Mesh-type and voxel-based computational phantoms comprise the current state of the art for internal dose assessment via Monte Carlo simulations but excel in different aspects, with mesh-type phantoms offering advantages over their voxel counterparts in terms of their flexibility and realistic representation of detailed patient- or subject-specific anatomy. We have developed PARaDIM (pronounced “paradigm”: Particle and Heavy Ion Transport Code System–Based Application for Radionuclide Dosimetry in Meshes), a freeware application for implementing tetrahedral mesh-type phantoms in absorbed dose calculations. It considers all medically relevant radionuclides, including α, β, γ, positron, and Auger/conversion electron emitters, and handles calculation of mean dose to individual regions, as well as 3-dimensional dose distributions for visualization and analysis in a variety of medical imaging software. This work describes the development of PARaDIM, documents the measures taken to test and validate its performance, and presents examples of its uses. Methods: Human, small-animal, and cell-level dose calculations were performed with PARaDIM and the results compared with those of widely accepted dosimetry programs and literature data. Several tetrahedral phantoms were developed or adapted using computer-aided modeling techniques for these comparisons. Results: For human dose calculations, agreement of PARaDIM with OLINDA 2.0 was good—within 10%–20% for most organs—despite geometric differences among the phantoms tested. Agreement with MIRDcell for cell-level S value calculations was within 5% in most cases. Conclusion: PARaDIM extends the use of Monte Carlo dose calculations to the broader community in nuclear medicine by providing a user-friendly graphical user interface for calculation setup and execution. PARaDIM leverages the enhanced anatomic realism provided by advanced computational reference phantoms or bespoke image-derived phantoms to enable improved assessments of radiation doses in a variety of radiopharmaceutical use cases, research, and preclinical development. PARaDIM can be downloaded freely at www.paradim-dose.org.

网格类型和基于体素的计算模型包括通过蒙特卡洛模拟进行内部剂量评估的最新技术，但在各个方面都表现出色，网格类型的模型在其灵活性和逼真的表示方面比体素模型具有优势详细的针对患者或受试者的解剖结构。我们已经开发了PARaDIM（发音为“范式”：基于粒子和重离子输运代码系统的网格中放射性核素剂量测定应用程序），该软件是免费的应用程序，用于在吸收剂量计算中实现四面体网格类型体模。它考虑了所有与医学相关的放射性核素，包括α，β，γ，正电子和俄歇/转换电子发射器，并负责计算各个区域的平均剂量，以及用于各种医学成像软件的可视化和分析的3维剂量分布。这项工作描述了PARaDIM的开发，记录了为测试和验证其性能而采取的措施，并提供了其用法示例。方法：使用PARaDIM进行人，小动物和细胞水平的剂量计算，并将结果与​​广泛接受的剂量测定程序和文献数据进行比较。使用计算机辅助建模技术开发或修改了几种四面体模型，以进行这些比较。结果：对于人体剂量计算，尽管所测试的幻像之间存在几何差异，但PARaDIM与OLINDA 2.0的一致性很好（对于大多数器官而言，在10％至20％之内）。在大多数情况下，与MIRDcell进行单元级S值计算的协议在5％以内。结论：PARaDIM通过提供用于计算设置和执行的用户友好的图形用户界面，将蒙特卡洛剂量计算的使用扩展到了核医学的更广泛社区。PARaDIM利用先进的计算参考体模或来自定制图像的体模提供的增强的解剖学真实性，可以在各种放射性药物使用案例，研究和临床前开发中改进对辐射剂量的评估。可以从www.paradim-dose.org免费下载PARaDIM。