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What is cone beam computed tomography?
“Cone-beam computed tomography (CBCT) is a digital imaging technology involving the use of a 3D light beam in conjunction with a surface detector.”
Definition (according to the German s2k standard)
“Under this (s2K) standard, the application domain of cone beam computed tomography is limited to the craniofacial region. The light beam is projected in the form of a cone (image intensifier) or pyramid (flat panel detector). A large number of projection images is generated in a circular path, where a 3D reconstruction of the imaged region is directly generated by means of a rear-projection process. The procedure commonly entails isometric spatial resolutions in reconstructions in all three spatial dimensions, as well as concentrating on high-contrast images, i.e. of the hard tissues. Compared to classic (single-line) CT, CBCT is limited, from a technical standpoint, by the use of a 3D utility light beam, as well as a 2D image receiver.”
(Source: s2k-Leitlinie Dentale digitale Volumentomographie)
Version Nr. 9 from 5. August 2013, URL:
http://www.awmf.org/uploads/tx_szleitlinien/083-005l_S2k_Dentale_Volumentomographie_2013-10.pdf, Version as per: 04. June 2014)
Benefits of the technology
Basically, three-dimensional imaging has one significant advantage over two-dimensional imaging technology: it can visualize anatomical structures without loss of dimension. Hence, the user can obtain more data from the information because the location of anatomical structures can only be discerned with a three-dimensional visualization. Accordingly, it helps make a safe diagnosis.
Reduction of radiation dosage
Patients also benefit from a CBCT scan because the radiation dosage is significantly lower than that of a conventional CT. In the latter case, the radiation source scans the region of the body that is to be examined in slices of 0.5 to 3.0mm; CBCT scans the entire section in one single rotation. As a result, the dosage is reduced by up to 80 percent as compared to a standard CT X-ray*.
* 1mm slice thickness, 1.5mm pitch, 120 mAS/rotation, 87mm scan height
Imaging in one rotation
Cone beam computed tomography provides dentists with an imaging technology that allows for reconstructions at various levels, as well as three-dimensional imaging. A complex mathematical algorithm calculates three-dimensional projection data on the basis of numerous two-dimensional X-rays. With the help of the so-called “filtered back projection” and state-of-the-art computer technology, the reconstruction is completed almost in real time. Consequently, the physician can use the 3D X-ray immediately to formulate a diagnostic assessment.
Spatial orientation based on conical X-ray beams
CBCT works on the basis of a cone-/pyramidal-shaped X-ray beam: for this purpose, a flat panel detector and an X-ray source are mounted on opposite sides of a rotating arm. The physician positions the patient in the isocenter, and the C-arm rotates at least 180° during the scanning process. While the scanner is rotating around the patient, the projection of a cylindrical volume is obtained at defined view angles with the cone-shaped X-ray beam.