表面剂量与原子数在兆电压光子束中的依赖性
Ahtesham Ullah Khan1, Indra J Das1
1Department of Radiation Oncology, Northwestern Memorial Hospital, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA.
Medical physics
|February 12, 2024
概括
现代放射治疗的表面剂量可以使用中高原子数 (Z) 吸收器来减少. 这项研究发现,增加吸收物Z始终降低了表面剂量,这挑战了以前关于中等Z材料最小值的结论.
科学领域:
- 医学物理 医学物理
- 辐射瘤学 辐射瘤学
- 放射治疗 物理 物理
背景情况:
- 在兆电压光子辐射疗法中,表面剂量显著影响肌肤节约效应.
- 之前的研究表明,中原子数 (Z) 吸收器降低了表面剂量,而高Z吸收器则增加了表面剂量.
- 这些先前的结论是基于关于电子和正电子对贡献的假设.
研究的目的:
- 重新评估关于放射治疗中表面剂量的已确定的结论.
- 通过使用现代线性加速器 (linac) 光子束,研究不同原子号 (Z) 吸收器对表面剂量的影响.
- 用蒙特卡洛模拟和实验测量来验证发现.
主要方法:
- 使用光子相互作用截面计算了带电粒子发射的度量 ().
- 用TOPAS MC代码模拟的表面剂量用于6和10 MV光子束和各种吸收器.
- 用6和10 MV光子束与锡和吸收器测量表面剂量.
主要成果:
- 在6和10MV光束中,随着Z的增加,该度量下降,这表明前置电子排放减少.
- 蒙特卡洛模拟和实验测量都显示,随着吸收器Z的增加,表面剂量持续下降.
- 在锡和吸收器之间没有观察到表面剂量的统计学上显著差异,这与之前的发现相矛盾,即在中等-Z.
结论:
- 现代光子束放射治疗中的表面剂量可以通过使用中等或高原子数 (Z) 的吸收器有效地减少.
- 随着吸收器的原子数 (Z) 的增加,表面剂量得到了持续的减少.
- 这些发现挑战了先前的文献,该文献建议在中等Z吸收器中使用最小表面剂量.
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