Chaoyue Wang¹, Stephen M. Smith¹, Fidel Alfaro-Almagro¹, Cristiana Fiscone², Richard Bowtell², Lloyd T. Elliott³, Karla L. Miller¹, and Benjamin C. Tendler^1
1Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom, ²Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom, ³Department of Statistics and Actuarial Science, Simon Fraser University, Vancouver, BC, Canada

UK Biobank aims to scan 100,000 participants and its brain protocol acquires susceptibility-weighted MRI (swMRI). To date, only the swMRI magnitude data were processed to produce T2* maps. The aim of this work is to develop a robust processing pipeline for QSM using the acquired swMRI phase data. We ran this pipeline on 2408 volunteers and report some preliminary results, including age-dependent curves and genetic associations. Significant correlations were found between susceptibility and age in subcortical structures. QSM discovered replicable genetic associations previously identified in T2*. Our results suggest that there is unique information in susceptibility maps compared to T2*.

Beata Bachrata^1,2,3, Bernhard Strasser^1,2,4, Wolfgang Bogner^1,2, Albrecht Ingo Schmid^1,5, Siegfried Trattnig^1,2,3, and Simon Daniel Robinson^1,2,6,7
1High Field MR Centre, Medical University of Vienna, Vienna, Austria, ²Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria, ³Christian Doppler Laboratory for Clinical Molecular MR Imaging, Vienna, Austria, ⁴Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States, ⁵Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria, ⁶Centre for Advanced Imaging, The University of Queensland, Brisbane, Australia, ⁷Department of Neurology, Medical University of Graz, Graz, Austria

The accuracy of Quantitative Susceptibility Mapping in fatty regions is adversely affected by the chemical shift effects and by the relaxation rate differences between fat and water. We propose using a recently developed water-fat separation technique based on multi-band principles, Simultaneous Multiple Resonance Frequency (SMURF) imaging, to correct for these effects. SMURF achieves clean water-fat separation in the head-and-neck, allowing the generation of recombined water-fat images fully corrected for chemical shift and relaxation effects. This makes bias-free Quantitative Susceptibility Mapping possible in body regions containing significant amounts of fat, with the free selection of echo-times, receiver bandwidths and flip angles.

Yang Gao¹, Xuanyu Zhu¹, Stuart Crozier ¹, Feng Liu¹, and Hongfu Sun^1
1University of Queensland, Brisbane, Australia

Deep learning frameworks are emerging methods for solving ill-posed inverse problems in medical imaging, including Quantitative Susceptibility Mapping (QSM). Previously, U-net has been successfully trained on susceptibility maps to learn the dipole inversion process; however, susceptibility contrast loss was observed in iron-rich deep grey matter regions. In this study, we propose an enhanced deep learning network “xQSM” using the state-of-the-art Octave Convolution, which shows more accurate susceptibility contrasts than the original U-net in both simulated and in vivo datasets.

Motofumi Fushimi^1,2, Thanh Nguyen², and Yi Wang^2,3
1Graduate School of Information Science and Technology, The University of Tokyo, Tokyo, Japan, ²Radiology, Weill Cornell Medical College, New York, NY, United States, ³Biomedical Engineering, Cornell University, Ithaca, NY, United States

We propose a simultaneous conductivity and susceptibility reconstruction method by estimating B1 phase and B0 distributions from a multi-echo gradient echo (mGRE) signal. B1 phase and B0 maps are simultaneously determined by applying nonlinear least squares method on the complex signal equation of the mGRE signal. The poor conditioned inversion of field (B1/B0) to source (conductivity/susceptibility) is regularized using anatomical information. This morphology enabled quantitative conductivity and susceptibility mapping (QCSM) was performed on healthy subjects and patients with brain tumors. Our preliminary in-vivo experiments demonstrated that the proposed QCSM method can reconstruct conductivity and susceptibility from a single mGRE acquisition.

Paul Rowley^1,2, Melanie Morrison, PhD¹, Yicheng Chen¹, Angela Jakary¹, Michael Geschwind, MD, PhD³, Alexandra Nelson, MD, PhD³, Duan Xu, PhD¹, Christopher Hess, MD, PhD¹, and Janine Lupo, PhD^1
1Radiology & Biomedical Imaging, University of California, San Francisco, San Francisco, CA, United States, ²University of Wisconsin School of Medicine and Public Health, Madison, WI, United States, ³Neurology, University of California, San Francisco, San Francisco, CA, United States

Ultra-high-field 7 Tesla (7T) MRI was acquired to examine and compare white matter microstructure and quantitative susceptibility in patients with premanifest (PM) and early manifest (EM) Huntington’s disease (HD) and age-matched healthy control (HC) subjects. Tract-averaged and along-tract fractional anisotropy (FA) and susceptibility (PPM) were calculated to determine the spatial spread of disease along motor tracks originating from the striatum and ending in the cortex. HC and PM patients demonstrated different areas of significantly increased susceptibility compared to EM at the tract-averaged level as well as significant focal along-tract variations in FA and susceptibility which were undetected by tract-averaged analysis. 

Xi Peng¹ and James G. Pipe^1
1Department of Radiology, Mayo Clinic, Rochester, MN, United States

This work presents a new feasibility to extract tissue susceptibility from gradient-echo MRE data and enables simultaneous QSM and MRE in a single scan. The proposed method builds on a new spiral staircase acquisition which enables high resolution often required by QSM using inherently improved through-plane parallel imaging. In-plane parallel imaging, constrained reconstruction and deblurring method are also integrated to generate high quality spiral images for QSM and MRE processing. In vivo experiment results demonstrate the capability of proposed method in producing high quality tissue susceptibility along with shear stiffness maps from a single 5-minute scan.

Michaël Bernier^1,2, Berkin Bilgic^1,2, Saskia Bollmann^1,2, Nina E. Fultz^1,3, and Jonathan R. Polimeni^1,2,4
1Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, ²Radiology, Harvard Medical School, Boston, MA, United States, ³Engineering, Boston University, Boston, MA, United States, ⁴5Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, United States

Vascular imaging acquisition techniques to extract veins and arteries are not impervious to flaws: venography by susceptibility weighted imaging is prone to blooming effects and false-negatives, and angiography from time-of-flight imaging is affected by veins detection and false-negatives. They also fail to provide quantitative measures of vascular physiology such as flow and susceptibility important for understanding the origin of vascular-based biases. Thus, we aimed to employ multi-orientation quantitative susceptibility mapping, multi-echo time-of-flight and quantitative phase-contrast to more accurately detect and quantify the susceptibility and flow along the vascular tree, paving the way for a joint anatomical/physiological vascular atlas at 7T.  

Rong Guo^1,2, Yudu Li^1,2, Yibo Zhao^1,2, Tianyao Wang³, Yao Li^4,5, Brad Sutton^1,2,6, and Zhi-Pei Liang^1,2
1Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States, ²Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, United States, ³Radiology Department, The Fifth People's Hospital of Shanghai, Shanghai, China, ⁴School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China, ⁵Med-X Research Institute, Shanghai Jiao Tong University, Shanghai, China, ⁶Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States

In this work, we present a new method to achieve high-resolution QSM for simultaneous QSM/MRSI experiments. This work extends SPICE with a novel data acquisition scheme that provides larger k-space coverage for the unsuppressed water signals. A union-of-subspaces model incorporating sensitivity encodings (parallel imaging) and pre-determined spatiospectral features is used to solve the underlying image reconstruction problem. High-resolution capability (on the order of 1.0 × 1.0 × 1.2 mm³) for QSM has been demonstrated in 3D in vivo simultaneous QSM/MRSI experiments.

Malte Brammerloh^1,2, Evgeniya Kirilina^1,3, Renat Sibgatulin⁴, Karl-Heinz Herrmann⁴, Tilo Reinert¹, Carsten Jäger^1,5, Primož Pelicon⁶, Primož Vavpetič⁶, Kerrin J. Pine¹, Andreas Deistung⁷, Markus Morawski⁵, Jürgen R. Reichenbach⁴, and Nikolaus Weiskopf^1,2
1Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, ²Faculty of Physics and Earth Sciences, Leipzig University, Leipzig, Germany, ³Center for Cognitive Neuroscience Berlin, Freie Universität Berlin, Berlin, Germany, ⁴Medical Physics Group, University Hospital Jena, Jena, Germany, ⁵Paul Flechsig Institute of Brain Research, Leipzig, Germany, ⁶Microanalytical Center, Department for Low and Medium Energy Physics, Jožef Stefan Institute, Ljubljana, Slovenia, ⁷Department of Radiology, University Hospital Halle, Halle, Germany

MRI-based quantification of dopaminergic neurons (DN) and their neuromelanin (NM) in substantia nigra (SN) has great potential to serve as a specific biomarker for neurodegeneration in movement disorders. We used 22-µm-resolution post mortem MR microscopy combined with ion beam microscopy to characterize the magnetic properties of DN. MR microscopy visualized individual DN and provided 3D cellular maps of the entire SN. Static dephasing was determined as main effective transverse relaxation mechanism of DN. We characterized the susceptibility of iron in DN and estimated that the contribution of DN to R2* and QSM may also be detected with in vivo MRI.