Air Kerma to H-P(3) Conversion Coefficients for Exposure of the Human Eye Lens to the Selected Standard X-Ray Beam Qualities

Abstract

International Commission on Radiological Protection (ICRP) has decreased the annual dose limit for the eye lens from 150 mSv down to 20 mSv for occupational exposures. The operational quantity Hp (3) has been defined for eye lens dosimetry, while cylindrical phantom approximating the shape of a head was suggested for calibration purposes. The aim of the work was to provide a set of conversion coefficients that could contribute to improving the overall quality of eye lens dose assessment. The work investigated the air kerma to Hp(3,iota)conversion coefficients, Hp(3,iota)/Ka (in Sv/Gy), based on Monte Carlo simulations for a standard beam qualities, different angulations and suitable cylindrical phantom. For incident angles iota from 0(o\) to 90(o)., the conversion coefficients Hp(3,iota)/Ka were in the range 0.44-0.88 for N-40, 0.72-1.06 for N-60, 0.91-1.63 for N-80, 1.08-1.52 for N-100, 1.22- 1.62 for N-120 and 0.14-1.56 for N-150 beam quality. The conversion factors Hp(3)/Ka provided in this work are related to standard beam qualities readily available in the calibration laboratories and are suitable for application in numerous workplace situations in medicine and industry.