At the end of the millennium, cone-beam computed tomography (CBCT) heralded a new dental technology for the next century. Owing to the dramatic and positive impact of CBCT on implant dentistry and orthognathic/orthodontic patient care, additional applications for this technology soon evolved. New software programs were developed to improve the applicability of, and access to, CBCT for dental patients. Improved, rapid, and cost-effective computer technology, combined with the ability of software engineers to develop multiple dental imaging applications for CBCT with broad diagnostic capability, have played a large part in the rapid incorporation of CBCT technology into dentistry.

Keywords

Cone beam computed tomography

Flat-panel silicon detector

DICOM viewer software

Beam-hardening artifacts

Key points

Introduction

Imaging with cone beam technology has rapidly become a popular and frequently used imaging modality to assist dentists and other health care professionals in a multitude of diagnostic tasks to improve patient care.

Cone beam imaging technology is most commonly referred to as cone beam computed tomography (CBCT). The terminology “cone beam” refers to the conical shape of the beam that scans the patient in a circular path around the vertical axis of the head, in contrast to the fan-shaped beam and more complex scanning movement of multidetector-row computed tomography (MDCT) commonly used in medical imaging.

First introduced at the end of the millennium,1,2 CBCT heralded a new dental technology for the twenty-first century. Its practical applications for implant dentistry and orthognathic/orthodontic patient care were the main applications at that time. Owing to the dramatic and highly positive impact that CBCT had on these disciplines, additional applications for this technology became apparent. New software programs were developed to improve the applicability and access of CBCT for the care of dental patients.

Two factors played a big part in the rapid incorporation of CBCT technology into dentistry, the first of which was the availability of improved, rapid, and cost-effective computer technology. The second was the ability of software engineers to develop multiple dental imaging applications for CBCT with broad diagnostic capability.

CBCT versus computed tomography

CBCT, by virtue of the terminology, is a form of computed tomography (CT). In a single rotation, the region of interest (ROI) is scanned by a cone-shaped x-ray beam around the vertical axis of the patient’s head. Digitized information of objects in the ROI such as shape and density is acquired from multiple angles. These imaging data are then processed by specialty software that ultimately constructs tomographic images of the ROI in multiple anatomic planes, namely the standard coronal, axial, and sagittal anatomic planes (Fig. 1) and their various paraplanar derivatives, the parasagittal, paracoronal and para-axial planes.

The historically standard and more sophisticated form of CT, present since the 1970s, was developed in part by British engineer and Nobel Prize winner Sir Godfrey Hounsfield. It is of interest that by the end of the decade, the technology of Hounsfield’s first scanner was followed by the development of a larger body scanner by a group of researchers in the United States headed by American dentist and physicist Robert S. Ledley.3 This more advanced form of CT is known as MDCT, although other terms such as multislice CT and multirow CT are used. Because MDCT is more commonly used in medicine, it is often referred to as medical CT. However, this term is a misnomer, as CBCT is now also being used and further modified for patient evaluations in medicine.4,5 A more appropriate term for MDCT might be “conventional CT.” Differences between CBCT and MDCT have been widely reported.6–9 However, owing to the specific advances and innovations of CBCT technology for the care of dental patients, it has become and will remain a vital and significant imaging modality in dentistry.

Historical development of CBCT units

During the early development of CBCT, the technology was being advanced primarily for the dental office. Subsequently, many of the earlier units were modified to include designs that more readily fit within dental offices and clinics. The integration of CBCT imaging in dentistry has in some ways paralleled the transition of panoramic imaging x-ray machines into dental offices. Early panoramic units were mainly sit-down,10,11 but there was also a lay-down unit.12 Several other sit-down machines were manufactured, but eventually units were made whereby the patient could stand upright for the panoramic exposure. Upright machines became preferable, as it is more convenient and takes less time to transfer patients into and out of these stand-up panoramic units.

The physical size and shape of CBCT units has paralleled this panoramic pathway. One of the very first commercially available cone beam machines, the NewTom 9000 (QR srl, Verona, Italy), was a large unit that scanned the patient lying in a supine position. It was followed by the NewTom 3G (Fig. 2A). These early NewTom units eventually lost favor to smaller, sit-down chair units or to stand-up units. These smaller units with better scanner quality more readily fit into dental office space and overhead budgets (see Fig. 2B–F). Despite the previous drawbacks of the NewTom prototypes, CBCT units that scan patients in a supine position have made a comeback; the NewTom 5G (QR srl) and the SkyView (MyRay, Imola, Italy) are currently available. These units, with upright patient loading and supine position for patient scanning, are presented in Fig. 2G–H. NewTom is also producing standing machines such as the VGi.

Effect of field of view on scanner type

The size of the scanned object...