The use of personal protection equipment for the absorbed doses of eye lens and thyroid gland in CBCT exams using Monte Carlo

The purpose of this study was to evaluate the absorbed dose in the thyroid and eye lens when the patient uses individual protection. For this purpose, Monte Carlo (MC) simulation was employed using five different field of view (FOV) sizes, available in the i-Cat classic CBCT equipment. To represent the patient, a male virtual anthropomorphic phantom was used. Three different models of lead eyewear and thyroid shield were evaluated, as well as the dose difference with and without the personal protection equipment. The difference in the absorbed dose in relation to the use of the lead eyewear presented a reduction of 19% for the 8 cm x 6 cm FOV (diameter x height), and 73% for the 14 cm x 22 cm FOV. In relation to the thyroid, only the shield that involved the whole neck contributed to the reduction of the absorbed dose by up to 72% for a 14 cm x 22 cm FOV. For the thyroid shields there was a maximum increase of 59% (14 cm x 6 cm FOV), consequently, increasing the effective dose for the protocol. The results showed that the lead eyewear contributed to the protection of the eye lens, but the efficiency of the thyroid shield depends on several factors, as FOV and shield model.