用于放疗量传的照射量、空气比释动能和水吸收剂量量值体系比较

用照射量和空气比释动能校准的电离室进行剂量测量时,依据IAEA TRS 277报告,需要经历四级量值转换过程,不确定度也较大,但目前仍是国内使用的量值体系.我国正在建立60Co γ射线以及高能光子下的水吸收剂量基准装置并进行国际比对,之后将拥有水吸收剂量的量值复现的能力.在60Co γ射线参考辐射场和加速器高能X射线辐射场下,使用NE2571和NE2570/1A、PTW TW30013和PTW UNIDOS两套电离室剂量仪,分别按照277和398报告的要求计算并比较2种方法计算出的水吸收剂量值,从而验证了277报告和398报告的一致性.

Comparison of Exposure,Air Kerma and Absorbed Dose to Water Used for Quantity Transmission in Radiotherapy

When the ionization chamber calibrated for the amount of exposure or air kerma is used in the process of dosimetry,according to the IAEA TRS 277 report,it requires four levels of magnitude conversion,where the uncertainty probably exists,but it still is the currently used value system in China.After the reference standard of absorbed dose to water in 60Co γ-ray and high-energy photon beams is established and the international comparison is completed,the ability of recovering and passing the quantity of absorbed dose to water wii be have.In the 60Co γ-ray reference radiation field and high energy photon beams,using the NE2571 and NE2570/IA,PTW TW30013,and PTw UNIDOS,respectively,and according to the requirements reported in 277 and 398,the absorbed dose to water is calculated and compared with the two methods,which confirming the consistency of the 277 and 398 reports.