Test-retest reliability of myelin imaging in the human spinal cord: Measurement errors versus region- and aging-induced variations

PLoS One. 2018 Jan 2;13(1):e0189944. doi: 10.1371/journal.pone.0189944. eCollection 2018.

Abstract

Purpose: To implement a statistical framework for assessing the precision of several quantitative MRI metrics sensitive to myelin in the human spinal cord: T1, Magnetization Transfer Ratio (MTR), saturation imposed by an off-resonance pulse (MTsat) and Macromolecular Tissue Volume (MTV).

Methods: Thirty-three healthy subjects within two age groups (young, elderly) were scanned at 3T. Among them, 16 underwent the protocol twice to assess repeatability. Statistical reliability indexes such as the Minimal Detectable Change (MDC) were compared across metrics quantified within different cervical levels and white matter (WM) sub-regions. The differences between pathways and age groups were quantified and interpreted in context of the test-retest repeatability of the measurements.

Results: The MDC was respectively 105.7ms, 2.77%, 0.37% and 4.08% for T1, MTR, MTsat and MTV when quantified over all WM, while the standard-deviation across subjects was 70.5ms, 1.34%, 0.20% and 2.44%. Even though particular WM regions did exhibit significant differences, these differences were on the same order as test-retest errors. No significant difference was found between age groups for all metrics.

Conclusion: While T1-based metrics (T1 and MTV) exhibited better reliability than MT-based measurements (MTR and MTsat), the observed differences between subjects or WM regions were comparable to (and often smaller than) the MDC. This makes it difficult to determine if observed changes are due to variations in myelin content, or simply due to measurement error. Measurement error remains a challenge in spinal cord myelin imaging, but this study provides statistical guidelines to standardize the field and make it possible to conduct large-scale multi-center studies.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aging / metabolism*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Myelin Sheath / metabolism*
  • Reproducibility of Results
  • Spinal Cord / diagnostic imaging
  • Spinal Cord / metabolism*
  • Young Adult

Grant support

This study was funded by the Canada Research Chair in Quantitative Magnetic Resonance Imaging (JCA), the Canadian Institutes of Health Research [CIHR FDN-143263] (JCA), the Canadian Institutes of Health Research [CIHR MOP-130341] (JCA and PR), the Fonds de Recherche du Québec—Santé [FRQS-28826] (JCA), the Fonds de Recherche du Québec—Nature et Technologies [2015-PR-182754] (JCA), the Natural Sciences and Engineering Research Council of Canada [NSERC-435897-2013] (JCA), the Natural Sciences and Engineering Research Council of Canada [NSERC 2016-06774] (NS), the Quebec BioImaging Network (JCA) and the Montreal Heart Institute Foundation (NS). Those funds were used for MRI data acquisition, computer and software resources and authors’ funding.