Monte Carlo modeling and simulation of a new 3D printed phantom for WBC calibration with ballistic gel as a tissue substitute

Abstract

Whole-body counter (WBC) systems are used for in vivo monitoring in occupational internal dosimetry, typically calibrated using physical anthropomorphic phantoms. Our research group previously 3D-printed the Reference Female Phantom for Internal Dosimetry (RFPID) without internal organs specifically designed for WBC calibration. The RFPID and it is intended to fill it homogenously with ballistic gel, which is commonly used as a tissue equivalent in ballistic studies. However, comprehensive characterization of its physicochemical properties and radiological behavior as a tissue surrogate for dosimetry is limited. This study aims to evaluate the suitability of ballistic gel as a tissue substitute for physical phantoms in WBC system calibration and to analyze the RFPID as a model for WBC calibration. Ballistic gel tests determined its density and attenuation coefficients, comparing it to muscle, water, and PMMA. The RFPID was modeled and simulated using MCNP6.2 code and placed in an in vivo monitoring system using an 8”x4″ NaI(Tl) scintillator detector previously validated. The simulations were repeated with the RCP_AF of ICRP-110. Results indicate that ballistic gel has a density approximately 6% different from muscle and shows similar linear attenuation coefficients to muscle at intermediate and high energy levels (186–2200 keV). Simulations revealed a disparity of less than 9% in counting efficiency between RFPID and RCP_AF for energies from 100 to 3000 keV, confirming the phantom's suitability for WBC calibration and ballistic gel's viability as a tissue surrogate in internal dosimetry.