AGH University of Science and Technology, Krakow, Poland.
Faculty of Materials Science and Physics, Cracow University of Technology, Krakow, Poland.
Med Phys. 2021 Sep;48(9):4743-4753. doi: 10.1002/mp.15142. Epub 2021 Aug 14.
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 ( ) and DVH quality assurance (QA) metrics on various elements of the therapy plan has not been systematically investigated.
A formal analysis of the relation between and DVH metrics has been undertaken, leading to a relationship which may partly approximate with respect to the DVH. This relationship was further validated by studying examples of simulated clinical radiotherapy plans and by studying the correlation between 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.
It is shown formally that there cannot be any correlation between and other commonly applied DVH-derived QA measures. However, may be partly approximated given the planned and measured DVH. The derived approximation (the " -slope indicator") may be clinically useful in some practical cases of radiotherapy plan QA.
In formal terms, there cannot be any correlation between 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 approximation derived in this study (the " -slope indicator") may in some cases offer a degree of correlation between and the PTV and OAR DVH QA metrics in measured and planned patient-specific dose distributions-which may be potentially useful in clinical practice.
通过伽玛指数（GI）和剂量-体积直方图（DVH）指标，常规评估实际剂量分布与放疗计划之间的吻合质量。虽然已经提出了这两种方法的误差检测率之间存在相关性，但从未令人信服地证明过这一点。GI 通过率（ ）与 DVH 质量保证（QA）指标之间的相关性强度取决于治疗计划的各种因素，这一点尚未得到系统研究。
对 GI 通过率（ ）与 DVH 指标之间的关系进行了正式分析，得出了一个与 DVH 部分近似的关系。通过研究模拟临床放疗计划的例子以及使用规划靶区（PTV）和危及器官（OAR）的简单二维表示来研究 与导出关系之间的相关性，进一步验证了这种关系。在这些例子中，我们系统地改变了半影区域、一致性容差和剂量传递误差等参数。
正式证明 与其他常用的基于 DVH 的 QA 度量之间不可能存在任何相关性。然而，给定计划和测量的 DVH， 可以部分近似。所得到的 近似值（“ 斜率指标”）在某些实际放疗计划 QA 情况下可能具有临床应用价值。
从形式上讲， 与 PTV 或 OAR 的任何常见基于 DVH 计算的患者特定度量之间都不可能存在任何相关性。然而，正如本文分析所示，并在我们的模拟研究中进一步证实，在这种情况下，本文推导的 近似值（“ 斜率指标”）可能在某些情况下在测量和计划的患者特定剂量分布中提供 与 PTV 和 OAR DVH QA 指标之间的相关性，这在临床实践中可能具有潜在的价值。
