全脑+同步推量放射治疗中海马保护计划设计研究

目的:探讨应用Elekta Synergy医用直线加速器容积旋转调强放射治疗(VMAT),实现全脑+转移灶同步推量放射治疗的海马保护计划设计。方法:选取10例肺癌脑转移患者进行全脑放射治疗+转移灶同步推量,并进行海马保护。勾画转移灶肿瘤靶区(GTV)、全脑临床靶区(CTV)、左右海马区,以及脑干、脊髓、眼球、晶体等其他正常组织,转移灶外扩3 mm形成计划肿瘤靶区(PGTV),全脑外扩3 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Pinnacle9.8治疗计划系统设计VMAT计划,处方剂量PGTV为45 Gy/15 F,PTV为36 Gy/15 F。结果:10例患者PGTV的45 Gy覆盖为99.8%,均匀性指数平均值为0.09。PTV的36 Gy靶区覆盖80%,30 Gy靶区覆盖90.1%,左、右海马平均体积分别为3.2 cm^3和2.8 cm^3,海马保护区域平均体积分别为25.2 cm^3和23 cm^3。左、右海马的平均剂量为6.91 Gy和5.32 Gy,最大剂量分别为10.7 Gy和8.3 Gy;左、右海马保护区域的平均剂量为7.93 Gy和10.3 Gy,最大剂量为14.8 Gy和13.5 Gy。左右晶体最大剂量平均值分别为5.56 Gy和5.69 Gy。结论:在全脑放射治疗中,利用ElektaSynergy直线加速器VMAT技术能在保证靶区剂量覆盖和靶区适形性、均匀性的情况下降低海马受照剂量,达到安全剂量范围,可实现对患者海马神经认知功能的保护。

Study on the design of protecting hippocampus plan in radiotherapy of simultaneously integrated boost for whole brain

Objective:To explore the application of Elekta Synergy linear accelerator volumetric modulated arc therapy(VMAT)in achieving the design of protecting plan for hippocampus in radiotherapy of simultaneously integrated boost for whole brain and metastatic lesion.Methods:Selecting 10 patients with lung cancer with brain metastases,and implementing radiotherapy for whole brain of them and simultaneously integrated boost for metastatic lesion,and implementing protection for hippocampus.Drawing the gross tumor volume(GTV)of metastatic lesion,clinical target volume(CTV)of whole brain,the left and right hippocampus,other normal tissues such as the brainstem,spinal cord,eyeball and crystal.The GTV was expanded 3 mm to form plan GTV(PGTV),and whole brain of them was expanded 3 mm to form plan target volume(PTV),and hippocampus was expanded 5 mm to form protecting area of hippocampus.The pinnacle 9.8 treatment planning system was used to design VMAT plan,and the prescribed dose of PGTV was 45 Gy/15 F,and that of PTV was 36 Gy/15 F.Results:The average 45 Gy coverage of PGTV of 10 patients was 99.8%,and the evenness index was 0.09.And the 36 Gy target area coverage of PTV was 80%,and that of 30 Gy was 90.1%.And the average volume of left and right hippocampus respectively was 3.2 cm^3 and 2.8 cm^3,and the average volume of protective area of left and right hippocampus respectively was 25.2 cm^3 and 23 cm^3.Besides,the average dose of left and right hippocampus was 6.91 Gy and 5.32 Gy,respectively,and the maximum dose of them was 10.7 Gy and 8.3 Gy,respectively,while the average doses of their protection areas was 7.93 Gy and 10.3 Gy,and the maximum doses of them was 14.8 Gy and 13.5 Gy.The average value of maximum doses of left and right crystal was 7.93 Gy and 10.3 Gy,respectively.Conclusion:In the radiotherapy for whole brain,Elekta Synergy linear accelerator with VMAT technique can reduce the exposure dose of hippocampus to achieve a safe dose range,and can achieve the protection for cognitive function of hippocampal nerve under the conditions that ensure the dose coverage of target area,and the conformal and uniformity of the target area.