Personal dose equivalent angular response factors for photons with energies up to 1 GeV

When performing personal dosemeter calibrations, the dosemeters are typically irradiated while mounted on slab-type phantoms and oriented facing the source. Performance testing standards or intercomparison studies may also specify various rotational angles to test the response of the dosemeter and associated algorithm as this rotation introduces changes in the quantity of delivered dose. Correction factors for rotational effects are available, but many have not been updated in recent years and were typically calculated using the kerma approximation. The personal dose equivalent, Hp(d), is the quantity recommended by the International Commission on Radiation Units and Measurements to be used as an approximation of the protection quantity effective dose when performing personal dosemeter calibrations. The personal dose equivalent can be defined for any location and depth within the body, but typically the location of interest is the trunk where personal dosemeters are worn and in this instance a suitable approximation is a 30 cm × 30 cm × 15 cm slab-type phantom. In this work personal dose equivalent conversion coefficients for photons with energies up to 1 GeV have been calculated for depths of 0.007, 0.3 and 1.0 cm in the slab phantom for rotational angles ranging from 15° to 75°. Angular response factors have been determined by comparing the conversion coefficients for each angle and energy to those reported in an earlier work for a non-rotational (e.g. perpendicular to the phantom face) geometry. The angular response factors were determined for discrete angles, but fits of the factors are provided.