Whole-Body Micro-Yucatan Minipig Computational Phantoms for Preclinical Radiopharmaceutical Dosimetry
Abstract
Purpose
In preclinical studies, animal models are widely used to estimate absorbed doses following the administration of radiopharmaceuticals. Mice are the most commonly used models; however, their small body size can lead to biased dose estimates when translating mouse dosimetry to humans. Owing to their human-comparable size and physiological similarity, minipigs have emerged as promising mid-size experimental models. To enable accurate preclinical dosimetry in minipigs, this study developed the first set of male and female micro-Yucatan whole-body minipig computational phantoms.
Methods
Male and female minipig phantoms were constructed by segmenting organs required for effective dose calculations from medical images (CT and MR) of 6-month-old micro-Yucatan minipigs. The segmented structures were exported as mesh models and refined to eliminate mesh defects, such as holes and self-intersections, while preserving anatomical topology. The developed phantoms were implemented in the PHITS Monte Carlo radiation transport code to compute specific absorbed fractions (SAFs) and radionuclide S values to investigate the dosimetric characteristics of minipigs as preclinical animal models.
Results
A set of male and female micro-Yucatan minipig computational phantoms were successfully developed in a tetrahedral-mesh format. The phantoms provide an anatomically realistic representation of the minipigs based on actual medical images and explicitly define the organs required for effective dose calculations. The calculated SAFs and S values indicated that the minipig phantoms exhibited larger values than the ICRP adult human male reference phantom and smaller values than the Mouse Whole-Body (MOBY) phantom.
Conclusion
The developed minipig phantoms are the first and only whole-body computational models representing both male and female micro-Yucatan minipigs with detailed internal anatomy. These phantoms will serve as valuable tools for advancing animal-to-human dose translation beyond mouse-only models. Future work will extend the models to microscale tissue geometries derived from micro-CT and histological images to support dosimetry of alpha particle–emitting radiopharmaceuticals.