A real time dose monitoring and dose reconstruction tool for patient specific VMAT QA and delivery
A real time dose monitoring and dose reconstruction tool for patient specific VMAT QA and delivery
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DOI：
10.1118/1.4764482
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发表时间：
2012-12-01
期刊：
影响因子：
3.8
通讯作者：
Yan, Di
中科院分区：
文献类型：
--
作者：
Tyagi, Neelam;Yang, Kai;Yan, Di
目的：开发一种实时剂量监测和剂量重建工具，以识别和量化患者特定体积调制弧形治疗 (VMAT) 输送和质量保证期间的误差源。方法：作者开发了一种名为直线加速器数据监视器的 VMAT 输送监测工具，该工具在临床模式下连接到直线加速器，记录、显示实时机器参数并将其与计划参数进行比较。一种称为积分误差的新测量方法可以计算每对叶片中叶片过冲和下冲误差的运行总和，乘以叶片宽度，以及监测单元传递中存在误差的时间量。另一个工具根据保存的机器日志文件重建 Pinnacle(3)(TM) 格式的交付计划，并重新计算患者解剖结构中的实际交付剂量。对 Elekta Axesse 和 Synergy 直线加速器上实施的各种标准分割和立体定向身体放射治疗 (SBRT) VMAT 计划的实施特征进行了量化。结果：所有治疗部位的 MLC 和机架误差分别为 0.00 +/- 0.59 毫米和 0.05 +/- 0.31 度，表明 MLC 增益校准良好。由于频繁的剂量率变化，标准分割计划比 SBRT 计划具有更大的机架误差。平均而言，MLC 误差可以忽略不计，但当剂量率频繁变化时，会出现高达 6 毫米和 2.5 度的较大误差。在加速和减速过程中会出现较大的龙门误差，并且与 MLC 误差有很好的相关性（r = 0.858，p = 0.0004）。 PTV 平均、最小和最大剂量差异分别为 0.87 +/- 0.21%、0.99 +/- 0.59% 和 1.18 +/- 0.52%。危及器官 (OAR) 剂量在 2.5% 以内，但某些 OAR 的最大剂量差异高达 5.6%。实时显示的归一化总正积分误差（归一化为总监测单位）与 MLC (r = 0.9279，p < 0.001) 和龙门误差 (r = 0.742，p = 0.005) 线性相关。总积分误差与 PTV 平均值 (r = 0.683，p = 0.015)、最小值 (r = 0.6147，p = 0.033) 和最大剂量 (r = 0.6038，p = 0.0376) 之间存在很强的相关性。 结论：在复杂的 VMAT 计划和实施过程中可能存在误差。直线加速器数据监视器能够检测和量化规划和交付各个阶段的机械和剂量测定误差。 (C) 2012 年美国医学物理学家协会。 [http://dx.doi.org/10.1118/1.4764482]
Purpose: To develop a real time dose monitoring and dose reconstruction tool to identify and quantify sources of errors during patient specific volumetric modulated arc therapy (VMAT) delivery and quality assurance.Methods: The authors develop a VMAT delivery monitor tool called linac data monitor that connects to the linac in clinical mode and records, displays, and compares real time machine parameters with the planned parameters. A new measure, called integral error, keeps a running total of leaf overshoot and undershoot errors in each leaf pair, multiplied by leaf width, and the amount of time during which the error exists in monitor unit delivery. Another tool reconstructs Pinnacle(3)(TM) format delivered plan based on the saved machine logfile and recalculates actual delivered dose in patient anatomy. Delivery characteristics of various standard fractionation and stereotactic body radiation therapy (SBRT) VMAT plans delivered on Elekta Axesse and Synergy linacs were quantified.Results: The MLC and gantry errors for all the treatment sites were 0.00 +/- 0.59 mm and 0.05 +/- 0.31 degrees, indicating a good MLC gain calibration. Standard fractionation plans had a larger gantry error than SBRT plans due to frequent dose rate changes. On average, the MLC errors were negligible but larger errors of up to 6 mm and 2.5 degrees were seen when dose rate varied frequently. Large gantry errors occurred during the acceleration and deceleration process, and correlated well with MLC errors (r = 0.858, p = 0.0004). PTV mean, minimum, and maximum dose discrepancies were 0.87 +/- 0.21%, 0.99 +/- 0.59%, and 1.18 +/- 0.52%, respectively. The organs at risk (OAR) doses were within 2.5%, except some OARs that showed up to 5.6% discrepancy in maximum dose. Real time displayed normalized total positive integral error (normalized to the total monitor units) correlated linearly with MLC (r = 0.9279, p < 0.001) and gantry errors (r = 0.742, p = 0.005). There is a strong correlation between total integral error and PTV mean (r = 0.683, p = 0.015), minimum (r = 0.6147, p = 0.033), and maximum dose (r = 0.6038, p = 0.0376).Conclusions: Errors may exist during complex VMAT planning and delivery. Linac data monitor is capable of detecting and quantifying mechanical and dosimetric errors at various stages of planning and delivery. (C) 2012 American Association of Physicists in Medicine. [http://dx.doi.org/10.1118/1.4764482]