Centre for Functional and Metabolic Mapping (CFMM), Robarts Research Institute, University of Western Ontario, London, Ontario, Canada.
Department of Medical Biophysics, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada.
J Magn Reson Imaging. 2022 Sep;56(3):893-903. doi: 10.1002/jmri.28106. Epub 2022 Feb 14.
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.
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%.
Prospective.
Twelve healthy C57Bl/6 mice.
FIELD STRENGTH/SEQUENCE: 9.4 T; magnetization transfer imaging using FLASH-3D Gradient Echo; T2-weighted TurboRARE spin echo.
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.
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.
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.
MTsat exhibited comparable reproducibility to MTR, while providing sensitivity to myelin with less T1 dependence than MTR. EVIDENCE LEVEL: 2 TECHNICAL EFFICACY: Stage 1.
与广泛应用的 MT 比（MTR）方法相比，磁化传递饱和（MTsat）成像旨在降低 T1 依赖性并提高髓鞘的特异性，同时保持可行的扫描时间。由于 MTsat 成像技术是一种新兴技术，因此必须评估 MTsat 与 MTR 的可重复性。
评估 9.4 T 下小鼠大脑中 MTR 和 MTsat 的测试-重测可重复性，并计算可能需要的样本量，以检测从 6%到 14%的效应大小。
前瞻性。
12 只健康的 C57Bl/6 小鼠。
磁场强度/序列：9.4 T；使用 FLASH-3D Gradient Echo 进行磁化传递成像；T2 加权 TurboRARE 自旋回波。
所有小鼠均在两个时间点（相隔 5 天）进行扫描。使用平均 ROI（胼胝体[CC]、内囊[IC]、海马[HC]、皮质[CX]和丘脑[TH]）和全脑体素分析来分析 MTR 和 MTsat 图。
使用 Bland-Altman 图评估测试-重测测量之间的偏差。通过组内和组间系数的变异（bsCV 和 wsCV，分别）评估测试-重测的可重复性。使用组内和组间方法计算了从 6%到 14%的效应大小所需的样本量（显著性水平：95%；功率：80%）。结果以 P≤0.05 为统计学显著。
Bland-Altman 图显示测试-重测之间的偏差可以忽略不计（MTR：0.0009；MTsat：0）。基于 ROI 和体素的 CV 显示 MTR 的重复性很高（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%）和 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%）。在 6 个样本的情况下，无论是在组内还是组间，MTR 和 MTsat 都可以检测到 15%左右的变化，而较小的变化（6%-8%）则需要 10-15 个样本的 MTR 和 15-20 个样本的 MTsat。
MTsat 与 MTR 具有相似的可重复性，同时提供了比 MTR 对髓鞘的敏感性，对 T1 依赖性较小。
2 技术功效：1 级。
