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

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 degrees, 30 degrees, and 45 degrees), and from the posterior mandible in 3 different lateral angulations (0 degrees, 20 degrees to the left, and 20 degrees 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 degrees and 45 degrees yielded a reduction in effective doses in all 3 devices. A 20 degrees 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 degrees and 45 degrees. For FOV in the posterior mandible, a 20 degrees 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.