全脑放疗中保护海马的调强计划设计

Whole brain intensity modulated radiotherapy with hippocampus protection

目的:探讨应用直线加速器调强技术实现全脑放疗并对海马保护。方法:选取8例接受全脑放疗+海马保护的乳腺癌脑转移患者,进行全脑临床靶区(CTV)和海马区的勾画,全脑外扩5 mm形成计划靶区(PTV),海马区外扩5 mm形成海马保护区域。利用Varian Eclipse 7.6治疗计划系统设计10野调强计划,处方剂量为3000 c Gy/10F。结果:8例病人的PTV V90平均值为99.5%,V95平均值为98.4%,均匀性指数平均值为0.09。海马平均体积为5.0 cm3,海马保护区域平均体积为26.2 cm3,占全脑体积的1.8%。海马的平均剂量为17.1 Gy,最大剂量为21.7 Gy;海马保护区域的平均剂量为22 Gy,最大剂量为29.3 Gy。海马平均剂量为靶区处方剂量的57%,海马保护区域平均剂量为靶区处方剂量的73%。晶体最大剂量平均值为6 Gy。结论:在全脑放疗中,利用直线加速器调强技术能在保证靶区剂量覆盖和靶区均匀性的情况下降低海马受照剂量,实现神经认知功能的保护。

Objective To discuss on the linear accelerator intensity modulated radiotherapy （IMRT） tbr whole brain radiotherapy and hippocampus protection; to analyze the dose distribution of IMRT for 8 patients and doses of hippocampus and organs at risk. Methods Eight breast cancer patients with brain metastases treated with whole brain radiotherapy with hippocampus protection were selected. The clinical target volume （CTV） of brain and the hippocampus region were contoured. The planning target volume （PTV） was the CTV with an expansion of 5 ram, and the hippocampus protection regions were the hippocampus regions with an expansion of 5 mm. The IMRT plan with 10 fields was designed by using Varian Eclipse 7.6 treatment planning system, and the prescription dose was 3000 cGy/10 f. Results The mean values of PTV V90 and V95 of 8 patients were respectively 99.5% and 98.4%, and the mean value of homogeneity index was 0.09. The average volume ofhippocampus was 5.0 cm3, and that of hippocampus protection regions was 26.2 cm3, accounted for 1.8% of whole brain volume. The mean doses of hippocampus and hippoeampus protection regions were respectively 17.1 Gy and 22 Gy; the maximum dose of hippocampus and hippocampus protection regions were respectively 21.7 Gy and 29.3 Gy. The mean dose of hippocampus occupied 57% of the prescription dose of the target volume, and the mean dose of hippocampus protection regions occupied 73% of the prescription dose. The mean value of the maximum doses of lens was 6 Gy. Conclusion In the case of ensuring target volume coverage and homogeneity, the linear accelerator IMRT in whole brain radiotherapy can reduce the radiation dose of hippocampus, protecting the neurocognitive function.