Dose contributions to the Swedish population from oral radiography.

The purpose of the present investigation was to elucidate some factors which may influence the absorbed doses to organs of special interest, to determine the energy imparted (epsilon) and the effective dose equivalent (HE) from intraoral radiography, to estimate the collective effective dose equivalent (SE) to the Swedish population from oral radiography and to discuss these results regarding the biological effect of oral radiography on the Swedish population. The absorbed doses were found to be small from intraoral radiography (IR), with a reduction by a factor of about 50 to many organs since the 1960s. The epsilon to the patient from IR (20 exposures, 65 kVp, D-film) was 10 mJ with a circular (55 mm in diameter) and 6 mJ with a rectangular collimator (35 mm X 44 mm). For one bitewing the corresponding values were 0.4 mJ and 0.3 mJ, respectively. The mean value of epsilon for an ordinary bitewing examination in Sweden was 0.48 mJ. Energy imparted from IR was totally 5,500 J to the Swedish population. This corresponds to some per cent of the mean value of the annual natural irradiation. The use of film in speed group E reduces the energy imparted by 40 per cent. From panoramic radiography (PR) and lateral cephalographic radiography (CR) the mean values in Sweden were 0.5 mJ per examination. PR and CR imparted 56 J to the population. HE was calculated for IR and was found to be 0.23 mSv (20 exposures, D-film, circular collimator) and 0.14 mSv for the rectangular collimator, which corresponds to 12 and 7 mu Sv per intraoral film, respectively. The risk from IR, PR and CR to the population can be assessed by risk factors from the literature and estimated both from the sum of epsilon and from the sum of HE. Proceeding from the sum of epsilon and transforming to HE by dividing the body weight the collective effective dose equivalent was 79 manSv (IR) and 1 manSv (PR and CR). Proceeding from the calculated value of HE for IR would give 190 manSv. The risk of fatal cancer thus theoretically calculated would be between 1-3 cases. The magnitude of epsilon as well as HE is so low that it seems to be a very favourable ratio between benefit and risk for IR, when such examinations are indicated.