How direct measurements of worker eyes with a Scheimpflug camera can affect lensdose coefficients in interventional...

The 2013/59/Euratom Directive reduced the occupational exposure limits for the lens. Since it has become crucial to estimate the dose absorbed by the lens, we have studied the individual variability of exposed workers' ocular conformations with respect to the data estimated from their personal dosimetry. The anterior eye conformations of 45 exposed workers were acquired using Scheimpflug imaging and classified according to their sight conditions (emmetropia, myopia or hypermetropia). Three eye models were computed, with two lens reconstructions, and implemented in an interventional radiology scenario using Monte Carlo code. The models were dosimetrically analysed by simulating setup A, a theoretical monoenergetic and isotropic photon source (10-150 keV) and setup B, a more realistic interventional setting with an angiographic x-ray unit (50, 75, 100 kV peak). Scheimpflug imaging provided an average anterior chamber depth of (6.4 ± 0.5) mm and a lens depth of (3.9 ± 0.3) mm, together with a reconstructed equatorial lens length of (7.1-10.1) mm. Using these data for model reconstruction, dose coefficients (DCs) were simulated for all ocular structures. Regardless of the eye model used, the DCs showed a similar trend with radiation energy, which highlighted that for the same energy and setup, no significant dependence on ocular morphology and workers' visual conditions was observed. The maximum difference obtained did not exceed 1% for all eye models or structures analysed. Therefore, the individual variabilities of worker ocular anatomy do not require any additional correction, compared to the personal dosimetry data measured with a dedicated lens dosimeter. To estimate the dose absorbed by the other eye structures, it is, instead, essential to know the spectrum of the source that has generated the irradiation, since there are differences between monoenergetic sources and more realistic angiographic units.