测量治疗床、SBRT体架及DAVID系统造成的剂量衰减

目的:通过测量6 MV的X线经过治疗床、SBRT体架和DAVID系统后的剂量衰减,为计划设计时的剂量补偿提供参考数据。方法:加速器与固体水之间无任何器材,源皮距(SDD)为100 cm,出束照射100 MU,利用电离室测量固体水下深度5 cm的剂量,作为基准剂量。同样条件下测量治疗床、SBRT体架和DAVID系统以不同组合在水下深度5 cm的剂量。结果:射线穿过治疗床剂量衰减了3.08%,经过治疗床和SBRT体架衰减了13.10%,经过治疗床、SBRT体架和DAVID系统衰减了13.10%,经过治疗床和DAVID系统衰减了10.88%,经过DAVID系统衰减8.07%。结论:在没有安装DAVID系统时,只有经过治疗床和SBRT体架的射线需要进行剂量补偿。安装了DAVID系统时,所有的射线束都需要计算DAVID系统对射线的衰减,经过治疗床和SBRT体架的射线还需要计算这两个器材对剂量的衰减。不同情况下衰减比例不同,需要补偿的剂量也不同。

The Mesurement of Dose Attenuation Caused by Treatment Table,Couch of SBRT and DAVID System

Objective： By measuring the dose attenuation of the 6 MV X-rays which go through the treatment table, the couch of SBRT and DAVID system, offer reference data for the dose compensation when designing treatment plans.Methods： There isn＇ t any device between the accelerator and solid water, the source skin distance （SDD） is 100 cm and the irradiated beams are 100 MU. We make use of the ionization chamber to measure the dose 5 cm below the surface of solid water and treat it as a standard. With the same condition, we measure the dose of treatment table, couch of SBRT and DAVID system which form different combinations 5 cm below the solid water.Results： The beams are weakened 3.08% after going through the treatment table, weakened 13.10% after going by the treatment table and the couch of SBRT, 13.10% after the table, the couch and the DAVID system, 10.88% after the table and DAVID system, and 8.07% after the DAVID system.Conclusions： Without the DAVID system, only the beams going through treatment table and SBRT couch need dose compensation. After installing the DAVID system, the attenuation caused by DAVID system to all beams should be calculated. For the beams going by treatment table and SBRT couch, the dose attenuation caused by these two devices also should be calculated. In different cases, the proportion of dose attenuation is different, and so does the necessary dose compensation.