Diffusion Tensor Imaging of the Spinal Cord: Insights From Animal and Human Studies
ABSTRACT Diffusion tensor imaging (DTI) provides a measure of the directional diffusion of water molecules in tissues. The measurement of DTI indices within the spinal cord provides a quantitative assessment of neural damage in various spinal cord pathologies. DTI studies in animal models of spinal cord injury indicate that DTI is a reliable imaging technique with important histological and functional correlates. These studies demonstrate that DTI is a non-invasive marker of microstructural change within the spinal cord. In human studies, spinal cord DTI shows definite changes in subjects with acute and chronic spinal cord injury, as well as cervical spondylotic myelopathy. Interestingly, changes in DTI indices are visualized in regions of the cord, which appear normal on conventional MRI and are remote from the site of cord compression. Spinal cord DTI provides data that can help us understand underlying microstructural changes within the cord, and assist in prognostication and planning of therapies. In this article, we review the use of DTI to investigate spinal cord pathology in animals and humans, and describe advances in this technique that establish DTI as a promising biomarker for spinal cord disorders.
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ABSTRACT: Traumatic spinal cord injury (SCI) causes long-term disability with limited functional recovery linked to the extent of axonal connectivity. Quantitative diffusion tensor imaging (DTI) of axonal integrity has been suggested as a potential biomarker for prognostic and therapeutic evaluation following trauma, but its correlation with functional outcomes has not been clearly defined. To examine this application, female Sprague-Dawley rats underwent mid-thoracic laminectomy followed by traumatic spinal cord contusion of differing severities or laminectomy without contusion. Locomotor scores and hindlimb kinematic data were collected for four weeks post-injury. Ex vivo DTI was then performed to assess axonal integrity using tractography and fractional anisotropy (FA), a numerical measure of relative white matter integrity, at the injury epicenter and at specific intervals rostral and caudal to the injury site. Immunohistochemistry for tissue sparing was also performed. Statistical correlation between imaging data and functional performance was assessed as the primary outcome. All injured animals showed some recovery of locomotor function while hindlimb kinematics revealed graded deficits consistent with injury severity. Standard T2 magnetic resonance sequences illustrated conventional spinal cord morphology adjacent to contusions while corresponding FA maps indicated graded white matter pathology within these adjacent regions. Positive correlations between locomotor (BBB score and gait kinematics) and imaging (FA values) parameters were also observed within these adjacent regions, most strongly within caudal segments beyond the lesion. Evaluation of axonal injury by DTI provides a mechanism for functional recovery assessment in a rodent spinal cord injury model. These findings suggest that focused DTI analysis of caudal spinal cord should be studied in human cases in relationship to motor outcome to augment outcome biomarkers for clinical cases.Journal of neurotrauma 04/2014; 31(15). DOI:10.1089/neu.2013.3238 · 3.97 Impact Factor
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ABSTRACT: To investigate the conventional magnetic resonance (MR) findings of cervical spinal cord, to explore the possible changes on diffusion tensor imaging (DTI) in patients with amyotrophic lateral sclerosis (ALS), and to assess the correlations between the changes on DTI and clinical parameters in patients with ALS. Conventional MR imaging (MRI) and DTI in 24 patients with ALS and 16 age-matched control subjects were obtained. On axial planes, regions of interest (ROIs) were marked in bilateral spinothalamic tracts (STs), posterior funiculus, and bilateral lateral corticospinal tracts (LCTs), respectively, at the levels of cervical 2-4 vertebral bodies. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values of these ROIs were estimated. Independent sample t test and Pearson correlation analysis were used. In patients with ALS, no abnormal findings were noted in the cervical spinal cord on conventional MRI. FA values of bilateral LCTs decreased significantly compared to those of the control group (P < .05), and ADC values of bilateral LCTs were significantly greater than those of the control group (P < .05). FA and ADC values of bilateral LCTs showed no significant difference between patients with definite and probable ALS (P > .05). No significant correlation existed between abnormal DTI parameters (FA and ADC values of bilateral LCTs) and clinical parameters (P > .05). Subtle abnormalities in bilateral LCTs in the "normal-appearing" cervical spinal cord can be detected using quantitative DTI technique in patients with ALS.Academic radiology 05/2014; 21(5):590-6. DOI:10.1016/j.acra.2014.01.014 · 2.08 Impact Factor
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ABSTRACT: A meta-analysis was conducted to assess alterations in measures of diffusion tensor imaging (DTI) in the patients of cervical spondylotic myelopathy (CSM), exploring the potential role of DTI as a diagnosis biomarker. A systematic search of all related studies written in English was conducted using PubMed, Web of Science, EMBASE, CINAHL, and Cochrane comparing CSM patients with healthy controls. Key details for each study regarding participants, imaging techniques, and results were extracted. DTI measurements, such as fractional anisotropy (FA), apparent diffusion coefficient (ADC), and mean diffusivity (MD) were pooled to calculate the effect size (ES) by fixed or random effects meta-analysis. 14 studies involving 479 CSM patients and 278 controls were identified. Meta-analysis of the most compressed levels (MCL) of CSM patients demonstrated that FA was significantly reduced (ES -1.52, 95% CI -1.87 to -1.16, P < 0.001) and ADC was significantly increased (ES 1.09, 95% CI 0.89 to 1.28, P < 0.001). In addition, a notable ES was found for lowered FA at C2-C3 for CSM vs. controls (ES -0.83, 95% CI -1.09 to -0.570, P < 0.001). Meta-regression analysis revealed that male ratio of CSM patients had a significant effect on reduction of FA at MCL (P = 0.03). The meta-analysis of DTI studies of CSM patients clearly demonstrated a significant FA reduction and ADC increase compared with healthy subjects. This result supports the use of DTI parameters in differentiating CSM patients from health subjects. Future researches are required to investigate the diagnosis performance of DTI in cervical spondylotic myelopathy.PLoS ONE 02/2015; 10(2):e0117707. DOI:10.1371/journal.pone.0117707 · 3.53 Impact Factor