A CT scan, short for computed tomography scan, is a medical imaging test that uses X-rays and computer technology to create detailed pictures of the inside of your body.
A CT scanner is a large, ring-shaped machine with an opening in the middle. You lie on a motorised table that moves slowly through the scanner. Inside, an X-ray tube rotates around your body, capturing images from different angles.
The computer processes these images into cross-sectional “slices” of your body. These slices can be viewed individually or built into a 3D image, giving doctors a detailed view of internal structures. This is particularly helpful when looking for small problems that might not be visible on a standard X-ray.
Doctors may recommend a CT scan for many reasons. It can be used to look for injuries after an accident, check for signs of disease, or guide certain treatments. For example, CT scans are often used to:
Detect internal bleeding or organ damage.
Locate tumours or monitor cancer treatment.
Examine the lungs for conditions like pneumonia or blood clots.
Help plan surgery or radiotherapy.
Guide a needle during a biopsy.
A CT scan can also be useful in emergency situations, as it is quick and provides detailed images that can be acted on straight away.
Before your CT scan, the hospital team will explain the procedure to you. They may ask questions about your health, any allergies you have, and whether there is a chance you could be pregnant. You might need to change into a hospital gown and remove jewellery, glasses, or hearing aids, as metal can interfere with the images.
In some cases, you may be given a special dye called a contrast medium. This helps certain areas of the body show up more clearly on the scan. The contrast medium can be swallowed, injected into a vein, or given as an enema, depending on which part of the body is being scanned. If you are having contrast, you may be advised not to eat or drink for a few hours beforehand.
When it’s time for the scan, you will lie down on the table, usually on your back. The radiographer will position you so that the part of your body being scanned is in the centre of the scanner ring. You will be asked to keep very still, as movement can blur the images. For scans of the chest or abdomen, you may need to hold your breath for a few seconds.
The radiographer will operate the scanner from a nearby room, but they can see and hear you through a window and an intercom. The scan is painless, although you may hear whirring or buzzing sounds as the machine works. If you have had a contrast injection, you might feel a warm sensation or a metallic taste in your mouth. These feelings are usually mild and pass quickly.
Once the scan is complete, you can usually go home straight away. If you have had a contrast injection, the team may ask you to stay for a short time in case of any reaction, which is rare. Drinking plenty of fluids afterwards can help flush the contrast medium out of your system.
The images from your CT scan will be reviewed by a radiologist. They will write a report for the doctor who referred you. Your doctor will then discuss the results with you and explain what they mean for your care.
Simple carousel diagram to show the CT scan procedure.
| Feature | CT Scan | MRI Scan |
|---|---|---|
| Technology | X-rays and computer processing | Magnetic fields and radio waves |
| Best for | Bones, lungs, chest, detecting bleeding | Soft tissues, brain, joints, spinal cord |
| Speed | Quick – usually 10–30 minutes | Slower – can take 30–60 minutes |
| Use of radiation | Yes | No |
Your doctor will decide which is more suitable based on the area of your body being examined and the detail needed.
CT scans use X-rays, which involve exposure to a small amount of radiation. The amount is more than you would receive from a standard X-ray but still considered low and unlikely to cause harm from a single scan. Doctors weigh the benefits of the scan against any potential risks before recommending it.
The contrast medium used in some CT scans is generally safe, but in rare cases, it can cause allergic reactions. If you have a known allergy or kidney problems, let the medical team know before your scan. Pregnant women are usually advised to avoid CT scans unless absolutely necessary, due to the potential risks to the baby.
You do not usually need to make major preparations for a CT scan, but following any instructions from the hospital is important. This might include fasting for a few hours before the test if contrast is required. Wearing comfortable clothing and leaving jewellery at home can make the process smoother. If you are nervous or have concerns about enclosed spaces, let the radiographer know — they can help you feel more comfortable during the scan.
CT scan results are not given immediately unless the scan is part of an emergency assessment. The radiologist will examine the images carefully and write a report for your doctor. The time it takes to get your results can vary depending on the reason for the scan and how urgent your case is. When you receive your results, your doctor will explain what they mean and whether you need further tests or treatment.
Within the NHS, CT scans are arranged by referral and prioritised based on urgency. Waiting times can vary from days to weeks. Private CT scans are available at independent clinics, often with shorter waits, but prices typically range from £350 to over £1,000 depending on the area scanned.
If you are referred for a CT scan, it can help to ask:
Why is it needed?
Are there other tests that could give the same information?
What are the risks of having it?
The NHS CT scan guide provides further details on what to expect and how to prepare.
A CT scan is a safe and effective way to get detailed images of the inside of your body. It can help diagnose injuries, detect diseases, and plan treatments. While it does involve some exposure to radiation, the benefits often outweigh the risks, especially when the scan can provide crucial information for your care. Preparing properly, understanding the process, and following medical advice will help ensure your scan goes smoothly.
Disclaimer: Seonat provides general health information for educational purposes only. This content is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your GP or another qualified health provider with any questions about a medical condition or before making health decisions.
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