CT Scans

GENERAL

Computerised (or computed) Tomography, and often formerly referred to as Computerised Axial Tomography (CAT) scan, is an X-ray procedure that combines many X-ray images with the aid of a computer to generate cross-sectional views and, if needed, three-dimensional images of the internal organs and structures of the body. Computerised Tomography is more commonly known by its abbreviated names, CT scan or CAT scan. A CT scan is used to define normal and abnormal structures in the body and/or assist in procedures by helping to accurately guide the placement of instruments or treatments.

A large doughnut-shaped X-ray machine or scanner takes X-ray images at many different angles around the body. These images are processed by a computer to produce cross-sectional pictures of the body. In each of these pictures the body is seen as an X-ray “slice” of the body, which is recorded on a film. This recorded image is called a Tomogram. Some studies produce 100s of images per investigation and highly skilled and experienced radiologists are required to evaluate and interpret the studies. Comparisons with previous studies can also be done and this provides very valuable information to influence treatment options by referring doctors.

WHAT DOES THE PROCEDURE ENTAIL?

Patients are placed on a movable table, and the table is slipped into the centre of a large doughnut-shaped machine, which takes the X-ray images around the body. The actual procedure can take from 15 minutes to an hour. If specific tests, biopsies, or interventions are performed by the radiologist during CT scanning, additional time and monitoring may be required. It is important during the CT scan procedure that the patient minimises any body movement by remaining as still and quiet as possible. This significantly increases the clarity of the X-ray images. The CT scan technologist tells the patient when to breathe or hold his/her breath during scans of the chest and abdomen. If any problems are experienced during the CT scan, the technologist should be informed immediately. The technologist directly watches the patient through an observation window during the procedure, and there is an intercom system in the room for added patient safety.

HOW DO I PREPARE FOR MY CT SCAN?

On confirmation of your appointment, you will be informed of any special preparations required for your procedure. CT studies of the abdomen often require that patients drink a contrast solution one to two hours before the start of the study. This will delineate the bowel during the investigation.

WHAT ARE THE RISKS?

The amount of radiation a person receives during a CT scan is minimal and carefully controlled. In men and non-pregnant women, it has not been shown to produce any adverse effects. Pregnant women should inform their doctor or the radiography team, and discuss other potential methods of imaging, such as an ultrasound.