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Keywords: Spinal Cord, fMRI (resting state), Functional Connectivity

The goal of this study was to detect and quantify how functional connectivity within networks in squirrel monkey spinal cord changes after a focal lesion of the primary motor cortex. We first used independent component analysis to identify 7 spatially independent functional hubs within each segment of the cervical spinal cord. The overall connectivity of these spinal cord networks increased after a lesion within M1, indicating plastic changes in spinal cord due to cortical injury. Distinct functional communities confined to neighboring spinal cord segments were identifiable one week after the injury, confirming spinal cord functional networks reorganized over that time.

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Keywords: Spinal Cord, Diffusion/other diffusion imaging techniques, trauma, spinal cord injury, post-mortem, wallerian degeneration, axons, ActiveAx, DTI

7T Diffusion Tensor Imaging (DTI) and ActiveAx analysis techniques were used to probe the microstructural properties of post-mortem human spinal cord injury tissue. A decrease in DTI fractional anisotropy was observed caudal to (below) the injury epicenter for descending tracts and rostral to (above) the injury epicenter for ascending tracts. All cords displayed increased axon diameter in ascending tracts rostral to the injury site, which may be evidence of axonal swelling. A decrease in axon density for the two subjects with the longest injury-to-death interval may indicate the time scale of Wallerian degeneration-induced axonal damage observable using ActiveAx. 

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Keywords: Spinal Cord, fMRI (resting state)

In recent years, while the exploration of spontaneous brain activity has shifted from static methods (i.e., examining average connectivity patterns over the entire run) towards dynamic approaches (i.e., accounting for the non-stationarity of resting-state fluctuations), the non-stationary nature of intrinsic activity in the spinal cord has seldom been studied. Here, we propose to probe time-varying functional connectivity patterns in the spinal cord using a sliding-window correlation approach, as commonly employed in the brain. Our results suggest the potential of this approach to unravel ventral-ventral and dorsal-dorsal correlation patterns, while also emphasizing their time-varying nature.

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Keywords: Spinal Cord, fMRI

A unilateral isometric hand-grip task was used to elicit motor neuron activation in spinal cord fMRI. As predicted, activation was lateralized to the ipsilateral hemicord. However, active voxels were also observed outside of the ventral horn and superior to C7. Reduced spatial precision and sensitivity in activation estimates, particularly along the cord axis, may be due to the combination of inter-individual differences in anatomy, imperfect registration to the standard spinal cord template, additional sensory activity associated with performing the task, and co-contraction of muscles not directly involved in hand-gripping.

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Keywords: Spinal Cord, fMRI (resting state)

We investigated the intra- and inter-session reliability of functional connectivity indices derived from resting-state fMRI in the lumbar spinal cord. Slicewise and average indices of connectivity for the ventral and dorsal networks were collected across three experiments in healthy participants at 3T. Intra-session reliability was high for back-to-back scans (ICC>0.9), and moderate-to-good when introducing repositioning, surveying and reshimming (COV=3-25%). Repeatability of indices across separate visits was low, although similar grey matter functional networks could be independently observed and showed high spatial overlap using ICA, a data-driven approach. This is the first evaluation of resting-state fMRI reliability in the lumbar cord.

Cuili Kuang¹, Yunfei Zha¹, and Weiyin Vivian Liu^2
1Renmin Hospital of Wuhan University, Wuhan, China, ²GE Healthcare, MR Research, Beijing, China

Keywords: Spinal Cord, Neurodegeneration, Cervical Spondylotic Myelopathy, Spinal Cord Toolbox

Associations between cross-sectional area and white matter area within the rostral spinal cord and gray matter volume in left supplementary motor area and right middle cingulate gyrus suggest a concordant change pattern and adaptive mechanisms for neuronal plasticity underlying remote neurodegeneration in early cervical spondylotic myelopathy. The atrophy of cross-sectional area within the upper spinal cord and gray matter volume loss in right postcentral gyrus can serve as potential neuroimaging biomarkers of early structural changes within spinal cord and brain preceding marked clinical disabilities in patients with cervical spondylotic myelopathy. 

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Keywords: Spinal Cord, Diffusion/other diffusion imaging techniques

This study used multi-factorial linear quantile mixed-effects regression models to predict the outcome of cervical spondylotic myelopathy (CSM) patients one year after surgery based on MRI. Six models were constructed using the linear quantile mixed model and linear mixed-effects regression model based on the diffusion magnetic resonance imaging (dMRI) data, all the imaging data (dMRI & Conventional MRI), and all the registered data (dMRI & Conventional MRI & clinical data). We found that fractional anisotropy (FA) values quantified by preoperative dMRI could predict the surgical outcome of CSM and showed a significant positive correlation with the postoperative outcome.

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Keywords: Spinal Cord, Segmentation, atrophy

Detecting atrophy in the spinal cord (SC) is highly relevant in multiple sclerosis (MS) and other neuroinflammatory and neurodegenerative diseases. The most used method is measuring mean upper cervical cord area (MUCCA) from SC images. MRI of SC is time consuming and not always available. We recently developed a method to measure MUCCA directly from conventional T1w brain images. This work compares MUCCA estimates derived from MPRAGE and MP2RAGE sequences, determine reference ranges from 98 healthy subjects and show their value to detect atrophy in patients with progressive MS and neuromyelitis optica. We observe very high agreement between methods.

Kristin P. O'Grady^1,2,3, Caroline Seehorn¹, Grace Sweeney¹, Logan Prock¹, Delaney Houston¹, Anna J.E. Combes¹, Kurt G. Schilling^1,2, Colin D. McKnight², Ryan K. Robison^1,2,4, and Seth A. Smith^1,2,3
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, ³Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, ⁴Philips, Nashville, TN, United States

Keywords: Spinal Cord, Diffusion Tensor Imaging

The lumbar spinal cord is significantly understudied with quantitative MRI methods such as diffusion tensor imaging (DTI), in part due to challenges of spatial and temporally-varying field inhomogeneities that cause distortion in commonly used single-shot EPI sequences. In this pilot study, we implemented IRIS Zoom, a multi-shot, reduced field-of-view method that corrects for shot-to-shot variations, phase errors (2D navigation), and T2* dephasing. Multi-shot EPI was successfully acquired in healthy volunteers at 3T, led to reduced geometric distortions, and provided quantitative DTI values comparable to those derived from single-shot EPI. Multi-shot EPI is feasible for high-resolution DTI of the lumbar cord.

Kristin P. O'Grady^1,2,3, Kritin Vasamreddy¹, Grace Sweeney¹, Logan Prock¹, Delaney Houston¹, Anna J.E. Combes¹, Trey McGonigle⁴, Simon Vandekar⁴, Margareta Clarke¹, Atlee A. Witt¹, Colin D. McKnight², Erik Landman², Ryan K. Robison^1,2,5, Francesca Bagnato⁶, and Seth A. Smith^1,2,3
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, ³Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, ⁴Department of Biostatistics, Vanderbilt University Medical Center, Nashville, TN, United States, ⁵Philips, Nashville, TN, United States, ⁶Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, United States

Keywords: Spinal Cord, Multiple Sclerosis, lumbar spinal cord

Improvements are needed in advanced anatomical imaging of the lumbar spinal cord. We implemented a T2*-weighted multi-echo gradient echo (mFFE) sequence that enables visualization of CSF, gray and white matter with an in-plane resolution of 0.65x0.65mm². Use of an MT-weighted pre-pulse and a respiratory navigator decreased SNR, but did not affect CNR, and qualitatively improved image quality and possibly multiple sclerosis lesion conspicuity. CNR/SNR were robust to biological factors known to affect signal quality (e.g. age, weight). The proposed sequence holds potential for improved visualization of anatomy, pathology, and morphometric measurements in the lumbar cord.

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Keywords: Spinal Cord, Software Tools

Ultra-High-Field MRI has opened new perspectives for spinal cord exploration due to improved spatial resolution and contrast. The present work proposes a dedicated 7T multimodal 3D qT1 and T2*w template and a parcellation including eight substructures within gray matter, thirty WM tracts and three inter-hemispheric ROIs, for an accurate atlas-based segmentation in the subject space. This atlas was interpolated in the 3D PAM50 space to benefit from the advanced functions for registration implemented in the SCT. A preliminary segmentation result in healthy subject gives promising perspectives for group studies.

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Keywords: Spinal Cord, Multiple Sclerosis

In this exploratory study focusing on MP2RAGE and MS lesions, we demonstrated the added value of 7T imaging for lesion detection, with +20-to-30% of additional lesions seen compared to 3T. We also demonstrated that both currently available automatic segmentation model in SCT and an exploratory model build and trained based on MP2RAGE 3T images were not optimal for detecting lesions in 7T images (although a small contribution with slightly higher PPV was obtained with our model). As 7T opens great perspectives, further study should now focus on specific training and analysis tools to deal with 7T resolution and contrasts.

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Keywords: Spinal Cord, Spinal Cord

FMRI of the spinal cord is challenging due to its small size, necessitating high resolution.  Increasing B₀ to 7T enables higher spatial resolution, and also enhances BOLD signal.  However, challenges related to B₀ homogeneity complicate spinal cord fMRI at 7T.  We present group-level stimulus task fMRI results in the spinal cord at 7T, and compare the performance of single-shot and multi-shot 2D EPI protocols.  Single-shot at 0.75mm in-plane resolution was most sensitive to activation, while multi-shot at 0.60mm provided the best-localized clusters.  The best choice of protocol depends on the importance of sensitivity versus spatial localization for a given experiment.

D Rangaprakash¹ and Robert L Barry^1
1Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States

Keywords: Spinal Cord, fMRI (resting state)

Spinal cord fMRI is an emerging field with clinical potential. Sub-millimeter in-plane fMRI acquisitions are desirable and achievable, but published studies have had modest temporal resolutions (>2s). Using a custom-built 7T spine coil, we demonstrate sub-second and sub-millimeter cervical cord fMRI for the first time. Employing a 3D multi-shot sequence with appropriate phase corrections and NORDIC denoising, our data demonstrated temporal signal-to-noise ratios similar to those of standard supra-second protocols, and we replicated functional connectivity patterns previously published in the cord. This opens new avenues of discovery similar to those realized through high spatiotemporal resolution brain fMRI.

Devon M Middleton¹, Yutong Li², Andrew Chen³, Russell T Shinohara³, John H Woo³, Adam E Flanders¹, Scott H Faro¹, Laura Krisa², and Feroze B Mohamed^1
1Radiology, Thomas Jefferson University, Philadelphia, PA, United States, ²Thomas Jefferson University, Philadelphia, PA, United States, ³University of Pennsylvania, Philadelphia, PA, United States

Keywords: Spinal Cord, Diffusion Tensor Imaging

This study uses longitudinal ComBat data harmonization on a multi-site/multi-scanner spinal cord DTI study with a traveling cohort imaged on four scanners.  The results show considerable improvement in correlation between scanners as well as decerased coefficient of variation.  This approach has potential benefits for large, multi-site spinal cord studies.