CT scan

The computed tomography (CT) scan is a medical imaging procedure that uses x-rays and digital computer technology to create detailed two or three-dimensional images. Unlike other forms of medical imaging, the CT scan can image every type of body structure at once including bone, blood vessels and soft tissue.

The equipment consists of a large square machine with a circular hole. Inside the machine is a rotating gantry that carries the x-ray source and electronic x-ray detectors. An attached table slides the reclining person into the hole.

Multiple x-rays are taken in thin cross-sections along the person’s body (imagine a loaf of sliced bread). The detectors collect the x-ray information from each cross-section and send them to a special computer that combines them into a single image.

The CT scan may also be referred to by its older name of computer assisted tomography or ‘CAT’ scan.

When a CT scan is used
Some of the common uses of the CT scan include:

• Assessment of a body part’s structure or shape
• Diagnosis of disease, particularly cancer
• Diagnosis of trauma or injury
• Diagnosis of vascular disease
• Aid to planning particular surgeries
• Aid to planning radiotherapy
• Visual aid to radiotherapy administration
• Visual aid to certain surgical procedures such as biopsy or needle aspiration
• Measurement of bone strength
• Alternative to some types of exploratory or diagnostic surgery.

• Tell the doctor if you are pregnant or think you may be pregnant. Another type of test may be recommended.
• Tell the doctor if you have allergies or diabetes.
• Tell the doctor if you experience claustrophobia. The doctor may give you mild sedatives to help you relax during the procedure.
• Tell the doctor about any implanted device you may have such as a pacemaker or medication pump, as metal objects may distort the images.
• Follow all the instructions you are given. Some CT scans require the use of contrast material to improve the image quality. You may have to go without food and drink for a certain length of time before the procedure. Your doctor will give you detailed instructions on how to prepare for the test and what to expect.
• A very obese person may be too big for the circular hole of the CT machine. The doctor may advise another type of medical imaging or diagnostic test.

• You may be given a large drink to consume before the procedure. This drink is a contrast agent that helps to enhance pictures of the stomach, small intestines and bowel. In some cases, the contrast agent is administered as an enema.
• You will be asked to undress and wear a hospital gown. You must remove all metal objects including jewellery and wristwatch.
• You lie down on the scanner table. The radiographer may use straps and foam pillows to position your body and help keep you still.
• You may be given an intravenous injection of an iodinated contrast medium (a type of dye) to help produce better images. This substance may cause a strange warm feeling that lasts for a few seconds.
• The table slides into the circular hole in the machine.
• Depending on the body part and particular condition being investigated, a number of images may be taken as the table edges forward.
• The gantry moves in a circle around you as it takes the x-ray images. Each revolution (turning) of the gantry takes less than a second and there may be a number of revolutions depending on the examination.
• Lie very still. This is very important, as movement will blur the images. You will be asked to hold your breath for a few seconds while the gantry rotates.
• The equipment makes noises such as clicks and buzzes while taking the images. Don’t be alarmed – this is normal.
• Depending on the nature of the medical investigation, the CT scan may take anywhere from a few minutes to half an hour or more.

• MRI scan
• Ultrasound
• Blood test
• Biopsy
• Exploratory surgery.

• Your doctor
• Radiographer
• Radiologist

• The CT scan is a medical imaging procedure that uses x-rays and digital computer technology to create detailed pictures of the body.
• It can image every type of body structure at once including bone, blood vessels and soft tissue.
• The CT scan is a non-invasive, painless and relatively safe procedure that doesn’t require any recovery time.

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