Abstract：
Dosimetry audits for passive motion management require dynamically-acquired measurements in a moving phantom to be compared to statically calculated planned doses. This study aimed to characterise the relationship between planning and delivery errors, and the measured dose in the Imaging and Radiation Oncology Core (IROC) thorax phantom, to assess different audit scoring approaches. Treatment plans were created using a 4DCT scan of the IROC phantom, equipped with film and thermoluminescent dosimeters (TLDs). Plans were created on the average intensity projection from all bins. Three levels of aperture complexity were explored: dynamic conformal arcs (DCAT), low-, and high-complexity volumetric modulated arcs (VMATLo, VMATHi). Simulated-measured doses were generated by modelling motion using isocenter shifts. Various errors were introduced including incorrect setup position and target delineation. Simulated-measured film doses were scored using gamma analysis and compared within specific regions of interest (ROIs) as well as the entire film plane. Positional offsets were estimated based on isodoses on the film planes, and point doses within TLD contours were compared. Motion-induced differences between planned and simulated-measured doses were evident even without introduced errors Gamma passing rates within target-centred ROIs correlated well with error-induced dose differences, while whole film passing rates did not. Isodose-based setup position measurements demonstrated high sensitivity to errors. Simulated point doses at TLD locations yielded erratic responses to introduced errors. ROI gamma analysis demonstrated enhanced sensitivity to simulated errors compared to whole film analysis. Gamma results may be further contextualized by other metrics such as setup position or maximum gamma.
摘要：
被动运动管理的剂量学审计需要在移动体模中动态获取的测量值与静态计算的计划剂量进行比较。这项研究旨在描述计划和交付错误之间的关系，以及成像和放射肿瘤学核心（IROC）胸部体模中的测量剂量，评估不同的审计评分方法。使用IROC体模的4DCT扫描创建治疗计划，配备胶片和热释光剂量计（TLD）。在来自所有箱的平均强度投影上创建计划。探索了三个级别的孔径复杂度：动态共形弧（DCAT），低,和高复杂度体积调制弧(VMATLo，VMATHI).通过使用等中心位移对运动进行建模来生成模拟测量的剂量。引入了各种错误，包括不正确的设置位置和目标轮廓。使用γ分析对模拟测量的胶片剂量进行评分，并在特定的感兴趣区域（ROI）以及整个胶片平面内进行比较。位置偏移是根据胶片平面上的等剂量估算的，并比较了TLD轮廓内的点剂量。即使没有引入错误，计划剂量和模拟测量剂量之间的运动引起的差异也很明显，以目标为中心的ROI内的Gamma通过率与错误引起的剂量差异很好地相关。而整部电影的通过率却没有。基于等剂量的设置位置测量显示出对误差的高灵敏度。在TLD位置的模拟点剂量对引入的错误产生了不稳定的反应。与整片分析相比，ROI伽马分析显示出对模拟误差的敏感性增强。伽玛结果可以通过诸如设置位置或最大伽玛之类的其他度量来进一步情境化。
