| 姚杏红,陈立新,靳光华.不同指形电离室测量高能光子束吸收剂量的比较[J].中华放射医学与防护杂志,2012,32(4):412-415 |
| 不同指形电离室测量高能光子束吸收剂量的比较 |
| Comparative determination of absorbed doses for high-energy photon beam with different cylindrical chambers |
| 投稿时间：2011-10-21 |
| DOI：10.3760/cma.j.issn.0254-5098.2012.04.023 |
| 中文关键词: 指形电离室 光子束 吸收剂量 TRS-277 TRS-398 |
| 英文关键词:Cylindrical chambers Photon beam Absorbed dose TRS-277 TRS-398 |
| 基金项目: |
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| 中文摘要: |
| 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Nx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6 MV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6 MV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Nx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kQ,Q0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Nx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。 |
| 英文摘要: |
| 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,w,Q0 in terms of absorbed dose to water were calculated from the air exposure calibration factors Nx, and were compared with the ND,w,Q0 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,Q0 as well as the water absorbed doses were compared. Results For the set of chambers, the difference between ND,w,Q0 computed from Nx and ND,w,Q0 obtained in European standard laboratory was 0.13%~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. |
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