单次大剂量照射后脑放射区域的活体MRS研究

目的 通过监测质子磁共振波谱(magnetic resonance spectroscopy，MRS)变化研究单次大剂量分割照射后脑照射区域内的代谢变化及放射性脑损伤的发生发展过程，为放射性脑病的早期发现和早期预防提供理论依据。材料与方法建立单次大剂量分割照射后放射性脑损伤实验兔动物模型，通过测量照射前后动物乳酸（Lactic aeid，Lac)、N-乙酰天门冬氨酸(N-acetylaspartate，NAA)、胆碱(Chollne，Cho)、肌酸(Creatine，Cr)等的波峰变化，比较照射前后不同时期各波峰变化情况并行统计学分析。结果 单次大剂量脑照射区域放射性损伤发生早期，质子MRS发生有统计学意义的降低。结论质子MRS分析可以作为早期检测放射性脑损伤的无创性、敏感性手段。

Single-fraction High-dose Brain Irradiation: Experimental MR Spectroscopy Study in Vivo

Objective To elucidate the pathogenesis and metabolic derangements of brain injury after single-fraction high-dose radiation in rabbits by means of proton (1-hydrogen) magnetic resonance spectroscopy ( 1H MRS), to provide basic theory for early detection of radiation-induced brain injury.Materials and Methods Experimental model of single-fraction high-dose radiation-injured brain was established in 40 rabbits, which were randomly divided into 4 groups and underwent 10Gy, 15Gy, 20Gy and 30Gy radiation, respectively. Proton MRS in a clinical MR imager was used to ascertain the amount of whole-brain N-acetylaspartate (NAA), lactic acid (Lac), choline (Cho), creatine (Cr) before and within 8 weeks after focused single-fraction high-dose irradiation therapy. Metabolic maps of NAA, Lac, Cho and Cr were created from MRS data set. Detection of irradiation injury among the tested models was assessed by receiver operating characteristic analysis and by quantitative signal intensity changes. The peak values of NAA, Lac, Cho and Cr on MRS before and after radiation were measured, the results were compared and statistically analyzed. Results A significant decrease in 1H MRS occurred at the early stage of brain injury induced by single-fraction high-dose irradiation.Conclusion 1H MRS may be regarded as a noninvasive and sensitive means for the detection of early radiation-induced brain injury.