Berumen Francisco, Ma Yunzhi, Ramos-Méndez José, Perl Joseph, Beaulieu Luc
Département de Radio-Oncologie et Axe oncologie du Centre de recherche du CHU de Québec, CHU de Québec, Québec, QC, Canada; Département de Physique, de Génie Physique et d'Optique et Centre de Recherche sur le Cancer, Université Laval, Québec, QC, Canada.
Department of Radiation Oncology, University of California San Francisco, San Francisco, CA.
Brachytherapy. 2021 Jul-Aug;20(4):911-921. doi: 10.1016/j.brachy.2020.12.007. Epub 2021 Apr 23.
The goal of this work is to validate the user-friendly Geant4-based Monte Carlo toolkit TOol for PArticle Simulation (TOPAS) for brachytherapy applications.
Brachytherapy simulations performed with TOPAS were systematically compared with published TG-186 reference data. The photon emission energy spectrum, the air-kerma strength, and the dose-rate constant of the model-based dose calculation algorithm (MBDCA)-WG generic Ir-192 source were extracted. For dose calculations, a track-length estimator was implemented. The four Joint AAPM/ESTRO/ABG MBDCA-WG test cases were evaluated through histograms of the local and global dose difference volumes. A prostate, a palliative lung, and a breast case were simulated. For each case, the dose ratio map, the histogram of the global dose difference volume, and cumulative dose-volume histograms were calculated.
The air-kerma strength was (9.772 ± 0.001) × 10 U Bq (within 0.3% of the reference value). The dose-rate constant was 1.1107 ± 0.0005 cGy h U (within 0.01% of the reference value). For all cases, at least 96.9% of voxels had a local dose difference within [-1%, 1%] and at least 99.9% of voxels had a global dose difference within [-0.1%, 0.1%]. The implemented track-length estimator scorer was more efficient than the default analog dose scorer by a factor of 237. For all clinical cases, at least 97.5% of voxels had a global dose difference within [-1%, 1%]. Dose-volume histograms were consistent with the reference data.
TOPAS was validated for high-dose-rate brachytherapy simulations following the TG-186 recommended approach for MBDCAs. Built on top of Geant4, TOPAS provides broad access to a state-of-the-art Monte Carlo code for brachytherapy simulations.
本研究的目的是验证基于Geant4的、用户友好的用于近距离放射治疗应用的蒙特卡罗工具包——粒子模拟工具（TOPAS）。
将使用TOPAS进行的近距离放射治疗模拟与已发表的TG - 186参考数据进行系统比较。提取了基于模型的剂量计算算法（MBDCA）-WG通用铱-192源的光子发射能谱、空气比释动能强度和剂量率常数。对于剂量计算，实施了径迹长度估计器。通过局部和全局剂量差异体积的直方图对四个联合美国医学物理学会/欧洲放射肿瘤学会/德国放射肿瘤学会MBDCA - WG测试案例进行了评估。模拟了一个前列腺、一个姑息性肺部和一个乳腺病例。针对每个病例，计算了剂量比图、全局剂量差异体积的直方图和累积剂量体积直方图。
空气比释动能强度为(9.772 ± 0.001)×10 U Bq（在参考值的0.3%以内）。剂量率常数为1.1107 ± 0.0005 cGy h U（在参考值的0.01%以内）。对于所有病例，至少96.9%的体素局部剂量差异在[-1%, 1%]内，至少99.9%的体素全局剂量差异在[-0.1%, 0.1%]内。实施的径迹长度估计器计分器比默认的模拟剂量计分器效率高237倍。对于所有临床病例，至少97.5%的体素全局剂量差异在[-1%, 1%]内。剂量体积直方图与参考数据一致。
按照TG - 186推荐的MBDCA方法，TOPAS在高剂量率近距离放射治疗模拟中得到了验证。TOPAS基于Geant4构建，为近距离放射治疗模拟提供了广泛使用最先进蒙特卡罗代码的途径。
