Kang Sang-Won, Chung Jin-Beom, Kim Kyeong-Hyeon, Park Ji-Yeon, Park Hae-Jin, Cho Woong, Olberg Sven, Suh Tae Suk, Park Justin C
Department of Biomedical Engineering, Department of Biomedicine and Health Sciences, College of Medicine, The Catholic University of Korea, Seoul, South Korea.
College of Medicine, Research Institute of Biomedical Engineering, The Catholic University of Korea, Seoul, South Korea.
Front Oncol. 2020 May 13;10:609. doi: 10.3389/fonc.2020.00609. eCollection 2020.
This study aimed to develop a volumetric independent dose calculation (vIDC) system for verification of the treatment plan in image-guided adaptive brachytherapy (IGABT) and to evaluate the feasibility of the vIDC in clinical practice with simulated cases. The vIDC is based on the formalism of TG-43. Four simulated cases of cervical cancer were selected to retrospectively evaluate the dose distributions in IGABT. Some reference point doses, such as points A and B and rectal points, were calculated by vIDC using absolute coordinate. The 3D dose volume was also calculated to acquire dose-volume histograms (DVHs) with grid resolutions of 1.0 × 1.0 (G), 2.5 × 2.5 (G), and 0.5 × 0.5 mm (G). Dosimetric parameters such as D and D doses covering 90% of the high-risk critical target volume (HR-CTV) and 2 cc of the organs at risk (OARs) were obtained from DVHs. D also converted to equivalent dose in 2-Gy fractions (EQD2) to produce the same radiobiological effect as external beam radiotherapy. In addition, D was obtained in two types with or without the applicator volume to confirm the effect of the applicator itself. Validation of the vIDC was also performed using gamma evaluation by comparison with Monte Carlo simulation. The average percentage difference of point doses was <2.28%. The DVHs for the HR-CTV and OARs showed no significant differences between the vIDC and the treatment planning system (TPS). Without considering the applicator volume, the D of the HR-CTV calculated by the vIDC decreases with a decreasing calculated dose-grid size (32.4, 5.65, and -2.20 cGy in G, G, and G, respectively). The overall D is higher when considering the applicator volume. The converted D by EQD2 ranged from -1.29 to 1.00%. The D of the OARs showed that the averaged dose deviation is <10 cGy regardless of the dose-grid size. Based on gamma analysis, the passing rate was 98.81% for 3%/3-mm criteria. The vIDC was developed as an independent dose verification system for verification of the treatment plan in IGABT. We confirmed that the vIDC is suitable for second-check dose validation of the TPS under various conditions.
本研究旨在开发一种体积独立剂量计算（vIDC）系统，用于图像引导自适应近距离放射治疗（IGABT）中治疗计划的验证，并通过模拟病例评估vIDC在临床实践中的可行性。vIDC基于TG-43形式体系。选择了4例宫颈癌模拟病例，回顾性评估IGABT中的剂量分布。vIDC使用绝对坐标计算了一些参考点剂量，如A点、B点和直肠点。还计算了三维剂量体积，以获取网格分辨率为1.0×1.0（G）、2.5×2.5（G）和0.5×0.5毫米（G）的剂量体积直方图（DVH）。从DVH中获得了覆盖90%高危关键靶区（HR-CTV）和2立方厘米危及器官（OAR）的剂量学参数，如D和D剂量。D也转换为2 Gy分次等效剂量（EQD2），以产生与外照射放疗相同的放射生物学效应。此外，D以有或无施源器体积两种类型获得，以确认施源器本身的影响。还通过与蒙特卡罗模拟比较，使用伽马评估对vIDC进行了验证。点剂量的平均百分比差异<2.28%。HR-CTV和OAR的DVH在vIDC和治疗计划系统（TPS）之间无显著差异。不考虑施源器体积时，vIDC计算的HR-CTV的D随计算剂量网格尺寸减小而降低（在G、G和G中分别为32.4、5.65和-2.20 cGy）。考虑施源器体积时，总体D更高。EQD2转换后的D范围为-1.29%至1.00%。OAR的D表明，无论剂量网格尺寸如何，平均剂量偏差<10 cGy。基于伽马分析，对于3%/3毫米标准，通过率为98.81%。vIDC被开发为一种独立的剂量验证系统，用于IGABT中治疗计划的验证。我们证实vIDC适用于在各种条件下对TPS进行二次检查剂量验证。
