Risks and Benefits
Radiation Exposure
You will be exposed to X-ray radiation, similar to the background radiation we encounter daily. The level of radiation varies depending on the scan but is generally equivalent to a few months to several years of natural exposure. The risk of developing cancer from a CT scan is minimal (less than 1 in 1,000). The benefits and risks are evaluated by your doctor and Radiology specialists before proceeding.
Contrast Injection
Most scans require a contrast dye injection containing iodine to highlight blood vessels and organs. Inform the Radiographers if you have allergies to iodine or contrast dye. Rarely, the dye can affect kidneys, especially in those with pre-existing conditions, so we may test your kidney function beforehand. There’s a small chance the injection can leak outside the vein, causing temporary swelling and discomfort in the arm; this is uncommon. On the day you will be asked to fill out a safety question.
Preparing for Your Scan
- Can I take my prescribed medicines as usual?
Yes, continue taking your regular medications as prescribed, unless instructed otherwise.
- What clothing should I wear?
Wear loose, easily removable clothing. If your clothes do not contain metal (such as zippers, buttons, bra wires, or decorations), you might not need to change into a hospital gown.
- Can I eat before my scan?
If a contrast injection is required, do not eat anything for two hours before your scan to minimise bowel gas and avoid nausea. You may drink water during this period.
Day of the Scan
Check your appointment letter for details. Upon arrival, reception will guide you to the waiting area where Radiology staff will verify your identity and provide you with two forms.
You will fill out a safety questionnaire about your medical history and medications to assess any risks with contrast dye. If you are of childbearing capacity aged 18- 55, you will also complete a menstrual cycle questionnaire to ensure you are not pregnant. If your last period was more than 10 days ago and pregnancy cannot be ruled out, your scan may need to be rebooked or you may be asked to take a pregnancy test.
During the Scan
After preparation, you will be taken to the CT room. The Radiographers will explain the process and answer any questions. The scan itself only takes a minute or two, but the preparation takes longer. If you are having an injection of contrast dye, a cannula (a small plastic tube) will be inserted into a vein in your arm. You should allow for approximately an hour from the start to end of your appointment.
If receiving a contrast injection, you may feel a warm sensation and a metallic taste. Inform the Radiographer if you experience discomfort in your arm during the injection.
You will lie on a table that moves through the scanner. Depending on the area scanned, you may need to hold your breath momentarily.
The scan itself should not be painful. The radiographer carrying out the scan can see and hear you at all times during the scan.
After the scan
Post-Scan Care:
You can leave shortly after the scan and resume normal activities, eating and drinking as you would usually.
If you had a contrast dye injection, we ask that you stay in the department for up to 20 minutes in case of delayed allergic reactions.
Following your scan, only if advised, drink plenty of fluids to better dilute the contrast and minimise the potential damage to your kidneys. Please consult your healthcare provider if on fluid restriction. If diabetic and taking metformin, we will speak to you about whether you need to stop taking medication for 48 hours after the scan and visiting your GP for a blood test.
If you had an injection of contrast dye, you may remove the gauze dressing from your arm after one hour.
Results:
The scan images will be reviewed by a Radiologist, and a report will be sent to the referring doctor. If you do not hear about the results within three weeks, contact the referring doctor.
Additional Resources
- The Society of Radiographers
- NHS Choices
- Oxford University Hospitals
