The effectiveness of lead glasses in reducing the doses to eye lenses during cardiac implantation procedures performed using x-ray tubes above the patient table.

The dose reduction factors (DRF) for different types of lead glasses and C-arm units with x-ray tubes placed above the patient table were calculated from the results of measurements by loose thermoluminescent dosimeters (TLDs) and EYE-D dosimeters using a Rando phantom. The DRF values were analysed for different positions of routine dosimeters worn outside lead eyewear and confronted with DRFs calculated as the ratio of the dose equivalent to the eye measured with and without the eyewear. Moreover, for eye lens dosimeters designed to be worn behind lead glasses, multiplicative factors for various positions of dosimeter were derived in order to account for the differences between the doses measured on the inner side of the glasses and the dose equivalent to the eye lens. The DRFs calculated for the position of a routine dosimeter worn outside lead glasses on the band near the left eye lens are 5.6 and 5.7 for goggles and metallic glasses, respectively, while the DRFs calculated as the ratio of doses to the eyes measured with and without the eyewear are 10.2 and 9.9, respectively. Therefore, for dosimeters routinely used outside lead eyewear, the DRF calculated for the position of the dosimeter should be used. Otherwise, we can anticipate an almost two-fold underestimation of the doses. When the dosimeter is worn behind lead glasses, up to two-fold differences between the dose equivalent to the eye lens and the dose measured at the inner side of the glasses were observed depending on the dosimeter position.