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在总散射因子计算中验证几何等效场概念,用于半,四分之一和离异中心不对称的正方形场
Mohammad Samir Hmodi1,2, Majeda Nahili1, Ioannis A Tsalafoutas3
1Department of Physics, Faculty of Sciences, Damascus University, Damascus, Syria.
几何等效平方场 (GESF) 概念准确地计算了不对称场的总散射因子 (Scp),这对于监视器单元验证至关重要. 这种方法对于大多数临床场景是可靠的,确保精确的辐射疗法输送.
科学领域:
- 医学物理 医学物理
- 辐射瘤学 辐射瘤学
- 剂量测量方法 剂量测量方法
背景情况:
- 监控单元 (MU) 验证对于精确的放射治疗至关重要.
- 总散射因子 (Scp) 是MU计算中的一个关键参数.
- 几何等效平方场 (GESF) 概念用于简化对不对称场的计算.
研究的目的:
- 测量各种不对称正方形场 (ASF) 的Scp.
- 评估GESF概念在计算ASFScp的准确性.
- 为了比较Scp在有效场中心 (EFC) 和同位中心 (IC) 的测量.
主要方法:
- 在Varian iX Linacs上创建了正方形半场 (SHF),正方形四分场 (SQF) 和正方形异心场 (SOF).
- 测量Scp使用一个半柔性离子室在10厘米深的水幻影.
- 通过基于EFC和IC之间的距离的离轴比率 (OAR) 校正IC上的Scp值.
主要成果:
- 在EFC的Scp独立于ASF类型和光束能量 (18/23 MV).
- 在EFC的Scp随着EFC和IC之间的距离 (r) 的增加而增加,在18/23 MV上高达2%,在6 MV上高达4%.
- 在18和23个MV光束之间没有观察到任何显著差异.
结论:
- 在大多数临床情况下,GESF概念为Scp计算ASF提供了可接受的准确性 (<2%).
- 对于MU验证计算,可以可靠地使用GESF概念.
- 对于长距离 (r) 上使用EFC的SOF,已注意到例外情况.
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