Magnetic resonance imaging (MRI) uses a very strong magnet, and radio waves, to make detailed pictures of organs inside your body. MRI is considered to give the best (clearest) images or pictures of the tissues around the rectum, for identifying the extent of any disease. It makes very accurate pictures of diseases involving the rectum, which is the lower part of the large bowel, near the anus (back passage).
An MRI scan of the Rectum is generally performed to look for tumour(cancer) & pus around the rectum.
Before your MRI examination can start, you will be asked a number of questions about metallic and/or electronic implants that you might have inside you. In some cases, such implants can be unsafe inside the MRI scanner, and another kind of test may then be needed.
Once the safety questions are finished, you will be asked to lie down on a narrow bed in the scan room.
You will be given headphones to wear; these protect your ears from loud rattling noises that are made by the scanner when it is making the pictures.
At some scanners you may be given an injection into a vein in your arm to slow down the normal movements of your bowel (these contractions can blur the MRI pictures). The injection may be called Buscopan (hyoscine) or glucagon. Some of these medications can worsen an eye disease called glaucoma, cause difficulty urinating (in those with prostate disease), and worsen some heart rhythm disturbances; you will be asked about all of these before any injection is given.
The technologist will use the scanner to make several sets, called “sequences”, of MRI pictures. Each set will last from 1 to several minutes, and it is very important not to move during any of the sequences. Whenever there is a rattling noise, the scanner is making more pictures.
The whole examination will take between 20 and 45 minutes.
A small proportion of people (2-5%) find MRI examinations difficult because of the partly enclosed nature of the scanner; the same people are often uncomfortable in lifts and other enclosed spaces.
This is less of a problem for rectal MRI exams than for some other MRI exams, because your head is near the opening of the magnet.
Many MRI centers offer mild sedation (relaxing tablets or injections) to patients who know that they will find the close surroundings of the magnet uncomfortable. These treatments reduce the anxiety about being in a confined space; they are not intended to put people to sleep. If you are given a sedative injection, a pulse oxymeter will be put on one of your fingers so that the technologists can monitor your pulse and breathing.
Although these injections appear to wear off quickly (in less than an hour), they slow reaction times for some hours. Driving, and travelling alone, may be unsafe for the rest of the day after such injections. If you know that you will need a sedating injection for the MRI exam, please arrange for someone to accompany you home after the test. If you are given such an injection, you should not return to work the same day.
There is no known adverse effect of the magnetic field and radio waves used in MRI on living tissues.