四种剂量探测器对放疗加速器常用剂量率的响应特性分析

The dose rate response characterization of four kinds of dosimeters for linear accelerator

目的探讨4种剂量探测器对放疗加速器常用剂量率的响应特性。方法在100—600cGy／min的剂量率范围内，分别测量PTw的0．6cm3电离室、0．015cm3电离室以及MatrixxEvolution二维电离室矩阵和MapCHECK二维半导体矩阵在同一测量条件和剂量下的剂量率响应；测量和分析0．6cm3电离室在不同能量和工作电压下的剂量率响应特性。结果PTw的0．6cm3电离室、0．015cm3电离室以及MatrixxEvolution二维电离室矩阵在6MVX射线能量下都表现一定的剂量率依赖性，差异均〈1％，在15MVX射线能量下，无剂量率依赖性。MapCHECK二维半导体矩阵在6MVX射线和15MVX射线能量下都显示了较强剂量率依赖性，响应差异在2％左右。结论依据剂量率变化治疗技术的放疗加速器的剂量测量，需要对测量设备进行剂量率响应测试和分析，以保证日常刻度和剂量验证的精度。

Objective To explore the dose rate response characterization of four kinds of dosimeters for clinical application. Methods Within the range of 100 - 600 cGy/min, the dose rate responses of the PTW 0. 6 cm3 ion chamber, 0. 015 cm3 ion chamber, Matrixx Evolution 2D diode array and MapCHECK 2D diode array under the same measuring conditions were measured. The dose rate response of the PTW 0. 6 cm3 ion chamber under different energy and working voltage were analyzed. Results All ionization chamber types of measured equipment showed certain dose rate dependence for 6 blV X-rays. All the differences were below 1%. The dose rate dependence disappeared for 15 MV X- rays. The 2D diode array had strong dose rate dependence and the response difference was about 2%. Conclusions It is necessary to test and analyze the dose rate response of the measured equipment in treatment technology with dose rate varying, in order to ensure the precision of daily calibration and dose verification.