三种放疗剂量学规程在^(60)Co辐射场中测量对比研究

Comparison Research on Three International Dosimetry Code in ^(60)Coγ-ray Beams

目的在我国放疗剂量检测不是直接测量水中的吸收剂量,而是先测量照射量或空气比释动能,再通过相关的剂量学规范采用多种修正因子把测量结果转换为吸收剂量,本文将探讨采用不同的剂量学规程测量吸收剂量所产生的偏差。方法本文利用ICRU23、IAEA 277和IAEA 398号技术报告三种放疗剂量学规程对不同型号的电离室在^(60)Coγ射线辐射场中同样条件下分别测量水中的吸收剂量,进行了比对实验研究,分析不同型号的探测器分别采用三种规程所测得的实际剂量差别。结果通过对10个6种型号的电离室在^(60)Coγ射线辐射场中同样条件下分别测量水中的吸收剂量,发现采用三种规程引起的偏差在2%以内,同时,发现不同型号的电离室之间也存在一定的分散性。结论使用不同的剂量学规程进行放疗剂量的测量会引入较大的偏差,为降低我国放疗剂量测量的不确定度,应尽快建立水吸收剂量量值传递系统。

Objective The code of practice for radiotherapy dosimetry in our country is not directly based on standards of absorbed dose to water,but based on exposure standards or air kerma standards firstly,and then transform the measurement into absorbed dose by adopting various modifying factors through dosimetry code involved.This essay will probe into the error caused by different codes of practice for radiotherapy dosimetry in terms of absorbed dose.Methods In this research,we adopt three radiotherapy dosimetry codes including ICRU23,IAEA TRS277 and IAEA TRS398,by which different types of chambers measure the absorbed dose to water respectively in ^（60）Coγ ray beams under same condition.We analyze the divergence produced by the three codes mentioned above.Results Having measured the absorbed dose to water through 10 six types of chambers under the same condition of ^（60）Coγ ray beams,we find that three codes in question produce divergences,which are within 2% respectively.Meanwhile,there is certain dispersal among different types of chambers as well.Conclusion Different measurements of radiotherapy dosimetry codes will produce bigger divergences.To reduce inaccuracy in modern radiation therapy in our nation,we should establish the calibration system of measuring absorbed doses to water as soon as possible.