Carlson Helen L, Laliberté Christianne, Brooks Brian L, Hodge Jacquie, Kirton Adam, Bello-Espinosa Luis, Hader Walter, Sherman Elisabeth M S
Alberta Children's Hospital, 2888 Shaganappi Tr NW, Calgary, AB T3B 6A8, Canada; Alberta Children's Hospital Research Institute (ACHRI), Room 293, Heritage Medical Research Building, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada.
Alberta Children's Hospital, 2888 Shaganappi Tr NW, Calgary, AB T3B 6A8, Canada.
Epilepsy Behav. 2014 Aug;37:116-22. doi: 10.1016/j.yebeh.2014.06.020. Epub 2014 Jul 10.
Diffusion tensor imaging (DTI) tractography is useful for isolating white matter (WM) trajectories and exploring microstructural integrity. Tractography can be performed on atypical brain anatomy when landmarks are malformed or displaced but has been criticized for its subjectivity even when investigators have advanced anatomical knowledge. Also, little is known about the variability and reliability of tractography as a tool for assessing white matter damage in clinical populations such as children with pediatric epilepsy.
Children diagnosed with epilepsy [N=43, mean age=11.7 years, standard deviation=3.7 years, 53% male] underwent a DTI sequence (6 directions, 2×2×3 mm voxels). Tractography for six white matter tracts (anterior forceps, fornices, bilateral arcuate fasciculi, and bilateral anterior cingula) was conducted twice by two experienced tractographers. Percent coefficient of variation (CV; for measuring variability) and intraclass correlation coefficients (ICCs; for measuring reliability) were calculated for tract volume and diffusion variables (fractional anisotropy [FA], mean diffusivity [MD], axial diffusivity [AD] and radial diffusivity [RD]).
Diffusion variables showed low variability (CV=2.7-8.8%) and very high reliability (ICC=.97-.99) except for limbic tracts [fornix (ICC=.75-.94); cingulum (ICC=.71-.98)]. Tract volume measurements showed high variability (CV=21.9-62.0%) and moderate reliability (ICC=.54-.99). Overall, tract volume measurements were much more variable and less reliable than diffusion characteristics. Limbic structures showed more variability compared with others.
This suggests that DTI tractography and resulting diffusivity variables can reliably inform on the integrity of WM structures in a clinical sample with pediatric epilepsy and highlights the importance of reporting reliability information in studies that aim to answer clinical questions about WM integrity.
扩散张量成像（DTI）纤维束成像有助于分离白质（WM）轨迹并探索微观结构完整性。当标志点畸形或移位时，纤维束成像可用于非典型脑解剖结构，但即使研究者具备先进的解剖学知识，其主观性也受到批评。此外，对于纤维束成像作为评估临床人群（如小儿癫痫患儿）白质损伤工具的变异性和可靠性知之甚少。
43名被诊断为癫痫的儿童[平均年龄=11.7岁，标准差=3.7岁，53%为男性]接受了DTI序列扫描（6个方向，体素大小为2×2×3毫米）。两名经验丰富的纤维束成像技术人员对六条白质束（前连合、穹窿、双侧弓状束和双侧前扣带回）进行了两次纤维束成像。计算了纤维束体积和扩散变量（分数各向异性[FA]、平均扩散率[MD]、轴向扩散率[AD]和径向扩散率[RD]）的变异系数百分比（CV；用于测量变异性）和组内相关系数（ICC；用于测量可靠性）。
除边缘束[穹窿（ICC=0.75-0.94）；扣带回（ICC=0.71-0.98）]外，扩散变量显示出低变异性（CV=2.7-8.8%）和非常高的可靠性（ICC=0.97-0.99）。纤维束体积测量显示出高变异性（CV=21.9-62.0%）和中等可靠性（ICC=0.54-0.99）。总体而言，纤维束体积测量比扩散特征更具变异性且可靠性更低。与其他结构相比，边缘结构显示出更大的变异性。
这表明DTI纤维束成像及其产生的扩散率变量能够可靠地反映小儿癫痫临床样本中WM结构的完整性，并强调了在旨在回答有关WM完整性临床问题的研究中报告可靠性信息的重要性。
