An MRI scan is a safe and painless test that can provide detailed pictures of organs and other structures inside your body.
Note: the information below is a general guide only. The arrangements, and the way tests are performed, may vary between different hospitals. Always follow the instructions given by your doctor or local hospital.
MRI stands for magnetic resonance imaging. An MRI scan uses a strong magnetic field and radio waves to create pictures, on a computer, of tissues, organs and other structures inside your body.
Your body contains millions of hydrogen atoms. When you are in an MRI scanner:
The MRI scanner is like a tunnel about 1.5 metres long, surrounded by a large circular magnet. You lie on a couch which then slides into the scanner. A 'receiving device', like an aerial, is placed behind, or around, the part of the body being examined. This detects the tiny radio signals emitted from your body. When each 'picture' is being taken you need to keep still for a few minutes, otherwise the scan picture may be blurred.
The scan itself is painless. The whole procedure can take 15-40 minutes. It may be a little uncomfortable lying still on the couch for this time. Small children may need a general anaesthetic to keep them still long enough for the pictures to be taken. In some cases, an injection of a special contrast dye is given into the bloodstream via a vein on the arm. This helps to give clearer pictures of certain tissues or organs being examined.
The radiographer sits in the control room next to the scanner and observes through the window. However, you can talk to them, usually via an intercom, and you will be observed at all times on a monitor.
The scanner is noisy so you will be given some headphones or earplugs to protect your ears from the noise. Quite often you can listen to the radio through the headphones or bring a CD to listen to.
An MRI scan can create clear pictures of most parts of the body. So, it is useful for all sorts of reasons where other tests (such as X-rays) do not give enough information required. It is commonly used to get detailed pictures of the brain and spinal cord, to detect abnormalities and tumours. Even torn ligaments around joints can be detected by an MRI scan. So, it is being used more and more following sports injuries.
Usually very little. Your local hospital should give you information about what is required before you come for the scan. The MRI scanner uses an extremely strong magnet, so people with certain types of medical implant cannot be scanned. This is because the magnet can potentially move medical devices with metal in them, or affect their function.
Therefore, before you enter the scanning area you should be asked if you have any medical devices in your body. (You may have to fill in a safety questionnaire that asks about things that may contain metal.) The following is not a definitive list but may help to remind you of the type of things radiographers need to know about:
It is also important to tell the radiographer if you have ever had any metal fragments lodged in your eyes or your body. In some cases you may need an X-ray before an MRI scan, to make sure you are safe to enter the scanner.
MRI scans are painless and thought to be safe. MRI scans do not use X-rays so the possible concerns associated with X-ray pictures and CT scans (which use X-rays) are not associated with MRI scans. However:
There are no after effects from the scan. You can return to your normal activities as soon as the scan is over. The pictures from the scan are studied by a specialist doctor (a radiologist) who sends a report to the doctor who requested the scan.