Dose conversion coefficients for photon exposure of the human eye lens

Abstract

In recent years, several papers dealing with the eye lens dose have been published, because epidemiological studies implied that the induction of cataracts occurs even at eye lens doses of less than 500 mGy. Different questions were addressed: Which personal dose equivalent quantity is appropriate for monitoring the dose to the eye lens? Is a new definition of the dose quantity H(p)(3) based on a cylinder phantom to represent the human head necessary? Are current conversion coefficients from fluence to equivalent dose to the lens sufficiently accurate? To investigate the latter question, a realistic model of the eye including the inner structure of the lens was developed. Using this eye model, conversion coefficients for electrons have already been presented. In this paper, the same eye model-with the addition of the whole body-was used to calculate conversion coefficients from fluence (and air kerma) to equivalent dose to the lens for photon radiation from 5 keV to 10 MeV. Compared to the values adopted in 1996 by the International Commission on Radiological Protection (ICRP), the new values are similar between 40 keV and 1 MeV and lower by up to a factor of 5 and 7 for photon energies at about 10 keV and 10 MeV, respectively. Above 1 MeV, the new values (calculated without kerma approximation) should be applied in pure photon radiation fields, while the values adopted by the ICRP in 1996 (calculated with kerma approximation) should be applied in case a significant contribution from secondary electrons originating outside the body is present.

Compilation of Conversion Coefficients for the Dose to the Lens of the Eye

“…Based on this information, a stylised eye phantom has been set up for the calculation of dose conversion coefficients (10, 11) , see Figure 1. This phantom contains the part of the lens that is sensitive to radiation and the part that is insensitive as separate regions.…”

“…This phantom contains the part of the lens that is sensitive to radiation and the part that is insensitive as separate regions. Conversion coefficients for photons and electrons (11, 12) have been calculated for both the radiation sensitive part of the lens and the complete lens. Additionally, conversion coefficients for neutrons (13) have been calculated for the sensitive part.…”

The effects of simulating a realistic eye model on the eye dose of an adult male undergoing head computed tomography

“…Several scientific groups investigated the dose values for the lens for electrons (Behrens et al 2009;Behrens 2013;Nogueira et al 2011), photons (Behrens and Dietze 2010), and neutrons (Manger et al 2012) in different irradiation scenarios. In CT examinations, the absorbed dose was calculated for a simple eyeball modeled in a stylized phantom (Akhlaghi et al 2015c), for eye, cornea, and lenses in a stylized head phantom , and also for eye bulb and lens using voxel phantoms (Akhlaghi et al 2015b;Lee et al 2011).…”

“…Till now, these models have been widely used for calculation of dose conversion coefficients of the eye lens (Behrens et al 2009;Behrens and Dietze 2010;Nogueira et al 2011;Manger et al 2012;Sakhaee et al 2015;Vejdani-Noghreiyan and EbrahimiKhankook 2016). One of the most detailed models is the one designed by Nogueira and co-workers, in which lens cells were divided into sensitive and insensitive, and GZ was considered as the sensitive zone to ionizing radiation (Nogueira et al 2011).…”

Development of an applicator for eye lens dosimetry during radiotherapy

“…[1][2][3][4][5][6][7] The maximum allowed dose to the lens has been limited to 7 Gy according to the results of the Radiation Therapy Oncology Group 0539 study. 8 Emami et al 9 showed that if the delivered dose to the lens was .10 Gy, the probability of cataract development within 5 years from radiotherapy is 5%.…”