Reference Male Phantom for Internal Dosimetry-RMPID: Physical model in 3D-printing for whole-body counter calibration

In vivo internal dosimetry can use a whole-body counter (WBC) to estimate radionuclides' incorporated activity (Bq) in internally contaminated individuals. The WBC must be calibrated to convert the count rate from the detector into activity incorporated in the person. Active physical phantoms could be used for the calibration procedure. Additive manufacturing allows the physical reproduction of ICRP computational models with good geometric fidelity. This study aims to develop imaging manipulation techniques to generate stereolithography (STL) parts for the 3D printing a male physical phantom based on the Adult Male Reference Computational Phantom (RCP_AM) model provided in the ICRP 110 publication. The Reference Male Phantom for Internal Dosimetry (RMPID) was developed based on the model provided by the ICRP in text file format containing the RCP_AM segmentation information. It was processed with an in-house C++ program that generated images in RAW format (Unprocessed images). The images were manipulated using freeware: ImageJ, MeshLab, FreeCAD, and Meshmixer. A set of 22 hollow portions, 44 pieces including the lids, which fit together, were obtained. The RMPID was printed in PLA (Polylactic Acid) on the Creality Ender 5 Plus 3D printer. The 3D-printed phantom parts passed leak tests, proving that imaging manipulation techniques resulted in well-sealed parts. That will allow the phantom to be safely filled with tissue-equivalent material containing a calibrated activity of the selected radionuclide. The design also makes the simulator easier to handle and to assemble during calibration routines.