Influence of CBCT exposure conditions on radiation dose.

Background: Cone-beam computed tomography (CBCT) has been changing the way dental practitioners use imaging. The radiation dose to the patient and how to effectively reduce the dose is still not completely clear to most users of this technology.

Objective: The objective of this study was to quantitate the change in radiation dose when using different CBCT settings.

Methods: A CBCT machine was modified to allow different setting combinations. The variables consisted of 4 different mA choices (2, 5, 10, and 15), 2 kVp choices (100 and 120), and 3 fields of view (6 inches, 9 inches, and 12 inches). A radiation phantom with 10 thermoluminescent dosimeters (TLD) was used to measure radiation dose. One specific setting (15 mA, 120 kVp, and 12-inch FOV) was scanned 3 times to determine consistency.

Results: The CBCT showed less than 5% variance in radiation dose values. An overall reduction in dose of about 0.62 times was achieved by reducing the kVp from 120 to 100. When reducing the field size the dose decreased 5% to 10%, while for organs that escaped the direct beam the reduction was far greater.

Conclusions: A reduction in radiation dose can be achieved by using the lowest exposure settings and narrow collimation.