Bragi Sveinsson^1,2, Robert L Barry^1,2,3, Olivia Rowe^1,2, Jason Stockmann^1,2, Daniel J Park¹, Peter J Lally⁴, Matthew S Rosen^1,2,5, and Reza Sadjadi^6
1Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Boston, MA, United States, ²Radiology, Harvard Medical School, Boston, MA, United States, ³Harvard-Massachusetts Institute of Technology Health Sciences and Technology, Cambridge, MA, United States, ⁴Brain Sciences, Imperial College London, London, United Kingdom, ⁵Physics, Harvard University, Cambridge, MA, United States, ⁶Neurology, Massachusetts General Hospital, Boston, MA, United States

Research has suggested elevated diffusivity in nerves of subjects with peripheral nerve disease. Obtaining quantitative estimates of diffusivity at small scales within peripheral nerves could therefore provide important information about disease progression. However, diffusion weighted imaging at such small scales is challenging due to low signal to noise ratio (SNR) and distortion. Here, we demonstrate the feasibility of obtaining high-SNR, high-resolution, low-distortion anatomical images and quantitative diffusivity estimates in individual nerve fascicles with the quantitative Double-Echo in Steady-State sequence at 7 Tesla.

Simon Lévy^1,2,3, Patrick Freund^4,5,6, Virginie Callot^1,2,3, and Maryam Seif^4,5
1CRMBM, Aix-Marseille University, CNRS, Marseille, France, ²CEMEREM, APHM, Hopital Universitaire Timone, Marseille, France, ³iLab-Spine International Research Laboratory, Marseille-Montreal, France, ⁴Spinal Cord Injury Center, University Hospital Balgrist, University of Zurich, Zurich, Switzerland, ⁵Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, ⁶Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, London, United Kingdom

In the search for a technique to assess spinal cord perfusion, the Intra-Voxel Incoherent Motion technique, previously implemented at 7T, was adapted to 3T. B-values were optimized based on phantom acquisitions. The final protocol was applied within 11 healthy volunteers and 2 Degenerative Cervical Myelopathy patients. The technique demonstrated sensitivity to perfusion in healthy volunteers and to capillary network orientations, with a clear depiction of the gray matter perfusion and inter-slice reproducibility. No significant difference could be shown between healthy volunteers and patients given the small sample size but more patients will be included in the near future.

Yihe Hua¹, Desmond TB Yeo¹, and Thomas K Foo^1
1GE Global Research, Niskayuna, NY, United States

PNS by the alternative magnetic field from the gradient coil is an important safety consideration in MRI scanning. Previous studies reported the chronaxie time of PNS in the arm by transcutaneous electrode stimulation (ES) might be very different from PNS by magnetic stimulation (MS). We simulated the electric field distributions and chronaxie of most sensitive nerve trajectories for both ES and MS cases in an anatomical real arm model and found the profile of the field distribution for both cases are very different but chronaxie values at the same order of magnitude.

Kurt G. Schilling^1,2, Shreyas Fadnavis³, Mereze Visagie², Eleftherios Garyfallidis³, Bennett A. Landman^2,4, Seth A. Smith^1,2, and Kristin P. O'Grady^1,2
1Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, United States, ²Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, United States, ³Intelligent Systems Engineering, Indiana University Bloomington, Bloomington, IN, United States, ⁴Electrical Engineering and Computer Science, Vanderbilt University, Nashville, TN, United States

Diffusion MRI (dMRI) is a promising tool for evaluating the spinal cord in health and disease, however low SNR can impede accurate, repeatable, quantitative measurements. Here, we apply a recently proposed denoiser, Patch2Self, that strictly suppresses statistically independent random fluctuations in the signal originating from various sources of noise. Typical spinal cord dMRI scans have a smaller number of gradient directions (10-20) making PCA based 4D denoisers (require at least 30) inapplicable. Using self-supervised learning, Patch2Self addresses these issues which we quantitatively show with an improvement in repeatability and conspicuity of pathology in the spinal cord.

Larry A. Kramer¹, Khader M. Hasan¹, Brandon R. Macias², Karina J. Marshall-Goebel³, Steven S. Laurie³, Refaat E. Gabr¹, Leela Chaudhary¹, and Alan R. Hargens^4
1Diagnostic Imaging, UTHSC-Houston, Houston, TX, United States, ²NASA, Houston, TX, United States, ³KBR, Houston, TX, United States, ⁴Orthopedic Surgery, UCSD, La Jolla, CA, United States

The application of lower body negative pressure in the supine position significantly reduces bulk cerebral arterial flow and cross-sectional area of the internal jugular vein compared to the supine position alone.  This is similar to the physiologic response expected with upright compared to supine positioning. Our results suggest that lower body negative pressure applied during spaceflight may help reduce headward fluid shift and venous congestion and mitigate the development of optic disc edema associated with long-duration spaceflight.

Kevin M Koch¹, V. Emre Arpinar¹, and Matthew Budde^2
1Radiology, Medical College of Wisconsin, Milwaukee, WI, United States, ²Neurosurgery, Medical College of Wisconsin, Milwaukee, WI, United States

Metal artifacts from commonly-encountered spinal fusion stabilization hardware have historically confounded quantitative MRI (qMRI) research investigations of the injured and damaged spinal cord in human subjects.  This report provides preliminary analysis of metal-artifact suppressed multi-spectral diffusion qMRI collected on instrumented degenerative cervical spondylotic myelopathy (CSM) subjects.  The results of the study demonstrate group trends of reduced diffusivity in the CSM group at spinal cord levels fused by hardware.  This is a unique finding in instrumented CSM subjects that may offer unique insight into the impact of spinal fusion interventions on conventional qMRI measures of the spinal cord.

Mengsha Zou¹, Hongzhang Zhu¹, Yunzhu Wu², and Zhiyun Yang^1
1Radiology, The first affiliated hospital of Sun Yet-sen University, Guangzhou, China, ²MR Sicentific Marketing, Siemens Healthineers, Shanghai, China

Dysthyroid optic neuropathy (DON) is one of the most severe types of Graves orbitopathy (GO) and requires urgent treatment to prevent blindness. However, DON is frequently difficult to diagnose clinically in its early stages because of confounding signs and symptoms of congestive orbitopathy. In our study, we evaluate orbital condition of DON patients by using quantitative multimodal MRI, which include anatomical and functional indicators. We found that mMI (at 21 mm) combined with the mean T2 value of the optical nerve can use as an effective imaging indicator for detecting DON. 

Ying Chu¹ and Jürgen Finsterbusch^1
1Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Germany

Combined fMRI T2*-weighted imaging of the human brain and cervical spinal cord has been accelerated by simultaneous multi-slice (SMS) imaging of the brain volume. The implementation has been tested and evaluated in phantoms and in vivo and shows a very similar performance to non-accelerated and brain-only measurements. With the much shorter acquisition times achievable it could help to improve brain volume coverage of cortico-spinal fMRI.

Arkiev D'Souza¹, Chenyu Wang^1,2, Sicong Tu^1,2, Dominic Soligo³, Matthew Kiernan^1,2,4, Michael Barnett^1,4, and Fernando Calamante^1,5,6
1Brain and Mind Centre, The University of Sydney, Sydney, Australia, ²Central Clinical School, The University of Sydney, Sydney, Australia, ³I-MED Radiology Network, Camperdown, Australia, ⁴Department of Neurology, Royal Prince Alfred Hospital, Camperdown, Australia, ⁵School of Biomedical Engineering, The University of Sydney, Sydney, Australia, ⁶Sydney Imaging, The University of Sydney, Sydney, Australia

Diffusion MRI has previously been used to quantify peripheral nerves; however, traditional post-processing techniques have several limitations. Here, we demonstrate the feasibility of using state-of-the-art diffusion analysis tools to reconstruct and quantify the ulnar nerve of the forearm. Constrained-spherical deconvolution was combined with probabilistic fibre-tracking to compute several track-weighted measurements in the ulnar nerve. The results suggest that a sample size of 22 would be sufficient to detect a 10% difference in any of the measured track-weighted metrics, and a sample size of 20 would be large enough to detect within-subject differences as small as 3%. 

Ju Young Lee¹, Andreas Mack², Thomas Shiozawa-Bayer², Marc Himmelbach³, Gisela Hagberg^1,4, and Klaus Scheffler^1,4
1Max Planck Institute for Biological Cybernetics, Tübingen, Germany, ²Eberhard Karls University Tuebingen, Tübingen, Germany, ³Hertie-Institue for Clinical Brain Research, Tübingen, Germany, ⁴University Hospital Tübingen, Tübingen, Germany

Layer specific MR properties have previously been observed in the superior colliculus in vivo at 9.4T. The present study investigates layer specific MR properties in R2* and R1 in more detail in post mortem brain stem samples at 14.1T. Similar to in vivo, one R2* maximum that likely corresponds to the superficial optic layer (layer III) was observed.  Ex vivo we could observe high R2* and R1 in an area likely corresponding to the deep white layer (layer VII) of the superior colliculus. In the R1maps, this area showed a strong contrast towards the periaqueductal gray.

bingbing gao¹, Yanwei Miao¹, Qingwei Song¹, Ailian Liu¹, and Jiazheng Wang^2
1the First Affiliated hospital of Dalian Medical university, Dalian, China, ²Philips Healthcare, BeiJing, China

Discrimination of gray and white matters on the axial-spinal-marrow MRI remains a challenge, due to the small structure size and motion artifacts from such as swallowing and blood flow. The present study aims to visualize the cervical spinal marrow with high resolution axial phase-sensitive inversion recovery (PSIR) and multiple Fast Field Echo (FFE) images, and further to detect the image quality differentially on gray and white matters. The “butterfly” structure could be seen on both of the two contrast images, but the PSIR images were associated with significantly higher signal-to-noise ratios.

Ming Lu^1,2,3, Gary Drake^1,2, Feng Wang^1,2, Chaoqi Mu^1,4, Limin Chen^1,2, John C. Gore^1,2,4, and Xinqiang Yan^1,2
1Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, United States, ²Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, United States, ³College of nuclear equipment and nuclear engineering, Yantai University, Yantai, China, ⁴Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, United States

Multiparametric MRI at high field provides comprehensive information to assess structural and functional changes that are important for clinical diagnosis and for evaluating therapies. Injuries may occur at different levels of the lumbar and thoracic cord, and the number of segments injured and their depths may vary along the spine, so it is challenging to build one universal RF coil that exhibits high-performance for all spinal cord imaging applications. We therefore developed an interchangeable RF coil system for a 9.4T small animal MRI scanner, and found the specialized coil has 2.4-fold SNR improvement compared to a commercial general-purpose sized coil.

Yunan Cui¹, Yanwei Miao¹, Ailian Liu¹, Zhiwei Shen², and Jiazheng Wang^2
1THE FIRST AFFILIATED HOSPITAL OF DALIAN MEDICAL UNIVERSITY, DALIAN, China, ²Philips Healthcare, BEIJING, China

Due to the difficulty in distinguishing the structure of spinal by conventional MR sequence. In this study, the fusion images of Phase Sensitive Inversion Recovery sequence (PSIR) and zoomed Diffusion Tensor Imaging (DTI) was used to quantify the diffusion indicators, such as fractional anisotropy (FA), apparent diffusion coefficient (ADC), axial dispersion (AD) and relative anisotropy (RA) in the normal spinal cord. We found that there were significant differences of above indicators in different regions of cervical cord including the white columns of the cervical cord, the ipsilateral white matter and in the left and right sides of the cervical cord.

Kevin M Koch¹ and Andrew S Nencka^1
1Radiology, Medical College of Wisconsin, Milwaukee, WI, United States

Morphological analysis of the spinal cord can provide valuable insight into injury and degeneration of damaged cord tissues.   Accurate morphological analysis requires high resolution 3D anatomic imaging to be utilized as inputs into automated or semi-automated post-processing analysis algorithms.  Historically, high resolution 3D imaging of the instrumented spinal cord has been difficult to achieve.   As a result, the substantial damage and pathology near hardware cannot be analyzed using advanced morphological tools.   In this technical feasibility study, isotropic 3D-MSI metal-artifact suppressed images are collected and utilized within a novel analysis framework constructed around the Spinal Cord Toolbox infrastructure.  

Renwang PU¹, Qingwei SONG¹, Ailian LIU¹, Zijing ZHANG¹, Nan ZHANG¹, Haonan ZHANG¹, Bingbing GAO¹, Lihua CHEN¹, and Liangjie LIN^2
1the First Affiliated Hospital of Dalian Medical Universityrsity, Dalian, China, ²Philips Healthcare, BEIJING, China

The 3D-NerveVIEW sequence with suppression of lipid and blood signals and a long echo time can obtain high-quality images for visualization of brachial plexus, while the long scan time may limit its clinical application. Compressed SENSE (CS) is a newly developed technique in MRI that enables accelerated acquisition with maintained image quality. By comparing results of 3D-NerveVIEW for brachial plexus imaging with acceleration by the conventional SENSE and the advanced CS with different acceleration factors. We found that the 3D-NerveVIEW for brachial plexus imaging with a CS acceleration factor of 4 can obtained favorable images within significantly reduced scan time.

Jian Wang¹, Yanjun Chen¹, Yingjie Mei², Jialing Chen¹, and Xiaodong Zhang^1
1Department of Medical Imaging, The Third Affiliated Hospital of Southern Medical University, Guangzhou, China, ²China International Center, Philips Healthcare, Guangzhou, China

The anatomy of lumbosacral plexus (LSP) is complex, patients with trauma, neoplasms, or infection may experience motor weakness, sensory loss, and/or debilitating pain. Accurate and fast MRN scanning is an invaluable tool for evaluation of LSP diseases. In this study, the feasibility and performance of compressed sensing (CS) in scanning LSP was investigated and compared with conventional 3D-FFE with principles of the selective excitation technique. The results show that 3D-FFE with CS could reduce scan time obviously, influence image quality mildly, and meet clinical diagnosis.

Geli Hu¹, Jiazheng Wang¹, Qingping Gu¹, Yang Zhang¹, and Jianxia Cao^1
1Philips Healthcare, Beijing, China

The balanced FFE (b-FFE) sequence has the advantages of high resolution, SNR, CNR and superior differentiation between fluid and tissue. Therefore, it can be used for lumbosacral plexus imaging [1]. However, black band-like artifacts are frequently observed due to intra-voxel signal dephasing at the presence of magnetic field inhomogeneity. Here we proposed using a RF phase cycling technique (b-FFE-XD) to suppress the banding artifacts. The RF phase was set as [0,180+1*X, 2*X, 180+3*X,4*X,…] in consequence to limit the intravoxel dephasing, where X=n*360/NSA, and n is the nth average. Results demonstrated successful removal of banding artifacts with the proposed technique.

Ryckie George Wade¹, Alexander Whittam², Irvin Teh¹, Gustav Andersson³, Fang-Cheng Yeh ⁴, Mikael Wiberg ³, and Grainne Bourke ^1
1University of Leeds, Leeds, United Kingdom, ²Sheffield Teaching Hospitals, Sheffield, United Kingdom, ³Umeå University, Umeå, Sweden, ⁴University of Pittsburgh, Pittsburgh, PA, United States

In this systematic review and meta-analysis we summarise the normal diffusion tensor imaging (DTI) metrics for roots of the brachial plexus. We included 9 studies describing 316 adults (1:1 male:female) of mean age 35 years (SD 6). The normal fractional anisotropy was 0.36 (95% CI 0.34, 0.38; Figure 4). The normal mean diffusivity was 1.51 x10-3 mm2/s (95% CI 1.45, 1.56; Figure 5). DTI metrics varied according to experimental conditions and participant factors. Our summary estimates from different conditions which may be valuable to researchers and clinicians alike.

Junjiao Hu¹, Kai Deng¹, Weijun Situ¹, and Huiting Zhang^2
1Department of Radiology, the Second Xiangya Hospital of Central South University, Changsha, China, ²MR Scientific Marketing, Siemens Healthcare Ltd., Wuhan, China

This retrospective study aimed to investigate the feasibility of preoperative MRI measurements of Meckel cavity volume using 3D SPACE sequence and its values in guiding percutaneous balloon compression of the trigeminal nerve. Our results showed that there was no statistically significant difference between the volume of Meckel cavity using the axis, coronal and sagittal directions of MRI images and intraoperative balloon filling volume. 3D SPACE is helpful to guide the operation in clinical application.