Find out what a CT scan is, how you have it and what happens afterwards.
A CT scan is a test that uses x-rays and a computer to create detailed pictures of the inside of your body. It takes pictures from different angles. The computer puts them together to make a 3 dimensional (3D) image.
CT (or CAT) stands for computerised (axial) tomography.
You usually have a CT scan in the x-ray (radiology) department as an outpatient. A radiographer operates the scanner. The whole appointment can take up to an hour and a half depending on which part of your body they are scanning.
Why you have it
You might have a CT scan of your tummy (abdomen) and chest. The scan is to check whether you have cancer anywhere else in your body. This is because in adults, cancer that has spread to the brain (secondary brain tumour) is much more common than cancer that started in the brain (primary brain tumour).
When you arrive
The radiographer might ask you to change into a hospital gown. You should remove jewellery and other metal objects, such as hair clips. Metal interferes with the images produced by the scanner.
In the scanning room
When you’re ready, the radiographer or assistant takes you into the scanning room. A CT scanning machine is large and shaped like a doughnut.
You might have an injection of contrast medium through a cannula in your arm. You may:
- feel hot and flushed for a minute or two
- have a metallic taste in your mouth
- feel like you’re passing urine but you aren’t – this feeling is common and passes quickly
Tell the radiographer if you feel anxious or clasutrophobic about having a scan. They can arrange for you to have some medicine to help you relax.
Having the CT scan
You usually lie down on the machine couch on your back. Once you’re in the right position, the radiographer leaves the room. They can see you on a TV screen or through a window from the control room. You can talk to each other through an intercom.
The couch slowly slides backwards and forwards through the hole of the scanner. The machine takes pictures as you move through it.
The scan is painless but can be uncomfortable because you have to stay still. Tell your radiographers if you’re getting stiff and need to move.
During the scan
You’ll hear a whirring noise from the scanner.
The radiographer might ask you to hold your breath at times.
When the scan is over, the radiographer comes back into the room and lowers the couch so you can get up.
The 2-minute video shows what happens when you have a CT scan.
Voiceover: A CT scan helps your doctor make a diagnosis, decide about what treatment you need or find out if your treatment is working.
This type of scan takes a series of x-rays and uses a computer to put them together.
Before your scan you may need to drink either half a litre of water or a type of dye called a contrast medium. This helps to make the scan clearer.
Before most scans you have a small tube put into your vein, which connects to a drip containing the dye. Again, this helps to show up the inside of your body more clearly on the scan.
During the scan the bed moves in and out of the scanner. You may find it a bit noisy.
As the drip goes in you’ll probably get a metallic taste in your mouth, feel warm and you might think you are passing urine, you’re not. These feelings pass quickly.
The radiographer controls the scan from a separate room. The CT machine takes pictures of your body from different angles and builds up a series of cross sections.
This creates a very detailed picture of the part of your body being scanned. Most scans take just a few minutes. The whole thing takes about 90 minutes and you usually get the results within a couple of weeks.
After your CT scan
You stay in the department for about 15 to 30 minutes if you had an injection of the dye. This is in case it makes you feel unwell, which is rare.
The radiographer removes the cannula from your arm before you go home.
You should be able to go home, back to work or the ward soon afterwards. You can eat and drink normally.
If you had medicine to help you relax you’ll need someone to take you home. Also for 24 hours after you shouldn’t drive, drink alcohol, operate heavy machinery or sign any legally binding documents.
Getting your results
You should get your results within 1 or 2 weeks.
Waiting for results can make you anxious. Ask your doctor or nurse how long it will take to get them. Contact the doctor who arranged the test if you haven’t heard anything after a couple of weeks.
You might have contact details for a specialist nurse and you can contact them for information if you need to. It may help to talk to a close friend or relative about how you feel.
A CT scan is a safe test for most people but like all medical tests it has some possible risks. Your doctor and radiographer make sure the benefits of having the test outweigh these risks.
The contrast medium injection can cause side effects. But these are usually mild and last for a short time.
- feeling or being sick
- a skin rash
- a headache
There is a risk that the contrast medium will leak outside the vein. This can cause swelling and pain in your arm but it’s rare.
Tell your radiographer if you have any swelling or pain. Tell your GP if it doesn’t get better or starts to get worse when you’re at home.