Abstract: Based on medical anatomy, radiation dosimetry and characteristic physical parameters of Chinese adults, a detailed model for equivalent dose of the eye lens was established. The model consists of two parts: binocular eyeball and head phantom; The model consists of two parts: binocular eyeball and head; the eyeball possesses a detailed anatomical structure consisting of 8 tissues, and the head is composed of soft tissue and hard bone; The left and right eyeballs are symmetrically placed inside the head model. By employing this model, the equivalent dose of the eye lens and the conversion coefficient H_lens/K_a were computed when the 0.01-10 MeV monoenergetic parallel photon beam was irradiated at 0°, 90°, and 180°. The results showed that the H_lens/K_a of photons which energy is less 40 keV at 0° and 90° incidence reported by ICRP 74 was 1.04-4.78 times higher than that of the proposed paper, mainly due to the increase of cornea and anterior chamber in the proposed model. H_lens/K_a of ICRP 110 reported was 0.43, 0.93 and 1.45-1.65 times higher than that in this paper of 10 keV, 20 keV and 3-10 MeV irradiated at 0°, and the model in this paper improved the underestimation and overestimation of the dose caused by the excessive thickness of the anterior tissue of the ocular lens in the ICRP 110 report. The H_lens/K_a of the Behrens model when irradiated with 30-60 keV and 100 keV-10 MeV photons at 180° was 4.05-1.18 and 0.86-0.92 times of that in this paper, the difference was that the head phantom was determined to be an elliptical cylinder with a skull reference to the human body size of Chinese adults. And the ratio of the binocular eye lenses was 130%-710% when irradiated at 90° by 20 keV-1 MeV photons, this indicates that special attention should be paid to the radiation risk caused by the non-uniform irradiation.

Key words: radiation dose, external exposure, lens of eye, Monte Carlo