Variations in head tilt during the acquisition of cone beam computed tomography scans and their effects on effective radiation dose.

Abstract

Objectives: This study evaluated the impact of variations in anteroposterior and lateral tilts of patients head on radiation-weighted doses to organs/tissues and effective doses using 3 different cone beam computed tomography (CBCT) machines.

Methods: An anthropomorphic phantom was used to estimate radiation doses in 3 CBCT machines (OP300, Eagle X 3D, and Eagle Edge). Thermoluminescent dosimeters were placed in regions corresponding to pre-stablished organ/tissues. CBCT examinations from the posterior mandible and anterior maxilla regions were acquired, with 3 different anteroposterior angulations (0°, 30°, and 45°), and from the posterior mandible in 3 different lateral angulations (0°, 20° to the left, and 20° to the right side). Radiation-weighted doses for each organ/tissue and effective doses were calculated for each machine and angulation.

Results: For the posterior mandible acquisitions, anteroposterior angulations of the head at 30° and 45° yielded a reduction in effective doses in all 3 devices. A 20° tilt to the right side resulted in lower doses than to the left [same side as the field of view (FOV)]. For the anterior maxilla, increased anteroposterior angulation was associated with reduction in effective dose in 2 devices.

Conclusions: Effective doses are lower when small FOV CBCT exams of the posterior mandible and anterior maxilla are acquired with increased anteroposterior head angulation at 30° and 45°. For FOV in the posterior mandible, a 20° lateral tilt towards the side opposite to the FOV also yields lower effective doses. The main contribution to these dose reductions is the decrease in dose to salivary glands.