A study of the underestimation of eye lens dose with current eye dosemeters for interventional clinicians wearing lead glasses

The reduction in the occupational dose limit of the eye lens has created the need for optimising eye protection and dose assessment, in particular for interventional clinicians. Lead glasses are one of the protection tools for shielding the eyes, but assessing the eye lens dose when these are in place remains challenging. In this study, we evaluated the impact of the position of H-p(3) dosemeters on the estimated eye lens dose when lead glasses are used in interventional settings. Using the Monte Carlo method (MCNPX), an interventional cardiology setup was simulated for two models of lead glasses, five beam projections and two patient access routes. H-p(3) dosemeters were placed at several positions on the operator and the obtained dose was compared to the dose to the sensitive part of the eye lens (H-lens). Furthermore, to reproduce an experimental setup, a reference dosemeter, H-p(3)(ref), was placed on the surface of the eye. The dose measured by H-p(3)(ref) was, on average, only 60% of H-lens. Dosemeters placed on the glasses, under their shielding, underestimated H-lens for all parameters considered, by from 10% up to 90%. Conversely, dosemeters placed on the head or on the glasses, over their shielding, overestimated H-lens, on average, up to 60%. The presence or lack of side shielding in lead glasses affected mostly dosemeters placed on the forehead, at the left side. Results suggest that both use of a correction factor of 0.5 to account for the presence of lead glasses in doses measured outside their shielding and placing an eye lens dosemeter immediately beneath the lenses of lead glasses may lead to the underestimation of the eye lens dose. Most suitable positions for eye lens dose assessment were on the skin, unshielded by the glasses or close to the eye, with no correction to the dose measured.