CT Scans (CBCT) at Woodbury Dental
Implant Clinic

What is CBCT?

To better explain what Cone Beam CT ( CBCT ) is, we should first explain what regular CT is:

Computed tomography (CT) imaging, also referred to as a computed axial tomography (CAT) scan, involves the use of rotating x-ray equipment, combined with a digital computer, to obtain images of the body. Using CT imaging, cross sectional images of body organs and tissues can be produced. Though there are many other imaging techniques, CT imaging has the unique ability to offer clear images of different types of tissue. CT imaging can provide views of soft tissue, bone, muscle, and blood vessels, without sacrificing clarity. Other imaging techniques are much more limited in the types of images they can provide.
To understand the difference between CT imaging and other techniques, consider an x-ray of the head. Using basic x-ray techniques, the bone structures of the skull can be viewed. With magnetic resonance imaging (MRI), blood vessels and soft tissue can be viewed, but clear, detailed images of bony structures cannot be obtained. On the other hand, x-ray angiography can provide a look at the blood vessels of the head, but not soft tissue. CT imaging of the head can provide clear images not only of soft tissue, but also of bones and blood vessels.

CT imaging is commonly used for diagnostic purposes. In fact, it is a chief imaging method used in diagnosing a variety of cancers, including those affecting the lungs, pancreas, and liver. Using CT imaging, not only can physicians confirm that tumors exist, but they can also pinpoint their locations, accurately measure the size of tumors, and determine whether or not they've spread to neighboring tissues.
In addition to the diagnosis of certain cancers, CT imaging is used for planning and administering radiation cancer treatments, as well as for planning certain types of surgeries. It is useful for guiding biopsies and a range of other procedures categorized as minimally invasive. Thanks to its ability to provide clear images of bone, muscle, and blood vessels, CT imaging is a valuable tool for the diagnosis and treatment of musculoskeletal disorders and injuries. It is often used to measure bone mineral density and to detect injuries to internal organs. CT imaging is even used for the diagnosis and treatment of certain vascular diseases that, undetected and untreated, have the potential to cause renal failure, stroke, or death.

Watch the video below for a better idea of how CT scanners work:

So, what exactly is Cone Beam CT?

In layman's terms, CBCT is a compact, faster and safer version of the regular CT. Through the use of a cone shaped X-Ray beam, the size of the scanner, radiation dosage and time needed for scanning are all dramatically reduced.
A typical CBCT scanner can fit easily into any dental ( or otherwise ) practice and is easily accessible by patients. The time needed for a full scan is typically under one minute and the radiation dosage is up to a hundred times less than that of a regular CT scanner.

Cost £ 199 compared to conventional CT scan £500+

Table 3.3

Where It's Done	Who Does It	How Long It Takes	Discomfort/Pain
Hospital radiology unit or outpatient diagnostic clinic.	Radiologist or technician.	30-45 minutes.	None unless contrast medium is used; some people find it uncomfortable to remain still during the test.

Results Ready When	Special Equipment	Risks/Complications	Average Cost
Often in a few hours; may take longer in some cases and other places.	Revolving CT scanner (camera), X-ray and computer equipment, and monitor.	Slight risk from radiation exposure; use of contrast agent (dye) can cause allergic reaction.	£500.00

Other names

Computed axial tomograph (CAT) scans.

Purpose

To obtain a two-dimensional view of a cross section of the brain or other internal organ.
To detect tumors, bleeding, and other abnormalities that may not show up on an ordinary X-ray.

How it works

Multiple X-rays are taken as the CT X-ray tube revolves around the patient.
A computer calculates the amount of X-ray penetration through the specific plane(s) of the body part(s) examined, and gives each a numeric value (density coefficient).
This information is fed into a computer, which translates the values into different shades of gray.
These images are displayed on a television monitor and photographed as a series of two-dimensional images depicting a cross section of the part under examination.

Preparation

You will be shown the CT machine and asked to express any concerns.
If you experience claustrophobia in small, enclosed spaces, you may be given a mild sedative to quell your anxiety.
If an intravenous contrast agent is to be used, you will be asked to abstain from ingesting food and water for at least four hours beforehand.
Before entering the unit, you will be asked to remove any jewelry or other objects that may interfere with clear X-ray images.

Test procedure

You will be asked to lie on a narrow examination table, which slides into the scanner (see figure 3.1).

FIGURE 3.1
In CT scanning of the head, the X-ray tube revolves around the area being examined as the table slowly moves the patient across the area in question.
As you lie as motionless as possible, the CT tube revolves slowly, taking multiple X-ray images, which are reconstructed into two-dimensional views of a cross section of the body.
The table is then moved slightly to take another set of images through another plane of the body; typically, three to seven planes are imaged, but this varies according to the part of the body under examination.
In some instances, the entire length of the body may be scanned; in others, only a relatively narrow section.

Variations

CT scanning may be performed in conjunction with other imaging studies and diagnostic procedures, such as X-rays of the joint or spinal column (eg, arthrography or myelography). This allows more detailed images of the entire joint structure than can be obtained from X-rays alone.
A relatively new innovation is spiral CT imaging, which allows for continuous scanning as the gantry table slides through the unit. This technique cuts the amount of time needed for whole-body scanning.

After the test

You may be asked to wait while a radiologist quickly reviews the images to make sure that the part of the body under study has been adequately photographed.
If necessary, you may be asked to return to the scanner for additional images. Otherwise, you will be able to resume normal activities.
If an intravenous contrast medium was used, you will be instructed to drink extra fluids to speed its removal from the body.
You should also watch for delayed allergic reactions, such as hives, a rash, itching, or perhaps a rapid heartbeat. Such symptoms usually appear within two to six hours; in severe cases, an antihistamine or steroid medication may be prescribed to ease discomfort.

Factors affecting results

Obesity, movement during the examination, and the presence of metallic objects can interfere with obtaining clear images.
In some cases, excessive gas or fecal material in the intestines can give misleading results in an abdominal CT scan

Interpretation

A radiologist will interpret the scans.

Advantages

CT scanning provides a painless, noninvasive method of obtaining a detailed view of internal organs.
In many instances, CT scanning eliminates the need for more invasive procedures

Disadvantages

The test is costly and may not be available in small hospitals and rural areas.
It is contraindicated during pregnancy, and may not be suitable for those who are very obese.

Based on The Yale University School of Medicine Patient's Guide to Medical Tests by Barry L. Zaret M.D., Senior Editor, Copyright (c) 1997 by Yale University School of Medicine and G. S. Sharpe Communications, Inc. Published under license from Houghton Mifflin Company.

V J Vadgama