Jan Valošek^1,2 and Julien Cohen-Adad^2,3
1Department of Neurology, Faculty of Medicine and Dentistry, Palacký University Olomouc, Olomouc, Czech Republic, ²NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal, Montreal, QC, Canada, ³Functional Neuroimaging Unit, CRIUGM, University of Montreal, Montreal, QC, Canada

Quantitative MRI (qMRI) of the spinal cord (SC), such as diffusion-weighted and magnetic transfer imaging can be used in diagnosis of many different diseases. In this study, we established normative qMRI metrics along C2-C5 cervical SC levels for different regions-of-interest (spinal cord, white and gray matter, white matter columns) for 3 major MRI vendors (Siemens, Philips, GE) in large open-access dataset of ~250 healthy subjects. Metrics showed dependency on vertebral levels and confirmed different microstructural organization along SC. Moreover, differences in qMRI metrics were observed between individual vendors suggesting the influence of different MRI scanner configurations.

Kurt G Schilling¹, Qi Yang², Vishwesh Nath³, Rutger Fick⁴, Kristin P O'Grady¹, Adam W Anderson², Bennett A Landman¹, and Seth A Smith^1
1Vanderbilt University Medical Center, Nashville, TN, United States, ²Vanderbilt University, Nashville, TN, United States, ³NVIDIA, Bethesda, MD, United States, ⁴TheraPanacea, Paris, France

A large number of models have been developed to describe the diffusion MRI signal as a sum of different neural compartments. However, development and optimization of these multicompartment models has largely focused on the brain. In this work, we apply and compare a combinatorially large number of biophysical models (N=480) in the in vivo human spinal cord, evaluating their ability to fit the signal and also predict unseen signal. We find that certain combinations of constraints and compartments better model the signal in the cervical spinal cord, and we give recommendations for future modeling of this structure with clinical acquisitions. 

Guillaume Frebourg^1,2, Aurélien Massire^1,2, Lauriane Pini^1,2, Maxime Guye^1,2, Bertrand Audoin^2,3, Annie Veschueren^2,4, Pierre-Hugues Roche⁵, and Virginie Callot^1,2
1Aix-Marseille University, CNRS, CRMBM, Marseille, France, ²AP-HM, Hôpital de la Timone, CEMEREM, Marseille, France, ³AP-HM, Hôpital de la Timone, Neurology Dept., Marseille, France, ⁴AP-HM, Hôpital de la Timone, Neuromuscular Disease Dept., Marseille, France, ⁵AP-HM, Hôpital Nord, Neurosurgery Dept., Marseille, France

In the context of fast expansion of 7T clinical MR systems for neurological applications, a retrospective evaluation of cervical spinal cord image quality acquired on 41 patients and 25 healthy controls was performed. Several morphometric parameters were collected, and four MR modalities were rated. Altogether, this study provides guidance for both clinicians and physicists, regarding current sequence robustness and most frequent problems to be addressed.

Anirban Sengupta¹, Arabinda Mishra¹, Feng Wang¹, Li Min Chen¹, and John C. Gore^1
1Vanderbilt University Medical Center, Nashville, TN, United States

The study objective was to detect and quantify correlations between resting state BOLD signals in WM of spinal cord (SC) as potential indicator of functional connectivity, and evaluate changes that occur following injury. At first, BOLD activation was detected in response to tactile stimuli in certain WM regions in the SC of squirrel monkeys. Next, localized BOLD activity was observed during resting state in SC regions which resembled closely to WM tracts. There was a drop in resting state WM correlations after injury, followed by gradual recovery with time which mimics the pattern of SC functional recovery after an injury.

Sarah Rosemary Morris^1,2,3, Andrew Yung^1,2,4, Valentin Prevost^1,2,4, Shana George¹, Andrew Bauman^1,2,4, Piotr Kozlowski^1,2,3,4, Farah Samadi^1,5, Caron Fournier^1,5, Lisa Parker⁶, Kevin Dong¹, Femke Streijger¹, Veronica Hirsch-Reinshagen^1,5,6, G.R. Wayne Moore^1,5,6, Brian K Kwon^1,7, and Cornelia Laule^1,2,3,5
1International Collaboration on Repair Discoveries (ICORD), Vancouver, BC, Canada, ²Radiology, University of British Columbia, Vancouver, BC, Canada, ³Physics & Astronomy, University of British Columbia, Vancouver, BC, Canada, ⁴UBC MRI Research Centre, Vancouver, BC, Canada, ⁵Pathology & Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada, ⁶Vancouver General Hospital, Vancouver, BC, Canada, ⁷Vancouver Spine Surgery Institute, Vancouver, BC, Canada

Using human spinal cord tissue donated to the International Spinal Cord Injury Biobank, we quantitatively correlated binarized histological stains for myelin and axons with myelin- and axon-sensitive advanced MRI metrics (myelin water fraction (MWF), inhomogeneous magnetization transfer (ihMT), diffusion tensor imaging (fractional anisotropy (FA), axial diffusivity (AD), radial diffusivity, RD), diffusion basis spectrum imaging (fibre fraction, FF)). MWF, ihMT and RD had significant, moderately strong correlations with Luxol fast blue staining for myelin phospholipids. FA, AD and FF did not have any significant correlation with phosphorylated neurofilament immunohistochemistry.

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

Functional MRI is an indirect measure of neural activity, being the convolution of the hemodynamic response function (HRF) and latent neural response. The HRF is variable across brain regions and individuals. However, resting-state spinal cord fMRI studies still largely ignore this variability, partly due to an incomplete understanding of HRF variability in the cord. To address this gap, we characterized within- and between-subjects HRF variability within the cervical spine (N=20). 6–9% HRF variability was observed in the gray matter, and 3–5% in the white matter. This is an important confound to be accounted for in future spinal cord fMRI studies.

Bhavana S Solanky¹, Ferran Prados^1,2, Francesco Grussu^1,3, Marco Battiston¹, Jon Stutters¹, Selma Al-Ahmad⁴, Baris Kanber², David Choi⁴, Jalesh Panicker⁵, and Claudia AM Gandini Wheeler-Kingshott^1,6,7
1NMR Research Unit, Queen Square MS Centre, Department of Neuroinflammation, UCL Queen Square Institute of Neurology, Faculty of Brain Sciences, University College London (UCL), London, United Kingdom, ²Centre for Medical Image Computing, Department of Medical Physics and Biomedical Engineering, University College London (UCL), London, United Kingdom, ³Radiomics Group, Vall d’Hebron Institute of Oncology, Vall d’Hebron Barcelona Hospital Campus, Barcelona, Spain, ⁴National Hospital For Neurology and Neurosurgery, London, United Kingdom, ⁵Department of Uro-Neurology, The National Hospital for Neurology and Neurosurgery and UCL Queen Square Institute of Neurology, London, United Kingdom, ⁶Department of Brain & Behavioural Sciences, University of Pavia, Pavia, Italy, ⁷Brain Connectivity Centre Research Department, IRCCS Mondino Foundation, Pavia, Italy

Sodium retention as a consequence of spinal cord injury is thought to impair the regenerative ability of neurons but also reduce damage. Pilot studies suggest a possible increase in total sodium concentration (TSC) in spinal cord injury. Here we report increases in spinal cord TSC in cervical myelopathy  patients relative to healthy controls. Given that the increase could be a consequence of intracellular accumulation of sodium or increases in extracellular sodium through enlarged extracellular space,  the correlations of sodium with microstructure were investigated using neurite orientation dispersion and density imaging (NODDI) and macromolecular tissue volume imaging. 

Shiva Shahrampour¹, Benjamin De Leener², Mahdi Alizadeh¹, Devon Middleton¹, Laura Krisa¹, Adam Flanders¹, Scott Faro¹, Julien Cohen-Adad², and Feroze Mohamed^1
1Thomas Jefferson University, Philadelphia, PA, United States, ²Polytechnique Montreal, Montreal, QC, Canada

White matter microstructure, essential for efficient and coordinated transmission of neural communications, undergoes pronounced development during the first years of life. Hence, systematic evaluation of white matter microstructure in the normative pediatric spinal cord is critical for assessing early development and improving diagnosis of spinal cord related diseases.

Anirban Sengupta¹, Arabinda Mishra¹, Feng Wang¹, Li Min Chen¹, and John C. Gore^1
1Vanderbilt University Medical Center, Nashville, TN, United States

The objective of this study was to identify fine-scale resting state functional networks within the spinal cord gray matter of squirrel monkeys, and measure the changes in functional connectivity within the cord after a targeted injury. Independent Component Analysis of resting state fMRI data detected robust BOLD signals localized at the bilateral intermediate and gray-commissure regions of the spinal cord as well at the ‘4 horns’. A unilateral section of dorsal column tract at C5 segment of spinal cord damaged the inter-segmental connectivity more than intra-segmental connectivity, as observed through individual connectivity measures and community structures generated by graph-theory principles.

Kimberly J Hemmerling^1,2 and Molly G Bright^1,2
1Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, IL, United States, ²Physical Therapy & Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States

It is important to perform visual inspection of spinal cord imaging data throughout an fMRI analysis pipeline. The method presented here is an extension of an existing technique developed for the brain, adapted to spinal cord fMRI. We create a two-dimensional heatmap of the spinal cord derived from four-dimensional imaging data, which can be co-visualized with traces of motion and physiological signals, and identify examples of structured variations in the heatmap that may be attributed to these nuisance signals. Implementing this visualization of spinal cord fMRI data is a simple and fast method to examine data quality.