A comparison of doses from contemporary extraoral bitewing radiography: Child and adult examinations

Objective To compare the effective doses (E) from two panoramic (PAN)/extraoral bitewing (EOBW) systems with an industry-standard intraoral bitewing (IOBW) system for adult and child phantoms. The feasibility and impact of thyroid shielding during EOBW was also evaluated. Study Design This preclinical experimental study utilizing anthropomorphic phantoms (average adult and 10-year-old child) modified to accept optically stimulated luminescence dosimeters evaluated E from two extraoral units: RayScan ALPHA (Buena Park, CA) and Sirona ORTHOPHOS SL (Charlotte, NC), and one conventional IO unit using circular (CC) and rectangular (RC) collimation (FOCUS Instrumentarium, Brea, CA). Phantom sequences were triplicated for all modality combinations and average E was calculated. Exposure parameters were: Orthophos- 85kV, 7-13mA, 5.1s; RayScan- 80kV, 12-14mA, 7.2s; Focus- 70kV, 7mA, 0.5-1.28s. Results E from child and adult PAN and EOBW examinations was significantly lower for Orthophos compared to RayScan (p<.0001). Standard adult EOBW E (µSv) was 4.3 and 28.1 (child) and 8.6 and 30.2 (adult) for Orthophos and RayScan, respectively. For both extraoral units, EOBW E was reduced compared to PAN E. IOBW E (µSv) ranged from 7.0-11.8 (child) and 4.6-14.2 (adult) for CC and RC, respectively. IOBW examinations with CC yielded higher E than Orthophos EOBW and lower E than RayScan EOBW for the adult phantom. Significant reductions in thyroid dose (53%) from EOBW examinations were achieved using shielding with RayScan adult scans (p<.0001). Shielding did not yield notable thyroid dose reductions for child EOBW scans and produced minor artifacts intermittently. Conclusion IOBW examinations employing RC continue to yield lower E than alternative EOBW systems for adults. Dramatic dose differences may be associated with extraoral equipment selection. Detector type (2D-array vs. flat-panel) may be an indicator of potential dose differences among machines. Shielding during EOBW imaging can reduce adult thyroid dose without negatively affecting image quality. Statement of Ethical Review Ethical review was sought and study was exempted from ethical review To compare the effective doses (E) from two panoramic (PAN)/extraoral bitewing (EOBW) systems with an industry-standard intraoral bitewing (IOBW) system for adult and child phantoms. The feasibility and impact of thyroid shielding during EOBW was also evaluated. This preclinical experimental study utilizing anthropomorphic phantoms (average adult and 10-year-old child) modified to accept optically stimulated luminescence dosimeters evaluated E from two extraoral units: RayScan ALPHA (Buena Park, CA) and Sirona ORTHOPHOS SL (Charlotte, NC), and one conventional IO unit using circular (CC) and rectangular (RC) collimation (FOCUS Instrumentarium, Brea, CA). Phantom sequences were triplicated for all modality combinations and average E was calculated. Exposure parameters were: Orthophos- 85kV, 7-13mA, 5.1s; RayScan- 80kV, 12-14mA, 7.2s; Focus- 70kV, 7mA, 0.5-1.28s. E from child and adult PAN and EOBW examinations was significantly lower for Orthophos compared to RayScan (p<.0001). Standard adult EOBW E (µSv) was 4.3 and 28.1 (child) and 8.6 and 30.2 (adult) for Orthophos and RayScan, respectively. For both extraoral units, EOBW E was reduced compared to PAN E. IOBW E (µSv) ranged from 7.0-11.8 (child) and 4.6-14.2 (adult) for CC and RC, respectively. IOBW examinations with CC yielded higher E than Orthophos EOBW and lower E than RayScan EOBW for the adult phantom. Significant reductions in thyroid dose (53%) from EOBW examinations were achieved using shielding with RayScan adult scans (p<.0001). Shielding did not yield notable thyroid dose reductions for child EOBW scans and produced minor artifacts intermittently. IOBW examinations employing RC continue to yield lower E than alternative EOBW systems for adults. Dramatic dose differences may be associated with extraoral equipment selection. Detector type (2D-array vs. flat-panel) may be an indicator of potential dose differences among machines. Shielding during EOBW imaging can reduce adult thyroid dose without negatively affecting image quality.