omography is the visualisation of the human anatomy in sections, which serves to eliminate body tissue outside the layer of interest without the need for surgery. Computed tomography or CT, as it is commonly known, is an advanced radiological examination, which uses ionising radiation and the wizardry of computers to produce transverse images of a particular segment of the body.  

CT is done with or without contrast agents. Contrast agents are needed to enhance visualisation of certain organs of interest. They may be introduced orally by ingestion, injected through a vein or artery; or through the rectum if the need arises. Patients who are asthmatic or with allergies will need to inform the radiologist or radiographer. In addition, pregnant patients should best avoid this examination unless advised otherwise by the attending doctor or radiologist.  

This examination takes between 15-45 minutes depending on the need for oral contrast medium, in which case the whole examination may take up to 1.5 hours. Regular medications should be continued, unless advised otherwise. If contrast medium is needed for the examination, then a needle or fine tube will be placed in the vein of the hand. If oral contrast medium is needed, the patient will be required to drink contrast medium and the CT will only be done 30 to 45 minutes later. The CT scanner is a rounded structure with a hollow centre, like a giant doughnut, through which the table and patient passes through. X-rays will pass through the patient. "Sliced" information of the patient is then processed by the computer, resulting in image formation on the TV monitor. The images can be reviewed, photographed on film and stored for future use. CT has progressed from purely imaging to allowing other applications such as biopsies and drainage of lesions using CT as guidance.  

The examination is painless and perfectly safe. The patient should relax and follow to the instructions of the radiographer. The contrast medium taken orally will be passed out normally in the stools, whereas the contrast medium injected into the vein will be excreted via the kidneys and in the urine. These contrast media are not radioactive and they are not harmful to anyone near the patient.  

CT has proven to be a useful and cost-effective tool for diagnosis and treatment, which obviates the need for more painful or invasive procedures. It is now the examination of choice in a wide variety of situations, particularly for trauma cases e.g. head, chest and abdomen injuries, to diagnose sinusitis and its complications, further evaluate lung lesions seen on chest radiographs, for further evaluation of a tumour in the abdomen or pelvis. It has become increasingly more available in this country making it easily accessible for quality diagnosis in improvement of health care.

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Last Updated:
Thursday, 21 August, 2003