距离变换器对接受质子笔光束扫描的患者中子暴露的贡献
Maite Romero-Expósito1,2, Malgorzata Liszka1, Athanasia Christou1
1The Skandion Clinic, Uppsala, Sweden.
Medical physics
|December 19, 2023
概括
在质子笔光束扫描 (PBS) 中使用距离变换器会增加中子剂量,特别是在距离目标的距离上. 然而,距离变换器的中子贡献通常很低,这使得它成为表面目标的可行选择.
科学领域:
- 医学物理 医学物理
- 辐射瘤学 辐射瘤学
- 微粒疗法是一种微粒疗法.
背景情况:
- 对表面目标的质子笔光束扫描 (PBS) 需要低能耗,这给效率和层要求带来了挑战.
- 射程变换器 (RS) 提供了一个替代方案,但引起了人们对中子产生和远处器官潜在辐射的担忧.
研究的目的:
- 在质子PBS中使用范围变换器 (RS) 来量化中子剂量等效 (Hn) 的增加.
- 评估一种分析模型,用于预测RS的中子产生.
主要方法:
- 两个相同的质子PBS计划提供60Gy (RBE) 被模拟使用MCNP代码为一个人形幻影,一个与RS.
- 评估了中子剂量等效 (Hn) 和器官等效剂量,并单独分析了RS和患者的中子产量.
- 使用高斯函数对距离场边缘的距离来建模Hn分布.
主要成果:
- 与没有RS的计划相比,RS增加了Hn的1.2到10倍,从场边进一步观察到更高的剂量.
- 在距离场边缘40厘米处的中子剂量在使用RS时从9.9到32μSv/Gy不等.
- 一个分析的三重高斯模型在2的系数内近似了器官等效剂量,尽管它倾向于低估值.
结论:
- 来自RS的中子主要影响距离场边缘大约25厘米以外的组织,剂量在msv范围内.
- 尽管增加了中子剂量,但PBS中范围转换器的总体贡献被认为是低的.
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