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使用百分比深度剂量重建方法估计光子束能量光谱的横向变化

Puspen Chakraborty¹, Hidetoshi Saitoh², Yuta Miyake³

¹Department of Radiological Sciences, Graduate School of Human Health Sciences, Tokyo Metropolitan University, Tokyo, Japan. puspen-chakraborty2@ed.tmu.ac.jp.

Radiological physics and technology

|September 6, 2024

概括

光子崩的圆卷积 (pCCC) 算法

科学领域:

医学物理医学物理
辐射瘤学辐射瘤学
计算剂量计计算剂量计.

背景情况:

摩纳哥处理规划系统的光子崩圆卷积 (pCCC) 算法假定一个恒定的中心轴能量频谱.
目前的方法使用离轴软化因子,可能无法准确捕捉侧向能量频谱变化.
不准确的侧向光谱表示可能导致剂量计算的差异,特别是在大型场中.

研究的目的:

为了评估当前pCCC离轴软化因子方法的准确性.
提出并验证一种用于准确估计侧向能量频谱变化的新方法.
为了提高pCCC算法对大辐射场的剂量计算精度.

主要方法:

通过比较6 MV光子束的计算和测量百分比深度剂量 (PDD) 和离轴比率 (OAR) 来评估现有的pCCC方法.
开发了一种新的方法,通过从蒙特卡洛模拟 (DOSRZnrc) 沿着离轴角度推导单能深度剂量 (MDD) 来重建能量光谱.
使用一般化-减小梯度方法优化能量光谱,以最大限度地减少重建和测量PDD之间的差异.

主要成果:

与测量相比,现有的pCCC方法显示相对差异超过±1%,表明精度的局限性.
拟议的方法准确地估计了侧面能量频谱的变化.
使用估计的能量光谱重建的PDD和计算的OAR显示与测量结果有很好的一致性 (相对差异在±0.5%内).

结论:

在pCCC算法中,当前的离轴软化因子不足以准确地建模横向能量频谱变化.
由MDD重建能量光谱的拟议方法提供了一个快速而准确的方法来解释这些变化.
实施拟议的方法可以显著提高pCCC算法的剂量计算精度,特别是对于大型辐射场.

关键词:

波束建模波束建模侧面能量频谱变化的变化.脱轴软化脱轴软化光子崩的圆卷积.

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