Development of Adult Filipino Mesh-Type Reference Computational Phantoms

Purpose Radiation dosimetry is concerned with the accurate calculation, measurement, and assessment of radiation doses. Human computational phantoms play a significant role in the assessment of tissue and organ doses within the body when exposed to ionizing radiation. However, existing international standards, such as the computational phantoms developed by the International Commission on Radiological Protection (ICRP), are based predominantly on Caucasian populations. This raises concerns about their applicability to other ethnic groups. This study aims to address this gap through the development of computational phantoms tailored to the adult Filipino population. Methods The computational phantoms were constructed using height and weight data from national surveys and organ measurements obtained from computed tomography (CT) images of patients at the Philippine General Hospital, using the body-size-dependent phantom library constructed from ICRP mesh-type reference computational phantoms of Hanyang University Radiation Engineering Laboratory (HUREL) as a base. Organ dose conversion coefficients were calculated using Particle and Heavy Ion Transport Code System (PHITS) for the AP irradiation geometry and photon energy of 0.02 to 10 MeV. Results Compared with ICRP phantoms, the Filipino MRCPs exhibit generally smaller body and organ dimensions. Despite these anatomical differences, organ dose coefficient ratios were close to unity (0.9-1.1) across most photon energies, indicating overall agreement. However, substantial deviations were observed at low energies (<50 keV) where dose ratios were amplified due to the dominance of the photoelectric effect. Conclusion These variations in organ dose coefficients were observed to be strongly influenced by organ depth and mass. Small differences can be significant in radiation protection and risk estimation, where dose coefficients are directly propagated into effective dose and epidemiological studies. Thus, population-specific phantoms remain essential for improving dosimetric accuracy.