Organ dose conversion coefficients calculated for Korean pediatric and adult voxel phantoms exposed to external photon fields.

Abstract

Dose conversion coefficients (DCCs) have been commonly used to estimate radiation dose absorbed in human organs from physical measurements of fluence or kerma. The International Commission on Radiological Protection (ICRP) reported a library of DCCs but few studies were conducted on their applicability to non-Caucasian populations. In the present study, we collected a total of eight Korean pediatric and adult voxel phantoms to calculate organ DCCs for idealized external photon irradiation geometries. We adopted one pediatric female phantom (ETRI Child), two adult female phantoms (KORWOMAN and HDRK Female), and five adult male phantoms (KORMAN, ETRI Man, KTMAN1, KTMAN2, and HDRK Man). A general-purpose Monte Carlo radiation transport code, MCNPX2.7, was employed to calculate dose conversion coefficients for 13 major radiosensitive organs in six irradiation geometries (antero-posterior, postero-anterior, right lateral, left lateral, rotational, and isotropic) and 33 photon energy bins (0.01 - 20 MeV). The DCCs for major radiosensitive organs (e.g., lungs and colon) in AP geometry reasonably agreed across the eight Korean phantoms whereas those for deep-seated organs (e.g., gonads) significantly varied. DCCs of the child phantom were overall greater than those of the adult phantoms. Comparison with the ICRP Publication 116 data showed reasonable agreements with Korean phantom-based data. The variations in organ DCCs were well explained using the distribution of organ depths from the phantom surface. A library of dose conversion coefficients for major radiosensitive organs in a series of pediatric and adult Korean voxel phantoms was established and compared with the reference data from ICRP. Comparison with the data from the ICRP reference adult voxel phantoms showed that our Korean phantom-based data is overall in a reasonable agreement with the ICRP reference data.