Kang Sang-Won, Chung Jin-Beom, Kim Kyeong-Hyeon, Choi Chang Heon, Kang Seonghee, Shin Dong-Seok, Cho Woong, Eom Kuen-Yong, Park Hae-Jin, Kim Jin-Young, Song Changhoon, Kim In Ah, Kim Jae-Sung, 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. 2021 Mar 9;11:647222. doi: 10.3389/fonc.2021.647222. eCollection 2021.
The aim of this study was to develop a dosimetric verification system (DVS) using a solid phantom for patient-specific quality assurance (QA) of high-dose-rate brachytherapy (HDR-BT). The proposed DVS consists of three parts: dose measurement, dose calculation, and analysis. All the dose measurements were performed using EBT3 film and a solid phantom. The solid phantom made of acrylonitrile butadiene styrene (ABS, density = 1.04 g/cm) was used to measure the dose distribution. To improve the accuracy of dose calculation by using the solid phantom, a conversion factor [CF(r)] according to the radial distance between the water and the solid phantom material was determined by Monte Carlo simulations. In addition, an independent dose calculation program (IDCP) was developed by applying the obtained CF(r). To validate the DVS, dosimetric verification was performed using gamma analysis with 3% dose difference and 3 mm distance-to-agreement criterion for three simulated cases: single dwell position, elliptical dose distribution, and concave elliptical dose distribution. In addition, the possibility of applying the DVS in the high-dose range (up to 15 Gy) was evaluated. The CF(r) between the ABS and water phantom was 0.88 at 0.5 cm. The factor gradually increased with increasing radial distance and converged to 1.08 at 6.0 cm. The point doses 1 cm below the source were 400 cGy in the treatment planning system (TPS), 373.73 cGy in IDCP, and 370.48 cGy in film measurement. The gamma passing rates of dose distributions obtained from TPS and IDCP compared with the dose distribution measured by the film for the simulated cases were 99.41 and 100% for the single dwell position, 96.80 and 100% for the elliptical dose distribution, 88.91 and 99.70% for the concave elliptical dose distribution, respectively. For the high-dose range, the gamma passing rates in the dose distributions between the DVS and measurements were above 98% and higher than those between TPS and measurements. The proposed DVS is applicable for dosimetric verification of HDR-BT, as confirmed through simulated cases for various doses.
本研究的目的是开发一种剂量验证系统（DVS），该系统使用固体模体对高剂量率近距离放疗（HDR-BT）进行患者特异性质量保证（QA）。所提出的DVS由三部分组成：剂量测量、剂量计算和分析。所有剂量测量均使用EBT3胶片和固体模体进行。由丙烯腈-丁二烯-苯乙烯（ABS，密度 = 1.04 g/cm）制成的固体模体用于测量剂量分布。为了提高使用固体模体进行剂量计算的准确性，通过蒙特卡罗模拟确定了根据水与固体模体材料之间径向距离的转换因子[CF(r)]。此外，通过应用获得的CF(r)开发了一个独立的剂量计算程序（IDCP）。为了验证DVS，针对三个模拟病例：单驻留位置、椭圆形剂量分布和凹形椭圆形剂量分布，使用3%剂量差异和3 mm距离一致性标准的伽马分析进行剂量验证。此外，评估了在高剂量范围（高达15 Gy）应用DVS的可能性。ABS与水体模之间的CF(r)在0.5 cm处为0.88。该因子随着径向距离的增加而逐渐增加，并在6.0 cm处收敛到1.08。源下方1 cm处的点剂量在治疗计划系统（TPS）中为400 cGy，在IDCP中为373.73 cGy，在胶片测量中为370.48 cGy。对于模拟病例，TPS和IDCP获得的剂量分布与胶片测量的剂量分布相比，单驻留位置的伽马通过率分别为99.41%和100%，椭圆形剂量分布为96.80%和100%，凹形椭圆形剂量分布为88.91%和99.70%。对于高剂量范围，DVS与测量之间剂量分布的伽马通过率高于98%，且高于TPS与测量之间的通过率。通过各种剂量的模拟病例证实，所提出的DVS适用于HDR-BT的剂量验证。
