Test-retest reproducibility of in vivo oscillating gradient and microscopic anisotropy diffusion MRI in mice at 9.4 Tesla

PLoS One. 2021 Nov 5;16(11):e0255711. doi: 10.1371/journal.pone.0255711. eCollection 2021.

Abstract

Background and purpose: Microstructure imaging with advanced diffusion MRI (dMRI) techniques have shown increased sensitivity and specificity to microstructural changes in various disease and injury models. Oscillating gradient spin echo (OGSE) dMRI, implemented by varying the oscillating gradient frequency, and microscopic anisotropy (μA) dMRI, implemented via tensor valued diffusion encoding, may provide additional insight by increasing sensitivity to smaller spatial scales and disentangling fiber orientation dispersion from true microstructural changes, respectively. The aims of this study were to characterize the test-retest reproducibility of in vivo OGSE and μA dMRI metrics in the mouse brain at 9.4 Tesla and provide estimates of required sample sizes for future investigations.

Methods: Twelve adult C57Bl/6 mice were scanned twice (5 days apart). Each imaging session consisted of multifrequency OGSE and μA dMRI protocols. Metrics investigated included μA, linear diffusion kurtosis, isotropic diffusion kurtosis, and the diffusion dispersion rate (Λ), which explores the power-law frequency dependence of mean diffusivity. The dMRI metric maps were analyzed with mean region-of-interest (ROI) and whole brain voxel-wise analysis. Bland-Altman plots and coefficients of variation (CV) were used to assess the reproducibility of OGSE and μA metrics. Furthermore, we estimated sample sizes required to detect a variety of effect sizes.

Results: Bland-Altman plots showed negligible biases between test and retest sessions. ROI-based CVs revealed high reproducibility for most metrics (CVs < 15%). Voxel-wise CV maps revealed high reproducibility for μA (CVs ~ 10%), but low reproducibility for OGSE metrics (CVs ~ 50%).

Conclusion: Most of the μA dMRI metrics are reproducible in both ROI-based and voxel-wise analysis, while the OGSE dMRI metrics are only reproducible in ROI-based analysis. Given feasible sample sizes (10-15), μA metrics and OGSE metrics may provide sensitivity to subtle microstructural changes (4-8%) and moderate changes (> 6%), respectively.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Anisotropy
  • Brain / diagnostic imaging*
  • Diffusion Magnetic Resonance Imaging / methods*
  • Mice
  • Mice, Inbred C57BL
  • Reproducibility of Results

Grants and funding

The authors would like to acknowledge the Canada First Research Excellence Fund (BrainsCAN - https://brainscan.uwo.ca/); the New Frontiers in Research Fund (NFRFE-2018-01290 - https://www.sshrc-crsh.gc.ca/funding-financement/nfrf-fnfr/index-eng.aspx), awarded to CB; the Natural Sciences and Engineering Research Council of Canada: Canada Graduate Scholarships - Master’s Program (NSERC-CGS M), awarded to NR; and the Ontario Graduate Scholarship (OGS), awarded to NR, for their funding contributions. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.