title: Dose conversion coefficients for monoenergetic electrons incident on a realistic human eye model with different lens cell populations.
abstract: The radiation-induced posterior subcapsular cataract has long been generally accepted to be a deterministic effect that does not occur at doses below a threshold of at least 2 Gy. Recent epidemiological studies indicate that the threshold for cataract induction may be much lower or that there may be no threshold at all. A thorough study of this subject requires more accurate dose estimates for the eye lens than those available in ICRP Publication 74. Eye lens absorbed dose per unit fluence conversion coefficients for electron irradiation were calculated using a geometrical model of the eye that takes into account different cell populations of the lens epithelium, together with the MCNPX Monte Carlo radiation transport code package. For the cell population most sensitive to ionizing radiation-the germinative cells-absorbed dose per unit fluence conversion coefficients were determined that are up to a factor of 4.8 higher than the mean eye lens absorbed dose conversion coefficients for electron energies below 2 MeV. Comparison of the results with previously published values for a slightly different eye model showed generally good agreement for all electron energies. Finally, the influence of individual anatomical variability was quantified by positioning the lens at various depths below the cornea. A depth difference of 2 mm between the shallowest and the deepest location of the germinative zone can lead to a difference between the resulting absorbed doses of up to nearly a factor of 5000 for electron energy of 0.7 MeV.
authors: Technological and Nuclear Institute, Estrada Nacional No 10, 2686-953 Sacavém, Portugal. pedro.nogueira@helmholtz-muenchen.de
authors: P
authors: P
authors: Nogueira
authors: M
authors: M
authors: Zankl
authors: H
authors: H
authors: Schlattl
authors: P
authors: P
authors: Vaz
mesh_terms: D000042:Absorption; D000465:Algorithms; D003198:Computer Simulation; D004583:Electrons; D006801:Humans; D007908:Lens, Crystalline / Q000166:cytology / Q000473:pathology / Q000528:radiation effects*; D008954:Models, Biological; D009010:Monte Carlo Method; D017785:Photons; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods* / Q000592:standards