Estimation of patient exposure in dental radiography

The purpose of this study was to determine patient exposure from the dose which can be easily measured in the X-ray room. Dose-area product was proved to be the best quantity for estimating mean energy imparted under appropriate conditions. The mean energy imparted could be estimated with reasonable accuracy from dose-area product at the same beam quality. There is a reasonable correlation between mean energy imparted and detrimental health effects for a wide range of x-ray examinations. The effective dose can be estimated from dose-area product with reasonable accuracy at the same beam quality and the same projection site. The effective dose should be estimated only at the same beam quality if the uncertainty factor of two is permissible. Effective dose for intraoral examination can be calculated practically only from the equivalent doses of the thyroid, red bone marrow, brain, bone surface, skin, upper esophagus and muscular substance. Of those, equivalent dose for the thyroid was the most effective. As the average absorbed dose for the thyroid is influenced significantly by positioning in the same site for the small field size as in intraoral examinations, this might result in a unstable effective dose. There is no such instability in the mean energy imparted. In an ideal x-ray department, patient dose measurement should be always carried out on every patient, including for the purpose of quality assurance procedures. The dose-area product method is more convenient for this purpose. (K.H.)