Centre for Medical Radiation Physics, University of Wollongong, Wollongong, New South Wales 2522, Australia.
Med Phys. 2009 Dec;36(12):5412-9. doi: 10.1118/1.3250857.
Previous Monte Carlo and experimental studies involving secondary neutrons in proton therapy have employed a number of phantom materials that are designed to represent human tissue. In this study, the authors determined the suitability of common phantom materials for dosimetry of secondary neutrons, specifically for pediatric and intracranial proton therapy treatments.
This was achieved through comparison of the absorbed dose and dose equivalent from neutrons generated within the phantom materials and various ICRP tissues. The phantom materials chosen for comparison were Lucite, liquid water, solid water, and A150 tissue equivalent plastic, These phantom materials were compared to brain, muscle, and adipose tissues.
The magnitude of the doses observed were smaller than those reported in previous experimental and Monte Carlo studies, which incorporated neutrons generated in the treatment head. The results show that for both neutron absorbed dose and dose equivalent, no single phantom material gives agreement with tissue within 5% at all the points considered. Solid water gave the smallest mean variation with the tissues out of field where neutrons are the primary contributor to the total dose.
Of the phantom materials considered, solid water shows best agreement with tissues out of field.
以往涉及质子治疗中次级中子的蒙特卡罗和实验研究采用了许多旨在代表人体组织的体模材料。在这项研究中，作者确定了常见体模材料在次级中子剂量测定中的适用性，特别是在儿科和颅内质子治疗中。
通过比较在体模材料和各种 ICRP 组织内产生的中子的吸收剂量和剂量当量来实现这一目标。选择用于比较的体模材料有有机玻璃、液体水、固体水和 A150 组织等效塑料。这些体模材料与脑、肌肉和脂肪组织进行了比较。
观察到的剂量大小小于以前包含在治疗头中产生的中子的实验和蒙特卡罗研究报告的剂量。结果表明，对于中子吸收剂量和剂量当量，没有任何一种体模材料在所有考虑的点上都能与组织的差异在 5%以内。在远离场的地方，固体水与组织的平均变化最小，而在远离场的地方，中子是总剂量的主要贡献者。
在所考虑的体模材料中，固体水与组织的一致性最好。
