辐射治疗对边缘回路白质纤维束的影响。
Radiation therapy effects on white matter fiber tracts of the limbic circuit.
机构信息
Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, USA.
出版信息
Med Phys. 2012 Sep;39(9):5603-13. doi: 10.1118/1.4745560.
PURPOSE
To segment fiber tracts in the limbic circuit and to assess their sensitivity to radiation therapy (RT).
METHODS
Twelve patients with brain metastases who had received fractionated whole brain radiation therapy to 30 Gy or 37.5 Gy were included in the study. Diffusion weighted images were acquired pre-RT, at the end of RT, and 1-month post-RT. The fornix, corpus callosum, and cingulum were extracted from diffusion weighted images by combining fiber tracking and segmentation methods based upon characteristics of the fiber bundles. Cingulum was segmented by a seed-based tractography, fornix by a region of interests (ROI)-based tractography, and corpus callosum by a level-set segmentation algorithm. The radiation-induced longitudinal changes of diffusion indices of the structures were evaluated.
RESULTS
Significant decreases were observed in the fractional anisotropy of the posterior part of the cingulum, fornix, and corpus callosum from pre-RT to end of RT by -14.0%, -12.5%, and -5.2%, respectively (p < 0.001), and from pre-RT to 1-month post-RT by -11.9%, -12.8%, and -6.4%, respectively (p < 0.001). Moreover, significant increases were observed in the mean diffusivity of the corpus callosum and the posterior part of the cingulum from pre-RT to end of RT by 6.8% and 6.5%, respectively, and from pre-RT to 1-month post-RT by 8.5% and 6.3%, respectively. The increase in the radial diffusivity primarily contributed to the significant decrease in the fractional anisotropy, indicating that demyelination is the predominant radiation effect on the white matter structures.
CONCLUSIONS
Our findings indicate that the fornix and the posterior part of the cingulum are significantly susceptible to radiation damage. We have developed robust computer-aided semiautomatic segmentation and fiber tracking tools to facilitate the ROI delineation of critical structures, which is important for assessment of radiation damage in a longitudinal fashion.
目的
分割边缘回路中的纤维束，并评估其对放射治疗（RT）的敏感性。
方法
本研究纳入了 12 例接受全脑分割放疗（30Gy 或 37.5Gy）的脑转移瘤患者。在 RT 前、RT 结束时和 RT 后 1 个月采集弥散加权图像。通过结合基于纤维束特征的纤维跟踪和分割方法，从弥散加权图像中提取穹窿、胼胝体和扣带回。扣带回通过基于种子的轨迹追踪进行分割，穹窿通过基于感兴趣区（ROI）的轨迹追踪进行分割，胼胝体通过水平集分割算法进行分割。评估结构弥散指数的放射诱导纵向变化。
结果
从 RT 前到 RT 结束，后扣带回、穹窿和胼胝体的各向异性分数分别下降了-14.0%、-12.5%和-5.2%（p<0.001），从 RT 前到 RT 后 1 个月分别下降了-11.9%、-12.8%和-6.4%（p<0.001）。此外，从 RT 前到 RT 结束，胼胝体和后扣带回的平均弥散度分别增加了 6.8%和 6.5%，从 RT 前到 RT 后 1 个月分别增加了 8.5%和 6.3%。径向弥散度的增加主要导致各向异性分数的显著降低，表明脱髓鞘是放射对脑白质结构的主要影响。
结论
我们的发现表明穹窿和后扣带回对放射损伤非常敏感。我们已经开发了强大的计算机辅助半自动分割和纤维追踪工具，以促进关键结构的 ROI 描绘，这对于纵向评估放射损伤非常重要。
Zotero 插件