小田径输出因子依赖于MR-Linac中的田径大小定义
Indra J Das1, Ahtesham U Khan1, Poonam Yadav1
1Department of Radiation Oncology, Northwestern Memorial Hospital, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA.
Medical physics
|May 9, 2025
概括
几何场面大小 (S) 准确地描述了MR-Linac系统中的辐射束,而不是剂量测量场面大小 (Sclin),它表现出不可靠的行为. 这一发现对于高级放射治疗中精确的小场定义至关重要.
科学领域:
- 医学物理 医学物理
- 辐射瘤学 辐射瘤学
- 放射治疗技术 放射治疗技术
背景情况:
- 辐射束的特征通常由场的大小来定义.
- 小型辐射场,特别是磁共振线性加速器 (MR-Linacs) 中,呈现出改变的场大小定义.
- 几何和剂量测量方法通常用于定义字段大小.
研究的目的:
- 研究横向电子不平衡和磁场对MR-Linac系统中小场大小定义的影响.
- 评估MR-Linac系统中几何场面大小 (S) 和剂量场面大小 (Sclin) 的准确性和可靠性.
- 将测量的现场输出因子 (FOF) 与处理计划系统 (TPS) 和蒙特卡洛模拟进行比较.
主要方法:
- 通过使用MR兼容的微探测器 (离子室,microDiamond,microSilicon,塑料闪器) 评估了一个0.35 T MRIdian Viewray系统.
- 在85厘米的SSD和5厘米深度的扫描水幻影中测量了光束形状和场输出因子 (FOF).
- 对TPS和蒙特卡洛模拟的几何场面大小 (S) 和剂量场面大小 (Sclin) 的有效性进行了评估.
主要成果:
- 剂量测量场尺寸 (Sclin) 测量是检测器和机器依赖的,而几何场尺寸 (S) 仅依赖机器.
- 场输出因子 (FOF) 显示出平滑且可重复的依赖于几何场大小 (S).
- 剂量测量场大小 (Sclin) 表现出不稳定的行为,表明可重现性较低.
结论:
- 几何场大小 (S) 是MR-Linac系统中辐射束的可靠参数.
- 剂量测量场大小 (Sclin) 不是MR-Linac环境中光束定义的可靠参数.
- 在MR-Linacs中准确的光束表征需要使用几何场面尺寸定义.
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