Description of the test
Magnetic resonance imaging (MRI) provides a detailed look at organs and structures in the body. This test uses a magnetic field and energy pulses to create images.
The machine used for an MRI is very large. It has a special compartment where a person's body, or part thereof, enters. In most cases, the test is performed by a qualified MRI technologist in a hospital or in a clinic that has an MRI machine.
An MRI machine
How often should this test be performed?
This test is done as needed when a doctor requires a detailed cross-sectional image of inside the body.
Why is this test performed?
Because an MRI scan creates detailed images of the body, doctors use this test as a tool to identify problems in people with various symptoms or conditions. An MRI can be used to detect tissue damage, tumors, infections, or blood flow problems. Also, it shows blood clots, brain damage, and nerve damage (as occurs in multiple sclerosis). The test can also detect damage to the heart and lungs, reproductive system, bladder, bones and joints (such as arthritis), and spine.
Sometimes the technologist will inject a special dye (also called contrast material, contrast dye, or contrast medium) into your arm. This makes images of any damaged or abnormal tissue clearer.
Are there any risks and precautions I should know about?
The powerful magnetic field used during an MRI does not hurt or cause damage to your body. The magnetic field and the pulses of energy do not cause cancer. However, the magnet can damage certain pacemakers, artificial limbs, and other metallic medical devices. Unsecured metal objects (such as watches or jewellery) must be removed prior to the scan or they will be rapidly pulled toward the magnet, potentially causing serious injury.
There is a slight risk of allergic reactions to the dyes used to provide clearer MRI pictures. It's important to tell your doctor and the radiologist if you have allergies of any kind, particularly to contrast dyes.
If you have any metal objects in your eye, tell your doctor or the person performing the test. The magnetic field may cause metal pieces to move which may damage the eye. Because the effects of MRI tests on unborn babies are not known, inform your doctor or the person performing the test if you are or may be pregnant.
If you are taking any medications in the form of a patch, make sure to tell your doctor about this before starting the MRI test. Patches with an aluminum or foil backing can react with the MRI test, leading to skin burns. These types of patches should be removed before the MRI test.