Radiation Oncology, Duke University Medical Center, Durham, North Carolina 27710, USA.
Int J Radiat Oncol Biol Phys. 2012 Oct 1;84(2):540-6. doi: 10.1016/j.ijrobp.2011.12.015. Epub 2012 Feb 22.
To demonstrate a new three-dimensional (3D) quality assurance (QA) method that provides comprehensive dosimetry verification and facilitates evaluation of the clinical significance of QA data acquired in a phantom. Also to apply the method to investigate the dosimetric efficacy of base-of-skull (BOS) intensity-modulated radiotherapy (IMRT) treatment.
Two types of IMRT QA verification plans were created for 6 patients who received BOS IMRT. The first plan enabled conventional 2D planar IMRT QA using the Varian portal dosimetry system. The second plan enabled 3D verification using an anthropomorphic head phantom. In the latter, the 3D dose distribution was measured using the DLOS/Presage dosimetry system (DLOS = Duke Large-field-of-view Optical-CT System, Presage Heuris Pharma, Skillman, NJ), which yielded isotropic 2-mm data throughout the treated volume. In a novel step, measured 3D dose distributions were transformed back to the patient's CT to enable calculation of dose-volume histograms (DVH) and dose overlays. Measured and planned patient DVHs were compared to investigate clinical significance.
Close agreement between measured and calculated dose distributions was observed for all 6 cases. For gamma criteria of 3%, 2 mm, the mean passing rate for portal dosimetry was 96.8% (range, 92.0%-98.9%), compared to 94.9% (range, 90.1%-98.9%) for 3D. There was no clear correlation between 2D and 3D passing rates. Planned and measured dose distributions were evaluated on the patient's anatomy, using DVH and dose overlays. Minor deviations were detected, and the clinical significance of these are presented and discussed.
Two advantages accrue to the methods presented here. First, treatment accuracy is evaluated throughout the whole treated volume, yielding comprehensive verification. Second, the clinical significance of any deviations can be assessed through the generation of DVH curves and dose overlays on the patient's anatomy. The latter step represents an important development that advances the clinical relevance of complex treatment QA.
展示一种新的三维（3D）质量保证（QA）方法，该方法提供全面的剂量验证，并有助于评估在体模中获得的 QA 数据的临床意义。还将该方法应用于研究颅底（BOS）强度调制放疗（IMRT）治疗的剂量学效果。
为 6 名接受 BOS IMRT 的患者创建了两种类型的 IMRT QA 验证计划。第一个计划允许使用瓦里安门户剂量测量系统进行常规的 2D 平面 IMRT QA。第二个计划允许使用人体头部模型进行 3D 验证。在后一种方法中，使用 DLOS/Presage 剂量测量系统（DLOS = Duke 大视场光学 CT 系统，Presage Heuris Pharma，Skillman，NJ）测量 3D 剂量分布，该系统在整个治疗区域内产生各向同性的 2mm 数据。在一个新颖的步骤中，将测量的 3D 剂量分布转换回患者的 CT 中，以计算剂量体积直方图（DVH）和剂量叠加。比较测量和计划的患者 DVH 以研究临床意义。
在所有 6 个病例中，均观察到测量和计算的剂量分布之间的紧密一致性。对于 3%、2mm 的伽马标准，门户剂量测量的平均通过率为 96.8%（范围，92.0%-98.9%），而 3D 的通过率为 94.9%（范围，90.1%-98.9%）。2D 和 3D 通过率之间没有明显的相关性。在患者的解剖结构上，使用 DVH 和剂量叠加评估计划和测量的剂量分布。检测到较小的偏差，并提出和讨论了这些偏差的临床意义。
这里提出的方法有两个优点。首先，通过在整个治疗体积中评估治疗准确性，实现了全面的验证。其次，通过在患者解剖结构上生成 DVH 曲线和剂量叠加，可以评估任何偏差的临床意义。后一步是一个重要的发展，提高了复杂治疗 QA 的临床相关性。
