Out-of-field photon and neutron dose equivalents from step-and-shoot intensity-modulated radiation therapy
Out-of-field photon and neutron dose equivalents from step-and-shoot intensity-modulated radiation therapy
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DOI：
10.1016/j.ijrobp.2004.12.091
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发表时间：
2005-07-15
影响因子：
7
通讯作者：
Rosen, II
中科院分区：
文献类型：
--
作者：
Kry, SF;Salehpour, M;Rosen, II
目的：测量不同治疗策略（传统与调强放射治疗 [IMRT]）在不同治疗能量下并由不同加速器传递的不同器官的光子和中子治疗场外剂量当量。方法和材料：对前列腺癌的 1 次常规 IMRT 治疗和 6 次 IMRT 治疗产生的光子和中子治疗场外剂量当量进行独立测量。常规治疗使用来自 Clinac 2100 的 18-MV 光束； IMRT 治疗使用来自 Varian Clinac 2100 加速器的 6-MV、10-MV、15-MV 和 18-MV 光束以及来自西门子 Primus 加速器的 6-MV 和 15-MV 光束。光子剂量是用 Rando 体模中的热释光剂量计测量的，中子注量是用金箔测量的。确定每种治疗方法的结肠、肝脏、胃、肺、食道、甲状腺和活性骨髓的剂量当量。结果：对于每种治疗方法，检查了每 MU 的剂量当量、距治疗野的距离和患者深度之间的关系。光子剂量当量随着距治疗场的距离大约呈指数下降。中子剂量当量与距治疗场的距离无关，并且随着组织深度的增加而减少。中子是射束能量 >= 15 MV 的场外剂量当量的重要贡献者。结论：可以根据该点到中心轴的距离和组织深度来估计接受类似治疗方法的患者体内任何点的场外光子和中子剂量当量。该信息可用于确定关键结构的剂量和评估相关致癌风险。 (c) 2005 年爱思唯尔公司。
Purpose: To measure the photon and neutron out-of-treatment-field dose equivalents to various organs from different treatment strategies (conventional vs. intensity-modulated radiation therapy [IMRT]) at different treatment energies and delivered by different accelerators.Methods and Materials: Independent measurements were made of the photon and neutron out-of-field dose equivalents resulting from one conventional and six IMRT treatments for prostate cancer. The conventional treatment used an 18-MV beam from a Clinac 2100; the IMRT treatments used 6-MV, 10-MV, 15-MV, and 18-MV beams from a Varian Clinac 2100 accelerator and 6-MV and 15-MV beams from a Siemens Primus accelerator. Photon doses were measured with thermoluminescent dosimeters in a Rando phantom, and neutron fiuence was measured with gold foils. Dose equivalents to the colon, liver, stomach, lung, esophagus, thyroid, and active bone marrow were determined for each treatment approach.Results: For each treatment approach, the relationship between dose equivalent per MU, distance from the treatment field, and depth in the patient was examined. Photon dose equivalents decreased approximately exponentially with distance from the treatment field. Neutron dose equivalents were independent of distance from the treatment field and decreased with increasing tissue depth. Neutrons were a significant contributor to the out-of field dose equivalent for beam energies >= 15 MV.Conclusions: Out-of-field photon and neutron dose equivalents can be estimated to any point in a patient undergoing a similar treatment approach from the distance of that point to the central axis and from the tissue depth. This information is useful in determining the dose to critical structures and in evaluating the risk of associated carcinogenesis. (c) 2005 Elsevier Inc.