Skip to main content
Test–Retest Reproducibility of In Vivo Magnetization Transfer Ratio and Saturation Index in Mice at 9.4 Tesla
Journal of Magnetic Resonance Imaging
  • Naila Rahman, Robarts Research Institute
  • Jordan Ramnarine, Robarts Research Institute
  • Kathy Xu, Robarts Research Institute
  • Arthur Brown, Robarts Research Institute
  • Corey A. Baron, Robarts Research Institute
Document Type
Publication Date
URL with Digital Object Identifier

Background: Magnetization transfer saturation (MTsat) imaging was developed to reduce T1 dependence and improve specificity to myelin, compared to the widely used MT ratio (MTR) approach, while maintaining a feasible scan time. As MTsat imaging is an emerging technique, the reproducibility of MTsat compared to MTR must be evaluated. Purpose: To assess the test–retest reproducibility of MTR and MTsat in the mouse brain at 9.4 T and calculate sample sizes potentially required to detect effect sizes ranging from 6% to 14%. Study Type: Prospective. Subjects: Twelve healthy C57Bl/6 mice. Field Strength/Sequence: 9.4 T; magnetization transfer imaging using FLASH-3D Gradient Echo; T2-weighted TurboRARE spin echo. Assessment: All mice were scanned at two timepoints (5 days apart). MTR and MTsat maps were analyzed using mean region-of-interest (ROIs: corpus callosum [CC], internal capsule [IC], hippocampus [HC], cortex [CX], and thalamus [TH]), and whole brain voxel-wise analysis. Statistical Tests: Bland–Altman plots were used to assess biases between test–retest measurements. Test–retest reproducibility was evaluated via between and within-subject coefficients of variation (bsCV and wsCV, respectively). Sample sizes required were calculated (significance level: 95%; power: 80%), given effect sizes ranging from 6% to 14%, using both between and within-subject approaches. Results were considered statistically significant at P ≤ 0.05. Results: Bland–Altman plots showed negligible biases between test–retest sessions (MTR: 0.0009; MTsat: 0). ROI-based and voxel-wise CVs revealed high reproducibility for both MTR (ROI-bsCV/wsCV: CC—4.5/2.8%; IC—6.1/5.2%; HC—5.7/4.6%; CX—5.1/2.3%; TH—7.4/4.9%) and MTsat (ROI-bsCV/wsCV: CC—6.3/4.8%; IC—7.3/5.1%; HC—9.5/6.4%; CX—6.7/6.5%; TH—7.2/5.3%). With a sample size of 6, changes on the order of 15% could be detected in MTR and MTsat, both between and within subjects, while smaller changes (6%–8%) required sample sizes of 10–15 for MTR, and 15–20 for MTsat. Data Conclusion: MTsat exhibited comparable reproducibility to MTR, while providing sensitivity to myelin with less T1 dependence than MTR. Evidence Level: 2. Technical Efficacy: Stage 1.

Citation Information
Naila Rahman, Jordan Ramnarine, Kathy Xu, Arthur Brown, et al.. "Test–Retest Reproducibility of In Vivo Magnetization Transfer Ratio and Saturation Index in Mice at 9.4 Tesla" Journal of Magnetic Resonance Imaging (2022)
Available at: