Calculation of the conversion coefficient from kerma to eye lens dose for computerized tomography head phantom

Personal dosemeters calibration relies on the air kerma conversion coefficients (CCs), which depends on the phantom and used exposure geometry. This study aims to calculate Hp(3) CCs for the computerized tomography (CT) phantom (16 cm diameter, 15 cm height) and compare them with CCs for head phantom (20 × 20 cm) given in the Part 3 of international standard ISO 4037 (ISO 4037-3) to improve eye lens dosimetry methodologies in Serbia. Monte Carlo radiation transport simulations using MCNP Version 6.1.0 were performed for S-Cs (662 keV) and S-Co (1.25 MeV) reference photon fields. Absorbed dose and air kerma values were derived to calculate Hp(3) CCs for both CT and ISO phantoms across all specified angles for two radiation qualities. Calculated CCs were compared against the CCs ISO phantom values and previously published data to evaluate the relative deviations. This work provides the necessary foundation to determine whether correction coefficients should be introduced during the calibration and type-testing of passive eye dosimetry systems. Highlights  MCNP 6.1.0 was used to derive conversion coefficients for a computerized tomography (CT) head phantom.The CT phantom caused backscatter deficits in S-Cs and S-Co photon fields.Posterior irradiation led to up to 20% overestimation for S-Cs.Dimension-specific corrections are needed for angular response testing.