Moving from gamma passing rates to patient DVH-based QA metrics in pretreatment dose QA
Moving from gamma passing rates to patient DVH-based QA metrics in pretreatment dose QA
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DOI：
10.1118/1.3633904
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发表时间：
2011-10-01
期刊：
影响因子：
3.8
通讯作者：
Tomeacute, Wolfgang A.
中科院分区：
文献类型：
--
作者：
Zhen, Heming;Nelms, Benjamin E.;Tomeacute, Wolfgang A.
目的：这项工作的目的是探索每个患者的治疗前剂量QA的伽马通过率度量的有用性，并验证一种新的基于患者剂量/DVH的方法及其准确性和相关性。具体而言，（1）三种3D剂量计探测器几何形状的伽马通过率与临床相关的基于患者DVH的度量之间的相关性;（2）整个患者剂量网格的伽马通过率与基于DVH的度量，（3）通过感兴趣区域（ROI）过滤的伽马通过率与基于DVH的度量，（4）分析了一种新的基于传统体模QA数据估计校正的患者剂量-DVH的软件算法的能力。九十六个独特的“不完美的”一步一拍IMRT计划，通过应用四种不同类型的错误24例临床头颈部患者。然后使用无误差射束模型重新计算3D患者剂量以及圆柱形QA体模的剂量，以作为模拟测量值进行比较。生成了计划与模拟测量的DVH指标的偏差，以及各种差异/距离标准的伽马通过率，包括：体模内剂量比较和患者体内剂量比较，以及在整个网格和每个ROI体积上计算的住院结果。最后，使用常规的每射束平面数据作为商业“计划剂量扰动”（PDP）算法的输入来预测患者剂量和DVH，并将这些预测的基于DVH的度量的结果与已知值进行比较。在临床相关患者DVH指标之间发现了一系列弱至中度相关性（CTV-D95、腮腺D均值、脊髓D1cc和喉部D均值）以及3D探测器和3D患者伽马通过率（3%/3 mm、2%/2 mm），用于体模中剂量沿着以及整个患者体积和过滤后的每个ROI的患者剂量。伽马通过率与基于DVH的度量曲线存在相当大的分散。然而，对于相同的输入数据，PDP估计与实际患者DVH results.Conclusions：伽玛通过率，即使计算的基础上，患者剂量网格，一般弱相关的关键患者DVH错误。然而，PDP算法被证明可以使用传统的平面QA结果准确预测DVH影响。使用基于患者-DVH的度量IMRT QA允许每个患者剂量QA基于既敏感又特异的度量。现在需要进一步的研究来分析与基于DVH的指标相关的新流程和行动水平，以确保临床环境中的有效性和实用性。(C)2011年美国医学物理学家协会。[DOI：10.1118/1.3633904]
Purpose: The purpose of this work is to explore the usefulness of the gamma passing rate metric for per-patient, pretreatment dose QA and to validate a novel patient-dose/DVH-based method and its accuracy and correlation. Specifically, correlations between: (1) gamma passing rates for three 3D dosimeter detector geometries vs clinically relevant patient DVH-based metrics; (2) Gamma passing rates of whole patient dose grids vs DVH-based metrics, (3) gamma passing rates filtered by region of interest (ROI) vs DVH-based metrics, and (4) the capability of a novel software algorithm that estimates corrected patient Dose-DVH based on conventional phan-tom QA data are analyzed.Methods: Ninety six unique "imperfect" step-and-shoot IMRT plans were generated by applying four different types of errors on 24 clinical Head/Neck patients. The 3D patient doses as well as the dose to a cylindrical QA phantom were then recalculated using an error-free beam model to serve as a simulated measurement for comparison. Resulting deviations to the planned vs simulated measured DVH-based metrics were generated, as were gamma passing rates for a variety of difference/distance criteria covering: dose-in-phantom comparisons and dose-in-patient comparisons, with the in-patient results calculated both over the whole grid and per-ROI volume. Finally, patient dose and DVH were predicted using the conventional per-beam planar data as input into a commercial "planned dose perturbation" (PDP) algorithm, and the results of these predicted DVH-based metrics were compared to the known values.Results: A range of weak to moderate correlations were found between clinically relevant patient DVH metrics (CTV-D95, parotid D-mean, spinal cord D1cc, and larynx D-mean) and both 3D detector and 3D patient gamma passing rate (3%/3 mm, 2%/2 mm) for dose-in-phantom along with dose-in-patient for both whole patient volume and filtered per-ROI. There was considerable scatter in the gamma passing rate vs DVH-based metric curves. However, for the same input data, the PDP estimates were in agreement with actual patient DVH results.Conclusions: Gamma passing rate, even if calculated based on patient dose grids, has generally weak correlation to critical patient DVH errors. However, the PDP algorithm was shown to accurately predict the DVH impact using conventional planar QA results. Using patient-DVH-based metrics IMRT QA allows per-patient dose QA to be based on metrics that are both sensitive and specific. Further studies are now required to analyze new processes and action levels associated with DVH-based metrics to ensure effectiveness and practicality in the clinical setting. (C) 2011 American Association of Physicists in Medicine. [DOI: 10.1118/1.3633904]