What is an MRI?

MRI is a painless test used to view the inside of the body without using x-rays. It uses a large magnet, safe low energy radiowaves and a computer, to produce two or three-dimensional pictures. Radiowaves are passed into your body and are absorbed by some of the tissues which in turn retransmit the radiowaves. The magnet is turned on and off, and reads the radio waves you are giving off. The computer picks up this information and generates a picture. Diseased tissue gives off a different signal than healthy tissue and the machine detects this.

When is an MRI used?

A MRI is used when simpler and less expensive tests have failed to give a diagnosis. It provides a detailed picture of any part of the body and it may mean that some of the less pleasant tests do not have to be done.

What do I need to do to prepare for the MRI?

You may be asked to restrict food and drink for a few hours before the test. You should tell the doctor who arranges the test if you have any metal clips on blood vessels in your brain, any metal foreign bodies in your eye, a pacemaker or a surgically implanted joint/pin, etc.

Small children and infants will be given a general anaesthetic to keep them completely still. They should not eat or drink anything for six hours before the test, and the doctor will discuss the procedure with you and answer any questions.

You will asked to sign a consent form allowing the test to be done.

What happens before the MRI?

You will be asked to change into a hospital gown and to remove all jewellery, hair pins, watches, and any clothing which contains metal decoration, zips or wire. It is important to leave your wallet outside the room, as the powerful magnet will wipe credit cards.

You will then be asked to lie on a narrow table and the staff will get you into the right position. The table will then move you into a tunnel. You will be in the tunnel (and room) by yourself, but you can talk to the staff at any time through an intercom. Fans will circulate air through the tunnel.

The table doesn't move during the test and nothing will touch you. The machine makes knocking noises as it takes the pictures, which can be quite loud, but most MRI machines have earphones through which music will be played to distract you. You may be given an injection of a contrast medium or dye that makes the pictures easier to read; this will be discussed before the procedure.

Once enough films have been taken, the table will slide out of the tunnel, and you can go and get dressed.

What happens after the MRI?

You can resume normal physical activity and return to work as soon as the test is finished.

The results will be sent to the doctor who referred you for the test, and a follow-up appointment will be made for you to discuss them.

What are the risks of having an MRI?

MRI itself has no known harmful effects. It is not, however, recommended during pregnancy. People who are very overweight cannot fit into the scanner, so it is not possible for them to have an MRI.

This test can be very frightening for people who are claustrophobic. If you think you could not lie still and relax, you should tell your doctor before you are sent for the test. Some people may have an allergic reaction to the dye which will be treated with drugs at the time.

Where do I go for an MRI?

MRI scanners are very expensive and are only available in main centres. The doctor in the public health system can refer you for a MRI if he or she thinks it is necessary. There may be a waiting list.

MRI scans vary in price. It depends on what part of your body is being scanned, and how many pictures need to be taken. If you choose to see a specialist privately, expect to pay anywhere from $800 to $1,500.

For further information and support talk to your doctor or practice nurse. Contact the hospital or radiology centre where you are having the MRI.