Magnetic Resonance Imaging (MRI)

This test is done in a hospital radiology department or in a free-standing MRI clinic. It is performed by a technician and supervised by a doctor. A registered nurse is generally always present, especially with patients who need an IV and contrast.

You will be asked to lie on a narrow table. Your head will be placed in a padded plastic cradle or on a pillow. The technician may place a “coil” over the part of your body that is being scanned. A coil can be like a Lego that snaps into the table or like a weighted blanket laid on top of you. Coils are needed to make the pictures. The technician may offer you earplugs or headphones and may ask what kind of music you like to listen to, which can help with any loud noises during the scan.  Once you are ready, the table will slide into a large tunnel-like tube in the scanner. You will be asked to breathe softly and normally but to stay very still. At times you will be asked to hold your breath for short periods. The more still you are, the better the pictures will be.

Lying inside a large, hollow magnet, you will be exposed to radio waves. This energy is directed at water molecules in the body, "exciting" and then "relaxing" the protons. Sometimes, parts of your body may feel warm as it is scanned. This is very normal and not harmful.

The MRI reads the energy from the water molecules and builds a 3-D image of the different types of tissue.

MRI often involves taking many sets of images, each lasting about 2 to 15 minutes.

Some people don’t feel comfortable in close or confined spaces. For this test, you do have to lie still on a hard table inside a narrow tube. If you have a history of anxiety or fear of closed spaces, you should talk to your health care team. You may be able to take a drug to relax you before the test, or find a location with an “open” MRI, which is not quite as confined. No other preparation is needed.

To get clearer images, your health care team may decide you need an IV placed for gadolinium contrast.

If you are generally healthy, there is little to no risk with MRI. This test cannot be done if you have any metal in your body, such as:

• Metal hip/knee/joint replacements
• Cardiac pacemaker/defibrillator or other implanted devices
• Brain aneurysm clips/coils
• Ear implants

The technician or health care team will ask if you have any metal in your body prior to the scan to prevent trauma or burn with an MRI.

Limitations

MRI does not work very well in the urinary tract. Its signals will not show calcifications in soft tissue and bladder abnormalities.

Also, MRI does not show bones clearly, so it’s less useful if your doctor is trying to see if cancer has spread to the bone.

MRI is very useful when gadolinium contrast is added. This results in much more detail for soft tissue than CT scans. But this should not be used if you have kidney or liver problems.

The whole test takes about 30 to 60 minutes. After the test you can go back to your normal daily activities.

Updated November 2024.