Cone Beam CT Scan

A cone beam CT scanner provides accurate imaging for diagnostics and prosthesis and surgical planning.

The following information describes what a Cone Beam CT Scanner is, how the scan is performed, its applications, and how it differs from conventional CT scans.

What is a Cone Beam CT Scanner?

A Cone Beam Computed Tomography (CBCT) Scanner - a specific type of CT scanner - can quickly and accurately build a 3D model of parts of the body by making use of high-speed x-rays. Conventional CT scans can only build an image of one side (a 2D image) per scan, while CBCT scans can create a 3D rendition of the examined tissue in one scan by rotating 360° around it.

CBCT scanners are most commonly deployed to scan the head for dentistry, orthodontics and corrective surgery. Specialized versions are currently being developed that are capable of scanning the heart as well.

How a CBCT Scanner Works

CT Scans Use X-Rays to Observe a Tissue Cross Section. Tomography refers to a diagnostic technique that generates an image of a slice or cross-section of the human body. In computerized tomography, x-rays are sent through a cross-section of scanned tissues. During the process, some of the energy in the initial x-ray waves are absorbed by the tissues. Detectors on the other side of the tissue read the change in energy after the x-rays have penetrated and send the information to a computer which then uses it to draft an accurate x-ray image.^[1]

Flat Beam CT Scanners Read Multiple Cross Sections at Once. When first invented, CT scanners could only scan one 2D cross-section of the body at a time. These days, the technology has been compounded, allowing for multiple cross-sections to be read at once. These are known as flat beam CT scanners and are the conventional CT scanner of choice.

Cone Beam CT scanners are one of the newest types of CT scanners to join the market. They are designed to rotate 360° while taking a scan of multiple cross-sections of tissue. The x-ray emission terminal and detector rotate in tandem around the scanned tissues. Computer software can then take the scan and build a far more accurate 3D representation than other types of CT scanning, saving more scan time and requiring less processing time to model the results.^[2]

How CBCT Scans Differ from Standard CT Scans

CBCT scanners differ from conventional (fan beam) CT scanners in the following ways:

Compact Design for Head Scans. CBCT scans are used primarily in dentistry for scanning the head, specifically the mouth, teeth and jawline. They are more compact than other scanners, originally designed as smaller alternatives that could fit into dentists’ offices and streamline the process for dental prosthetics and surgical planning.

Appearance. They typically have a headrest to hold the patient’s head still between two rotating arms joined above, referred to as a gantry. The x-rays are emitted from one arm to the detector on the other while rotating around the patient’s head. Larger CBCT scanners may allow for the patient to sit in a chair with similar components. Other CT scanners do not have parts that rotate during the scan and often scan more of the body while the patient lays down horizontally on a stretcher inside the scanner.

Time. By comparison to conventional CT scans, CBCT scanners save a lot of time. The scan is over in 10-70 seconds and takes all the required information in one slice as opposed to requiring multiple scans.

Image Resolution. The depth of CBCT scanners is also deeper than flat beam CT scanners, providing images with a much higher resolution. The latest software can offer more 3D representations with respect to CBCT scans as well, allowing for more accurate 3D images, panoramic images, cross-sections and birds-eye views all from one scan. Some technology also offers healthcare professionals the option of looking at teeth with or without metal fillings or other objects that may stand in the way of diagnostics.

Radiation. The radiation levels that patients are exposed to with CBCT scans are 98% less than in other types of CT diagnostics.

CBCT Scanner Applications and Uses

Dentistry. The most common designs of CBCT scanners pertain to dentistry and observing the bone structures in the head and jaw. CBCT scanners are mainly used by dentists to design tooth implants, bracers and prosthetics, as well as for planning dental operations.

Non-Dentistry CBCT Scan Applications include:

• Diagnosing and assessing the severity of temporomandibular joint disorder
• Diagnosing, assessing and treating jaw tumors
• Cephalometric analysis of craniofacial fractures
• Evaluating the nasal cavity, sinuses and related nerves
• Assessing the head prior to corrective surgery

Cardiac CBCT Scans. Cardiac CT scans are usually offered as multidetector CT (MDCT) scans which are often inaccurate as the heart beats too fast for the scanner to take clear images. When compounded, the result tends to be blurry or have streaks. Forms of CBCT are currently being developed for cardiac scans, known as robotic C-arm CBCT. A team at the University of Sydney has recently developed the ACROBEAT system (Adaptive CaRdiac cOne BEAm computed Tomography) that uses the patient’s ECG to regulate the rotational speed of the gantry during the scan. This allows for high-resolution heart images without streaks, botches or blurs. This is expected to replace standard cardiac CBCT scans in the future.^[3]

Are CBCT Scans Harmful?

CBCT scanners are considered to be less harmful than most standard CT scanners available, as they emit substantially less radiation.

Despite emitting less radiation, CBCT scanners are still associated with increasing the risk for cancer due to inducing DNA damage and inflammation^[4]. Studies have revealed that dental CBCT scans are a particular risk to children who are more sensitive to the effects of radiation.^[5]

The FDA has put out a warning as well with regard to the effects of dental CBCT scans for children, advising both parents and practitioners to minimize their exposure as much as possible and only make use of CBCT scans if absolutely necessary. For interested adults, it is also important to minimize exposure to radiation, particularly if at risk of contracting cancer.

Conclusion

A Cone Beam CT scan is one of the most advanced radio-imaging technology available currently for the head and jaw. They have favorable applications in dentistry and orthodontics, with future promise in cardiology diagnostics. CBCT scans provide very quick and accurate 3D imaging of the bone structures in the head due to making use of a rotating gantry. While they are known to emit less radiation than a conventional CT scan, caution should be taken with respect to children requiring craniofacial imaging as they are more vulnerable to the effects of radiation.

Sources: