CT Scanner
The CT Scanner uses x-rays to obtain pictures. Older CT Scanners take a number of pictures as slices, a little like the slices of a loaf of bread. The newer scanners collect so much information that we have the whole loaf and can cut it up afterwards however we like, to best see the inside of the body. Unlike the MRI Scanner, as you can see, the whole in the middle of the CT Scanner is much larger and the tube through which you pass is much shorter. Most of the time you can see out of either one side or the other of the scanner and therefore it is much less of a problem for people who feel claustrophobic.CT scanning is becoming used increasingly throughout radiology for investigating the whole of the body. It is particularly good at looking at areas that may contain gas (like the bowel or liver) that cannot be looked at with ultrasound. It also acquires its pictures much more rapidly than MRI and is much more available throughout the country than MRI and is therefore often the investigation of choice for many conditions.
Following receipt of your appointment, you will often be asked to come to the department up to one hour before the investigation. This is to allow time for you to drink some dye, which enables the radiologist to see the bowel more clearly. This needs time to pass through as far as the colon. For investigations of bones or the chest, often you will come just shortly before your appointment time. Many of the investigations that are undertaken now also require the injection of dye into the arm. This dye contains iodine, it is not radioactive, but shows up as white areas on the scans, helping the radiologist to tell the difference between blood vessels and other structures. You will be asked about allergies and your tablets, to ensure that there is no risk of allergies or interactions. When the radiographers are ready to scan you, you will be taken into the CT room and asked to lie on the couch. As metal buckles and buttons can cause problems with the pictures, you will often be asked to either remove these items or put them in a position where they are not in the area to be scanned. The scans themselves are often very quick, taking between 10 and 20 minutes to acquire. If you do receive an injection of contrast (dye) during the investigation, this will often make you feel warm and some people feel as though they wish to pass water. Don't worry, you won't, it just gives you that sensation. Whilst the pictures are being taken, we need you to lie as still as possible. For many of the investigations, you will also be given clear instructions on when to hold your breath. Many patients are worried about whether they will be able to lie still and hold their breath long enough. Don't worry about this, you will be given clear instructions to help you with any problems. Unlike the MRI scanner, the CT scanners are often quite quiet. At the end of the procedure, the computers collect all the information and start to process it. This usually means that the information is not available instantaneously and usually has to be inter preted by the radiologist before a report is available. Whilst the radiographer can reassure you that the appropriate images have been obtained, we will usually not be able to give you any idea of the results at that time.