The Basics of Maxillofacial Cone Beam Computed Tomography

Cone beam computed tomography (CBCT) is an imaging modality that is being more frequently applied to orthodontic assessment. With the rapid 180° or more rotation (most frequently 360°) of an x-ray tube and digital detector, CBCT provides essentially immediate and accurate two- and three-dimensional radiographic images of an anatomical structure, limited only by the system's innate or selected field of view. Although CBCT equipment has existed for a quarter of a century, only over the past decade has it become possible to produce clinical systems that are both inexpensive and small enough to be used in the orthodontist's office. Technological and application-specific factors converging to make this possible include: the development of compact, relatively low cost, high quality, large, flat-panel detector arrays; the availability of low cost computers with processing power sufficient for cone-beam image reconstruction; the fabrication of highly efficient x-ray tubes capable of multiple exposures necessary for cone beam scanning at prices lower than those currently used for fan-beam computerized tomography; and limited volume scanning (eg, head and neck) eliminating the need for subsecond gantry rotation speeds. CBCT provides three-dimensional images that facilitate the transition of orthodontic imaging from initial diagnosis to image guidance throughout the treatment phase. This technology provides increased precision, lower doses, and lower costs when compared with medical fan-beam computerized tomography. It provides the third dimension in orthodontic and dental imaging and is extending dental imaging from diagnosis to image guidance.