Department of Radiology, University of Iowa Hospitals and Clinics, Iowa City, Iowa 52242.
Department of Physics, University of Iowa, Iowa City, Iowa 52242.
Radiat Res. 2020 Jun 1;193(6):531-542. doi: 10.1667/RR15563.1.
We report the generation of dose point kernels for clinically-relevant radionuclide beta decays and monoenergetic electrons in various tissues to understand the impact of tissue type on dose point kernels. Currently available voxel-wise dosimetry approaches using dose point kernels ignore tissue composition and density heterogeneities. Therefore, the study on the impact of tissue type on dose point kernels is warranted. Simulations were performed using the GATE Monte Carlo toolkit, which encapsulates GEANT4 libraries. Dose point kernels were simulated in phantoms of water, compact bone, lung, adipose tissue, blood and red marrow for radionuclides 90Y, 188Re, 32P, 89Sr, 186Re, 153Sm and 177Lu and monoenergetic electrons (0.015-10 MeV). All simulations were performed by assuming an isotropic point source of electrons at the center of a homogeneous spherical phantom. Tissue-specific differences between kernels were investigated by normalizing kernels for effective pathlength. Transport of 20 million particles was found to provide sufficient statistical precision in all simulated kernels. The simulated dose point kernels demonstrate excellent agreement with other Monte Carlo packages. Deviation from kernels reported in the literature did not exceed a 10% global difference, which is consistent with the variability among published results. There are no significant differences between the dose point kernel in water and kernels in other tissues that have been scaled to account for density; however, tissue density predictably demonstrated itself to be a significant variable in dose point kernel distribution.
我们报告了在各种组织中与临床相关的放射性核素β衰变和单能电子的剂量点核的生成，以了解组织类型对剂量点核的影响。目前，使用剂量点核的基于体素的剂量计算方法忽略了组织成分和密度不均匀性。因此，有必要研究组织类型对剂量点核的影响。模拟使用 GATE 蒙特卡罗工具包进行，该工具包封装了 GEANT4 库。在水、致密骨、肺、脂肪组织、血液和红骨髓的模型中模拟了放射性核素 90Y、188Re、32P、89Sr、186Re、153Sm 和 177Lu 以及单能电子（0.015-10 MeV）的剂量点核。所有模拟均假设在同质球形模型的中心有一个各向同性的电子点状源。通过归一化有效路径长度的核来研究核之间的组织特异性差异。发现传输 2000 万个粒子可以为所有模拟核提供足够的统计精度。模拟的剂量点核与其他蒙特卡罗软件包非常吻合。与文献中报告的核的偏差不超过 10%的全局差异，这与已发表结果的可变性一致。在已根据密度进行缩放以考虑密度的水的剂量点核与其他组织的剂量点核之间没有显着差异；但是，组织密度显然是剂量点核分布的重要变量。
