Radiotherapy CT scan with contrast

This information is about radiotherapy therapy planning CT scans using a contrast (dye).

Before the CT scan

Before the CT scan, you’ll need to complete a questionnaire. This lets the radiographer know about any allergies you have, for example if you’re allergic to the contrast (dye).

If you have diabetes and take metformin, please let the radiographers know and follow the advice given by them and your doctor.

You can eat and drink normally on the day of your CT scan, unless you have been told not to.

Giving your permission (consent)

We want to involve you in decisions about your care and treatment. If you decide to have the procedure or treatment, we will ask you to sign a consent form. This says that you understand what is involved and agree to have the treatment.

Read more about our consent process.

Contrast

During your CT scan, we’ll use contrast (dye) to help us see inside your body more clearly. A contrast liquid will be injected into a vein in your arm, or you might drink a small amount of it with water. Your doctor will decide the best way to get the contrast into your body.

You might also have a blood test before your planning appointment. This is to check that your kidneys are working well.

It is sometimes not possible to use the contrast injection for medical reasons, or if we can’t get to your veins. If this happens, the CT scan will be done without contrast.

Contrast side effects

Some people get side effects from the contrast. The most common side effects are a feeling of warmth in your body, and a metallic taste in your mouth.

Other side effects include:

• feeling sick (nausea)
• being sick (vomiting)
• headache
• high or low blood pressure
• diarrhoea

If you have any questions or would like more information on the possible side effects of the contrast, please ask your radiographer before your scan.

During the CT scan

For the scan, you will be asked to lie on a flat bed. The scan is done by radiographers. They will move you into the position that you will need to be in for all your radiotherapy treatments.

The bed will move slowly through the CT scanner. A CT scanner is shaped like a large ring, and you will go through the hole in the middle.

You will not feel anything and nothing will touch you. Your radiographer might give you instructions for breathing during the scan, to help us get the best images possible.

You can tell the radiographers if you feel uncomfortable at any time, or if you have any concerns.

How long you will be in hospital

The appointment should last about 2 hours. You might want to bring something to eat and drink with you, especially is you have diabetes.

When the scan is complete, you will need to stay in hospital for about 15 minutes. This is to check if you feel unwell or get any side effects. If you don’t feel well, tell a doctor or nurse.

After leaving hospital

You should monitor your symptoms when you leave the hospital.