Comparative dose measurements in dentomaxillofacial imaging procedures: are Barium and Bismuth shields useful for the protection of eyes and thyroid glands?

Dose measurements were performed at the eye lens and thyroid level using TLD dosimeters, in different configurations (with and without shields) and using standard protocols with different values of voltage (kV) and current-time product (mAs). A total of 103 exposures were performed on patients, 84 of them using a MSCT GE Lightspeed 16 equipment and the remaining 19 using a CBCT NewTom GiANO equipment. These exposures were subdivided into 22 smaller samples (19 samples with 5 exposures each, 1 sample with 4 exposures and 2 samples with 2 exposures each), in accordance with the protocols and configurations adopted. 54 were performed without the use of shields and the remaining 49 with the use of shields, namely, a bismuth shield for the thyroid, a barium shield for the eye lens and, also, a bismuth shield for the breast, which was tested only in the routine MSCT protocol.