鼻咽癌放射治疗后“正常脑白质”的DTI及DSC-PWI研究

DTI and DSC-PWI on normal appearing white matter after radiotherapy for nasopharyngeal carcinoma

目的探讨鼻咽癌放疗后急性期与早期迟发性反应期双侧颞叶脑白质磁共振扩散张量成像(DTI)及动态敏感对比增强灌注加权成像(DSC-PWI)的变化特点。方法鼻咽癌放疗前及放疗后复查患者各16例,放疗前患者作为对照组,放疗后患者处于放疗后0～6个月内,即放疗后急性期与早期迟发性反应期,作为试验组。两组间性别、年龄、受教育程度、吸烟及饮酒等因素无统计学差异。所有受试者均行扩散张量成像(DTI)及动态敏感对比增加灌注加权成像(DSC-PWI)检查,原始图像进行后处理后,测量各组双侧颞叶DTI的各向异性分数(FA)、平行本征值(λ║)及垂直本征值(λ⊥),以及各组双侧颞叶PWI的相对血流量(rCBF),所得数据进行两独立样本t检验。结果放疗后FA值与对照组相比显著降低,放疗后λ║与放疗前相比显著降低,放疗后λ⊥与放疗前相比显著升高;放疗后rCBF值比对照组明显降低,且差异有统计学意义。结论 DTI和DSC-PWI可以显示放疗后神经组织及血管的显微损伤,血管损伤及其所致的血流量减低可能参与了放射治疗诱发的早期脑组织损伤。

Objective To detect the changes of temporal lobes white mater after radiation therapy （RT） for nasopharyngeal carcinoma （NPC） using diffusion tensor imaging （DTI） and dynamic susceptibility contrast-enhanced perfusion-weighted imaging （DSC-PWI）. Methods The study included 32 subjects, who had or had not undergone radiotherapy for naso-pharyngeal carcinoma of these, 16 were pre-treatment patients; the remaining 16 were post-radiation patients. The pre-ra- diation subjects constituted the control group. The post-radiation patients, who had undergone radiation therapy less than 6 months prior, representing an acute response in the early period after radiation therapy, were the experimental group. There were no statistically significant differences between the groups with respect to age, gender, duration of education, cigarette smoking or alcohol consumption. DTI and DSC-PWI were performed for each subject. After data post-processing, the mean fractional anisotropy （FA）, axial diffusivity （λ｜ ）, radial diffusivity （λ⊥） and relative celebral blood flow （rCBF） were calculated in bilateral temporal lobe. To find the layer of cerebral peduncle, one ROI was then marked on unilateral temporal lobe white matter in each subject. These ROIs were of equal area. The average of these values in the temporal lobes white matter was accepted as the final value. For all the data, two-sample t-test was performed. Results FA value and λ｜ decreased significantly in the post-radiation group compared to the pre-radiation group; λ⊥ increased significantly in the post-radiation group compared to the pre-radiation group; rCBF decreased significantly in the post-radiation group compared to the pre-radiation group. Conclusion The results of the present study illustrated micro injury of nerve tissue and blood vessel can be detected by DTI and DSC-PWI. Vascular damage and the resulting decrease in blood flow may participant in neural tissue injury in the early stage after radiotherapy.