Cone Beam Computed Tomography (CBCT) is a specialized medical imaging technique that utilizes X-rays to generate three-dimensional (3D) representations of anatomical structures. Unlike traditional X-rays, which only produce flat, two-dimensional images, CBCT captures volumetric data of hard tissues such as bone, teeth, and cartilage. This technology has become widely adopted, particularly in dentistry and maxillofacial surgery, to provide highly detailed, non-distorted views of the head and neck.
How Cone Beam Technology Creates 3D Images
The process begins with the CBCT scanner rotating a full 360 degrees around the patient’s head in a single pass, which typically lasts less than a minute. During this rotation, the X-ray source emits a divergent, cone-shaped beam that covers the entire area of interest, capturing a large volume of data simultaneously. A flat-panel detector positioned opposite the source collects the attenuated X-rays that pass through the patient’s tissues.
This single rotational scan captures hundreds of individual two-dimensional projection images from various angles. Specialized computer software then takes these multiple projections and employs complex reconstruction algorithms to assemble them into a single 3D data set. This reconstructed volume is composed of tiny, cube-shaped units of information known as voxels, which are the 3D equivalent of pixels in a 2D image.
The resulting volumetric data set allows the clinician to view the anatomy from any perspective, including axial (top-to-bottom), coronal (front-to-back), and sagittal (side-to-side) planes. The software can render cross-sectional slices of the anatomy at millimeter or sub-millimeter increments, providing an accurate, complete picture of the internal structures.
Key Advantages Over Standard X-rays
The primary benefit of CBCT over conventional two-dimensional (2D) X-rays, like panoramic or periapical images, is the elimination of image superimposition. In 2D radiography, overlapping anatomical structures can obscure pathology or distort measurements, making accurate diagnosis uncertain. The 3D nature of CBCT separates these structures, providing true anatomical accuracy of the jawbone, teeth, and surrounding tissues.
CBCT imaging allows for precise, undistorted linear measurements of bone height, width, and volume. This dimensional accuracy is valuable for assessing bone density and determining the exact relationship between structures like tooth roots and nerves. While optimized for hard tissue, CBCT can also visualize surrounding soft tissue contours, which helps in surgical planning, although it does not provide the same contrast resolution for soft tissues as a medical CT scan.
Common Medical and Dental Uses
The applications of CBCT are numerous, particularly in specialized dental and maxillofacial fields where precise structural information is required. Clinicians use the 3D scan to map the precise location of sensitive structures, such as the mandibular nerve canal and the maxillary sinuses, to prevent surgical complications.
CBCT is used for:
Dental implantology, to accurately measure available jawbone volume and density for stable implant placement.
Endodontics (root canal therapy), to identify complex root canal anatomy, locate extra canals, diagnose subtle root fractures, or assess periapical lesions.
Orthodontics, to aid in treatment planning by localizing impacted teeth and performing skeletal analysis of the jaw relationship.
Diagnosing and analyzing temporomandibular joint (TMJ) disorders.
Evaluating facial trauma.
Precisely mapping the boundaries of cysts or tumors within the jawbone.
Understanding Radiation Exposure
Concerns about radiation exposure are associated with any X-ray based imaging, and CBCT is no exception. While CBCT utilizes ionizing radiation, the dose is generally significantly lower than that of a conventional medical computed tomography (CT) scan of the head. This difference stems from the cone-shaped beam and the single rotational scan, which is more efficient than the fan-beam, multi-slice approach of a traditional CT.
The exact dose varies based on the field of view (FOV), which determines the size of the scanned area, and the machine settings. By using a small or limited FOV focused only on the area of interest, the radiation exposure can often be minimized to a fraction of a medical CT dose. Treatment providers adhere to the ALARA principle (“As Low As Reasonably Achievable”), meaning CBCT is only recommended when the diagnostic information gained is unobtainable by less-radiating methods and the benefits outweigh the associated risk.