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What is a Computed Tomography Scan?

Computed tomography (CT) scan or computerised axial tomography (CAT) scan is an imaging technique that uses a special x-ray imaging equipment to create cross-sectional images or slices of the body. A number of successive slices, also called tomographic images, are collected from the computer and stacked together digitally to form a three-dimensional image of the patient. This imaging technique helps doctors to identify internal bleeding, broken bones, blood clots, signs of heart disease, possible tumour formations and cancers in the body.

  1. Why is a Computed Tomography Scan performed?
  2. How do you prepare for a Computed Tomography Scan (CT Scan)?
  3. How is a Computed Tomography Scan (CT Scan) performed?
  4. What do CT scan results mean?

CT scans are used to identify injuries or diseases in various parts of the body.

  • CT scan of the head can help identify clots that might lead to stroke, haemorrhage or tumours in the head.
  • CT scan of the heart can help detect any abnormalities in the heart or the presence of heart disease.
  • CT scan of lungs can help identify excess fluid, tumours or blood clots in lungs and it also detects various conditions affecting lungs like pneumonia and emphysema.

As CT scans offer more detailed images than conventional x-rays, they are primarily used to procure complex images of bone fractures, bone tumours and severely degenerated joints.

  • Individuals can continue to take prescription medications as usual before going for a CT scan. However, they should inform the doctor about the list of medications including the name, dose and dose frequency of the medications.
  • Women should inform the technician if they are pregnant or suspect that they are pregnant.
  • Avoid eating solid food items 4 hours before the test. Instead, you can drink juices, decaffeinated tea or coffee, water and other fluids.
  • People with insulin-dependent diabetes can take insulin prescriptions and drink excess fruit juices to compensate during the 4-hour solid-food fasting period.
  • In certain types of CT scans like the abdominal CT scan, a technician might instruct the individual to drink an oral contrast medium 1 hour before the test. The contrast solution helps better visualisation of the structures in abdomen.
  • Individuals will be asked to change into a gown and remove any pieces of jewellery that might interfere with the test.
  • They will be asked to lie down still on a table for the entire test duration. The table enters the CT scan machine through a large, ring-like structure.
  • The device emits rotating beams of x-rays from different angles and takes pictures of body.
  • If required or prescribed by the doctor, the technician might inject a contrast agent as an enema or via an intravenous (IV) line in an arm.
  • Individuals should inform the doctor if they experience any reaction to the contrast dye solution, such as itching or difficulty in breathing.
  • The scanner is equipped with speakers and intercom, which allows the individual to interact with the technician in case of any difficulty during the test.

Even though a CT scan procedure is painless, it has some risks as the body is exposed to ionising radiations. These risks include developing cancer in later life, loss of hair and reddening of skin. Allergic reactions to the contrast dye are also possible. Contrast dye should not be administered to people with kidney problems as it might further reduce kidney function and cause temporary or permanent kidney damage. People with iodine allergies might experience nausea, itching, vomiting or sneezing when administered with contrast dye.

Normal results:

CT scan results are considered normal if body structures and organs examined in the scan appear healthy.

Abnormal results:

Abnormal CT scan results depend on the body part being studied. The report will clearly mention any observed abnormalities. It is best to consult a doctor to resolve any queries or concerns regarding CT scan results and what it means in clinical terms.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. This information is purely from an educational point of view and is in no way a substitute for medical advice by a qualified doctor.


  1. US Food and Drug Administration (FDA) [internet]; What is Computed Tomography?
  2. National Cancer Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Computed Tomography (CT) Scans and Cancer
  3. National Institute of Biomedical Imaging and Bio engineering [internet]. Bethesda (MD); US Department of Health and Human Services; Computed Tomography (CT)
  4. Center for Disease Control and Prevention [internet], Atlanta (GA): US Department of Health and Human Services, Radiation in Medicine: CT Scans
  5. UnConnhealth [internet], Farmington (CT), University of Connecticut, CT Scan
  6. Medline plus [internet]: US National Library of Medicine; CT scan

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