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Abstract：
OBJECTIVE: The quality of a measured distribution of dose delivered against its corresponding radiotherapy plan is routinely assessed by gamma index (GI) and dose-volume histogram (DVH) metrics. Any correlation between error detection rates, as based on either of these approaches, while argued, has never been convincingly demonstrated. The dependence of the strength of correlation between the GI passing rate ( γ P ) and DVH quality assurance (QA) metrics on various elements of the therapy plan has not been systematically investigated.
METHODS: A formal analysis of the relation between γ P and DVH metrics has been undertaken, leading to a relationship which may partly approximate γ P with respect to the DVH. This relationship was further validated by studying examples of simulated clinical radiotherapy plans and by studying the correlation between γ P and the derived relationship using a simple two-dimensional representations of the planning target volume (PTV) and organs at risk (OAR), where penumbra regions, distance-to-agreement tolerances and dose delivery errors were systematically varied.
RESULTS: It is shown formally that there cannot be any correlation between γ P and other commonly applied DVH-derived QA measures. However, γ P may be partly approximated given the planned and measured DVH. The derived γ P approximation (the \" γ -slope indicator\") may be clinically useful in some practical cases of radiotherapy plan QA.
CONCLUSIONS: In formal terms, there cannot be any correlation between γ P and any common DVH-calculated patient-specific measures, with respect to PTV or OAR. However, as demonstrated analytically and further confirmed in our simulation studies, the γ P approximation derived in this study (the \" γ -slope indicator\") may in some cases offer a degree of correlation between γ P and the PTV and OAR DVH QA metrics in measured and planned patient-specific dose distributions-which may be potentially useful in clinical practice.
METHODS: A formal analysis of the relation between γ P and DVH metrics has been undertaken, leading to a relationship which may partly approximate γ P with respect to the DVH. This relationship was further validated by studying examples of simulated clinical radiotherapy plans and by studying the correlation between γ P and the derived relationship using a simple two-dimensional representations of the planning target volume (PTV) and organs at risk (OAR), where penumbra regions, distance-to-agreement tolerances and dose delivery errors were systematically varied.
RESULTS: It is shown formally that there cannot be any correlation between γ P and other commonly applied DVH-derived QA measures. However, γ P may be partly approximated given the planned and measured DVH. The derived γ P approximation (the \" γ -slope indicator\") may be clinically useful in some practical cases of radiotherapy plan QA.
CONCLUSIONS: In formal terms, there cannot be any correlation between γ P and any common DVH-calculated patient-specific measures, with respect to PTV or OAR. However, as demonstrated analytically and further confirmed in our simulation studies, the γ P approximation derived in this study (the \" γ -slope indicator\") may in some cases offer a degree of correlation between γ P and the PTV and OAR DVH QA metrics in measured and planned patient-specific dose distributions-which may be potentially useful in clinical practice.
摘要：
目的：通过伽玛指数（GI）和剂量-体积直方图（DVH）指标常规评估针对其相应的放射治疗计划所测量的剂量分布的质量。错误检测率之间的任何相关性，基于这些方法中的任何一种，虽然争论，从未令人信服地证明过。尚未系统地研究GI通过率（γP）和DVH质量保证（QA）指标之间的相关性强度对治疗计划各个要素的依赖性。
方法：对γP和DVH指标之间的关系进行了形式化分析，导致与DVH可能部分接近γP的关系。通过研究模拟临床放疗计划的实例，并通过使用计划目标体积（PTV）和危险器官（OAR）的简单二维表示研究γP与推导关系之间的相关性，进一步验证了这种关系。在半影区域，距离-协议公差和剂量输送误差是系统变化的.
结果：正式显示，γP与其他常用的DVH衍生的QA度量之间不存在任何相关性。然而,在给定计划和测量的DVH的情况下，γP可以部分近似。推导出的γP近似值（“γ-斜率指标”）在某些放射治疗计划QA的实际情况下可能在临床上有用。
结论：在正式术语中，γP与任何常见的DVH计算的患者特定指标之间不存在任何相关性，关于PTV或OAR。然而,正如我们的模拟研究中分析和进一步证实的那样，本研究中得出的γP近似值("γ-斜率指标")在某些情况下,在测量和计划的患者特定剂量分布中,γP与PTV和OARDVHQA指标之间存在一定程度的相关性,这在临床实践中可能有用.
方法：对γP和DVH指标之间的关系进行了形式化分析，导致与DVH可能部分接近γP的关系。通过研究模拟临床放疗计划的实例，并通过使用计划目标体积（PTV）和危险器官（OAR）的简单二维表示研究γP与推导关系之间的相关性，进一步验证了这种关系。在半影区域，距离-协议公差和剂量输送误差是系统变化的.
结果：正式显示，γP与其他常用的DVH衍生的QA度量之间不存在任何相关性。然而,在给定计划和测量的DVH的情况下，γP可以部分近似。推导出的γP近似值（“γ-斜率指标”）在某些放射治疗计划QA的实际情况下可能在临床上有用。
结论：在正式术语中，γP与任何常见的DVH计算的患者特定指标之间不存在任何相关性，关于PTV或OAR。然而,正如我们的模拟研究中分析和进一步证实的那样，本研究中得出的γP近似值("γ-斜率指标")在某些情况下,在测量和计划的患者特定剂量分布中,γP与PTV和OARDVHQA指标之间存在一定程度的相关性,这在临床实践中可能有用.
