. GO-Active is a novel acquisition technique which is a combination of active contour and convex optimization where active contour was used to obtain arbitrary k-space trajectory and convex optimization was employed to optimize the gradients based on hardware constraints. Reconstruction was performed using Non Uniform Fast Fourier Transform and compressed sensing. Retrospective study was performed on six brain datasets and phantom, where as prospective study was carried out on the phantom respectively. Current and Future work involves application of GO-Active on in vivo data prospectively.

Pavan Poojar¹ and Sairam Geethanath^1
1Medical Imaging Research Centre, Dayananda Sagar College of Engineering, Bangalore, India

3D Variable density spiral (VDS)–“beachball” was designed and generated to cover 3D k-space efficiently. Beachball is obtained by rotating along one axis of a 2D VDS for various number of shots. Beachball was demonstrated in-silico by analyzing point spread function and restrospective analysis of a in-vitro water phantom. Reconstruction was done using NUFFT. Optimal gradient waveforms were generated for beachball by using convex optimization formulations based on the constraints of maximum gradient amplitude and slew rate. This trajectory provides for smoother coverage and densely sampled at the centre of k-space and allows implementation of silent MR. 

Julie POUJOL^1,2, Pierre-André VUISSOZ^1,2, Jacques FELBLINGER^1,2,3, and Freddy ODILLE^1,2,3
1Imagerie Adaptative Diagnostique et Interventionnelle, Université de Lorraine, Nancy, France, ²U947, INSERM, Nancy, France, ³CIC-IT 1433, INSERM, Nancy, France

DCE-MRI protocol is the reference technique to detect and characterize breast lesions. Due to the high spatial resolution needed to detect small lesions, the temporal resolution of the DCE-MRI protocol is limited to 90 seconds. A good fat suppression is also needed and a spectral inversion preparation is commonly used for it. To provide more information about lesion vascularization, temporal resolution need to be increased. We have developed a method to implement a smart k-space trajectory allowing both standard DCE-MRI protocol reconstruction and accelerated DCE-MRI protocol via Compressed-Sensing reconstruction compatible with fat suppression.

Jeehun Kim¹ and Jongho Lee^1
1Laboratory for Imaging Science and Technology, Department of Electrical and Computer Engineering, Seoul national university, Seoul, Korea, Republic of

In this study, we propose a new fast acquisition trajectory, Dual Echo Trajectory (DuET), to accelerate spin echo imaging. The proposed method allowed a 2-fold increase in acquisition speed with minimum image artifacts. 

Somaie Salajeghe¹, Paul Babyn², and Gordon E. Sarty^1
1Biomedical Engineering, University of Saskatchewan, Saskatoon, SK, Canada, ²Medical Imaging, University of Saskatchewan, Saskatoon, SK, Canada

RF phase encoded MRI uses spatial RF phase gradients in place of B₀ gradients coils to encode information. Using a nonlinear RF phase gradient coil instead of linear one leads to a larger field of view. However, this coil will generate an in-homogeneous B₁ field which result in pulse imperfection. To minimize the effect of pulse imperfection, the application of composite pulses is required. Current composite pulses were designed to use in current MRIs (having gradient coils and uniform RF coil), so the feasibility of working composite pulses with an RF encoded coil needs to be checked. 

Gregor Körzdörfer¹, Thorsten Feiweier¹, Yun Jiang², and Mathias Nittka^1
1Siemens Healthcare GmbH, Erlangen, Germany, ²Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States

Quantitative parameter maps obtained from Magnetic Resonance Fingerprinting (MRF) are sensitive to B1+ inhomogeneities. In principle, one could reduce this dependency by using a dictionary with an additional B1+ dimension. However, if the dictionary entries are not well distinguishable, the simultaneous pattern matching of three parameters (T1, T2, B1+) will not work reliably. In order to improve the separation of data in the B1+ dimension, we implemented a novel B1+ sensitive encoding. This approach employs a dedicated composite RF excitation pulse which directly encodes B1+ magnitude information into the phase of the acquired signal. Here we present an experimental proof of principle using a 1D projection MRF sequence.

Takashi Nishihara¹, Kuniaki Harada¹, Noriko Itabashi¹, Kuniharu Oka¹, and Hiroyuki Itagaki^1
1Healthcare Company, Hitachi, Ltd., Chiba, Japan

We confirmed that 2D beam excitation presaturation-pulse (hereafter Beam Sat pulse) can saturate the vessels selectively and visualized hemodynamics in brain and liver. Although Beam Sat can visualize portal vein and hepatic artery, right hepatic artery (RHA) cannot visualize clearly because T1 relaxation of saturated blood magnetizations is short. In this study, 2D excitation pulse was used as IR pulse (hereafter Beam IR pulse), and we showed that the Beam IR pulse can clearly visualize a flow phantom and RHA of healthy volunteers.

Emre Kopanoglu¹, Haifeng Wang¹, Gigi Galiana¹, Dana C. Peters¹, and Robert Todd Constable^1,2
1Diagnostic Radiology and Biomedical Imaging, Yale University, New Haven, CT, United States, ²Neurosurgery, Yale University, New Haven, CT, United States

rOi-Space is a region-of-interest imaging technique.  The method uses a nonlinear gradient field for improved accelerated imaging similar to O-Space but focuses the encoding effort to the region-of-interest rather than imaging the whole field-of-view. Simulations showed improved reconstruction compared to radial acquisitions for acceleration factors between 2.2 and 14.2 and up to 70% reduction in reconstruction error, for acceleration factors of around 4. Noise performance comparisons demonstrate some degraded SNR performance due to intra-voxel dephasing. Experiments showed improved resolution inside the ROI at the expense of SNR performance. Hence, the method can be used for resolution enhancement in applications with adequate SNR.

Sophie Shermer^1,2 and Aled Issac^1
1College of Science (Physics), Swansea University, Swansea, United Kingdom, ²Medical Imaging, Swansea University, Swansea, United Kingdom

We illustrate some key basic concepts in MRI such as resonance, frequency-based slice selection and readout, as well as relaxation using tuning forks and sound waves.

Matthias Weigel^1
1Dept. of Radiology, Radiological Physics, University of Basel Hospital, Basel, Switzerland

The Extended Phase Graph (EPG) calculus can be understood as a solution of the Bloch equation using its k-space representation. The ability to represent magnetization in phase state configurations frequently enables an intuitive and pictorial understanding of echo formation and assignment. A class of functions that allows for the easy calculation and simulation of EPGs for arbitrary MR sequences was developed (EPGspace) and its key points are presented. The EPGspace source code is made publically available for download in the internet.

Shaihan J Malik¹, Alessandro Sbrizzi², Hans Hoogduin², and Joseph V Hajnal^1
1Imaging Sciences & Biomedical Engineering, King's College London, London, United Kingdom, ²Imaging Division, University Medical Centre, Utrecht, Utrecht, Netherlands

Extended Phase Graphs and Isochromat-summation are two leading methods for simulating MR signals. The latter method is more intuitive, but choice of the number and distribution of isochromats significantly affects results. It is well known that the two methods are related by Fourier Transform, but precise equivalence is not widely understood. We demonstrate conditions under which they are exactly equivalent and related by DFT. Choice of isochromats is shown to be a sampling problem and conditions for accurate isochromat-based simulations are given.  Matlab code is provided as a direct illustration.

Shuo Han¹ and Daniel A. Herzka^1
1Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, United States

Analytical Fourier transforms (FT), such as FT of 2D and 3D Shepp-Logan phantoms, enable accurate arbitrary k-space sampling of digital phantoms. Here, we present and demonstrate a computationally efficient MATLAB implementation of the analytical FT of polyhedral phantoms with uniform intensity or non-uniform intensities. The computation time of the implementation is presented, as well as demonstrations showing its feasibility of simulating physiologically relevant phantoms and evaluating non-Cartesian sampling trajectories and parallel imaging algorithms. The implementation is now available through the Mathworks user community and GitHub. 

Cristoffer Cordes¹, Thorsten Honroth¹, Daniel Hoinkiss¹, Saulius Archipovas¹, David Porter¹, and Matthias Günther^1,2
1Fraunhofer MEVIS, Bremen, Germany, ²University of Bremen, Bremen, Germany

The interactions of MRI sequence components within complex techniques are hard to explain, grasp and extend using common modularity approaches. This results in poor developability and calculation efficiency. The proposed algorithm yields a new sequence description approach that resolves the component parameter dependencies and enables the calculation of arbitrary module parameters using the least amount of calculation steps. The algorithm has been used on a twice-refocused, spin-echo diffusion MRI sequence to simplify its description and boost the calculation of critical parameters during sequence preparation calculation.

Fang Liu¹, Richard Kijowski¹, Wally Block², and Alexey Samsonov^1
1Department of Radiology, University of Wisconsin-Madison, Madison, WI, United States, ²Department of Medical Physics, University of Wisconsin-Madison, Madison, WI, United States

Numerical simulation dramatically improves the understanding and development of new MR imaging methods. We proposed an improved version of MR simulation package named as MRiLab with the feature of incorporating a generalized exchange tissue model to facilitate flexible and realistic MR signal simulation for complex tissue structures. 

Nicholas Dwork¹, Brian A. Hargreaves², and John M. Pauly^1
1Electrical Engineering, Stanford University, Stanford, CA, United States, ²Radiology, Stanford University, Stanford, CA, United States

In this document we show that we can represent MRI signal progression as a sum of Cellular Automata processes.

Xiaoguang Lu¹, Peter Speier², and Ti-chiun Chang^3
1Medical Imaging Technologies, Siemens Healthcare, Princeton, NJ, United States, ²Siemens Healthcare, Erlangen, Germany, ³Siemens Corporate Technology, Princeton, NJ, United States

Resolving slice thickness for better MR reconstruction is desirable, where actual slice profile plays a crucial role. Conventional blind deconvolution formulation includes both original signals and slice profile as unknowns, which is an ill-posed problem with high complexity. We propose a convolutional forward model (CFM), leveraging additional orthogonal stack(s) with an added convolution process in the formulation to fit actual forward imaging process accurately, resulting in a significantly simplified slice profile estimation problem. The actual slice profile is calculated through a data-driven approach. Experimental results demonstrate that the proposed method is robust to handle various challenges.

Ryoichi Kose¹ and Katsumi Kose^2
1MRTechnology Inc., Tsukuba, Japan, ²University of Tsukuba, Tsukuba, Japan

We have developed a GPU optimized fast 3D MRI simulator for pulse sequence developments. We compared simulation and experimental results for gradient echo images of water phantoms that contains an air-filled cylinder and air-filled sphere. The agreements between simulation and experiments were good if the calculation matrix was more than two times that of original images. Because the processing speed of our simulator varied from 2.2 to 3.1 TFLOPS, we concluded that our simulator is useful for development of MRI pulse sequences. 

Hao Song¹, John Hazle¹, and Jingfei Ma^1
1Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, United States

Fully-balanced steady-state free precession (bSSFP) is clinically useful because of its high SNR efficiency, imaging speed and unique T₂/T₁ contrast. A geometric solution to bSSFP has been derived and provides a simple and intuitive understanding of how the complex steady-state signals are formed.  However, T₁ and T₂ relaxation has generally been ignored. In this work, we present an exact geometric solution to the bSSFP signals by including the T₁ and T₂ relaxation effects. The results are consistent with those based on matrix calculations, and are useful in understanding different aspects of bSSFP signal behavior. 

Dianning He^1,2, Wei Qian^1,3, Lisheng Xu^1,4, and Xiaobing Fan^2
1Sino-Dutch Biomedical and Information Engineering School, Northeastern University, Shenyang, China, People's Republic of, ²Radiology, University of Chicago, Chicago, IL, United States, ³Electrical and Computer Engineering, University of Texas at El Paso, El Paso, TX, United States, ⁴Key Laboratory of Medical Image Computing, Ministry of Education, Shenyang, China, People's Republic of

Numerical simulations were performed to study analytical mathematical models for fitting tissue contrast agent concentration curves obtained from DCE-MRI. Randomly generated K^trans and v_e were used to calculate the curves using the Tofts model. A total of five analytical mathematical models, empirical mathematical model, modified logistic model, modified sigmoidal function, Weibull model, and extended phenomenological universalities were compared and evaluated in terms of how well they fitted to 100 curves. Statistical analysis showed that the empirical mathematical model provided the best fit out of those models. The analytical mathematical models were different despite having the same number of parameters.  

Jean-François Cabana¹, Ye Gu², Mathieu Boudreau³, Ives R. Levesque³, Yaaseen Atchia⁴, John G. Sled⁴, Sridar Narayanan³, Douglas L. Arnold³, Bruce G. Pike⁵, Julien Cohen-Adad⁶, Tanguy Duval⁶, Manh-Tung Vuong⁶, and Nikola Stikov^6
1Medical Physics, University of Montreal, Montreal, QC, Canada, ²NeuroRX, Montreal, QC, Canada, ³McGill University, Montreal, QC, Canada, ⁴University of Toronto, Toronto, ON, Canada, ⁵University of Calgary, Calgary, AB, Canada, ⁶Ecole Polytechnique, Montreal, QC, Canada

We have developed a free, open source software (qMTLab) that unifies the most widely used quantitative magnetization transfer imaging (qMTI) methods in a simple and easy to use graphical interface.qMTLab allows to easily simulate qMTI data, compare the performance of the methods under various experimental conditions, define new acquisition protocols, fit acquired data, and visualize the fitted parameter maps. In this presentation, we will offer a brief introduction on the theory behind qMTI, present the current acquisition and analytical methods, and present the functionality of the qMTLab software and its utility in basic and clinical research. 

Stefan Kroboth¹, Katharina E. Schleicher¹, Kelvin J. Layton¹, Axel J. Krafft^1,2,3, Klaus Düring⁴, Feng Jia¹, Sebastian Littin¹, Huijun Yu¹, Jürgen Hennig¹, Michael Bock¹, and Maxim Zaitsev^1
1Medical Physics, University Medical Center Freiburg, Freiburg, Germany, ²German Cancer Consortium (DKTK), Heidelberg, Germany, ³German Cancer Research Center (DKFZ), Heidelberg, Germany,⁴MaRVis Medical GmbH, Hannover, Germany

In order to capture intra-voxel dephasing in simulations, the object has to be modeled with a very large number of spins per voxel. We present a method to improve and speed up simulations by explicitly modelling intra-voxel dephasing. The method is evaluated by simulating an MR-safe guidewire. The iron particles in the wire create dipole fields, which lead to dephasing in the proximity of the wire. We show that a substantial reduction of the required number of spins by a factor of ~5.4 is possible, without sacrificing image quality.  This reduces the memory requirements and speeds up simulations.

Thorsten Honroth¹, Cristoffer Cordes^1,2, Saulius Archipovas¹, Daniel Christopher Hoinkiss¹, Matthias Günther^1,2,3, and David Porter^1
1Fraunhofer MEVIS, Bremen, Germany, ²University of Bremen, Bremen, Germany, ³mediri GmbH, Heidelberg, Germany

A platform-independent rapid clinical prototyping environment for MR sequences is demonstrated. Fully interactive product-like sequences can be defined without coding or compiling software. They are saved as plain text files and run by a generic pre-installed software module at the scanner that never needs modifications by a user. Sub-groups of sequence elements can be exported as macros and reused in other sequences.

Matthieu Ruthven^1,2, Andreia C. Freitas³, Stephen F. Keevil^2,4, and Marc E. Miquel^1
1Clinical Physics Department, Barts Health NHS Trust, London, United Kingdom, ²Imaging Sciences & Biomedical Engineering Research Division, King's College London, London, United Kingdom, ³William Harvey Research Institute, Queen Mary University of London, London, United Kingdom, ⁴Medical Physics Department, Guy's and St Thomas' NHS Foundation Trust, London, United Kingdom

Clinical velopharyngeal closure assessment involves imaging patients while they perform standard speech tasks.   Real-time MRI could offer an alternative to the imaging techniques used at present, however, there is currently no consensus on the optimal temporal resolution.   The purpose of this study is to determine an optimal temporal resolution by comparing the numbers of velopharyngeal closures in high temporal resolution and simulated lower temporal resolution datasets of healthy adult volunteers.   The results of this study suggest that the optimal temporal resolution is between 7.5 and 10 frames per second.   Future work will aim to pinpoint and validate this resolution.

Arun Antony Joseph^1,2, Dirk Voit¹, Klaus-Dietmar Merboldt¹, and Jens Frahm^1,2
1Biomedizinische NMR Forschungs GmbH, Max-Planck-Institute for Biophysical Chemistry, Goettingen, Germany, ²DZHK, German Center for Cardiovascular Research, Goettingen, Germany

MRI has become the preferred technique to study the dynamics of tongue and vocal tract during speech, singing or instrument playing. Recent advances provide access to qualitative information of fast tongue movements at very high temporal resolution. In this study, real-time MRI using highly undersampled radial FLASH with regularized nonlinear inverse reconstruction was used to monitor the dynamics of the tongue at 10 ms, 18 ms and 33 ms resolution. The effect of different temporal resolutions on the tongue and oral cavity during speech will be compared and analyzed.

Wendy Harris^1,2, Fang-Fang Yin^1,2, Chunhao Wang^1,2, Zheng Chang^1,2, Jing Cai^1,2, You Zhang^1,2, and Lei Ren^1,2
1Department of Radiation Oncology, Duke University, Durham, NC, United States, ²Medical Physics Graduate Program, Duke University, Durham, NC, United States

A novel technique has been developed to generate ultra-fast high-quality volumetric cine MRI (VC-MRI) using patient prior information. The VC-MRI was generated by deforming the prior volumetric MRI images based on ultra-fast on-board 2D-cine MRI and patient PCA-based respiratory breathing model. The ultra-fast 2D-cine images were acquired by sampling about 10% of k-space. The undersampled cine images were reconstructed using an iterative MR reconstruction algorithm with a total generalized variation penalty. The technique was evaluated using both anthropomorphic digital phantom and patient data. Results demonstrated the feasibility of generating ultrafast-VC-MRI for both inter-and intra-fraction verification of moving targets in radiotherapy.  

Susanne Schnell¹, Can Wu¹, Pierre-Francois Van de Moortele², Bharathidasan Jagadeesan³, Kâmil Ugurbil², Michael Markl¹, and Sebastian Schmitter^2
1Radiology, Northwestern University, Chicago, IL, United States, ²Center for Magnetic Resonance in Research, University of Minnesota, Minneapolis, MN, United States, ³Neurosurgery Department, University of Minnesota, Minneapolis, MN, United States

Dual-venc 4D flow MRI was applied in 6 healthy volunteers at a 7T MRI scanner at two different approximately isotropic spatial image resolutions, low resolution with (1.1mm)³ and high resolution with (0.8mm)³ voxel volumes. The aim of this study was to systematically investigate the potential of high-resolution k-t GRAPPA accelerated dual-venc 4D flow MRI compared to the low-resolution scan with standard GRAPPA with respect to improved image quality (vessel sharpness and depiction of small intracranial vessels) and quantification of intracranial flow parameters (net flow, peak velocity).

Haris Saybasili¹ and Ning Jin^2
1MR R&D, Siemens Healthcare USA, Inc., Chicago, IL, United States, ²MR R&D, Siemens Healthcare USA, Inc., Columbus, OH, United States

Flow quantification on uncooperative patients that cannot hold their breath may be performed by real-time free-breathing flow acquisitions that generally cover multiple heart-beats. However, heart-rate fluctuations, low SNR, and respiratory motion associated with such acquisitions may impede flow quantification process. In this study, we are extending our unsupervised motion correction method for real-time free-breathing cine imaging to flow imaging, and comparing the results with gold standard ECG gated, breath-held, segmented flow acquisition. Preliminary results indicate net forward volumes in agreement with the reference, with comparable image quality.

Keigo Kawaji¹, Mita B. Patel¹, Marco Marino¹, Roberto M. Lang^1,2, Hui Wang³, Yi Wang⁴, and Amit R. Patel^1,2
1Medicine, The University of Chicago, Chicago, IL, United States, ²Radiology, The University of Chicago, Chicago, IL, United States, ³Philips Healthcare, Cleveland, OH, United States, ⁴Biomedical Engineering and Radiology, Cornell University, New York, NY, United States

Assessment of diastolic function using cine-CMR is limited by its temporal resolution. A high-temporal cine-CMR approach that yields comparable temporal resolution to echocardiography was recently developed using radial trajectories with a custom spoke ordering that exploits the property of prime numbers (Modulo-Prime Spokes, or MoPS), as well as a radial UNFOLD-type streaking artifact removal step.  In this study, we validate the functional cine-assessment parameters associated with systolic and diastolic performance of the left ventricle (LV) by comparing the measurements derived from time-volume curves between the proposed radial MoPS-Cine and the clinically employed Cartesian Cine reference.

Anjali Datta¹, Corey A Baron¹, R Reeve Ingle², Joseph Y Cheng¹, and Dwight G Nishimura^1
1Electrical Engineering, Stanford University, Stanford, CA, United States, ²HeartVista, Inc., Menlo Park, CA, United States

bSSFP is commonly used for cardiac cine imaging due to its high myocardium-blood contrast but suffers from signal nulls due to off-resonance. By modifying the slow frequency modulation scheme for use in the heart, we acquire interleaved phase-cycles within a breath-hold for banding artifact reduction.  Because a constant heart rate cannot be assumed, the phase increment increases slowly for a time equal to the shortest expected RR interval and then remains constant until the next trigger.  In vivo results indicate that the proposed method is comparable to standard phase-cycling but with shorter scan time and interleaved phase-cycle acquisition.

Corey Allan Baron¹, Tiffany Jou¹, Anjali Datta¹, John M Pauly¹, and Dwight G. Nishimura^1
1Electrical Engineering, Stanford University, Stanford, CA, United States

In phase cycled bSSFP, there is considerable motivation to use undersampling to mitigate long scan times. Direct application of a GRAPPA or SPIRiT reconstruction involves performing calibration separately for each phase cycled image. However, the receiver sensitivities are equivalent for all phase cycles, and this redundancy should be accounted for to improve calibration quality. Here, we describe a method for calculation of a single GRAPPA kernel over all phase cycles simultaneously, which is shown to improve calibration quality.

Zijing Dong¹, Fuyixue Wang¹, Xiaodong Ma¹, Erpeng Dai¹, Zhe Zhang¹, and Hua Guo^1
1Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, China, People's Republic of

A novel compression method, shot-coil compression, is developed and implemented to a k-space reconstruction method SYMPHONY for computation acceleration. By this technique, high resolution multishot diffusion images can be reconstructed with much less reconstruction time. The basic idea of the proposed method is to remove the redundant multi-coil and multi-shot data while reserving most useful information. Simulation and in-vivo experiment were designed and the results validated the effectiveness of the shot-coil compression method. 

JungHyun Song¹, Seon Young Shin¹, Yeji Han¹, and Jun-Young Chung^1
1Gachon Advanced Institute for Health Science and Technology, Gachon University, Incheon, Korea, Republic of

In this study, the effects of the aspect ratio of ACS lines with respect to the phase-encoding and partition-encoding steps are investigated for 3D GRAPPA reconstruction algorithms such as EX-3D-GRAPPA and SK-3D-GRAPPA. When the ACS lines are acquired by carefully considering the dimensions of the image matrices, the quality of the reconstructed images can be improved. 

Steen Moeller¹, Sudhir ramanna¹, Kamil ugurbil¹, and Essa Yacoub^1
1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States

Investigation on the effect of reference or calibration scans needed to reconstruct undersampled MRI data. The study covers 3 different acceleration factors, and 6 different reference acquisitions. It is found that scan to scan variability for common acceleration factors is larger than any difference in tSNR between FLASH and FLEET, and that segmented EPI and single-shot are inferior to FLASH and FLEET acquisitions.

Jing Cheng¹, Leslie Ying², Shanshan Wang¹, Xi Peng¹, Yuanyuan Liu¹, Jing Yuan³, and Dong Liang^1
1Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology,Chinese Academy of Sciences, shenzhen, China, People's Republic of, ²University at Buffalo,The State University of New York, New york, NY, United States, ³Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, Hong Kong

Compressed sensing based parallel imaging is an essential technique for accelerating MRI scan. However, most existing methods are still suffering from fine structure loss. This paper proposes an iterative feature refinement scheme for improving the reconstruction accuracy. We have incorporated the feature descriptor into the self-feeding sparse SENSE (SFSS) framework. Results on in-vivo MR dataset have shown that the descriptor is capable of capturing image structures and details that are discarded by SFSS and thus presents great potential for more effective parallel imaging.

Frank Zijlstra¹ and Peter R Seevinck^1
1Image Sciences Institute, UMC Utrecht, Utrecht, Netherlands

We studied the effect of sampling density and randomness in Variable Density Poisson Disk (VDPD) undersampling patterns on Parallel Imaging Compressed Sensing (PICS) reconstruction errors. PICS reconstructions were performed on 3 datasets (knee, prostate, and brain) which were retrospectively undersampled with 110 VDPD undersampling patterns each. We found major differences in Normalized Root Mean Squared Errors when using different sampling densities, while the influence of randomness in patterns of the same sampling density was minor. Furthermore, the optimal sampling density varied per dataset. This shows that ad hoc choices of VDPD sampling density can result in significantly worse PICS reconstructions.

Tianrui Luo¹, Jon-Fredrik Nielsen¹, and Douglas C. Noll^1
1University of Michigan, Ann Arbor, MI, United States

A method of suppressing incomplete aliasing artifacts in accelerated MRI by combining inner-volume steady-state imaging with parallel imaging (GRAPPA) is proposed. Its effectiveness is evaluated across different net acceleration factors (R=1.75-3.64). The normalized root mean squared error inside the region of interest is generally suppressed by approximately a factor of 2 when inner volume excitation is adopted.

Seon Young Shin¹, JungHyun Song¹, Yeji Han¹, and Jun-Young Chung^1
1Gachon Advanced Institute of Health Sciences and Technology, Gachon University, Incheon, Korea, Republic of

To compare the volumetric GRAPPA algorithms in the presence of physiological artifacts, five different algorithms were used, i.e., 2D-GRAPPA-OP, 3D-GRAPPA, EX-3D-GRAPPA and SK-3D-GRAPPA. The performance of algorithms were compared using the root mean squared error (RMSE) of the image reconstructed from fully acquired 3D in-vivo k-space data and the image reconstructed using different reconstruction algorithms from undersampled dataset. 

Mark Chiew¹ and Karla L Miller^1
1FMRIB, University of Oxford, Oxford, United Kingdom

In this work we demonstrate a simple method for reducing error in k-t under-sampled parallel imaging by subtracting a dynamic, low-rank time-series estimate prior to un-aliasing reconstruction. This estimate is generated directly from the under-sampled data by selecting the first $$$r$$$ components of a singular value decomposition after sliding-window reconstruction, and removes signal variance that might otherwise contribute to residual aliasing. This method is motivated by the observation that the highest variance components in time-series data are typically low-frequency, and well characterised by a sliding window filter.

Wenchuan Wu¹, Karla L Miller¹, Benedikt A Poser², and Peter J Koopmans^1
1FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom, ²Maastricht Brain Imaging Center, Department of Cognitive Neuroscience, Maastricht University, Maastricht, Netherlands

In this work, we developed and evaluated a method for reducing motion sensitivity of auto-calibration data for parallel imaging in 3D MRI, with application to high-resolution diffusion imaging at ultra-high field. With the proposed Slice-FLEET method, we successfully achieve high resolution (1mm isotropic) diffusion MRI with high SNR and high b values.

Taisuke Harada^1,2, Kohsuke Kudo¹, Ikuko Uwano³, Fumio Yamashita³, Hiroyuki Kameda^1,3, Tsuyoshi Matuda⁴, Makoto Sasaki³, and Hiroki Shirato^2
1Department of Diagnostic and Interventional Radiology, Hokkaido University Hospital, Sapporo, Japan, ²Department of Radiation Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan, ³Division of Ultrahigh Field MRI, Institute for Biomedical Sciences, Iwate Medical University, Yahaba, Japan, ⁴MR Applications and Workflow, GE Healthcare, Tokyo, Japan

The aim of our study was to compare the homogeneity of B1+ map and clinical gradient-echo images at 7T between two-channel pTx and qTx. MRS phantom with a water pack and six volunteers were scanned by 7T MRI, and the homogeneity was evaluated by coefficient of variation of region-of-interest analysis. The signal homogeneities of B1+ map and GRASS image were better in pTx than in qTx, however the homogeneity of SPGR images had no difference between pTx and qTx, in both phantom and volunteer studies. These results might facilitate the development of pTx.

Wang Bin¹, Zhu Gaojie¹, Luo Hai¹, Zhou Xiang¹, and Zha Leping^1,2
1Alltech Medical Systems, Chengdu, China, People's Republic of, ²Alltech Medical Systems America, Cleveland, OH, United States

Images from accelerated acquisition and ESPIRiT reconstruction show inhomogeneous intensity from the original array coil sensitivity distributions, because of the arbitrarily scaled sensitivity (eigenvector) maps. We propose to use the corresponding eigenvalues to restore the proper relative sensitivity scaling in the maps as a method of intensity bias correction, to help better visualization of the anatomies.

Kilian Weiss^1,2, David Maintz², and Daniel Giese^2
1Philips Healthcare, Hamburg, Germany, ²Department of Radiology, University Hospital of Cologne, Cologne, Germany

In this work a new multi shell variable density k-t space sampling scheme for highly accelerated acquisitions with sheared grid k-t space sampling and an adapted reconstruction framework based on a linear reconstruction is proposed. The proposed method is evaluated on numerical phantom data and compared to a conventional k-t PCA acceleration. The proposed method is shown to be comparable to conventional k-t PCA for moderate acceleration factors while outperforming conventional k-t PCA for high accelerations factors allowing for ultra-fast dynamic MRI.

Sajan Goud Lingala¹, Yinghua Zhu¹, Yunhua Ji², Asterios Toutios¹, Wei-Ching Lo³, Nicole Seiberlich³, Shrikanth Narayanan¹, and Krishna Nayak^1
1Electrical Engineering, University of Southern California, Los Angeles, CA, United States, ²Biomedical Engineering, University of Southern California, Los Angeles, CA, United States, ³Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States

Real-time MRI (RT-MRI) is a powerful tool to safely assess and quantify the vocal tract dynamics during speech production. In this work, we evaluate the potential of a fast linear reconstruction method through-time GRAPPA (TT-GRAPPA) to efficiently exploit the acceleration capabilities offered by a custom 8-channel upper-airway coil and spiral trajectories and utilize it to improve RT-MRI of speech in visualizing rapid articulatory dynamics. We report feasibilities of 3 to 4 fold acceleration, and demonstrate up to 52 frames per second (18ms/frame) in single slice (2.4 mm2), and three-slice (4.5mm2) imaging. imaging. 

Bryan Clifford¹, Fan Lam², Qiegen Liu², Chao Ma², and Zhi-Pei Liang^1
1Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States, ²Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, United States

We present a method which reduces the acquisition time of 3D 1H-MRSI through the integration of parallel imaging and subspace-based imaging. The proposed method enables a better combination of speed, resolution, and SNR than can be provided by parallel imaging or subspace-based imaging alone; however, the removal of nuisance signals from under-sampled MRSI data requires significantly higher reconstruction accuracy than in conventional parallel imaging applications. We solve this problem by incorporating spatial and spectral constraints as well as sensitivity encoding into a recently proposed Union-of-Subspace model. We demonstrate the effectiveness of our method using in vivo data of the brain.

Mengye Lyu^1,2, Yilong Liu^1,2, Victor B. Xie^1,2, Yanqiu Feng^1,2, Zhe Zhang³, Hua Guo³, and Ed X. Wu^1
1Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong SAR, China, People's Republic of, ²Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong SAR, China, People's Republic of, ³Department of Biomedical Engineering, Tsinghua University, Beijing, China, People's Republic of

This work addresses three problems for in-plane SENSE-accelerated PROPELLER: generally amplified noise, increased artifact with narrow blades, and degraded motion correction with wide blades. We show that a novel reconstruction method - multi-step join-blade (MJB) SENSE can lead to higher SNR and less narrow-blade artifact than conventional SENSE reconstruction. In addition, k-space truncation is used to improve the motion correction robustness. We also show that additional iterations can enhance MJB SENSE. This new method can greatly benefit future SENSE PROPELLER studies with improved image quality. 

Yanqiu Feng^1,2,3, Mengye Lyn^1,2, Yilong Liu^1,2, Victor X Bin^1,2, and Ed X Wu^1,2
1Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong SAR, China, People's Republic of, ²Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong SAR, China, People's Republic of, ³School of Biomedical Engineering and Guangdong Provincial Key Laboratory of Medical Image Processing, Southern Medical University, Guangzhou, China, People's Republic of

This work develops a novel super slice interpolation (SSI) method that exploits sensitivity variation along the slice direction to decrease slice thickness in multi-slice MRI. The phantom and in vivo head imaging results demonstrate that SSI successfully generates thinner slice images from a set of thick images acquired with multiple receiver coils, without the need of modifying pulse sequences. The proposed SSI method has potential to obtain more slices with decreased thickness in scenarios where acquisition window or specific absorption rate limits the available number of slices.

Jingyuan Lyu¹, Ukash Nakarmi¹, Yihang Zhou¹, Chaoyi Zhang¹, and Leslie Ying^1,2
1Electrical Engineering, The State University of New York at Buffalo, Buffalo, NY, United States, ²Biomedical Engineering, The State University of New York at Buffalo, Buffalo, NY, United States

This abstract presents a novel reconstruction method for parallel imaging that does not require auto-calibration data. The method formulates the image reconstruction problem as a multichannel blind deconvolution problem in k-space where the data are randomly undersampled in all channels. Under this formulation, the k-spaces of the desired image and coil sensitivities are jointly recovered by finding a rank-1 matrix subject to the data consistent constraint. Experimental results demonstrate that the proposed method is able to achieve better reconstruction results than the state-of-the-art calibration-less parallel imaging methods.

Jisu Hu^1,2, Zhigang Wu³, Wenxing Fang³, Ming Li⁴, Bing Zhang⁴, and Feng Huang^3
1Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou, China, People's Republic of, ²The Laboratory for Medical Electronics, School of Biological Sciences and Medical Engineering, Southeast University, Nanjing, China, People's Republic of, ³Philips Healthcare, Suzhou, China, People's Republic of, ⁴Department of Radiology, the Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, China, People's Republic of

A new reconstruction method is presented for high-resolution DWI in zoomed FOV imaging with parallel acquisitions. this method can reduce noise and artifact in the reconstructed images compared to conventional SENSE magnitude average.

José P. Marques¹ and David G. Norris^1
1Donders Centre for Cognitive Neuroimaging, Radboud University, Nijmegen, Netherlands

To improve the conditioning of GRAPPA enabled in-plane acceleration by using phase encoding shifts of spatially neighbouring slices. Parallel imaging offers the possibility to reduce acquisition time or echo train lengths needed to fully encode a given object. New k-space trajectories and reconstruction techniques offer the possibility of large acceleration factors in the slice direction (in the case of SMS) or in either of the two phase encoding directions in volumetric imaging. While 2D and 3D reconstructions can be seen on a common framework, it is not straightforward to, in conventional multi-slice imaging, have more than 3-4 fold inplane acceleration.

Arjan D. Hendriks¹, Cezar B.S. Alborahal², Michel G.M. Italiaander², Dennis W.J. Klomp^1,2, and Natalia Petridou^1
1Department of Radiology, University Medical Center Utrecht, Utrecht, Netherlands, ²MR Coils B.V., Drunen, Netherlands

There is an overall drive to high speed, high resolution brain MRI. High density receive arrays have proven to be a very valuable tool in this process. However, alternative acquisition strategies like 2DCAIPIRINHA have shown to be highly effective in acceleration. We investigated whether a 256ch high density receive array with or without 2DCAIPIRINHA can still outperform a 32ch array with 2DCAIPIRINHA.

Yulin V Chang¹, Marta Vidorreta², Ze Wang³, and John A Detre^2
1Radiology, University of Pennsylvania, Philadelphia, PA, United States, ²Neurology, University of Pennsylvania, Philadelphia, PA, United States, ³Hangzhou Normal University, Hangzhou, Zhejiang, China, People's Republic of

In SPIRiT image reconstruction the kernel usually consists of all elements within a square. The number of elements in such a kernel increases rapidly as the kernel size increases, especially for 3D reconstructions. Thus, a large kernel requires a sizable calibration region in k-space and demands significant time for calibration. In this work we proposed and validated a new image reconstruction approach that uses a custom SPIRiT kernel geometry, which we call SPOT. We show that a SPOT kernel is much faster to compute and results in no loss of image quality compared to the traditional SPIRiT kernel.

Dallas C Turley¹ and James G Pipe^1
1Neuroimaging Research, Barrow Neurological Institute, Phoenix, AZ, United States

DSC-MRI requires high temporal resolution to accurately measure perfusion parameters in vivo. Using GRAPPA parallel imaging, it is possible to achieve whole-brain coverage while maintaining high temporal sampling.  The proposed method combines a 3D dual echo spiral sequence with through-time GRAPPA for whole-brain coverage with < 1 second temporal resolution.

Gaojie Zhu¹, Hai Luo¹, Bin Wang¹, Xiang Zhou¹, and Leping Zha^1,2
1Advanced Application, Alltech Medical Systems, Chengdu, China, People's Republic of, ²Advanced application, Alltech Medical Systems America, Cleveland, OH, United States

Simultaneous multi-slice (SMS) acquisitions with SENSE reconstruction rely greatly on the fidelity of coil sensitivity maps. Due to the difficulty on choosing polynomial orders, traditional polynomial fitting method often results in residual spatial oscillations or influence from imaging content, which compromise the reconstruction quality. ESPIRiT (An Eigenvalue approach to auto-calibrating parallel MRI) is a new technique to estimate sensitivity map from auto-calibration signal. It is a sub-space based method that is highly robust to many types of errors because the estimated subspace automatically adapts to inconsistencies in the data.  We propose to extend the simultaneous multi-slice imaging with ESPIRIT for higher-fidelity sensitivity distribution estimation and highly robust reconstruction.

Lucilio Cordero-Grande¹, Anthony Price¹, Jana Hutter¹, Emer Hughes¹, and Joseph V. Hajnal^1
1Center for the Developing Brain, King's College London, London, United Kingdom

A 2D CG-SENSE framework is proposed aiming at an integrated treatment of the main error sources in SMS-EPI reconstruction. Our pipeline jointly estimates the sensitivity profiles, Nyquist ghosting parameters, and image to be unfolded. In addition, an artifact-SNR tradeoff is established at a pixel level. Assessment by a phantom experiment has shown that all the main functionalities of the method do help diminish reconstruction artifacts. Stable results have been obtained when applying the framework in a large cohort of motion corrupted fMRI and DWI neonatal studies.

Weiran Deng¹, Michael Herbst¹, and V Andrew Stenger^1
1University of Hawaii JABSOM, Honolulu, HI, United States

This abstract presents a method that applies sine waveforms to the imaging gradients in radial sampling. This concept is similar controlled aliasing in Parallel Imaging (CAIPI). It enhances the encoding power of coil sensitivities by introducing spatially varying convoultion. Improvement in image quality are observed in images reconstructed from undersampled (R=8) wave-radial data compared to images from undersampled (R=8) radial data acquired at 3T.

Mengye Lyu^1,2, Yilong Liu^1,2, Victor B. Xie^1,2, Yanqiu Feng^1,2, Zhe Zhang³, Hua Guo³, and Ed X. Wu^1
1Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong SAR, China, People's Republic of, ²Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong SAR, China, People's Republic of, ³Department of Biomedical Engineering, Tsinghua University, Beijing, China, People's Republic of

For simultaneous multislice (SMS) PROPELLER, we propose multi-step joint-blade (MJB) SENSE reconstruction. In MJB SENSE, all blades are jointly reconstructed in three steps without relying on iterations. Compared to separately reconstructing individual blades, MJB SENSE substantially reduces noise amplification and narrow-blade artifact. MJB SENSE is also compatible with motion correction. With these advantages, MJB SENSE can be used to achieve very high MB factors in SMS PROPELLER.

Hiroshi Toyoda¹, Naoya Yuzuriha², Sosuke Yoshinaga², and Hiroaki Terasawa^2
1CiNet, National Institute of Information and Communications Technology, Suita, Japan, ²Department of Structural BioImaging, Kumamoto University, Kumamoto, Japan

We proposed an iterative reconstruction method which was effective and valid in reducing artifacts in dual-band EPI in animal scanners. This iterative reconstruction method could accurately separate collapsed k-space data acquired simultaneously from multiple slice locations. Our findings give rise to a more efficient multi-band EPI technique that can be used even with a scanner system equipped with relatively few receiver coil elements.

Erpeng Dai¹, Xiaodong Ma¹, Zhe Zhang¹, Chun Yuan^1,2, and Hua Guo^1
1Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, China, People's Republic of, ²Vascular Imaging Laboratory, Department of Radiology, University of Washington, Seattle, WA, United States

Simultaneously multi-slice (SMS) has been a powerful tool for single-shot EPI DWI acceleration, but still not well established for interleaved EPI (iEPI) DWI acceleration. The main challenge is how to effectively combine slice un-folding and inter-shot phase correction. In this study, a 3D k-space reconstruction method for navigated SMS accelerated iEPI DWI has been proposed. An optimized acquisition for navigator is designed. Then slice un-folding and inter-shot phase correction are performed in a SMS 3D k-space. The performance is compared with ssEPI and un-accelerated iEPI DWI, and has been shown to be applicable for both 4-sh and 8-sh iEPI DWI.

Klaus Eickel^1,2,3, Lutz Lüdemann³, David Porter¹, and Matthias Günther^1,2
1Fraunhofer MEVIS, Bremen, Germany, ²mediri GmbH, Heidelberg, Germany, ³University Hospital Essen, Essen, Germany

The application of simultaneous multi-slice imaging to a segmented EPI allows the acquisition of multiple contrasts while retaining sufficient temporal resolution and spatial coverage. Contrast-enhanced perfusion measurements were performed on a pig’s hip/leg resulting in mainly muscle-perfusion images with separated S₀ and T2* maps. The separation of the different signal contributions potentially allows for a quantitative analysis in contrast-enhanced dynamic imaging.

W. Scott Hoge¹, Kawin Setsompop², and Jonathan R. Polimeni^2
1Radiology, Brigham and Women's Hospital, Boston, MA, United States, ²Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States

This work presents a new approach to reconstruct SMS-EPI data that employs  Dual-Polarity GRAPPA (DPG).  DPG accurately models non-linear EPI phase errors between data sampled on positive versus negative readout gradients.  When applied to SMS-EPI data, DPG can simultaneously and robustly perform slice separation, recovery of missing data from in-plane acceleration, and slice-specific ghost correction.  Phantom and in vivo results are compared to a conventional SMS reconstruction, and demonstrate that DPG reduces residual ghosts and ghosting-related phase interference artifacts.

Huihui Ye^1,2, Berkin Bilgic¹, Stephen Cauley¹, Borjan Gagoski³, Jianghui Zhong², Yiping Du², Lawrence L. Wald¹, and Kawin Setsompop^1
1MGH/A.A. Martinos Center for Biomedical Imaging, Charlestown, MA, United States, ²Zhejiang University, Hangzhou, China, People's Republic of, ³Boston Children's Hospital, Charlestown, MA, United States

Susceptibility weighted FLASH imaging provides exquisite soft tissue contrast at high spatial resolution and low distortion, but at a cost of lengthy acquisition time. In this work, we developed a highly efficient Echo-Shift wave-CAIPI technique and demonstrated its ability to provide 18-fold acceleration for FLASH acquisitions with minimal noise and artifact penalties. Instead of conventional single slice or slab echo-shift, we propose an echo-shift Simultaneous MultiSlice method to enable improved controlled aliasing and desirable volumetric noise averaging while avoiding slab edge artifacts. With this technique, we demonstrated high-quality 1.5 mm isotropic whole-brain susceptibility weighted FLASH at 3T and 7T in 36s. 

V. Andrew Stenger¹, Weiran Deng¹, Michael Herbst¹, and Andrii Petrov^1
1John A Burns School of Medicine, University of Hawaii, Honolulu, HI, United States

This abstract presents a circular echo planar imaging sequence for simultaneous multi-slice imaging. A generalized SENSE reconstruction framework with ghost correction was utilized. Different sampling strategies including wave modulation, blipped-CAIPI, and hexagonal were examined. Phantom as well as human fMRI scanning at 3T are shown.

Kangrong Zhu¹, Hua Wu², Robert F. Dougherty², Matthew J. Middione³, John M. Pauly¹, and Adam B. Kerr^1
1Electrical Engineering, Stanford University, Stanford, CA, United States, ²Center for Cognitive and Neurobiological Imaging, Stanford University, Stanford, CA, United States, ³Applied Sciences Laboratory West, GE Healthcare, Menlo Park, CA, United States

Several parallel imaging reconstruction algorithms have been proposed for simultaneous multi-slice (SMS) imaging, yet a thorough comparison of the algorithms still awaits investigation. In this study, the performance of four reconstruction algorithms are compared. Relative root-mean-squared error, g-factor, signal leakage, and reconstruction time are used as metrics for evaluating the performance. This work may provide a reference for the SMS community to choose from different reconstruction algorithms.

Anthony N Price^1,2, Shaihan J Malik², Jana Hutter², Martin Bührer³, Lucilio Cordero-Grande², Rui Teixeira², Emer J Hughes¹, Mary A Rutherford¹, and Joseph V Hajnal^1,2
1Centre for the Developing Brain, King's College London, London, United Kingdom, ²Biomedical Engineering, King's College London, London, United Kingdom, ³GyroTools, Zurich, Switzerland

Single-shot Turbo Spin-Echo (ss-TSE) sequences can provide excellent anatomical images of the fetal brain. However, due to the surrounding maternal tissue, full field of view encoding leads to long echo train lengths, impacting efficiency, causing high SAR and increased risk of motion artefact. In this abstract we present the implementation of multiband accelerated ss-TSE of the fetal brain, with a zoom variant that reduces both overall scan time and the need to encode a large FOV. In addition simultaneous sampling multiple slice locations should benefit the image registration step in subsequent 3D slice-to-volume reconstructions.

Anthony N Price¹, Jana Maria Hutter¹, Lucilio Cordero Grande¹, Emer Judith Hughes¹, Kelly Pegoretti¹, Andreia Oliveira Gaspar¹, Laura McCabe¹, Mary Rutherford¹, and Joseph V Hajnal^1
1Centre for the developing brain, King's College London, London, United Kingdom

This abstract demonstrates combined multiband and multiplex imaging for fetal EPI based sequences such as used in diffusion and functional MRI. This application lends itself naturally to multiplex imaging, due to PNS and noise restrictions, EPI readout speeds are inherently limited so offsets the inevitable TE penalty from multiplex imaging.

Ting Zhang¹, Congbo Cai², Lin Chen¹, Jianpan Huang¹, and Shuhui Cai^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

As a recently launched method, spatiotemporally encoded (SPEN) magnetic resonance imaging (MRI) has been broadened from single-slice scan to multi-slice scan. A new single-shot multi-slice full-refocusing SPEN MRI sequence was proposed. By utilizing a segment-selective pulse and a 180° chirp pulse and sequentially acquiring the signals of every slice among the encoded segment, the new method can lower the specific absorption rate (SAR) and improve the image quality compared to the existing one. Experimental results of phantom and in vivo rat brain verified the above conclusion.

Jenni Schulz¹, Lauren J Bains¹, José P Marques¹, and David G Norris^1
1Donders Institute for Cognitive Neuroimaging, Radboud University Nijmegen, Nijmegen, Netherlands

HASTE sequences have high RF power deposition which particularly limits their use at high resolutions and high field strengths. In this work,  TRAPS and fixed SAR Power Independent of Number of Slices (PINS)-refocusing pulses were used to reduce the power deposition.  Multiband excitation pulses were added to enable arbitrary user-defined slice orientations, with the added benefit of accelerating the acquisition due to the simultaneous excitation of multiple slices.  Good image quality was obtained for a MB4-HASTE protocols with 3.1 and 1.1 mm resolution, and a whole-brain MB6-HASTE protocol with 1.1 mm resolution.

Naoharu Kobayashi¹, Kamil Ugurbil¹, and Xiaoping Wu^1
1CMRR, Radiology, University of Minnesota, Minneapolis, MN, United States

Current high resolution, whole brain diffusion MRI protocol at 7T for the Human Connectome Project uses linear phase multiband (MB) refocusing pulses that have duration longer than 10 ms. Recent studies show that shorter duration can be obtained by designing nonlinear phase MB refocusing pulses. In this study, we designed root-flipped MB and hyperbolic secant (HS1) based MB refocusing pulses and investigated how the variable rate selective excitation (VERSE) principle can be used to further reduce the pulse duration. Our results suggest that both root-flipped and HS1 based MB refocusing pulses can be shortened by VERSE.

Adam Scott Bernstein¹, Derek Pisner², Aleksandra Klimova², Lavanya Umapathy³, Loi Do¹, Scott Squire⁴, Scott Killgore², and Theodore Trouard^1
1Biomedical Engineering, University of Arizona, Tucson, AZ, United States, ²Psychiatry, University of Arizona, Tucson, AZ, United States, ³Electrical and Computer Engineering, University of Arizona, Tucson, AZ, United States, ⁴Radiology, University of Arizona, Tucson, AZ, United States

Multiband imaging allows for greater imaging speeds when collecting diffusion weighted MR images.  As shown in this work, this saving in time results in small changes in several stages of diffusion image processing including tensor fitting and the associated calculation of scalar values such as FA, fiber orientation distribution calculation as in constrained spherical deconvolution, and tractography.

Rasim Boyacioglu^1,2, Jenni Schulz¹, and David G. Norris^1,3
1Radboud University, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, Netherlands, ²Radiology, Case Western Reserve Univesity, Cleveland, OH, United States, ³Erwin L. Hahn Institute, University Duisberg-Essen, Essen, Germany

Multiband Echo-Shifted EPI (MESH) is a combination of echo shifted 2D multi-slice EPI, in-plane and multiband acceleration. An additional EPI readout is inserted in the dead-time between slice selection and the multiband EPI readout. It is useful especially for low static magnetic field strengths (long optimal TE) and lower spatial resolutions (short EPI readout). It is shown that echo shifting gradients do not affect tSNR. Compared to standard and multiband EPI similar RS fMRI results are obtained at the group and individual subject level. MESH offers a further acceleration in image acquisition for fMRI at no loss in sensitivity.

Giulio Ferrazzi¹, Rui Pedro A. G. Teixeira¹, Jana M. Hutter¹, Lucilio Cordero-Grande¹, Emer Hughes¹, Anthony N. Price¹, and Joseph V. Hajnal^1
1Centre for the Developing Brain, Department of Perinatal Imaging and Health, King's College London, London, United Kingdom

Multislice multishot Inversion Recovery sequences as implemented in standard systems are often not optimized for efficiency. This becomes a critical factor when imaging neonates, where T1 is longer and the Inversion Time needs to increase to maintain the desired contrast. In this study, we have optimized a standard Inversion Recovery sequence and used it for an optimised neonatal protocol. The proposed sequence provides a total scan time reduction of 44% with identical imaged contrast and resolution.

Benjamin Zahneisen¹, Murat Aksoy¹, Julian Maclaren¹, Christian Wuerslin¹, and Roland Bammer^1
1Stanford University, Stanford, CA, United States

Simultaneous-Multi-Slab-Imaging is a promising approach for high resolution DW-EPI (<1mm) where the slice profile of a typical multi-band RF-pulse limits the spatial resolution for single-shot DW-EPI. Like every multi-band technique, slab separation during a parallel imaging reconstruction requires a combination of coil sensitivity variation and k-space encoding. The most prominent way is blipped-CAIPIRINHA where k-space encoding along the slice direction is achieved by adding small gradient blips in z-direction to the EPI readout. Here we demonstrate how multi-band RF phase modulation can be used as an alternative way to encode along the slab dimension without affecting intra-slab phase encoding. The use of phase modulated RF-pulses decouples encoding between the logical intra- and inter-slab directions that are otherwise linked because there is only one physical z-gradient axis.

Andrii Y Petrov¹, Michael Herbst^1,2, and V Andrew Stenger^1
1Department of Medicine, University of Hawaii, Honolulu, HI, United States, ²Department of Radiology and Medical Physics, University Medical Center Freiburg, Freiburg, Germany

Sub-second whole brain imaging using Simultaneous Multi-Slice (SMS) imaging is of particular interest in Blood Oxygen Level Dependent (BOLD) functional Magnetic Resonance Imaging (fMRI). Faster acquisitions with higher temporal sampling of the BOLD time course provides several advantages including increased sensitivity in detecting functional activation,  the possibility of filtering out physiological noise for improving temporal SNR, and freezing out head motion. The most commonly used strategy to accelerate image acquisition time using SMS involves using parallel imaging methods. We propose to accelerate SMS imaging by under sampling the number of excited slices in the k_z-t domain and L+S matrix decomposition method for reconstruction of slice aliased functional images. We  present human fMRI results at 3T using 3D spiral sampling with SMS excitation and L+S reconstruction of the aliased slice data.

Sebastian Rosenzweig¹ and Martin Uecker^1,2
1Department of Diagnostic and Interventional Radiology, University Medical Center Göttingen, Göttingen, Germany, ²German Centre for Cardiovascular Research (DZHK), University Medical Center Göttingen, Göttingen, Göttingen, Germany

Multiband MRI can be used to acquire several slices at the same time. Here, we propose a new method of multiband MRI based on Regularized Nonlinear Inversion (NLINV). This method does not require a priori knowledge about the coil sensitivities. Simultaneous estimation of images and coil sensitivities of two slices is demonstrated from six-fold undersampled data for a simulated multi-band acquisition.

John Grinstead¹, Valerie Anderson², Manoj Sammi², and William Rooney^2
1Siemens Healthcare, Portland, OR, United States, ²Oregon Health & Science University, Portland, OR, United States

Parametric T₁ mapping using inversion recovery has competing requirements for speed, SNR, spatial resolution, anatomical coverage, and adequate sampling of the longitudinal magnetization recovery. Potential sources of slice-to-slice variability in quantitative T₁ maps are investigated, including slice cross talk due to imperfect slice profiles, and the range of TIs used to fit each slice. It is demonstrated that T₁ relaxometry benefits significantly from slice acceleration techniques in not only scan time & slice coverage, but in its ability to reduce quantitative errors by allowing the same TI sampling across all slices. 

Steen Moeller¹, Sebastian Schmitter¹, and Mehmet Akcakaya^1,2
1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States, ²Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, United States

An investigation into the noise and resolution performance of SLIDER using a series of shifted low-resolution images to obtain a single high-resolution. The evaluation is performed both theoretical and experimentally using a FLASH acquisition, to remove experimental limitations from understanding the merits of the technique.

Dingxin Wang^1,2, Xiufeng Li², Xiaoping Wu², and Kamil Ugurbil^2
1Siemens Healthcare, Minneapolis, MN, United States, ²Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States

Dixon technique requires at least two images with different echo times, which increases TSE echo spacing and TR, and therefore prolongs total acquisition time. Slice acceleration may help improve imaging efficiency of TSE fat-water Dixon imaging. In this study, we develop a multiband slice accelerated TSE Dixon sequence and demonstrate the feasibility of SMS TSE Dixon acquisition for efficient T2-weighted fat-water imaging.

Jorge E Jimenez¹, Kevin M Johnson¹, Leah C Henze Bancroft¹, Diego Hernando², Roberta M Strigel^1,2, Scott B Reeder^2,3, and Walter F Block^1,2,3
1Department of Medical Physics, University of Wisconsin-Madison, Madison, WI, United States, ²Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States, ³Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States

We present a 3D T1-Weighted radial trajectory suited to work with IDEAL fat/water separation. Some relevant characteristics are: rapid acquisition, reliable fat suppression, and high resolution despite significant data undersampling. The method is demonstrated in 3T bilateral breast MR imaging where isotropic resolution of 0.8 mm is achieved. In addition, we show the value of high count channel array for breast imaging.

Stefan Ruschke¹, Holger Eggers², Hendrik Kooijman³, Houchun H. Hu⁴, Ernst J. Rummeny¹, Axel Haase⁵, Thomas Baum¹, and Dimitrios C. Karampinos^1
1Department of Diagnostic and Interventional Radiology, Technische Universität München, Munich, Germany, ²Philips Research, Hamburg, Germany, ³Philips Healthcare, Hamburg, Germany, ⁴Radiology, Phoenix Children’s Hospital, Phoenix, AZ, United States, ⁵Zentralinstitut fu¨r Medizintechnik, Technische Universität München, Garching, Germany

As the spatial resolution of a multi-echo gradient-echo imaging sequence increases, the echo time step increases resulting in an increased echo time step and an echo time selection that degrades the noise performance of water-fat separation. Time-interleaved gradient echo imaging combined with bipolar (flyback) gradients can achieve reasonable echo time steps at high resolution without dramatically increasing scan time. However, bipolar gradients are associated with known phase errors problems, which can lead to fat quantification errors. The present work develops a methodology for acquiring bipolar time interleaved multi-echo gradient echo data and for correcting the relevant phase errors.

Ken-Pin Hwang¹, Jingfei Ma¹, Lloyd Estkowski², Ann Shimakawa², Kang Wang², Daniel Litwiller², Zachary Slavens², Ersin Bayram², and Bruce Daniel^3
1Department of Imaging Physics, The University of Texas M.D. Anderson Cancer Center, Houston, TX, United States, ²MR Applications and Workflow, GE Healthcare, Waukesha, WI, United States,³Department of Radiology, Stanford University, Stanford, CA, United States

Separation of silicone, fat, and water is performed by using a two-step Dixon processing algorithm and a bipolar triple-echo readout in a 3D FSE sequence. The echoes are spaced for conventional water-fat separation, but the first and last echoes are also used to generate a phase map with double the phase evolution for resolving fat from silicone, which are relatively close in terms of chemical shift. Individual images of each of the three species are reconstructed in phantom and human data. The proposed method demonstrates improved SNR efficiency and robustness to field inhomogeneity compared to conventional saturation and inversion recovery techniques.

Holger Eggers¹, Liesbeth Geerts-Ossevoort², Gert Mulder², and Clemens Bos^3
1Philips Research, Hamburg, Germany, ²Philips Healthcare, Best, Netherlands, ³Imaging Division, University Medical Center Utrecht, Utrecht, Netherlands

The robustness of Dixon methods often deteriorates close to large main field inhomogeneity. To resolve this problem, the exploitation of prior knowledge of magnet imperfections is considered in this work. Magnet-induced main field inhomogeneity is modeled to predict and correct spatial variations of the phase in single-echo images before the separation of water and fat signal. Improved fat suppression is demonstrated with this approach in first-pass peripheral angiography, in particular in the corners of the large FOVs.

Stephen Bawden^1,2, Carolyn Chee³, Caroline Hoad¹, Guruprasad Aithal², Ian Macdonald³, Richard Bowtell¹, and Penny Gowland^1
1Sir Peter Mansfield Imaging Centre, University of Nottingham, Nottingham, United Kingdom, ²NIHR Nottingham Digestive Diseases Research Unit, University of Nottingham, Nottingham, United Kingdom, ³School of Life Sciences, University of Nottingham, Nottingham, United Kingdom

This study compared hepatic fat fraction measured using MRS and gradient echo MRI at 3T. Fitting algorithms using a single fat peak and multiple fat peaks were compared with MRS data at TE=20ms and also T2-corrected MRS. Individual differences between T2 values of water and fat calculated from MRS were also used to estimate the difference between R2*-water and R2*-fat and included in the multi peak fitting per subject. The results showed a good correlation between multi-peak and MRS data (R² = 0.9), but applying T2-correction to MRS increased the scatter (R² = 0.67) and systematic error (gradient = 1.34). Using the new R2* corrected fitting algorithm resulted in similar scatter (R² = 0.66) but improved systematic error (gradient = 1.09). The results from this study indicate the dual-R2* fitting is important at 3T and further developments should be made to optimize these methods.

Laura Jane King¹, Rick Millane¹, Hans Weber², Brian Hargreaves², and Phil Bones^1
1Electrical and Computer Engineering, University of Canterbury, Christchurch, New Zealand, ²Radiology, Stanford University, Stanford, CA, United States

Being able to perform robust Dixon imaging near metal implants would allow for improved contrast-enhanced fat suppression. This requires accurate calculation of the phase shift due to the B0 field variation. We present a new technique where the phase is first estimated at the outer edges of the image. The method works inwards along a set of adjacent paths, finishing at the boundary of the implant. The described method is used to successfully separate fat and water in the vicinity of a titanium hip replacement, with phantom results shown.

Felix Lugauer^1,2, Dominik Nickel³, Stephan A. R. Kannengiesser³, Samuel Barnes⁴, Barbara Holshouser⁴, Jens Wetzl¹, Joachim Hornegger¹, and Andreas Maier^1,2
1Pattern Recognition Lab, Department of Computer Science, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany, ²Research Training Group 1773 “Heterogeneous Image Systems”, Erlangen, Germany, ³MR Applications Predevelopment, Siemens Healthcare GmbH, Erlangen, Germany, ⁴Department of Radiology, Loma Linda University Medical Center, Loma Linda, CA, United States

Magnitude-based parameter fitting is commonly used for relaxometry and multi-echo Dixon but introduces a bias for relaxation and fat fraction estimates, particularly for a low signal-to-noise ratio and high relaxation. The application of an automated, patchwise denoising to the multi-echo image series prior to parameter fitting, considerably increased the SNR; thus, reducing the bias and standard deviation in the estimates of the fit. Our findings were validated on both numerical and in-vivo experiments.

Chuanli Cheng^1,2, Chao Zou¹, Hairong Zheng¹, and Xin Liu^1
1Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China, People's Republic of, ²University of Chinese Academy of Sciences, Beijing, China, People's Republic of

A novel two-point fat water separation method using safest path region growing with self-feeding phasor estimation algorithm is proposed. The phasor map is estimated by multiresolution region growing scheme where the seed pixels identification and region growing scheme is performed independently between coarser resolutions, avoiding the erroneous propagation between resolutions. The “self-feeding” mechanism when merging the phasor maps ensures the reliability of seed pixels selection at the finest resolution. The algorithm was tested on c-spine and abdomen data and shown to be robust in fast varying field and disjoint areas.

Johan Berglund¹, Henric Rydén¹, and Mikael Skorpil^1
1Karolinska University Hospital, Stockholm, Sweden

An imaging method for mapping Fatty Acid Composition using three triglyceride spectrum model parameters (FAC3) was modified into mapping Fatty Acid Composition with only one spectrum model parameter (FAC1), namely the average number of double bonds per triglyceride (ndb). Images of a patient with a lipoma were reconstructed using both methods. The FAC3 ndb map showed large-scale variation from left to right, giving significant variation between subcutaneous adipose tissue locations. Measurements from the FAC1 ndb map were consistent within the adipose tissue, offering a higher level of confidence and more precise measurements.

Chen Cui¹, Abhay Shah¹, Cameron M. Cushing², Vince Magnotta³, Xiaodong Wu^1,2, and Mathews Jacob^1
1Electrical and Computer Engineering, University of Iowa, Iowa City, IA, United States, ²Radiology Oncology, University of Iowa Hospitals and Clinics, Iowa City, IA, United States, ³Radiology, University of Iowa Hospitals and Clinics, Iowa City, IA, United States

Phase wrapping is a classic problem in many fields of study. In MRI, Unwrapping the phase in the estimation of B0 field inhomogeneity maps is challenging commonly due to the presence of a large field inhomogeneity, anatomical discontinuities or low SNR in certain regions of the map (e.g. boundaries). We propose a general phase unwrapping method that exploits the smoothness of the field map in three spatial dimensions. The method is solved using a linear-convex constrained graph search algorithm that provides the globally guaranteed optimal solution without over-smoothing effect. The proposed scheme aims to produce a robust solution for field map estimation that will further improve the quality of quantitative susceptibility mapping (QSM). 

James H Holmes¹, Diego Hernando², Kang Wang¹, Ann Shimakawa³, Nate Roberts², and Scott B Reeder^2,4,5,6
1MR Applications and Workflow, GE Healthcare, Madison, WI, United States, ²Radiology, University of Wisconsin-Madison, Madison, WI, United States, ³MR Applications and Workflow, GE Healthcare, Menlo Park, CA, United States, ⁴Medical Physics, University of Wisconsin-Madison, Madison, WI, United States, ⁵Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States,⁶Emergency Medicine, University of Wisconsin-Madison, Madison, WI, United States

Multi-echo chemical shift encoded techniques provide accurate fat quantification over a broad range of fat-fractions and acquisition parameters. In order to be accurate, these techniques must correct for all relevant confounding factors. Emerging applications (eg: fat quantification with high spatial resolution or in iron overloaded tissues) can result in data with significantly lower signal-to-noise ratio (SNR) compared to previously established applications. In this work, we characterize the accuracy of current noise bias correction techniques for fat quantification in the low SNR regime and show simple modifications may enable accurate fat quantification for a wider range of SNR. 

Samir D. Sharma¹, Diego Hernando¹, Takeshi Yokoo², Mustafa R. Bashir^3,4, Jean Shaffer^3,4, Qing Yuan², Stefan Ruschke⁵, Dimitrios C. Karampinos⁵, Jean H. Brittain¹, and Scott B. Reeder^1,6
1Radiology, University of Wisconsin - Madison, Madison, WI, United States, ²Radiology, UT Southwestern Medical Center, Dallas, TX, United States, ³Radiology, Duke University, Durham, NC, United States, ⁴Center for Advanced Magnetic Resonance Development, Duke University, Durham, NC, United States, ⁵Diagnostic and Interventional Radiology, Technische Universität München, Munich, Germany, ⁶Medical Physics, University of Wisconsin-Madison, Madison, WI, United States

The need for rapid and non-invasive assessment of fat and iron deposition has become increasingly important given the high prevalence of obesity and obesity-related comorbidities as well as the need for monitoring chelation treatment in patients with iron overload. Recent advances in gradient-echo imaging have enabled the simultaneous quantification of fat and iron concentrations throughout the body. To ensure fidelity of these quantitative techniques, validation studies must be performed, ideally with initial testing in phantoms.  In this work, we report on the development of a water-fat-iron MRI phantom that exhibits single-R2* decay, with controllable proton-density fat fraction (PDFF) and iron concentration. The purpose of this work is: 1) to describe the development of the water-fat-iron phantom, and 2) to assess the multi-center, multi-vendor reproducibility of joint fat and iron quantification using this phantom.

Junying Cheng^1,2, Yingjie Mei^2,3, Biaoshui Liu², Xiaoyun Liu¹, Ed. X. Wu^4,5, Wufan Chen^1,2, and Yanqiu Feng^2,4,5
1School of Automation Engineering, University of Electronic Science and Technology of China, Chengdu, China, People's Republic of, ²School of Biomedical Engineering and Guangdong Provincial Key Laboratory of Medical Image Processing, Southern Medical University, Guangzhou, China, People's Republic of, ³Philips Healthcare, Guangzhou, China, People's Republic of, ⁴Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong SAR, China, People's Republic of, ⁵Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong SAR, China, People's Republic of

Current phase-unwrapping algorithms are challenged by rapid phase variations, noise and disconnected regions. We propose a novel phase-unwrapping method based on the observation the phase local difference (pLD) and complex local difference (cLD) maps.  The proposed  algorithm first clusters pixels into disconnected regions by thresholding the cLD map and then performs local polynominal surface fitting (LPSF) to unwrap phase with the knowledge of wrapping locations identified by thresholding the pLD map. Both simulation and in vivo results demonstrate that the proposed method can correctly unwrapped phase even in the presence of rapid phase variation, low SNR, and disconnected regions, and has great potential application to phase-related MRI in practice.

Holger Eggers^1
1Philips Research, Hamburg, Germany

Chemical shift encoding-based water-fat imaging, or Dixon imaging, is of recent interest in MRA. Single-echo Dixon methods are particularly appealing for this application because of their potential for decreasing scan times. This work suggests modifications to existing single-echo Dixon methods and demonstrates their benefits, primarily improvements in SNR and CNR, in contrast-enhanced peripheral MRA.

Steve Cheuk Ngai Hui¹, Teng Zhang¹, Defeng Wang¹, and Winnie Chiu Wing Chu^1
1Dept. of Imaging and Interventional Radiology, The Chinese University of Hong Kong, Hong Kong, Hong Kong

This abstract introduces the use of wheel-template to perform segmentation on subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) at the abdominal region. The proposed method detects narrow regions between SAT and VAT, and uses line cut to separate two types of tissues based on MRI data. It performs well on obese individuals and the obtained results are correlated to those obtained from a semi-automatic method. A quantitative measurement of SAT and VAT is important as they are developed from different pathways and suggested to be related to different chronic diseases.

Jonathan Andersson¹, Filip Malmberg¹, Håkan Ahlström¹, and Joel Kullberg^1
1Radiology, Uppsala University, Uppsala, Sweden

When reconstructing chemical shift encoded water-fat images so called water-fat swaps due to incorrect phase maps can be a significant problem, limiting clinical assessment and quantitative measurements. A method is presented for solving the problem in the case of 3 echoes, assuming only a fix intra-echo spacing.  Two possible solutions are analytically calculated for each voxel. The correct global solution is then found using a graph-cut method. The method succeeds where a region-growing reference method fails at low SNR. The presented method runs quickly and uses only one parameter that can be set automatically, which should allow for online implementation. 

Victor B. Xie^1,2, Mengye Lyu^1,2, Yilong Liu^1,2, Yangqiu Feng^1,2, Hua Guo³, and Ed X. Wu^1,2
1Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong SAR, China, People's Republic of, ²Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong SAR, China, People's Republic of, ³Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, China, People's Republic of

In this abstract, we proposed to use parallel imaging method to remove the fat residue in EPI applications.  In EPI, fat is shifted along the phase encoding direction and can be treated as another simultaneously exited slice with controlled aliasing together with the water image. By applying SENSE, water and fat residue can be effectively separated. We have presented this simple method to separate water and fat in EPI images and successfully applied it to remove fat residue in the brain and abdomen fat-suppressed EPI and DW-EPI images.

Gregory Simchick¹, Jinjian Wu², Guangming Shi², Hang Yin³, and Qun Zhao^1
1Bioimaging Research Center, University of Georgia, Athens, GA, United States, ²Xidian University, Xian, China, People's Republic of, ³Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, United States

Differentiation of brown adipose tissue (BAT) from white adipose tissue (WAT) using magnetic resonance imaging (MRI) is clinically important to treat obesity, diabetes and heart disease. In contrast to the traditional Dixon model of single fat- and water-peak or fixed multi-fat-peak models, we propose a Multi-Varying-Peaks MR Spectroscopic (MVP-MRS) model, based on MR imaging data acquired with multiple echoes, to better characterize chemical structures of the fatty acid (saturated vs. unsaturated). Compared with traditional classification of BAT and WAT using fat fraction or proton relaxation time,  the proposed MVP-MRS model can achieve a correct classification rate of 95% between BAT and WAT for in vivo mouse data implying great potentials in future longitudinal imaging of BAT and WAT. 

Lena Trinh¹, Emelie Lind¹, Pernilla Peterson¹, and Sven Månsson^1
1Dept. of Translational Medicine, Medical Radiation Physics, Skåne University Hospital, Lund University, Malmö, Sweden

Chemical shift-encoded imaging is a quantitative method commonly used to estimate fat fraction (FF) in various body parts. However, for a reliable assessment, this technique requires short inter echo spacing which can be challenging if high spatial resolution is desirable. An alternative quantitative method, based on the difference in T2-relaxation time between fat and water, was examined and compared to the chemical shift-encoded imaging method. This T2-based technique successfully estimated FF in phantoms at high resolution and large matrix size, when the chemical shift-encoded method failed.

Tao Zhang^1,2, Yuxin Chen³, Marcus Alley¹, Brian Hargreaves^1,2, John Pauly², and Shreyas Vasanawala^1
1Radiology, Stanford University, Stanford, CA, United States, ²Electrical Engineering, Stanford University, Stanford, CA, United States, ³Statistics, Stanford University, Stanford, CA, United States

Dixon techniques offer robust water/fat separation in the presence of static field inhomogeneity. Two-point Dixon imaging with flexible echo times is desirable because of its high scan efficiency and flexibility. A major challenge in two-point Dixon imaging is how to estimate the phase error resulting from field inhomogeneity. In this work, we formulate a binary quadratic optimization and propose a fast projected power method to resolve the phase ambiguity in two-point Dixon imaging.

Gabriele Beck¹, Alan Huang¹, Adri Duijndam¹, and Lars van Loon^1
1Philips Healthcare, Best, Netherlands

While Dixon provides superb fat suppression over large imaging volumes, motion can be a challenge in specific anatomies. This work evaluates a comprehensive approach to reduce motion artifacts in Dixon TSE and FFE sequences, combining a novel Dixon decorrelation approach, partial averaging, modulus in-phase (IP) – out-phase (OP) combinations and saturation of the physiological motion artifact sources by the means of saturation pulses and variable refocusing flip angle sweeps. We are able to show that this approach allows us to effectively remove motion artifacts improving the diagnostic quality of Dixon scans.

Shivani Kumar^1,2,3, Robba Rai², Daniel Moses^1,4, Armia George^2,3, Lois Holloway^1,2,3,5,6, Shalini VInod^1,2, and Gary Liney^1,2,3,7
1The University of New South Wales, Sydney, Australia, ²Liverpool Cancer Therapy Centre, Liverpool, Australia, ³Ingham Institute of Applied Medical Research, Liverpool, Australia, ⁴Prince of Wales Hospital, Randwick, Australia, ⁵Institute of Medical Physics, University of Sydney, Sydney, Australia, ⁶Centre for Medical Radiation Physics, University of Wollongong, Wollongong, Australia, ⁷University of Wollongong, Wollongong, Australia

Dynamic contrast enhanced (DCE) MRI is becoming an increasingly important tool for assessing tumour response, however it's application in lung  is limited by respiratory motion. We propose the use of radial acquisition technique to minimise motion by oversampling the centre of k-space albeit with reduced temporal resolution. The initial results show that the radial k-space trajectory is a suitable method for motion compensation which provided a DCE scan of sufficient image quality and temporal resolution which can be used as part of a complete free breathing lung MRI protocol.   

Eddy Solomon¹, Gilad Liberman¹, Noam Nissan², and Lucio Frydman^1
1Chemical Physics Department, Weizmann Institute of Science, Rehovot, Israel, ²Biological Regulation Department, Weizmann Institute of Science, Rehovot, Israel

A recently proposed single-shot MRI methodology, SPatio-temporal ENcoding (SPEN), was evaluated for its usefulness in DTI experiments. SPEN’s direct image acquisition is not bound by k-space sampling criteria, thereby enabling the use of stronger gradients during its monitoring of the low-bandwidth dimension.  This helps it to overcome image distortions arising from field inhomogeneities, eddy currents and heterogeneous chemical environments. Single-shot and interleaved DTI SPEN measurements were tested under various pre-clinical and clinical settings, and the formalism needed to extract reliable DTI maps from SPEN data was derived. Substantial advantages in terms of overcoming EPI distortions were observed.

Christopher L Lankford¹ and Mark D Does^1,2
1Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, ²Electrical Engineering, Vanderbilt University, Nashville, TN, United States

This abstract provides a simple criterion by which to determine whether refocusing pulse flip angle should be fitted or constrained to a measured B₁⁺ map in multiple spin echo (MSE) based T₂ mapping protocols. Using propagation of error theory including the Cramér-Rao lower bound, it was discovered that T₂ estimate precision is improved through constraint when the signal-to-noise ratio (SNR) of the B₁⁺ map is at least one-half the SNR of the MSE measurement. The accuracy cost of constraint is also evaluated and presented.

Yasuhiko Terada^1
1Institute of Applied Physics, University of Tsukuba, Tsukuba, Japan

NMR microscopy provides a variety of image contrast with a high spatial resolution. However, 3D NMR multi-parameter mapping with large matrix sizes is time consuming and practically difficult to apply to living samples. Here we introduced magnetic resonance fingerprinting (MRF) technique to 3D NMR multi-parameter microscopy, which could reduce the scan time largely. We verified the feasibility of the relaxation and proton density mapping using a vertical wide bore superconducting magnet. The 3D MRF for a grape berry provided the T1, T2, and proton density maps in the short measurement time that can be used to extract important structural information.

Eric James Keller¹, Laura Kulik², James C. Carr¹, Michael Markl^1,3, and Jeremy Douglas Collins^1
1Radiology, Northwestern University, Chicago, IL, United States, ²Gastroenterology and Hepatology, Northwestern University, Chicago, IL, United States, ³Biomedical Engineering, Northwestern University, Evanston, IL, United States

The success of surgical and transarterial therapies for hepatocellular carcinoma relies on hepatic hemodynamics. Non-contrast 4D flow MRI can quantify hepatic blood flow at the lobar arterial and portal vein levels with a low relative error and clearly evaluate portosystemic shunts; however, segmental flow quantification remains limited. By pairing 4D flow MRI with HCC surveillance MR imaging, lobar flow per volume can also be assessed, providing valuable information for surgical planning.

Anh Tu Van¹, Barbara Cervantes², Ernst J Rummeny², Axel Haase¹, and Dimitrios Karampinos^2
1Zentralinstitut für Medizintechnik, Technische Universität München, Garching, Germany, ²Diagnostic and Interventional Radiology, Technische Universität München, Munich, Germany

Diffusion-preparation is regaining popularity recently thanks to its compatibility with any type of readout scheme. Using Bloch simulations, the current work provides understanding of the motion-induced magnitude and phase modulation of the signal obtained with diffusion-prepared sequences. When motion induces a constant phase across the voxel, dephasing signal before tipping up and rephasing it before readout should be used to remove motion-induced magnitude modulation. When the induced phase is not constant, smaller voxel sizes assist towards stabilizing both magnitude and phase of the signal. In vivo data using diffusion-prepared 3D TSE are shown supporting the observations of the Bloch simulations.  

Kathryn E Keenan¹, Karl F Stupic¹, Michael A Boss¹, Stephen E Russek¹, Tom L Chenevert², Pottumarthi V Prasad³, Wilburn E Reddick⁴, Kim M Cecil⁵, Jie Zheng⁶, Peng Hu⁷, Edward F Jackson⁸, and Ad Hoc Committee for Standards in Quantitative MR^9
1Physical Measurement Laboratory, National Institute of Standards and Technology, Boulder, CO, United States, ²University of Michigan, Ann Arbor, MI, United States, ³NorthShore University Health System, Evanston, IL, United States, ⁴St. Jude Children's Research Hospital, Memphis, TN, United States, ⁵Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States, ⁶Washington University in St. Louis, St. Louis, MO, United States, ⁷University of California Los Angeles, Los Angeles, CA, United States, ⁸University of Wisconsin, Madison, WI, United States, ⁹ISMRM, Berkeley, CA, United States

We used the ISMRM/NIST system phantom to assess variations of T1 measurements across MRI systems at 1.5 T and 3 T, to determine the repeatability and reproducibility of the T1 measurements. This study demonstrates that T1 variations from NMR-measured value are correlated site-to-site within a vendor and by position within the head coil. The deviation from the NMR-measured values is greater at 3 T than at 1.5 T. The VFA data has a larger variation than IR; B1 inhomogeneity could contribute to the larger systematic error in VFA measurements. The ISMRM/NIST system phantom is an excellent tool for evaluating multi-site MRI acquisition protocols.

Dharmesh Tailor, MSE, MD, PhD^1
1Radiology Specialists of Florida, Florida Hospital, Adventist Health System, Orlando, FL, United States

Accurate and precise mapping of metabolically active eloquent foci in the brain, differentiating recurrent neoplasm from pseudo-progression, differentiating tumefactive demyelination from neoplasm, delineating the actual stroke penumbra, and early detection of neurodegenerative disease, all require high-resolution imaging of underlying relative brain oxygen metabolism. At the present time, however, there is no robust technique that can map brain metabolism at a high spatiotemporal resolution. This work derives and demonstrates a model for imaging of relative CMRO₂ with T_1ρ-weighted MRI which can be readily performed on any clinical MRI scanner with a simple pulse sequence and without the need for hardware modification. This novel approach is optimized to yield a spatial resolution of 0.2 mm³ and temporal resolution of 3.2 sec, and developed to work without exogenous tracer or contrast agent administration, blood sampling, or statistical parametrization of the image data.

Yun Jiang¹, Dan Ma², Kathryn E. Keenan³, Karl Stupic³, Vikas Gulani^1,2, and Mark A. Griswold^1,2
1Department of Biomedical Engineering, Case Western Reserve University, Clevleand, OH, United States, ²Department of Radiology, Case Western Reserve University, Clevleand, OH, United States,³Physical Measurement Laboratory, National Institute of Standards and Technology, Boulder, CO, United States

In order to promote the clinical acceptance of quantitative relaxometry techniques as a valid biomarker, a fast quantitative method that can measure the relaxation parameters with high repeatability is needed. This study evaluates the repeatability of MRF with the standardized relaxometry phantom developed through collaboration between the ISMRM Ad Hoc Committee on Standards for Quantitative MR and the National Institute of Standards and Technology (NIST) over 35 consecutive days. A less than 5% variation on T₁ and T₂ estimations of MRF was observed in NIST standardized phantoms with a wide range of T1 and T2 values.

Jennifer G Whisenant¹, Richard D Dortch¹, Lori A Arlinghaus¹, William A Grissom¹, Hakmook Kang¹, and Thomas E Yankeelov^1
1Vanderbilt, Nashville, TN, United States

This study evaluated the ability of Bloch-Siegert B1 mapping to improve the accuracy and precision of variable flip angle (VFA)-derived T1 measurements of the breast at 3.0 T. Accuracy was evaluated by comparing VFA T1 values to inversion recovery measurements in a cohort of 16 healthy women. A reproducibility analysis from test-retest sessions within the same cohort was used to evaluate precision. After Bloch-Siegert B1 correction, accuracy of T1 measurements in the fat and fibroglandular tissue improved and measurement variability decreased. Thus, these results suggest that Bloch-Siegert B1 mapping is an attractive correction method for quickly obtaining accurate and precise measurements of T1 values of the breast at 3.0 T.

Dian Liu¹, Andreas Steingoetter^1,2, Jelena Curcic^1,2, and Sebastian Kozerke^1
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland, ²Division of Gastroenterology and Hepatology, University Hospital Zurich, Zurich, Switzerland

Dual and triple echo steady state (DESS and TESS) schemes have enabled rapid measurements of transverse relaxation times (T₂). However, it has been shown that TESS may result in errorneous T₂values when applied to articular cartilage. Since cartilage is a multi-compartment tissue, chemical shift-related signal fluctuations in the TESS echo modes need to be considered. The purpose of this work was to investigate the accuracy of T₂ quantification of multi-compartmental tissue using DESS and TESS based on computer simulations, in vitro and in vivo measurements. Results show that multi-compartment effects can significantly limit the accuracy of T₂ quantification and hence require careful attention.

Sulaiman A Al Hasani¹, Zhaolin Chen ², Gary F Egan², and Jingxin Zhang^3
1Department of ECSE, Monash University, Melbourne, Australia, ²Monash Biomedical Imaging, Melbourne, Australia, ³Swinburne University of Technology/School of Software and Electrical Engineering, Melbourne, Australia

Spread spectrum based encoding methods have recently been investigated to spread the energy of MR signal in k-space and hence allowing for optimal incoherent sampling and hence higher performance of CS reconstruction. In this work, we extend the use of spread spectrum based encoding to 3D GRE sequence. The proposed encoding scheme can enhance the performance of multi-receive CS reconstruction at high acceleration factors and preserve resolution of small anatomical structures and preserve susceptibility contrast for Susceptibility-weighted imaging (SWI). 

Manojkumar Saranathan¹, Puneet Sharma¹, Unni Udayasankar¹, and Rihan Khan^1
1Dept. of Medical Imaging, University of Arizona, Tucson, AZ, United States

Conventional MPRAGE imaging is an integral part of most neuroimaging protocols. We investigated a new radial fan beam ordered MPRAGE sequence for its motion robustness and compared it to conventional MPRAGE imaging on 29 patients. The radial fan beam ordering had significantly better image quality than conventional centric ordered MPRAGE when rated for motion artifacts and overall diagnostic quality by 2 trained neuroradiologists.

Ayodeji L. Adams¹, Peter R. Luijten¹, and Jaco J.M. Zwanenburg^1
1Radiology, University Medical Center Utrecht, Utrecht, Netherlands

Pulsatile brain tissue motion, driven by the cardiac cycle, is important for maintaining homeostatic processes in the brain, and increased pulsatility is linked to diseases such as dementia. In this study, we demonstrate the feasibility of measuring whole brain volumetric strain with 2 mm isotropic resolution at 7T MRI in 8 healthy volunteers. Maximum volumetric strain was (2.3 ± 1.5) x 10^-3, and showed considerable inter-subject and inter-slice variability that was much larger than could be explained from intrinsic measurement errors as assessed from a gel phantom. This method has potential for studying the brain pulsatility in disease.

Romain Nicolas Froidevaux¹, Markus Weiger¹, David Otto Brunner¹, Bertram Jakob Wilm¹, Benjamin Emanuel Dietrich¹, and Klaas Paul Pruessmann^1
1Institute for Biomedical Engineering, University and ETH Zurich, Zürich, Switzerland

Often used for the imaging of compounds with short relaxation times, 3D center-out sequences performing broadband excitation on a ramped-up strong gradient provide very short acquisition delays and high bandwidth. In turn, data located around the k-space center is missed and needs to be recovered. Different approaches, like algebraic ZTE, WASPI  or PETRA are used today. An important but still open question is how the relation of the deadtime and the T2s involved affect image quality. We show that critical situations occur for similar values of deadtime and T2, frequently encountered when imaging ultra-short-T2s in solid tissues or hardware parts.

Jianping Zhong^1,2, Weiwei Ruan¹, Xianping Sun¹, Chaohui Ye^1,2, and Xin Zhou^1
1State Key Lab Magnet Resonance & Atom & Mol Phys, Wuhan Inst Phys & Math, Chinese Acad Sci, Wuhan, China, People's Republic of, ²School of Physics, Huazhong University of Science and Technology, Wuhan, China, People's Republic of

In hyperpolarized gas MRI, the accurate flip angle calibration and T₁ measurements are important. Traditional flip angle calibration methods are time-consuming and suffer from polarization losses during T₁ relaxation. In this study, we propose a method to simultaneously calibrate flip angles and measure T₁ in vivo during a breath-hold time of less than 4 seconds. The so-called single-breath method is magnitude based and simple to use. We demonstrate the accuracy of this method and contrast it with traditional methods. The results of the calibration verified that it is robust and repeatable.

Shelley HuaLei Zhang¹, Jr-Yuan George Chiou¹, Robert Vincent Mulkern¹, Pelin Aksit Ciris², Stephan Maier¹, and Lawrence Panych^1
1Radiology, Brigham and Women's Hospital, Boston, MA, United States, ²Department of Biomedical Engineering, Akdeniz University, Antalya, Turkey

Magnetic resonance spectroscopic imaging (MRSI) technique is often plagued by signal contamination (e.g. from fat) from outside the tissue of interest, particularly near organ boundaries. The goal is to demonstrate and validate in phantoms and healthy volunteers a spatial localization technique that features localized signal excitation and therefore eliminates the need for post-processing filtering. Here we demonstrated superior PSF’s at prostate-relevant metabolic peaks for a 2D Gaussian-based PSF-Choice encoding scheme. The reduction of contamination from signals in surrounding tissue was further demonstrated in an in-vitro phantom. The feasibility of the method was demonstrated in a small group of prostate MRSI studies with normal volunteers.

Bogdan Dzyubak¹, Yogesh K. Mariappan², Kevin J. Glaser¹, Sudhakar K. Venkatesh¹, and Richard L. Ehman^1
1Radiology, Mayo Clinic, Rochester, MN, United States, ²Royal Philips, Bangalore, India

Specialized spin-echo-based sequences have been developed to perform MRE in patients with short T2* where traditional MRE fails. This work demonstrates that these sequences are able to salvage such exams by improving SNR and MRE inversion confidence to the levels of successful GRE MRE exams. Additionally, the stiffnesses calculated by spin-echo and spin-echo-echo-planar acquisitions are equivalent to each other.

Dan Ma¹, Shivani Pahwa¹, Vikas Gulani¹, and Mark Griswold^1
1Radiology, Case Western Reserve University, Cleveland, OH, United States

The goal of this study is to characterize and improve the accuracy and repeatability of 2D MRF scans in the presence of slice profile imperfections. Slice profile imperfection causes deviation between the actual flip angles and nominal flip angles, which affects the accuracy of measured T1 and T2 values. This error can be corrected by simulating the RF excitation pulse in the dictionary. No extra scan time or post-processing time is needed once the new dictionary is simulated. The accuracy of both T1 and T2 is improved after slice profile correction. MRF also demonstrates good repeatability, with the coefficient of variance (CV) of 1.17% for T1 and 3.08% for T2.

Felix T Kurz^1,2, Thomas Kampf³, Lukas R Buschle², Sabine Heiland¹, and Christian H Ziener^1,2
1Heidelberg University Hospital, Heidelberg, Germany, ²E010 Radiology, German Cancer Research Center, Heidelberg, Germany, ³Wuerzburg University, Wuerzburg, Germany

Microscopically small early stage lung pathologies like emphysematous alterations of local lung tissue are usually not detectable on clinical MR images. The presented model connects defining tissue parameters for an MR imaging voxel, i.e. local alveolar radius and air-tissue ratio as well as diffusion coefficient and air-tissue susceptibility gradient, to CPMG relaxation rate dispersion over a range of inter-echo times. The model shows an excellent agreement with data from ageing hydrogel foam that mimics lung tissue.

Michael Goetz¹, Christian Weber¹, and Klaus H. Maier-Hein^1
1Medical Image Computing, German Cancer Research Center (DKFZ) Heidelberg, Heidelberg, Germany

To compare the information content of different MR sequences often regions of interests (ROI) are used. A way to avoid observer-dependencies is to use ROIs from different observer, but this leads to the question how to fuse them. We propose a new method to combine the information obtained by multiple ROIs depending on their similarity, making our method less sensitive to outlier. We evaluate our method by comparing the results obtained from the traditional merging method with the proposed algorithm. The results indicate that our method can be a valuable extension to ROI-based, multi-observer studies.

David Gay¹, Marie Chupin^1,2, Jean-François Mangin^1,3, Cyril Poupon^1,4, Hugo Dary¹, Takoua Kaaouana², Paulo Loureiro de Sousa⁵, Christine Delmaire⁶, Ludovic De Rochefort⁷, Jean-Marie Bonny⁸, and Alexandre Vignaud^4
1CATI Multicenter Neuroimaging Platform, cati-neuroimaging.com, Paris, France, ²ICM - Institut du Cerveau et de la Moelle Epinière, Paris, France, ³CEA, DSV, I2BM, NeuroSpin, UNATI, Gif-sur-Yvette, France, ⁴CEA, DSV, I2BM, NeuroSpin, UNIRS, Gif-sur-Yvette, France, ⁵Université de Strasbourg, CNRS, ICube, FTMS, Strasbourg, France, ⁶Neuroradiology, CHRU Roger Salengro, Lille, France, ⁷Université Paris-Sud, CNRS, IR4M UMR8081, Université Paris-Saclay, Orsay, France, ⁸INRA, UR370 QuaPA, Saint-Genès Champanelle, France

The purpose of this work is to report the implementation of a T2* map in multicenter neuroimaging studies. We focus on T2* because it is an endogenous biomarker for paramagnetic products like iron or melanin, which is very interesting to assess, among other diseases, Parkinson’s disease. We developed a MR sequence which meets several specific requirements. This sequence is accessible on 3 major manufacturer 3T MRI scanners and ensures good measurement accuracy at a standard millimeter isotropic resolution. This “universal” sequence allows to acquire, in a reliable and repeatable way, T2* maps of the whole brain.

Denis Kokorin¹, Jürgen Hennig¹, and Maxim Zaitsev^1
1Medical Physics, University Medical Center Freiburg, Freiburg, Germany

In this work, we investigated the application of B₀ shimming with constraints, in order to accomplish an intrinsic fat suppression during 2D EPI-based pulses. For this purpose, we simulated shimming in an ROI confined to part of the abdomen. Our initial results along with the experimental tests demonstrate the possibility for such a fat suppression method. However, the residual inhomogeneity in the main excitation ROI might become very substantial, if the restriction area for fat frequencies is too narrow.

Dong Kyu Kim¹ and Mark D Does^1,2,3
1Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, ²Vanderbilt University Institute of Imaging Sciences, Vanderbilt University, Nashville, TN, United States,³Department of Electrical Engineering, Vanderbilt University, Nashville, TN, United States

Zero Echo Time (ZTE) imaging is a technique with clinical potential for imaging tissues with very short T2 relaxation times. Due to the presence of a gradient during RF excitation, there is a slice profile effect that creates artifacts in the reconstructed image. This can be corrected prior to image reconstruction, at the cost of image SNR. Increasing pulse duration increases the signal acquired while reducing it lessens this profile effect. Hence, there exists an optimal pulse duration that balances these sources of signal loss. Herein, we present an optimized approach to maximizing SNR in ZTE imaging.