State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Department of Radiation Oncology, Sun Yat-sen University Cancer Center, 651 Dongfeng Road East, Guangzhou, 510060, People's Republic of China.
Radiat Oncol. 2018 Mar 15;13(1):42. doi: 10.1186/s13014-018-0993-2.
Conventional phantom-based planar dosimetry (2D-PBD) quality assurance (QA) using gamma pass rate (GP (%)) is inadequate to reflect clinically relevant dose error in intensity-modulated radiation therapy (IMRT), owing to a lack of information regarding patient anatomy and volumetric dose distribution. This study aimed to evaluate the dose distribution accuracy of IMRT delivery for nasopharyngeal carcinoma (NPC), which passed the 2D-PBD verification, using a measurement-guided 3D dose reconstruction (3D-MGR) method.
Radiation treatment plans of 30 NPC cases and their pre-treatment 2D-PBD data were analyzed. 3D dose distribution was reconstructed on patient computed tomography (CT) images using the 3DVH software and compared to the treatment plans. Global and organ-specific dose GP (%), and dose-volume histogram (DVH) deviation of each structure was evaluated. Interdependency between GP (%) and the deviation of the volumetric dose was studied through correlation analysis.
The 3D-MGR achieved global GP (%) similar to conventional 2D-PBD in the same criteria. However, structure-specific GP (%) significantly decreased under stricter criteria, including the planning target volume (PTV). The average deviation of all inspected dose volumes (D) and volumetric dose (V) parameters ranged from - 2.93% to 1.17%, with the largest negative deviation in V100% of the PTVnx of - 15.66% and positive deviation in D1cc of the spinal cord of 6.66%. There was no significant correlation between global GP (%) of 2D-PBD or 3D-MGR and the deviation of the most volumetric dosimetry parameters (D or V), when the Pearson's coefficient value of 0.8 was used for correlation evaluation.
Even upon passing the pre-treatment phantom based dosimetric QA, there could still be risk of dose error like under-dose in PTVnx and overdose in critical structures. Measurement-guided 3D volumetric dosimetry QA is recommended as the more clinically efficient verification for the complicated NPC IMRT.
传统的基于体模的二维平面剂量学（2D-PBD）质量保证（QA），使用伽马通过率（GP（%）），由于缺乏有关患者解剖结构和体积剂量分布的信息，无法反映调强放射治疗（IMRT）中临床相关的剂量误差。本研究旨在评估使用测量指导的三维剂量重建（3D-MGR）方法，通过二维平面剂量学（2D-PBD）验证的鼻咽癌（NPC）调强放疗的剂量分布准确性。
分析了 30 例 NPC 患者的放射治疗计划和他们的治疗前二维平面剂量学数据。使用 3DVH 软件在患者的计算机断层扫描（CT）图像上重建三维剂量分布，并与治疗计划进行比较。评估了全局和器官特异性剂量 GP（%），以及每个结构的剂量-体积直方图（DVH）偏差。通过相关分析研究了 GP（%）与体积剂量偏差之间的相关性。
3D-MGR 在相同标准下达到了与传统 2D-PBD 相似的全局 GP（%）。然而，在更严格的标准下，包括计划靶区（PTV），结构特异性 GP（%）显著降低。所有检查的剂量体积（D）和体积剂量（V）参数的平均偏差范围为-2.93%至 1.17%，最大的负偏差出现在 PTVnx 的 V100%为-15.66%，而脊髓的 D1cc 出现正偏差为 6.66%。当使用 Pearson 相关系数值为 0.8 进行相关性评估时，2D-PBD 或 3D-MGR 的全局 GP（%）与大多数体积剂量学参数（D 或 V）的偏差之间没有显著相关性。
即使通过了治疗前的基于体模的剂量学 QA，仍然存在剂量误差的风险，如 PTVnx 中的剂量不足和关键结构中的剂量过量。建议使用测量指导的三维体积剂量学 QA 作为更具临床效率的复杂 NPC-IMRT 验证方法。
