摘要
目的比较不同指形电离室依据国际原子能机构（IAEA）TRS-277和TRS-398号报告测量高能光子束吸收剂量的差异。方法针对6种不同型号的指形电离室，依据照射量校准因子N。分别计算其60co水吸收剂量校准因子ND,w,Q0，与欧洲标准实验室的测定值比较；依据TRS-277号报告分别计算其水中测量6MV光子束吸收剂量的射线质修正因子kQ,Q0，与TRS-398号报告给出的值比较；比较其依据TRS．277和TRS-398号报告测量6MV光子束的吸收剂量实际测量数据。结果对上述6种指形电离室，依据N，计算出的ND,w,Q0与欧洲标准实验室直接测定的ND,w,Q0．的差异在0．13％～1．30％之间；依据TRS．277号报告计算的kQ,Q0与TRS-398号报告给出的☆D10。的差异在0．09％～0．45％之间；依据两个报告在水中测量的吸收剂量差异在0．27％～1．40％之间。吸收剂量的主要差异来源于两个报告校准因子Ⅳ。和ND,w,Q0的不同。结论不同指形电离室依据两个报告测量水吸收剂量的差异属于临床可接受的范围，使用TRS-398号报告摆位更方便，计算更简单，测量不确定度降低。
Objective To study the difference between the IAEA code of practice TRS-277 and TRS-398 in the determination of the absorbed dose to water for high-energy photon beams using several cylindrical chambers. Methods For 6 different types of cylindrical chambers, the calibration factors ND in terms of absorbed dose to water were calculated from the air exposure calibration factors N , and were compared with the ND,w,Qo measured in European standard laboratory. Accurate measurements were performed in Varian 6 MV photon beam using 6 cylindrical chambers according to TRS-277 and TRS-398. The beam quality correction factors kQ,Qo as well as the water absorbed doses were compared. Results For the set of chambers, the difference between ND,w,Qo computed from N and ND,w,Qo obtained in European standard laboratory was O. 13% - 1.30%. The difference of beam quality correction factors for TRS-277 and TRS-398 was 0. 09% -0.45%. The distinction of the water absorbed doses obtained according to the two different protocols was 0. 27% - 1.40% , and was primarily due to their different calibration factors. Conclusions The discrepancy in absorbed doses determined according to two protocols using different cylindrical chambers is clinically acceptable. However, TRS-398 allows a more convenient localization of chambers, provides a more simple formulation, and offers the reduced uncertainty in the dosimetry of radiotherapy beams.
出处
《中华放射医学与防护杂志》
CAS
CSCD
北大核心
2012年第4期412-415,共4页
Chinese Journal of Radiological Medicine and Protection
