Raja Rajikha, Na Xiaoxu, Glasier Charles, Badger Thomas, Akmyradov Chary, Ou Xiawei
Department of Radiology, University of Arkansas for Medical Sciences.
Department of Pediatrics, University of Arkansas for Medical Sciences.
Proc SPIE Int Soc Opt Eng. 2022 Feb-Mar;12036. doi: 10.1117/12.2607490. Epub 2022 Apr 4.
Structural substrates of sex differences in human function and behavior have been elucidated in previous studies. Diffusion weighted magnetic resonance imaging (DW-MRI) is a widely used non-invasive imaging technique in studying human brain white matter structural organization. While many DW-MRI studies reporting sex differences in WM structure are based on diffusion tensor imaging (DTI) measures, tract specific microstructural differences require further investigation. In this study, we aim to investigate sex differences and sex-specific hemispheric differences in white matter microstructural development in healthy 8-year-old children based on novel track weighted imaging (TWI) analysis. Average pathlength map (APM) is a TWI contrast in which the average length of fibers passing through a voxel is utilized. In this study, we employed tract specific APM measures to evaluate sex differences in WM microstructural development. A total of 37 WM tracts were analyzed including 7 commissural tracts, 9 bilateral association tracts and 6 bilateral projection tracts. APM maps were generated for each tract. Tract-wise group tests were done using the mean values of APM maps. Sex differences were tested using general linear model based group comparisons. Age and total brain volume were included as covariates in the group analysis. Sex specific hemispheric differences were performed for the 15 bilateral tracts. One sample t-tests were done independently for left>right and right>left cases and the APM measures were controlled for age and total cerebral hemispheric volume. P-values<0.05 were considered significant after correcting for multiple comparisons accounting for the total number of tracts. Significant sex differences were revealed in APM measures between boys and girls in 11 WM tracts including rostral body of corpus callosum (CC), left inferior fronto-occipital fasciculus (IFOF), right cingulum, bilateral first and second segments of superior longitudinal fasciculus (SLF), right middle longitudinal fasciculus (MLF), bilateral fronto-pontine (FPT) and right parieto-occipital pontine tracts (POPT). The sex differences showed higher APM values for these 11 tracts in boys as compared to that of girls. In hemispheric differences analysis for both boys and girls, 2 tracts, arcuate fasciculus and optic radiation showed higher APM in left tracts as compared right; 5 tracts, IFOF, MLF, third segment of SLF, FPT and superior thalamic radiation showed higher APM in right tracts as compared to left. This indicates that boys and girls possess similar lateral asymmetries in these 7 tracts. Additionally, anterior thalamic radiation (ATR) showed higher APM in left tract and 4 tracts, first segment of SLF, POPT, inferior longitudinal fasciculus and cortico-spinal tract showed higher APM in right for boys. In girls, second segment of SLF and uncinate fasciculus showed higher APM in right hemisphere. These results indicate different lateral asymmetries between boys and girls for 7 tracts. Overall, boys showed higher average fiber length in most of the tracts, even after controlling for total brain volume.
以往研究已阐明人类功能和行为性别差异的结构基础。扩散加权磁共振成像（DW-MRI）是一种广泛应用于研究人类脑白质结构组织的非侵入性成像技术。虽然许多报告白质结构性别差异的DW-MRI研究是基于扩散张量成像（DTI）测量，但特定脑区的微观结构差异仍需进一步研究。在本研究中，我们旨在基于新型轨迹加权成像（TWI）分析，调查8岁健康儿童白质微观结构发育中的性别差异和性别特异性半球差异。平均路径长度图（APM）是一种TWI对比度，其中利用了穿过体素的纤维的平均长度。在本研究中，我们采用特定脑区的APM测量来评估白质微观结构发育中的性别差异。共分析了37条白质束，包括7条连合束、9条双侧联合束和6条双侧投射束。为每条束生成了APM图。使用APM图的平均值进行逐束组检验。使用基于一般线性模型的组比较来检验性别差异。在组分析中纳入年龄和全脑体积作为协变量。对15条双侧束进行性别特异性半球差异分析。分别对左>右和右>左的情况进行单样本t检验，并对APM测量值进行年龄和全脑半球体积校正。在考虑束总数进行多重比较校正后，P值<0.05被认为具有显著性。在11条白质束中发现男孩和女孩之间的APM测量存在显著性别差异，包括胼胝体膝部（CC）、左侧额枕下束（IFOF）、右侧扣带束、双侧上纵束（SLF）的第一和第二段、右侧中纵束（MLF）、双侧额桥束（FPT）和右侧顶枕桥束（POPT）。这些11条束的性别差异显示男孩的APM值高于女孩。在男孩和女孩的半球差异分析中，2条束，即弓状束和视辐射，左侧束的APM高于右侧；5条束，即IFOF、MLF、SLF的第三段、FPT和丘脑上辐射，右侧束的APM高于左侧。这表明男孩和女孩在这7条束中具有相似的侧向不对称性。此外，男孩的丘脑前辐射（ATR）左侧束的APM较高，4条束，即SLF的第一段、POPT、下纵束和皮质脊髓束右侧的APM较高。在女孩中，SLF的第二段和钩束右侧半球的APM较高。这些结果表明男孩和女孩在7条束中存在不同的侧向不对称性。总体而言，即使在控制全脑体积后，男孩在大多数束中显示出更高的平均纤维长度。
