Dental radiology accounts for 26% of all medical radiological examinations worldwide and 0.2% of the overall collective dose. The most common dental exposure is intraoral bitewing radiography, which is a procedure used to examine the interproximal surfaces of the teeth and is particularly useful for the detection of dental caries and the evaluation of alveolar bone levels. In Sweden, regulations require patients to have a 0.25 mm lead-equivalent thyroid shield during intraoral exposures. The aim of this project is to do a Monte Carlo simulation of the absorbed doses from a bitewing exposure and investigate the radiation protection effect of a lead collar. In this study, a Monte Carlo simulation was done of an intraoral bitewing examination, using the latest International Commission on Radiological Protection (ICRP) human adult mesh phantom. A thyroid collar was added to the mesh phantom to generate the exposure situation of a bitewing exposure. A 60 kV bitewing exposure was simulated using the Monte Carlo software MCNP6.3. The radiation source was simulated using RQR60 with 107 simulated X-ray photons. The simulations were performed both with and without thyroid collar. Absorbed doses were calculated for different organs and tissues in the ICRP adult mesh phantom. The results are calculated for a bitewing exposure with a tube voltage of 60 kV and an exposure time of 0.25 s on a phosphor plate receptor and 0.05 s for the digital sensors. The thyroid protection collar examined in this study did not significantly impact the absorbed dose to the thyroid. However, the absorbed dose to several other organs and tissues was reduced. The absorbed dose reduction was dependent on the distance to the X-ray primary beam, where a greater distance resulted in a greater reduction. The difference in effective dose between use of lead apron and without lead apron is, however, neglectable.
Andersson et al. (Tue,) studied this question.