Computed Tomography, commonly called a CT or CAT scan, is an imaging test that uses X-rays and computer processing to create detailed cross-sectional images of the body. Unlike a standard X-ray, which produces a two-dimensional image, CT shows structures in multiple slices and planes. These images can also be reconstructed to provide three-dimensional views when required.
CT can examine almost any part of the body, including the brain, head and neck, chest, abdomen, pelvis, bones and soft tissues. In cancer care, it may be used to identify an abnormality, assess its size and location, determine whether it has spread, plan treatment and monitor response.
A CT finding alone does not always confirm cancer. Depending on the results, additional imaging, endoscopy, laboratory testing or a biopsy may be required to establish the diagnosis.
Role in Cancer Care
What to Expect
Before the Test
Preparation depends on the part of the body being examined and whether contrast is required.
Before the scan, inform the care team if you:
Are pregnant or may be pregnant
Have kidney disease or reduced kidney function
Have diabetes
Have previously experienced a reaction to contrast material
Have asthma or significant allergies
Take prescription medicines, over-the-counter medicines or supplements
Have recently undergone another scan involving contrast material
Blood tests may be required to assess kidney function before intravenous contrast is given, particularly in patients with known kidney disease or other relevant risk factors.
You may be asked to avoid food or drink for a few hours before certain contrast-enhanced scans. Do not stop regular medicines unless specifically instructed. Jewellery, metal objects and clothing containing metal may need to be removed, and you may be asked to change into a hospital gown.
Previous scans and reports should be made available whenever possible, as comparison with earlier imaging can help assess changes over time.
During the Test
You will lie on a motorised table, which moves through the centre of the CT scanner. The scanner is open at both ends and does not enclose the entire body like a tunnel.
The technologist will position you according to the area being examined. Supports or straps may be used to help you remain still. You may be asked to hold your breath briefly while some images are taken, particularly during scans of the chest or abdomen.
If intravenous contrast is required, it will usually be given through a cannula placed in the hand or arm. You may briefly experience:
A warm sensation through the body
A metallic taste in the mouth
A feeling as though you need to pass urine
These sensations are usually temporary and pass quickly. Tell the technologist immediately if you develop itching, breathing difficulty, swelling, dizziness or any other unusual symptoms.
The scan itself is painless. Most routine CT examinations are completed within a few minutes, although the overall appointment may take longer when preparation, contrast or additional imaging phases are required. The technologist can see, hear and speak with you throughout the scan.
After the Test
Most patients can resume their usual activities immediately after a routine CT scan. If contrast has been given, you may be advised to drink fluids, unless you are on a fluid restriction or have been given different instructions.
The IV cannula will usually be removed after the scan. In some cases, you may be observed briefly, particularly if you have a history of allergies or have experienced symptoms following contrast administration. Seek medical advice promptly if you develop breathing difficulty, facial or throat swelling, widespread rash, severe dizziness or another significant reaction after leaving the imaging centre.
A radiologist will examine the images and prepare a report for the doctor who requested the scan. The findings will be interpreted together with your medical history, examination findings and results from other investigations.
Potential Benefits
- Detailed imaging: CT provides clear cross-sectional views of organs, bones, soft tissues and blood vessels.
- Rapid examination: Images can be acquired quickly, which can be useful when timely assessment is required.
- Broad coverage: A single examination can assess large areas of the body, such as the chest, abdomen and pelvis.
- Accurate localisation: CT can help show the size and position of a tumour and its relationship to nearby structures.
- Procedure guidance: Real-time or sequential CT images can help guide biopsies and selected minimally invasive treatments.
- Treatment planning: CT findings may contribute to surgical, radiation and other treatment planning.
- Response assessment: Scans taken at different points in treatment can be compared to evaluate changes in tumour size and disease extent.
- Widely applicable: CT can contribute to the evaluation of many cancer types, although its precise role varies according to the organ, tumour and clinical situation.
