Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America.
Department of Neurosurgery, Shanghai Institute of Neurosurgery, Shanghai Changzheng Hospital, Shanghai, China.
PLoS One. 2018 May 10;13(5):e0197056. doi: 10.1371/journal.pone.0197056. eCollection 2018.
Peritumoral edema impedes the full delineation of fiber tracts due to partial volume effects in image voxels that contain a mixture of cerebral parenchyma and extracellular water. The purpose of this study is to investigate the effect of incorporating a free water (FW) model of edema for white matter tractography in the presence of edema.
We retrospectively evaluated 26 consecutive brain tumor patients with diffusion MRI and T2-weighted images acquired presurgically. Tractography of the arcuate fasciculus (AF) was performed using the two-tensor unscented Kalman filter tractography (UKFt) method, the UKFt method with a reduced fiber tracking stopping fractional anisotropy (FA) threshold (UKFt+rFA), and the UKFt method with the addition of a FW compartment (UKFt+FW). An automated white matter fiber tract identification approach was applied to delineate the AF. Quantitative measurements included tract volume, edema volume, and mean FW fraction. Visual comparisons were performed by three experts to evaluate the quality of the detected AF tracts.
The AF volume in edematous brain hemispheres was significantly larger using the UKFt+FW method (p<0.0001) compared to UKFt, but not significantly larger (p = 0.0996) in hemispheres without edema. The AF size increase depended on the volume of edema: a significant correlation was found between AF volume affected by (intersecting) edema and AF volume change with the FW model (Pearson r = 0.806, p<0.0001). The mean FW fraction was significantly larger in tracts intersecting edema (p = 0.0271). Compared to the UKFt+rFA method, there was a significant increase of the volume of the AF tract that intersected the edema using the UKFt+FW method, while the whole AF volumes were similar. Expert judgment results, based on the five patients with the smallest AF volumes, indicated that the expert readers generally preferred the AF tract obtained by using the FW model, according to their anatomical knowledge and considering the potential influence of the final results on the surgical route.
Our results indicate that incorporating biophysical models of edema can increase the sensitivity of tractography in regions of peritumoral edema, allowing better tract visualization in patients with high grade gliomas and metastases.
由于影像体素中包含脑实质和细胞外水的混合物，因此瘤周水肿会阻碍纤维束的完全描绘，产生部分容积效应。本研究的目的是探讨在存在水肿的情况下，纳入水肿的自由水（FW）模型对白质束追踪的影响。
我们回顾性评估了 26 例连续的脑肿瘤患者，这些患者在术前均接受了弥散 MRI 和 T2 加权成像检查。使用双张量无迹卡尔曼滤波束追踪（UKFt）方法、降低纤维追踪停止各向异性分数（FA）阈值的 UKFt 方法（UKFt+rFA）以及添加 FW 隔室的 UKFt 方法（UKFt+FW）进行弓状束（AF）的束追踪。应用自动化白质纤维束识别方法来描绘 AF。定量测量包括束体积、水肿体积和平均 FW 分数。三位专家进行了视觉比较，以评估检测到的 AF 束的质量。
与 UKFt 相比，在水肿脑半球中，使用 UKFt+FW 方法时 AF 体积显著更大（p<0.0001），但在无水肿的半球中则无显著差异（p=0.0996）。AF 大小的增加取决于水肿的体积：与水肿（相交）的 AF 体积相关的 AF 体积变化与 FW 模型之间存在显著相关性（Pearson r=0.806，p<0.0001）。在与水肿相交的束中，FW 分数的平均值显著更大（p=0.0271）。与 UKFt+rFA 方法相比，使用 UKFt+FW 方法时，与水肿相交的 AF 束的体积显著增加，而整个 AF 体积相似。基于 5 例 AF 体积最小的患者的专家判断结果表明，根据他们的解剖学知识和考虑最终结果对手术路径的潜在影响，专家读者通常更喜欢使用 FW 模型获得的 AF 束。
我们的结果表明，纳入水肿的生物物理模型可以提高瘤周水肿区域束追踪的敏感性，使高级别胶质瘤和转移瘤患者的束可视化更好。
