Difference between CT scanner and CBCT scanner

This page compares CT scanner vs CBCT scanner and mentions difference between CT scanner and CBCT scanner. CT stands for Computerized Tomography and CBCT stands for Cone Beam Computed Tomography.

What is Computed Tomography (CT)?

Conventional radiography is 2-dimensional image formed by superimposition of images from successive layers of body in the path of X-rays. The image of one layer is obscured by superimposition of images of above and below layers. Tomography is invented to overcome this issue. Computerized axial tomography combines tomography imaging with computer techniques. The computed tomography (CT) scanner was invented by Godfrey Newbold Hounsfield in England. CT scan makes use of computer processed combinations of many X-ray images taken from different angles to generate cross sectional images.

In computed tomography, X-ray source and array of detectors are mounted on opposite to each other. X-ray source transmits fan beam which covers entire section of the body. The radiation after passing through the body of the patient is sensed by array of detectors. The patient is made to move inside chamber which contains X-ray tube and detectors on a trolley. The detectors can move in one axial direction and machine is called computerized axial tomography (CAT). The purpose of the computer is to reconstruct the images of the body layers from output of the detectors. Refer working principle, advantages and disadvantages of computed tomography (CT) scanner >>.

What is Cone Beam Computed Tomography (CBCT) ?

It is a variation on traditional computerized axial tomography (CAT) scanner. Unlike CT scanner, it uses X-ray tube and detector panel which rotates around the patient capturing data in cone shaped X-ray beam instead of slices as captured by Computed Tomography (CT).

Cone Beam Computed Tomography for CBCT scanning

X-ray source and detector moves through arc of 180 to 360 degrees to produce multiple planar projection images. Refer working principle, advantages and disadvantages of CBCT scanner >>.

Difference between CT and CBCT scanning

The figure below depicts comparison between working of CT and CBCT techniques.

Following table mentions difference between CT and CBCT scanner used for CT scanning and CBCT scanning respectively.

CT scanner	CBCT scanning
It uses fan shaped beam from X-ray source.	It uses cone shaped beam from X-ray source.
Traditional CT uses high output rotating anode X-ray tube.	CBCT utilizes low power medical fluoroscopy tube which provides continuous imaging throughout the scan.
It records data from fan shaped beam using image detector arranged in an arc around the patient. It uses several rows of circular detector arrays.	It captures image from cone shaped beam using Solid State Area Sensor (or flat panel detector) .
It produces single slice image per scan i.e. dataset comprised of 2D slices.	It produces complete volume image in single rotation i.e. volumetric dataset.
It is slower due to spiral motion. It requires hundreds of rotations. Hence scan time is longer.	It is quicker than CT scan. It requires only one or two 360 degree rotations. Average time for CBCT scan is about 30 seconds.
It has high radiation dose.	It has lower radiation dose.
To collect adequate image formation, overlapping of radiation is required.	No concept of overlapping of slices.
Only one jaw can be visualized at one time.	Both jaws can be imaged at the same time.
High contrast resolution	Poor contrast resolution, hence soft tissues can not be viewed.
The cost of CT equipment is high.	The cost of equipment is approx. 3 to 5 times less than traditional CT.
It can cause claustrophobia.	The open design of cone beam CTs virtually eliminates claustrophobia. This enhances patient comfort and acceptance to a greater extent.

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