Department of Radiation Oncology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
Med Phys. 2010 Feb;37(2):869-76. doi: 10.1118/1.3298008.
For a given radionuclide, there are several photon spectrum choices available to dosimetry investigators for simulating the radiation emissions from brachytherapy sources. This study examines the dosimetric influence of selecting the spectra for 192Ir, 125I, and 103Pd on the final estimations of kerma and dose.
For 192Ir, 125I, and 103Pd, the authors considered from two to five published spectra. Spherical sources approximating common brachytherapy sources were assessed. Kerma and dose results from GEANT4, MCNP5, and PENELOPE-2008 were compared for water and air. The dosimetric influence of 192Ir, 125I, and 103Pd spectral choice was determined.
For the spectra considered, there were no statistically significant differences between kerma or dose results based on Monte Carlo code choice when using the same spectrum. Water-kerma differences of about 2%, 2%, and 0.7% were observed due to spectrum choice for 192Ir, 125, and 103Pd, respectively (independent of radial distance), when accounting for photon yield per Bq. Similar differences were observed for air-kerma rate. However, their ratio (as used in the dose-rate constant) did not significantly change when the various photon spectra were selected because the differences compensated each other when dividing dose rate by air-kerma strength.
Given the standardization of radionuclide data available from the National Nuclear Data Center (NNDC) and the rigorous infrastructure for performing and maintaining the data set evaluations, NNDC spectra are suggested for brachytherapy simulations in medical physics applications.
对于给定的放射性核素，有几种光子能谱可供剂量学研究人员选择，以模拟近距离放射治疗源的辐射发射。本研究考察了为 192Ir、125I 和 103Pd 选择谱对最终估算比释动能和剂量的影响。
对于 192Ir、125I 和 103Pd，作者考虑了两到五个已发表的能谱。评估了接近常见近距离放射治疗源的球形源。比较了 GEANT4、MCNP5 和 PENELOPE-2008 在水和空气中的比释动能和剂量结果。确定了 192Ir、125I 和 103Pd 光谱选择的剂量学影响。
在所考虑的光谱中，当使用相同的光谱时，基于蒙特卡罗代码选择，比释动能或剂量结果之间没有统计学上的显著差异。由于光谱选择，对于 192Ir、125 和 103Pd，分别观察到约 2%、2%和 0.7%的水比释动能差异（独立于径向距离），当考虑每 Bq 的光子产额时。对于空气比释动能率也观察到类似的差异。然而，当选择各种光子光谱时，它们的比值（如在剂量率常数中使用）并没有显著改变，因为当将剂量率除以空气比释动能强度时，差异相互补偿。
鉴于国家核数据中心（NNDC）提供的放射性核素数据的标准化以及用于执行和维护数据集评估的严格基础设施，建议在医学物理应用中为近距离放射治疗模拟使用 NNDC 光谱。
