HUGO W. MOSER RESEARCH INSTITUTE AT KENNEDY KRIEGER, INC.
Grant: $281,750 - National Institutes of Health - Apr. 30, 2009
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Award Description: Relationship of MRI to ASIA Impairment Scale in Chronic Spinal Cord Injury. The objective of this investigation is two-fold: 1) to add to the classification value of the American Spinal Injury Association (ASIA) Impairment Scale by establishing imaging criteria for chronic spinal cord injury (SCI), 2) to use advanced MR imaging techniques as tools to understand the structural variables that contribute to residual neurological function and the capacity for recovery. A preserved rim of white matter at the injury epicenter characterizes SCI pathology, and the integrity of this tissue determines the amount of preserved function. High resolution imaging is necessary to visualize the subtle structural differences that are responsible for differing levels of function both at the site of and distal to the injury epicenter. Spinal cord imaging is complicated by the small size of the cord, interference from surrounding bone, respiratory and cardiovascular related motion and cerebrospinal fluid pulsation artifacts. Recently, investigators at the F.M. Kirby Research Center for Functional Brain Imaging at Kennedy Krieger Institute have successfully used Diffusion Tensor Imaging (DTI) and Magnetization Transfer (MT) to visualize over sixty injured spinal cords. These imaging techniques are of sufficient resolution and quality to correlate DTI- and MT-derived metrics sensitive to white matter disruption with neurological function in chronic SCI. We address the specific hypothesis that neurological function/deficit clinically defined through the ASIA criteria is related to disordered white matter pathways in persons with chronic SCI through tract specific DTI-derived metrics such as: fractional anisotropy (FA), average diffusion coefficient (MD), parallel and perpendicular eigenvalues (?|| and ??) and MTCSF (magnetization transfer weighted image normalized by cerebrospinal fluid), but not conventional T1- and T2- weighted imaging. One hundred and twenty individuals divided amongst four ASIA classes (ASIA A-C and E) will be imaged using conventional (T1, T2) and advanced (DTI, MT) MRI techniques. The integrity of white matter both at the site of and distal to the epicenter of the lesion in these subjects will be defined in a tract specific manner using DTI and MT and will be tested for relationships to ASIA clinical classification and neurological motor and sensory testing (Aim1) and to quantitative vibration threshold sensory testing (Aim2).
Project Description: This work is accepted for publication in NMR in Biomed. We demonstrate a combined MT and DTI analysis of the cervical spinal cord (SC) at 3T. DTI-reconstructed tractograms of the large columns (dorsal, lateral) of the cervical cord were obtained and overlaid on the quantitative images derived from MT and DTI: i.e. tract profiles. Finally, this study detailed the variability and differences between raters and times with the thrust of benchmarking expected variability for longitudinal and clinical studies utilizing MT and DTI in the cervical cord 1. Currently, no tract-derived, individual column MTCSF and DTI quantities are available in the literature for comparison with our results, but whole-cord values 2 and ROI based examination of the MTCSF value in the columns of the spinal cord have been reported 3. Our column-specific measurements of ?|| are at the high end of the previously reported whole-cord range; our ?? measurements are in the middle of the reported range. The column-specific MD is in the middle of the whole-cord range, whereas the measured FA values are at the higher end of the whole-cord range. The indices that we studied didn’t show differences between the lateral and dorsal columns. For the MTCSF imaging method, this is justified by the fact that on average, the dorsal and lateral columns contain approximately the same amount of myelin per voxel. In regard to diffusion indices this sensitivity is mitigated by methodological limitations. These experiments use a relatively low b-value for diffusion weighting to minimize signal attenuation in a strongly restricted environment such as the cord. It is hypothesized that a tract-specific study of diffusion over a wider range of b-values will demonstrate the microstructural differences that are known to exist histologically between the two columns 1. Following this publication, we have scanned and processed data from 8 SCI subject (2 ASIA A, 3 ASIA C, and 3 ASIA D).
Jobs Summary: The Recovery Act funds awarded in this grant enabled the Institute to retain the following position: Research Coordinator IV. This position directs and performs research projects related to regeneration of the injured spinal cord following cell transplantation and functional electrical stimulation. (Total jobs reported: 1)
Project Status: Less Than 50% Completed
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