Absorbed Organ Doses and Effective Doses in Intraoral Radiography of Left Upper Molar of Adult Patient: A Computational Study

Objectives. To investigate effective doses and relevant absorbed organ doses for typical intraoral radiographic imaging procedures in adult patients. Variations of relevant absorbed organ doses and effective doses due to changes in imaging parameters and X-ray tube positioning were investigated. Conversion factors for estimating effective doses from incident air kerma (Ka,i) and kerma area product are proposed. Materials and Methods. Different imaging parameters and geometries obtained from previously published data from Serbia were simulated using Monte Carlo simulation and a computational anthropomorphic phantom. The relevant absorbed organ doses and effective doses for different exposure parameters and geometries were then compared to Ka,i and analyzed. Since an obsolete intraoral unit with a focus-to-skin distance of 10 cm, a 50 kVp beam and circular collimator with 5 cm diameter was found in the previous investigation, these imaging parameters were also included in the simulations. Results. For typical Ka,i for imaging protocols found in Serbia, effective doses for imaging of the left upper molar in an adult person were 2.9 µSv and 5.4 µSv for 60 kVp and 70 kVp beams, respectively. The highest absorbed organ doses were observed for the thyroid, eye lenses, salivary glands and brain, reaching up to 47.2 µGy, 71.4 µGy, 63.1 µGy and 26.2 µGy, respectively. For poorly optimized imaging protocols, these values were higher. Furthermore, for the obsolete intraoral units used, all doses were considerably higher and the typical effective dose was 16.8 µSv with thyroid dose of 105.3 µGy. Using rectangular instead of circular collimators decreased effective dose by 25% to 52.7% and absorbed organ doses by 43.3% to 84.5% in all simulated situations. Simulated positioning errors could change eye lens or thyroid absorbed organ dose by up to a factor of two when a rectangular collimator is used and up to four times when a circular collimator is used. Conclusions. Though the effective and absorbed organ doses from intraoral imaging are very low, this imaging can be further optimized by using optimal exposure parameters, rectangular collimators, and proper positioning of the X-ray tube.