Measurement of magnetization transfer ratio (MTR) from cervical spinal cord: Multicenter reproducibility and variability

Abstract

Background Assessing the multicenter variability of magnetization transfer ratio (MTR) measurements in the spinal cord of healthy controls is the first step toward investigating its clinical use as a biomarker. Purpose To analyze the between‐session, between‐participant, and between‐scanner variability of MTR measurements in automatically extracted regions of interest in the cervical cord of healthy controls. Study Type Control study. Population Forty‐four participants, distributed across five MRI scanners (all from the same manufacturer). Ten participants were scanned twice in the same scanner, and 10 others were scanned twice in two different scanners. Field Strength/Sequence 3D‐gradient echo images, centered on C5, without and with magnetization transfer prepulse at 3T. Assessment We calculated the mean MTR for different vertebral levels in the whole cord (WC), as well as in the white matter and gray matter, and determined the between‐session, between‐participant, and between‐scanner variabilities. Statistical Tests Coefficients of variation and intraclass correlations (ICCs) for the different variabilities and their associated confidence intervals. Results The MTR measurements for Levels C4‐C6 (near the slab center) exhibited a mean value in WC of 34.6 pu and a pooled standard deviation of 0.9 pu. The between‐session coefficient of variation was estimated as 2.3% (ICC = 0.63), the between‐participant coefficient as 1.6% (ICC = 0.32), and the between‐scanner coefficient as 0.7% (ICC = 0.05). The resulting aggregate coefficient of variation was 2.9%, which was sufficiently low to detect an MTR reduction of 1 pu between groups of about 45 participants (Type‐I error rate: 0.05; Type‐II error rate: 0.10). Data Conclusion The good between‐scanner reproducibility and low overall variability in cervical spinal cord MTR measurements in a control population might pave the way for multicenter analyses in various neurological diseases with moderate cohort sizes. Level of Evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:1777–1785.

Advanced spinal cord MRI in multiple sclerosis: Current techniques and future directions

“…MT imaging has been extensively explored in the brain and, to a lesser degree, in the SC, primarily due to the simplicity of the pulse sequence and relative ease of post-processing. The MT Ratio (MTR) has been shown to be sensitive to de- and re-myelination ( Chen et al, 2008 ), yet uncertainty still remains about its specificity for myelin ( Vavasour et al, 2011 ) and its reproducibility ( van der Weijden et al, 2021 ), including in the SC specifically ( Combès et al, 2019 , Lévy et al, 2018 ). As such, it is not ideally positioned to be considered for large, multi-center trials due to its sensitivity to pulse sequence design, non-physiological indices, vendor differences, and field strength.…”

Effect of distortion corrections on the tractography quality in spinal cord diffusion‐weighted imaging

“…In the present study, spinal cord DWI data of healthy subjects were extracted from the EMISEP (Early Spinal Cord Lesions and Late Disability in Relapsing Remitting Multiple Sclerosis Patients) database. The EMISEP study was a prospective, multicenter (five centers), longitudinal study that recruited healthy subjects and patients with multiple sclerosis for cranial and spinal cord MRI (Clinical Trials ID: NCT02117375) 31 . The institutional review board (IRCB: 2013‐A00333‐42) approved the study, and written informed consent was obtained from all participants.…”

“…The EMISEP study was a prospective, multicenter (five centers), longitudinal study that recruited healthy subjects and patients with multiple sclerosis for cranial and spinal cord MRI (Clinical Trials ID: NCT02117375). 31 The institutional review board (IRCB: 2013-A00333-42) approved the study, and written informed consent was obtained from all participants.…”