Radiation doses in extraoral bitewing radiography compared with intraoral bitewing and panoramic radiography

Objectives: We compared the effective dose (E) and thyroid equivalent dose of 2 extraoral bitewing (EOBW) units and compared E with their respective panoramic (PAN) modes and with intraoral bitewing radiography (IOBW).

Study design: Child and adult anthropomorphic phantoms with dosimeters were used to evaluate Orthophos SL, Rayscan α+, and 1 intraoral unit using rectangular and circular collimation. Extraoral bitewing thyroid equivalent dose was assessed without and with thyroid shielding.

Results: Child and adult E values of EOBW were lower with Orthophos (3.6 and 8.6 μSv) than with Rayscan (28.1 and 30.2 μSv). For IOBW, E was lower with rectangular vs circular collimation for child (7.0 vs 11.8 μSv) and adult (4.6 vs 14.2 μSv). E values of EOBW were lower than PAN for Orthophos. The IOBW E was lower than Rayscan EOBW for child (≤11.8 vs 28.1 μSv) and adult (≤14.2 vs 30.2 μSv). Adult E for rectangular IOBW (4.6 μSv) was lower than EOBW with Orthophos (8.6 μSv) and Rayscan (30.2 μSv). Thyroid shielding reduced EOBW thyroid equivalent dose with Rayscan in the adult from 190.7 to 89.0 μSv.

Conclusion: Orthophos provides significantly lower EOBW E than Rayscan, thus EOBW recommendations must be unit specific. For children, Orthophos EOBW could be an alternative to IOBW, for which rectangular collimation is recommended. Thyroid shielding reduced adult Rayscan equivalent dose but added imaging artifacts.