Ecole polytechnique de Montreal, Dipartement de ginie informatique et ginie logiciel, 2500 chemin de Polytechnique, Montreal, Quebec, H3T 1J4 Canada.
Med Phys. 2011 Jul;38(7):4101-7. doi: 10.1118/1.3598441.
To validate GPUMCD, a new package for fast Monte Carlo dose calculations based on the GPU (graphics processing unit), as a tool for low-energy single seed brachytherapy dosimetry for specific seed models. As the currently accepted method of dose calculation in low-energy brachytherapy computations relies on severe approximations, a Monte Carlo based approach would result in more accurate dose calculations, taking in to consideration the patient anatomy as well as interseed attenuation. The first step is to evaluate the capability of GPUMCD to reproduce low-energy, single source, brachytherapy calculations which could ultimately result in fast and accurate, Monte Carlo based, brachytherapy dose calculations for routine planning.
A mixed geometry engine was integrated to GPUMCD capable of handling parametric as well as voxelized geometries. In order to evaluate GPUMCD for brachytherapy calculations, several dosimetry parameters were computed and compared to values found in the literature. These parameters, defined by the AAPM Task-Group No. 43, are the radial dose function, the 2D anisotropy function, and the dose rate constant. These three parameters were computed for two different brachytherapy sources: the Amersham OncoSeed 6711 and the Imagyn IsoStar IS-12501.
GPUMCD was shown to yield dosimetric parameters similar to those found in the literature. It reproduces radial dose functions to within 1.25% for both sources in the 0.5< r <10 cm range. The 2D anisotropy function was found to be within 3% at r =5 cm and within 4% at r = 1 cm. The dose rate constants obtained were within the range of other values reported in the literature.
GPUMCD was shown to be able to reproduce various TG-43 parameters for two different low-energy brachytherapy sources found in the literature. The next step is to test GPUMCD as a fast clinical Monte Carlo brachytherapy dose calculations with multiple seeds and patient geometry, potentially providing more accurate results than the TG-43 formalism while being much faster than calculations using general purpose Monte Carlo codes.
验证基于 GPU（图形处理单元）的新的快速蒙特卡罗剂量计算软件 GPUMCD，作为特定种子模型的低能单源近距离治疗剂量计算的工具。由于目前低能近距离治疗计算中接受的剂量计算方法依赖于严重的近似，因此基于蒙特卡罗的方法将产生更准确的剂量计算，同时考虑患者解剖结构以及种子间衰减。第一步是评估 GPUMCD 再现低能单源近距离治疗计算的能力，这最终将导致快速准确的基于蒙特卡罗的常规计划近距离治疗剂量计算。
混合几何引擎被集成到 GPUMCD 中，能够处理参数化和体素化几何。为了评估 GPUMCD 在近距离治疗计算中的性能，计算了几个剂量学参数，并与文献中的值进行了比较。这些参数由 AAPM 任务组第 43 号定义，分别是径向剂量函数、二维各向异性函数和剂量率常数。这三个参数是为两种不同的近距离治疗源计算的：安玛西亚 OncoSeed 6711 和 Imagyn IsoStar IS-12501。
GPUMCD 产生的剂量学参数与文献中的值相似。它在 0.5< r <10cm 范围内再现了两种源的径向剂量函数，误差在 1.25%以内。在 r = 5cm 处，二维各向异性函数的误差在 3%以内，在 r = 1cm 处的误差在 4%以内。获得的剂量率常数在文献中报道的其他值的范围内。
GPUMCD 被证明能够再现文献中两种不同低能近距离治疗源的各种 TG-43 参数。下一步是使用多个种子和患者几何形状测试 GPUMCD 作为快速临床蒙特卡罗近距离治疗剂量计算，提供比 TG-43 公式更准确的结果，同时比使用通用蒙特卡罗代码的计算快得多。
