Improving the Detection of Myelin Integrity in Multiple Sclerosis Using Selective Inversion Recovery for MRI With Quantitative Magnetization Transfer

Background: Selective inversion recovery quantitative magnetization transfer (SIR-qMT)-derived macromolecular to free water pool size ratio (PSR) and diffusion tensor imaging (DTI)-derived radial diffusivity (RD) are potential metrics for assessing myelin integrity in multiple sclerosis (MS). However, establishing their accuracy in identifying tissue injury is essential for clinical translation.

Purpose: To compare the accuracy and Cohen's effect size (ES) of PSR and RD in detecting and quantifying tissue injury in early MS.

Study type: Cross-sectional prospective study.

Subjects: Fourty-three subjects with newly diagnosed MS (mean age 38 ± 11 years, 70% females) and 18 age- and sex-matched healthy controls (HCs; age 38 ± 12 years, 62.5% females).

Field strength/sequence: 3-T MRI using T₁-weighted (T₁-w) turbo spin echo, T₂-w fluid-attenuated inversion recovery (FLAIR), DTI, and SIR-qMT sequences.

Assessment: T₂-lesions were identified as hyperintense on T₂-w-FLAIR, and chronic black holes (cBHs) by simultaneous T₂-w-FLAIR hyperintensity and T₁-w hypointensity. Regions of interest (ROIs) in normal-appearing white matter (NAWM) were classified as proximal (p) or distant (d) to lesions, while normal white matter (NWM) was identified in HCs. PSR and RD values of T₂-lesions and cBHs were compared to their matched p/dNAWM and NWM in HCs. Comparisons were also made between T₂-lesions and cBHs.

Statistical tests: Receiver operating characteristic curves evaluated metric accuracy, and paired t tests compared ES values of PSR and RD, with significance set at P < 0.050.

Results: We identified 823 T₂-lesions, 392 cBHs, 426 p-, and 213 d-NAWM ROIs in patients, and 162 NWM ROIs in HCs. PSR differed significantly in all comparisons, while RD was differed in all except cBHs vs. T₂-lesions (P = 0.051). PSR had significantly higher accuracy in differentiating T₂-lesions from p/dNAWM and NWM, with a larger ES when comparing T₂-lesions to p/dNAWM and NWM and cBHs to pNAWM and NWM.

Data conclusion: PSR offers superior accuracy and ES over RD in detecting tissue injury in MS.

Level of evidence: 1 TECHNICAL EFFICACY: Stage 2.