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Scan-rescan of axcaliber, macromolecular tissue volume, and g-ratio in the spinal cord.

ABSTRACT: PURPOSE:Recent MRI techniques have been introduced that can extract microstructural information in the white matter, such as the density or macromolecular content. Translating quantitative MRI to the clinic raises many challenges in terms of acquisition strategy, modeling of the MRI signal, artifact corrections, and metric extraction (template registration and partial volume effects). In this work, we investigated the scan-rescan repeatability of several quantitative MRI techniques in the human spinal cord. METHODS:AxCaliber metrics, macromolecular tissue volume, and the fiber g-ratio were estimated in the spinal cord of eight healthy subjects, scanned and rescanned the same day in two different sessions. RESULTS:Scan-rescan repeatability deviation was 3% for all metrics, in average in the white matter of all subjects. Intraclass correlation coefficient was up to 0.9. A three-way analysis of variance showed significant effects of white matter pathway, laterality, and subject. CONCLUSION:The present study suggests that quantitative MRI gives stable measurements of white matter microstructure in the spinal cord of healthy subjects. Our findings remain to be evaluated in diseased populations. Magn Reson Med 79:2759-2765, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

SUBMITTER: Duval T

PROVIDER: S-EPMC5821542 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature

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Scan-rescan of axcaliber, macromolecular tissue volume, and g-ratio in the spinal cord.

Duval Tanguy T Smith Victoria V Stikov Nikola N Klawiter Eric C EC Cohen-Adad Julien J

Magnetic resonance in medicine 20171010 5

<h4>Purpose</h4>Recent MRI techniques have been introduced that can extract microstructural information in the white matter, such as the density or macromolecular content. Translating quantitative MRI to the clinic raises many challenges in terms of acquisition strategy, modeling of the MRI signal, artifact corrections, and metric extraction (template registration and partial volume effects). In this work, we investigated the scan-rescan repeatability of several quantitative MRI techniques in th ...[more]

PMID: 28994487

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Project description:Background/objectiveWe have recently developed monitoring from the injury site in patients with acute, severe traumatic spinal cord injuries to facilitate their management in the intensive care unit. This is analogous to monitoring from the brain in patients with traumatic brain injuries. This study aims to determine whether, after traumatic spinal cord injury, fluctuations in the monitored physiological, and metabolic parameters at the injury site are causally linked to changes in limb power.MethodsThis is an observational study of a cohort of adult patients with motor-incomplete spinal cord injuries, i.e., grade C American spinal injuries association Impairment Scale. A pressure probe and a microdialysis catheter were placed intradurally at the injury site. For up to a week after surgery, we monitored limb power, intraspinal pressure, spinal cord perfusion pressure, and tissue lactate-to-pyruvate ratio. We established correlations between these variables and performed Granger causality analysis.ResultsNineteen patients, aged 22-70 years, were recruited. Motor score versus intraspinal pressure had exponential decay relation (intraspinal pressure rise to 20 mmHg was associated with drop of 11 motor points, but little drop in motor points as intraspinal pressure rose further, R2 = 0.98). Motor score versus spinal cord perfusion pressure (up to 110 mmHg) had linear relation (1.4 motor point rise/10 mmHg rise in spinal cord perfusion pressure, R2 = 0.96). Motor score versus lactate-to-pyruvate ratio (greater than 20) also had linear relation (0.8 motor score drop/10-point rise in lactate-to-pyruvate ratio, R2 = 0.92). Increased intraspinal pressure Granger-caused increase in lactate-to-pyruvate ratio, decrease in spinal cord perfusion, and decrease in motor score. Increased spinal cord perfusion Granger-caused decrease in lactate-to-pyruvate ratio and increase in motor score. Increased lactate-to-pyruvate ratio Granger-caused increase in intraspinal pressure, decrease in spinal cord perfusion, and decrease in motor score. Causality analysis also revealed multiple vicious cycles that amplify insults to the cord thus exacerbating cord damage.ConclusionMonitoring intraspinal pressure, spinal cord perfusion pressure, lactate-to-pyruvate ratio, and intervening to normalize these parameters are likely to improve limb power.

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Scan-rescan of axcaliber, macromolecular tissue volume, and g-ratio in the spinal cord.

Publications

Scan-rescan of axcaliber, macromolecular tissue volume, and g-ratio in the spinal cord.

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