Can modifying shielding, field of view, and exposure settings make the effective dose of a cone-beam computed tomography comparable to traditional radiographs used for orthodontic diagnosis?

OBJECTIVES: To analyze the effect of changes in exposure settings, field of view (FOV), and shielding on radiation to an adult and child phantom from cone-beam computed tomography (CBCT) imaging compared to panoramic and lateral cephalometric radiographs. MATERIALS AND METHODS: The effective dose to an adult and child anthropomorphic phantom by the CS 9300 using various scan protocols was recorded. Absorbed radiation was measured with optically stimulated luminescence dosimeters and effective dose calculated using 2007 International Commission on Radiological Protection tissue weighting factors. Scan protocols included different FOVs, voxel sizes, and standard versus low-dose protocols. Radiation shielding was used when it did not interfere with FOV. Panoramic and lateral cephalometric radiographs were taken with the Orthophos SL. RESULTS: Even with shielding, smaller FOVs, and increased voxel sizes, the effective dose of standard CBCT scans was higher than panoramic and lateral cephalometric radiographs. A shielded limited FOV standard scan combined with a lateral cephalometric radiograph resulted in a lower dose (P < .001) than a full FOV standard scan. Low-dose shielded scans resulted in significant dose reductions to the adult (P < .05) and child (P < .001) phantoms compared to the respective panoramic and lateral cephalometric radiographs combined. Image quality analysis was not possible with radiation equivalent phantoms. CONCLUSIONS: Unlike standard CBCTs, shielded low-dose CBCT protocols in the CS 9300 have lower effective doses than conventional radiographs for adult and child phantoms. If high resolution and cranial base visualization are necessary, combining a shielded LFOV standard exposure with a cephalometric radiograph is recommended.

Dose reduction in head and neck organs through shielding and application of different scanning parameters in cone beam computed tomography: an effective dose study using an adult male anthropomorphic phantom.

OBJECTIVES: The aim of this study was to determine the effect of shielding and scanning parameters on radiation dose reduction to the organs in the head and neck region in cone beam computed tomography (CBCT). STUDY DESIGN: An anthropomorphic phantom and optically stimulated luminescent dosimeters were used to calculate the changes in effective or equivalent doses to 9 anatomic structures through the addition of a thyroid collar, radiation safety glasses, and a radiation safety cap and by using different scanning protocols on a CS 9300 CBCT unit. RESULTS: The thyroid collar alone yielded dose reductions of 46% to the thyroid gland and at least 38% to the esophagus, but no more than 12% to the salivary glands. The radiation safety cap significantly reduced doses to the brain and the pituitary gland. Full shielding resulted in dose reductions of at least 50% to the thyroid gland, at least 47% to the esophagus, and approximately 35% to the brain and the pituitary gland. Significant dose reductions were recorded for all tissues with the "low dose" setting compared with the standard setting. CONCLUSIONS: Increased protection of the organs in the head and neck regions can be achieved by using various forms of shielding in CBCT imaging, with selection of the most appropriate scanning parameters based on the purpose of the examination.