A review of dental cone-beam CT dose conversion coefficients.

OBJECTIVE

The purpose of this study was to review the literature to examine the usage and magnitude of effective dose conversion factors (DC) for dental cone beam CT (CBCT) scanners.

METHODS

A PubMed literature search for publications relating to radiation dosimetry in dental radiography was performed. Papers were included if they reported DC, or reported ICRP 103 effective dose and dose-area product. 71 papers relating to dental CBCT dosimetry were found, of which eight reported effective dose conversion factors or provided enough information to calculate dose conversion factors. Scanner model, effective dose, dose-area product, tube voltage, field of view size and DC were extracted from the papers for analysis.

RESULTS

DC values ranged from 0.035 to 0.31 µSv/mGy-cm with a mean of 0.129 µSv/mGy-cm (SD = 0.056). When categorized into small (<100 cm), medium (100-225 cm) and large (>225 cm) fields of view (FOV), linear fits to the effective dose and dose-area product yielded slopes of 0.129, 0.111 and 0.074 µSv/mGy-cm for small, medium and large FOVs respectively.

CONCLUSION

The range of reported DC values and spread with respect to field of view category suggests that DC values that depend on FOV would provide more accurate effective dose estimates. Tube voltage was found to be a smaller factor in determining DC. Reasonable values for DC taking into account FOV size were obtained. There is considerable room for more work to be done to examine the behaviour of DC with changes to patient age and dental CBCT imaging parameters.