Suboptimal patient positioning with panoramic and CBCT imaging: effects on dose.

OBJECTIVE

This study examined the effects of changes in patient positioning on radiation exposure for panoramic and cone beam computed tomography (CBCT) radiographic examinations by measuring effective dose (E) and equivalent doses.

STUDY

DESIGN

Simulated radiographic examinations with optimal and suboptimal positioning-anterior shift by 1 centimeter (cm), posterior shift by 1 cm, chin lowered by 10 degrees (°), chin elevated by 10°, rotation by 10°, and lateral shift by 1 cm-were conducted using a tissue-equivalent phantom and optically-stimulated luminescent dosimeters. Exposures were made with the RAYSCAN Alpha Plus 160 X-ray unit using the following exposure parameters: panoramic, 80 kVp, 14 mA, and 13.9s; CBCT (10 x 10 cm FOV), 90 kVp, 10 mA, and 14.0s; CBCT (16 x 10 cm FOV), 90 kVp, 11 mA, and 14.0 s.

RESULTS

All suboptimal panoramic conditions except rotation demonstrated significant decreases in E. Chin elevation during CBCT imaging reduced E with the 10 × 10 cm FOV (P = .0003) and 16 × 10 cm FOV (P < .0001), as well as the equivalent dose to the thyroid gland (P < .0001 for both FOVs).

CONCLUSIONS

Suboptimal positioning did not significantly increase E for either panoramic or CBCT exposures. Chin elevation decreased E in the CBCT protocols, with notable decreases in equivalent dose to the thyroid gland.