简化调强技术在脑转移瘤外照射中应用的剂量学研究

目的：通过比较脑转移瘤三维适形放疗（3D-CRT）、调强放疗（IMRT）和简化调强放疗（sIMRT）技术靶区剂量分布均匀性、适形度,危及器官受照体积、剂量,以及实施治疗的机器跳数,对比三者放疗技术的剂量学差异,探讨sIMRT应用于脑转移瘤治疗的可行性。方法：针对10例脑转移瘤患者分别设计3种放疗计划：三维适形放疗、调强放疗和简化调强放疗。保证靶区和危及器官满足临床要求前提下,分别比较3种计划的靶区剂量分布、靶区均匀指数和适形指数、危及器官受照剂量、机器跳数（MU）等,探讨其剂量学差异。结果：3种照射技术均满足临床要求,靶区（PGTV）均匀指数三者没有差异。靶区（PTV）均匀指数sIMRT逊于IMRT,但与3D-CRT无差异。靶区（PGTV、PTV）适形指数sIMRT逊于IMRT而强于3D-CRT。危及器官的保护例如左、右晶体和脑干,sIMRT优于3D-CRT但与IMRT无区别,对左、右视神经和视交叉的保护,IMRT最好,sIMRT和3D-CRT差异不大。机器跳数（MU）以IMRT最多,sIMRT居中,3D-CRT最少,但3D-CRT二程计划增加照射次数,提示实际治疗时间以sIMRT最优。结论：sIMRT可减轻工作人员劳动强度,缩短治疗时间,节省资源,是一种性价比较高的放疗技术,适用于脑转移瘤放疗。

Dosimetric Study of Simplified Intensity Modulated Radiation Therapy for Brain Metastasis Tumors

Objective： To compare the homogeneity and conformity of dose distribution in the target and the dose to the organs at risk among 3-dimensional conformal radiation therapy （3D-CRT）, intensity-modulated radiation therapy （IMRT） and simplified intensity-modulated radiation therapy（sIMRT）, and then to evaluate the clinical value of sIMRT for brain metastasis tumor. Methods： The clinical data of 10 patients with brain metastasis tumor, were used to design 3 plans： 3D-CRT, IMRT and sIMRT. Dose-volume-histogram（DVH） analysis was used to compare dose results, monitor unit（MU）, and delivery time. Results： Among the three radiotherapy techniques, which met the clinical requirements. There was no significant difference about the conformity of dose distribution of the target （PGTV）. IMRT had the best homogeneity of dose distribution of the target（PTV）, while there was not much difference between slMRT and 3D-CRT. According to the conformity of dose distribution of the target （PGTV and PTV）, slMRT was better than 3D-CRT, but worse than IMRT. Between IMRT and slMRT plans, the no statistically significant differences were found in Dmax and Dmean of the left lens, the right lens and the brain stem, 3D-CRT was the worst. But, about Dmax of the Left optic nerve, the right optic nerve and the optic chiasm. IMRT was the best, followed by slMRT and 3D-CRT. About the monitor unit （MU） per faction, 3D-CRT was least, slMRT was second, IM- RT was followed. However, because the number of treatment of 3D-CRT was increased, so sIMRT decreased delivery time.Conclusions： slMRT could reduce the work intensity of the staff, shorten the treatment time per fi＇action, and saved resource, which is cost-effective and suitable in the treatment of brain metastasis tumor.