超急性期放射性脑损伤的MRS和DTI研究

MR Spectroscopy and Diffuse Tensor Imaging in Super-acute Stage of Radiation Induced Brain Injury

目的:探讨MRS和扩散张量成像(DTI)对超急性期放射性脑损伤的诊断价值。方法:18例经病理证实的鼻咽癌初诊患者,在放疗前及放疗后接受总放射剂量分别为20Gy、40Gy和60Gy时,进行颅脑MRI常规扫描、双侧颞叶1H-MRS多体素成像和DTI,将不同时期MRS检查所获得的颞叶Cho/Cr、NAA/Cr和NAA/Cho及DTI检查所测量的表观扩散系数(ADC)和部分各向异性(FA)值进行对比分析。结果:接受放射总剂量60Gy后,所有患者常规MRI扫描均未发现异常信号。MRS检查显示双侧颞叶前部的各代谢物比值在接受放射治疗后降低,并且所测各值的变化与放疗剂量呈负相关改变;DTI结果显示ADC值升高,FA值降低。结论:MRS和DTI能从组织细胞功能代谢水平对放射性脑损伤超急性反应进行评价,为临床对该疾病的病理发展过程进行研究提供客观可行的检测方法。

Objective：To evaluate the value of MR spectroscopy （MRS） and diffuse tensor imaging （DTI） in the diagnosis of super-acute stage of radiation-induced brain injury after radiotherapy for nasopharyngeal carcinoma. Methods： Radiotherapy was performed in 18 patients with initial diagnosis as nasopharyngeal carcinoma. Bilateral temporal lobes underwent ^1H-MRS and DTI before and after radiotherapy with radiation dosage of 20,40 and 60Gy respectively, MR scanning was routinely performed as well. The Cho/NAA, Naa/Cr, NAA/Cho of MRS as well as the apparent diffusion coefficient （ADC） and fractional anisotropy （FA） of DTI in bilateral temporal lobes were measured and analyzed in different .stages before and after radiation therapy. Results： After the total radiation dosage reached 60Gy,no abnormal signal intensities were revealed on MRI. All of the above-mentioned parameters in the anterior half of the temporal lobes descended obviously after radiotherapy. In addition,there was correlation between all the above-mentioned parameters and the dosagee of radiation. The ADC value increased,and the FA value decreased. Conclusion：^1H-MRS and DTI could be used to evaluate the functional and metabolism changes at the histo-cytology level in different stages of radiation-induced brain injury, these techniques pro vided objective basis for the clinical study of pathology process of the disease.