Your CT scan

Information for patients who have been advised to have a CT scan. 


You have been advised by your doctor to have a Computerised Tomography investigation which is more commonly referred to as a CT scan. This leaflet will explain what CT is, the benefits and risks, as well as what the examination involves. If you have any further questions please speak to your doctor, nurse or radiographer looking after you.

 CT scans take place in the Imaging department which can also be known as the Radiology or X-ray department. This is the facility within a hospital that carries out radiological examinations such as X-rays, CT scans, Magnetic Resonance Imaging (MRI) scans, Ultrasound scans along with other types of radiological investigations. 

Radiologists are doctors specially trained to interpret the images and carry out more complex examinations. They are supported by highly trained operators, known as radiographers, that carry out X-rays and other imaging procedures.

What is a CT scan?

A Computerised Tomography (CT) scanner is a machine that uses ionising radiation (X-rays) and a computer to produce very detailed cross-sectional images of any part of the body. The information is then built up into a series of pictures for the radiologist to view.

What are the risks and benefits of having a CT scan?

A CT scan involves the use of ionising radiation (X-rays); we are all exposed to natural background radiation every day from radioactivity in the air, food that we eat and even from space. Exposure to ionising radiation from a CT scan carries a small risk, however, the main benefit of having the scan is to get an accurate diagnosis so that you can get the right treatment for you. A specialist will have agreed that the benefit of the scan outweighs the risk of the ionising radiation, and we can assure you that all safeguarding to minimise ionising radiation exposure is taken.

If you are between the age of 12 and 55 years of age and there is any chance that you could be pregnant then please contact the Imaging department before you attend for your appointment. The contact details will be on your appointment letter.

Patients should ideally be scanned within the first 10 days of their menstrual cycle. If you are between the age of 12 and 55 and your appointment does not lie within this timeframe, or you are or may be pregnant please contact the Imaging department before you attend. The contact details can be found on your appointment letter.

Some patients will require an injection of contrast medium, also described as X-ray dye, for their scan which increases the amount of information seen on the scan. There is a small chance of an allergic reaction to the injection of contrast medium, however, the Imaging team are trained to deal with any complication, and the risk is very small.

The Imaging team will make sure you are feeling alright and have recovered before letting you leave the department.

Is there anything I need to do before my CT scan?

  • Please read your appointment letter as this will give you specific details of how to prepare before your CT scan.
  • If your appointment letter asks you to drink water before your scan please do so, slowly, over one hour prior to your appointment time. This will keep you hydrated and will also highlight the bowel if we are imaging your abdomen and pelvis. You do not require a full bladder for your CT scan.
  • If you are taking any medication prescribed from your doctor, please continue to take these as normal, unless told otherwise by your doctor. 
  • If you are asthmatic please bring your inhaler with you to your appointment.
  • It is recommended that you attend your appointment in clothing that doesn’t contain any metal fastenings, zips or decoration as they show up on the CT scan. If this is not possible, we may require you to change into a hospital gown which will be provided. 
  • Please be punctual to your appointment time. We are a busy department and if you are late for your appointment, we may not be able to fit you in. If you are running late on the day of your appointment, then please let us know by contacting our booking office on 0117 414 8989. If we know you may be delayed, then we may be able to rearrange things to fit you in.

What happens during my CT scan?

  • From the reception waiting area you will be escorted through to the CT waiting area. From this point onwards you will be cared for by a small team of radiographers, image support workers and possibly a radiologist. The radiographer will be the professional carrying out your CT scan.
  • In the CT waiting area a member of the CT team will begin to get you ready for your scan. If necessary, you will be asked to change into a hospital gown or to remove any metallic items from the area being scanned.
  • The radiographer will take you through to the CT scan room and, if necessary, assist you onto the CT scan couch. The radiographer will then raise the couch up and move it into the CT scanner until the part of the body we need to scan is in the centre of the hole in the middle of the CT scanner. 
  • Once you are in the correct position the radiographer will leave the room to perform your scan in an adjacent room. The radiographers can always see and hear you throughout your CT scan and can communicate with you through an intercom if required.
  •  You will be required to keep still throughout your CT scan to avoid blurry images being produced. You might also be asked to follow breathing instructions given by the CT scanner which the radiographer will explain to you before they leave the scan room. 
  • If an injection of contrast medium or X-ray dye is required, a cannula will be placed into a vein in your arm. The radiographer will connect this to a machine called an injector pump that will administer the dye during the scan. When the contrast is injected, it is common for some patients to feel a sensation of warmth around their body, a metallic taste in the mouth or throat and the sensation of peeing. These feelings are normal and are just sensations, they usually pass within the first 30 seconds. Please be assured that the feeling of peeing is just a feeling and not actually happening. Not all patients will experience these feelings.

How long will my CT scan take?

If you have been given an injection of contrast media as part of your CT scan, then you will be required to stay in the department for an extra 15 minutes after your scan has finished. This is so that we can ensure that you have not had an allergic reaction.

If you have not received an injection of contrast media, then in most cases, you will be able to leave the department immediately after your CT scan has been completed. You can eat and drink as normal after your scan. 

If you experience any problems after your CT scan, then please contact your GP or 111.

How will I get the results of my CT scan?

After your appointment, your CT scan images will be reviewed by a radiologist. The radiologist will write a report which is then sent to the doctor who requested a scan for you. The doctor who requested your scan will inform you of the results.


National Health Service: Your CT scan: Available from https:// [Accessed on 07/02/2022] 

United States Food and Drug Administration: Computed Tomography (CT). Available from Computed Tomography (CT) | FDA [Accessed 07/02/2022] 

Computed Tomography (CT or CAT scan) Procedures (

Radiation Dose from X-Ray and CT Exams (

© North Bristol NHS Trust. This edition published August 2023. Review due August 2026. NBT002000.

Your CT scan