What is a CT scan?
A computerised tomography (CT) scan uses X-Rays (radiation) and a computer to create detailed images of the inside of the body; within a single breath hold.
A CT scanner is a ‘polo-mint’ shaped machine containing a bank of X-Ray tubes/detectors which spin around an axis in order to create 3D images through the body. A patient lies on the scanner bed and moves in and out of the ‘polo-mint’; the scans are very quick and take a matter of minutes and the machine sounds like a washing machine during a spin cycle.
Are there any associated risks?
The risk of radiation from a CT can be described in relation to the level of background radiation we receive naturally every year. Background radiation is the radiation to which you are naturally exposed resulting from low levels of radiation in rocks, food and the atmosphere. The main risk from exposure to X-Rays (as used in CT) is the possibility that the patient may develop cancer at some time after the exposure – this may be a number of decades after the initial exposure.
All requests made to CT are justified and authorised by Radiology staff to ensure that the benefit from an X-Ray exposure outweighs the risk.
The below table outlines some ‘average’ adult risks associated with common CT scans; this is a rough guide and individual risk assessments can be completed or discussed with Radiology and Medical Physics.
| CT scan(body part) | Approximate additional lifetime risk of cancer | Risk Category |
| CT Head | 1 in 10,000 | Low |
| CT Chest | 1 in 1,700 | Low |
| CT Abdomen + Pelvis | 1 in 2,400 | Low |
| CT Chest, Abdomen + Pelvis | 1 in 1,300 | Low |
How do I prepare for the test?
You will be given an appointment letter; please read this letter carefully as it will tell you which hospital your CT scan has been booked at and the time of your appointment.
It is advisable to attend wearing comfortable clothing, you may be asked to remove clothing which has any metal e.g. zips, belts, braces and underwired bras.
There is no need to stop taking any medication before the scan however you may wish to avoid eating 1hr prior to scanning as this can sometimes make you feel queasy when combined with the CT contrast media injection.
Please contact the department, using the number on your appointment letter if you answer ‘Yes’ to any of the following statements:
Are you or is there any chance that you could be pregnant?
Have you previously had or been told that you have had an allergic reaction to CT contrast media?
Are you allergic to iodine?
Have you recently had a CT scan performed outside of Leeds Teaching Hospitals?
What will happen during my examination?
Your scan may require an injection of CT contrast media; this is a clear liquid which is given during your scan to provide more information on your images. If your scan requires this injection then you will be asked to complete a safety questionnaire prior to a cannula (small plastic tube) being placed in your arm or hand.
The CT contrast media injection can make you feel warm all over your body and give you a metallic taste. On rare occasion people may be allergic to the CT contrast media (please see statements above regarding contacting the department). Extravasation (leakage) of the contrast outside the vein may also occur in rare instances; causing localised pain or swelling around the injection site.
Radiology staff will check that it is safe to continue with the CT contrast injection before your scan.
Once you are ready for the scan, you will be asked to lie down on the scanner bed. Depending on the body part being imaged you may be asked to lie in different positions. The scan will take between 10-20 minutes, you may be asked to remain still and hold your breath for parts of the scan.
We attempt to stay on-time; however the CT service also provides imaging for the emergency department and wards. We sometimes have to accommodate very ill patients and this can delay the list.
After your test
The CT contrast media, if given, will be naturally excreted by your body; however it is helpful to ensure you drink plenty of fluids for the next few days. You may eat and drink normally.
Who will perform the test?
A Radiographer will carry out the examination. Radiographers are specially trained Allied Healthcare Practitioners who have completed a degree and have expertise in radiographic technique and radiation protection. It is the Radiographers job to ensure that all CT exposures are/have been justified, doses are as low as reasonably practicable and that images are diagnostic to answer the clinical question.
How will I get the results?
After your scan
A Radiologist or Reporting-Radiographer will review your images and produce a report which is sent back to your referrer to share with you and action or continue any required treatment.
If you have not had any results after four weeks, please contact your referrer. Radiology cannot give any results out directly to patients.
Anything else?
Please be aware that Radiology staff will not be able to look after any children during your examination and your children cannot enter the scan room.
The waiting space available in Radiology is limited so please do not from bring lots of friends or relatives with you wherever possible. There is waiting space outside of Radiology and staff may ask for anyone who is not attending for an appointment to wait there in busy times.
Your letter will indicate if you have any transport booked for you.