A Computerised Tomography (CT) scan uses x-rays and a computer to create detailed images of the inside of your body. It is similar to how an x-ray machine works but the x-ray tube spins around you taking lots of pictures that are then re-arranged to appear as ‘slices’ through the body. The x-rays pass through the body and hit a detector which converts the signals into pictures. Large complex computers convert all this data into slices through the body that can then be used by Radiographers and Radiologists.
The data gathered from the scan can also be used to produce 3D images of certain body parts, for example blood vessels or a particular bone. CT scans are useful for looking at bones, lungs and other organs, and blood vessels. CT scans are also used to look at a wide range of conditions and pathologies.
The CT scanner is doughnut shaped and tends to be wider in the middle compared to an MRI scanner and not as long. You will be asked to lie on the CT table which automatically passes through the centre of the scanner, known as the gantry bore.
You may be given an injection of ‘contrast media’ to help enhance the pictures. The contrast media allows us to see certain structures like blood vessels. The whole process of having a scan usually takes 10-15 minutes depending on the complexity of the scan being performed. The actual scan itself can take a matter of seconds though.
The CUH CT department is specialised and receives patients from all around the country, providing a range of procedures, including all body CT scanning, cardiac scans, CT colonography, enterographys and CT Post Mortem. We have close links with Cambridge University and participate in a variety of research trials with many different research institutions.
Currently we have five CT scanners at CUH, one of which is located in the PET-CT department, as well as a CT unit located at the Sawston Medical Practice site.
Preparing for your scan
Please read your appointment letter carefully for guidance on which location to come to, the arrival time and any advice on eating and drinking before your scan.
In some cases, you may be asked to drink water beforehand or to take some oral contrast. This will depend on the area of your body being scanned.
Arriving for your appointment
Please allow plenty of time to get to the department, you will be asked to come to either Addenbrooke’s Hospital CT Department or Sawston Medical Practice. Travel details should be sent with your appointment letter.
Unlike MRI, metal can go in the CT scanner room and pass through the scanner. However, it must not be in the way of the part of the body we want to scan as it will affect the quality of the image. To avoid unnecessary waiting time and an effective examination, we recommend patients remove all metal and jewellery from the body part to be scanned and ideally wear clothes without any metal i.e. avoid under-wired bras.
Before your scan, one of our team members may ask you to change into a hospital gown, however the majority of patients can be scanned in their clothes.
During a CT scan it may be necessary to give you an injection of iodine-based contrast (a type of dye that highlights blood vessels and other structures in the body). This contract injection will be administered by the radiographer, through a cannula (small plastic tube), which is usually placed in a vein in your arm.
The injection may make you feel warm as the contrast is kept in an incubator. Patients tend to get a warm feeling as the dye moves through the blood vessels down the body. Sometimes the contrast dye can have side effects such as feeling nauseous, developing a skin rash, headache or dizziness. These side effects are usually mild and don't last very long.
If you are currently breastfeeding, you can continue to do so, after the injection of contrast media. More information can be found in this patient information leaflet.
During the scan
The procedure will be fully explained to you. Please feel free to ask the radiographer any questions before your scan. You will be asked to lie down on the scanner table and keep as still as possible. It is important to keep very still during the CT scan however it will normally not last more than five or ten minutes depending on the particular examination. The first picture taken gives us an overview of your body from which we then plan the ‘main scans’ from. If you are having the contrast injection then you will have this first and wait a few seconds for the ‘main scans’ to start.
The radiographer will leave the room whilst the scan is taking place. They can still see you on a TV screen. The scanner has a microphone built into it, so you can communicate with staff and also the radiographer can communicate with you.
If you are anxious about going into the CT scanner you can arrange to visit the department to view the scanner in advance of your appointment. Please be aware the department itself is not able to give any medication to help calm patients. This will need to be prescribed in advance by your doctor.
Should you have any doubt about your examination please contact the CT Department as outlined in your letter.
After the scan
If you have had an injection we will ask to remain in the department for 15 minutes to check you are feeling okay before you are go home.
After the scan, you can resume normal activities immediately. But if you have had a sedative, a friend or relative will need to take you home and stay with you for the first 24 hours.
Your CT scan needs to be reviewed by a radiologist (a doctor trained in interpreting scans and X-rays) and possibly discussed with other specialists. The radiographer will not be able to tell you what is on the scan.
The radiologist will send a report to the doctor who arranged the scan, who will discuss the results with you.
Contact Sawston CT department
Parking: Free parking is available at Sawston Medical Centre. If you drive round the car park and as you return to the entrance you will see a sign to turn left and drive parallel to the main road, where there is parking near to the Sawston CT.