Departments of Radiology,; Neuroscience, and.
Neuroscience, and.
Neuroimage. 2022 Sep;258:119360. doi: 10.1016/j.neuroimage.2022.119360. Epub 2022 Jun 10.
T1-weighted divided by T2-weighted (T1w/T2w) myelin maps were initially developed for neuroanatomical analyses such as identifying cortical areas, but they are increasingly used in statistical comparisons across individuals and groups with other variables of interest. Existing T1w/T2w myelin maps contain radiofrequency transmit field (B1+) biases, which may be correlated with these variables of interest, leading to potentially spurious results. Here we propose two empirical methods for correcting these transmit field biases using either explicit measures of the transmit field or alternatively a 'pseudo-transmit' approach that is highly correlated with the transmit field at 3T. We find that the resulting corrected T1w/T2w myelin maps are both better neuroanatomical measures (e.g., for use in cross-species comparisons), and more appropriate for statistical comparisons of relative T1w/T2w differences across individuals and groups (e.g., sex, age, or body-mass-index) within a consistently acquired study at 3T. We recommend that investigators who use the T1w/T2w approach for mapping cortical myelin use these B1+ transmit field corrected myelin maps going forward.
T1 加权与 T2 加权（T1w/T2w）比值脑白质图谱最初是为神经解剖学分析而开发的，例如识别皮质区域，但它们越来越多地用于个体之间和具有其他感兴趣变量的群体之间的统计比较。现有的 T1w/T2w 脑白质图谱包含射频发射场（B1+）偏差，这些偏差可能与这些感兴趣的变量相关，从而导致潜在的虚假结果。在这里，我们提出了两种使用发射场的显式测量值或与 3T 下的发射场高度相关的“伪发射”方法来校正这些发射场偏差的经验方法。我们发现，校正后的 T1w/T2w 脑白质图谱既是更好的神经解剖学指标（例如，用于跨物种比较），也是更适合个体和群体之间相对 T1w/T2w 差异的统计比较（例如，性别、年龄或体重指数），在 3T 下进行一致采集的研究中。我们建议使用 T1w/T2w 方法进行皮质髓鞘映射的研究人员在未来使用这些校正 B1+发射场的髓鞘图谱。
