Cone beam computed tomography for dental and maxillofacial imaging: technique improvement and low-dose protocols

Abstract

The aim of this study was to evaluate images quality and radiation doses of Cone Beam Computed Tomography (CBCT) for dental and maxillofacial imaging testing five different acquisition protocols. Dose measurements of different acquisition protocols were calculated for Pax Zenith three-dimensional (3D) Cone Beam (Vatech, Korea) and for conventional orthopantomography (OPT) and cephalometric skull imaging Ortophos (Sirona Dental Systems, Bernsheim, Germany). The absorbed organ doses were measured using an anthropomorphic phantom loaded with thermoluminescent dosimeters at 58 sites related to sensitive organs. Five different CBCT protocols were evaluated for image quality and radiation doses. They differed in FOV, image resolution, kVp, mA, acquisition time in seconds and radiation dose. Measurements were then carried out with the orthopantomograph. Equivalent and effective doses were calculated. The reference protocol with large FOV, high resolution quality images, 95kVp, 5mA and acquisition time of 24s resulted in a DAP value of 1556mGycm2 instead the protocol with reduced kVp from 95 to 80kVp translated into a value of DAP inferior to 35% (from 1556 to 1013mGycm2). Going from a high resolution to a normal resolution, there was a reduction of the acquisition time to 15s which allowed further dose reduction of approximately 40% (628mGycm2); this protocol resulted in a value of effective dose of 35 microSievert (μSv). Moreover, the effect of changing FOV has been evaluated, considering two scans with a reduced FOV (160×140 and 120×90mm, respectively). CBCT low-dose protocol with large FOV, normal resolution quality images, 80kVp, 5mA and acquisition time of 15s resulted in a value of effective dose of 35 microSievert (μSv). This protocol allows the study of maxillofacial region with high quality of images and a very low radiation dose and, therefore, could be proposed in selected case where a complete assessment of dental and maxillofacial region is useful for treatment planning.