扩散张量成像评价鼻咽癌放疗后颞叶“正常脑白质”的临床应用研究

Clinical application of DTI on normal appearing white matter of temporal lobes in nasopharyngeal carcinoma after radiotherapy

目的:研究鼻咽癌患者放疗后在常规磁共振成像(MRI)中表现正常的颞叶脑白质在放疗前后不同阶段水分子的弥散特征,为放射性脑损伤的监测提供量化指标。方法:回顾性分析86例行常规MRI和扩散张量成像(DTI)检查的鼻咽癌患者的临床和影像资料。以放疗前15例患者作对照组,放疗后71例患者作为放疗组。测量各组患者的各向异性分数(FA)、平均扩散系数(MD)、表观扩散系数(ADC)、平行本征值(λ_‖)及垂直本征值(λ_⊥)等参数值,对各组数据进行单因素方差分析。结果:放疗后6个月内平均λ_‖值较放疗前明显减低(P<0.05),6个月后平均λ_‖值基本恢复至治疗前水平。放疗后12个月内平均λ_⊥值较放疗前明显升高(P<0.05),而12个月后平均λ_⊥值基本恢复至治疗前水平。放疗后12个月内平均FA值比放疗前明显下降(P<0.05)。结论:DTI可在常规MRI发现异常前检测到脑组织中尤其是白质微观结构的改变,有助于监测放射线的损伤程度,了解其修复过程的变化规律。

Objective:To study the diffusion characteristics of water molecules in normal temporal lobe white matter in conventional MRI after radiotherapy in patients with nasopharyngeal carcinoma, so as to provide quantitative indicators for the monitoring of radiation-induced brain injury. Methods:The clinical and imaging data of 86 patients with nasopharyngeal carcinoma who underwent routine MRI and DTI were analyzed retrospectively. 15 patients without radiotherapy were selected as the control group and 71 patients with radiotherapy were as the experimental group. The anisotropy fraction(FA),mean diffusion coefficient(MD),apparent diffusion coefficient(ADC),parallel eigenvalue(λ_‖) and vertical eigenvalue(λ_⊥) of each group were measured,and the data of each group were analyzed by one-way ANOVA. Results:The mean λ_‖value in 6 months after radiotherapy was significantly lower than that before radiotherapy(P<0.05). After 6 months,the mean λ_‖value basically recovered to the level before treatment. After 12 months of radiotherapy,the average λ_⊥ value was significantly higher than that before radiotherapy(P<0.05),but after 12 months,the average λ_⊥ value basically recovered to the level before treatment. The average FA value in 12 months after radiotherapy was significantly lower than that before radiotherapy(P<0.05). Conclusion: DTI can detect the changes of brain tissue, especially the microstructure of white matter, before finding abnormalities in conventional MRI,which is helpful to monitor the degree of radiation damage and understand the change rule of its repair process.