In fields of dentistry where 3D imaging is necessary, CBCT is considered by some to be the standard of care . CBCT is accomplished by using a rotating gantry to which an X-ray source and detector are fixed. A divergent pyramidal- or cone-shaped source of ionizing radiation is directed through the middle of the area of interest onto an area X-ray detector on the opposite side of the patient. The X-ray source and detector rotate around a fixed fulcrum within the region of interest (ROI). During the exposure sequence hundreds of planar projection images are acquired of the field of view (FOV) in an arc of at least . In this single rotation, CBCT provides precise, essentially immediate and accurate 3D radiographic images. As CBCT exposure incorporates the entire FOV, only one rotational sequence of the gantry is necessary to acquire enough data for image reconstruction. CBCT is a complementary modality for specific applications rather than a replacement for 2D imaging modalities .
The Food and Drug Administration (FDA) approved the first CBCT unit for dental use in the United States in March 8, 2001—the NewTom DVT 9000 (Quantitative Radiology srl, Verona, Italy). FDA approval for three more CBCT units quickly followed in 2003 followed for the 3D Accuitomo, (J. Morita Mfg. Corp., Kyoto, Japan) in March 6, the i-CAT (Imaging Sciences International, Hatfield, PA) in October 2, and the CB MercuRay (Hitachi, Medical Corp., Kashiwa-shi, Chiba-ken, Japan) on October 20. Since 2003, a number of other CBCT units have been FDA approved in the United States, including the Kodak 9000 3D, (Carestream/Trophy, Marne-la-Vallée, France), which is currently the highest resolution unit . Several additional units are in various stages of development, testing, or application for FDA approval.