Magnetic Resonance Imaging
What is it?
A magnetic resonance (REZ-oh-nans) imaging scan is usually called an MRI. It may also be called a nuclear magnetic resonance (NMR) or a magnetic field scan. It is a medical test that takes pictures of the inside of the body. Each picture or "slice" shows only a few layers of body tissue at a time. The MRI machine uses a large magnet, and a computer to make pictures of your body. Pictures taken this way may help caregivers find and see problems in the body more easily. This test usually takes between 15 and 90 minutes.
Why do I need an MRI?
The pictures made during an MRI help caregivers learn more about the cause of your health problem. An MRI can be used to evaluate brain, neck, and spinal cord problems. It can also help caregivers look at problems with your chest, heart, abdomen, joints, or blood vessels. Nearly every part of the body can be studied with an MRI.
When should a person not have an MRI?
- MRI is usually avoided during the first trimester (the first three months) of pregnancy. Talk with your pregnancy caregiver before having an MRI during this time.
- You should not have an MRI if you have anything in your body that attracts a magnet. You may not be able to have an MRI if you have any of the following things in or on your body:
- Aneurysm clips.
- Artificial or prosthetic limbs or joints, such as an artificial knee joint.
- Bullets or pieces of shrapnel.
- Cochlear (ear) implants.
- Heart pacemaker or artificial heart valve.
- Implanted cardiac defibrillator.
- Implanted IV ports
- Implanted spinal stimulator.
- Insulin pump.
- Intrauterine device or "IUD."
- Medication patch. A medication patch is also called a "transdermal" or "skin" patch. Some medication patches may have metal in or on them. This could cause a skin burn during an MRI. Examples of medication patches are nicotine, birth control, and nitroglycerin patches. Ask your caregiver if your patch should be taken off your skin during the MRI.
- Metal pins, plates, screws, or surgical staples (In most cases these things will not cause a problem with an MRI if they have been in you for more than four to six weeks)
- Pieces of metal fragments in your eyes from welding.
- Tattoos and permanent eyeliner because the paint used has lead in it that the magnet can pull out.
- Aneurysm clips.
How does the MRI work?
The MRI machine is large and looks like a hollow tube. The table that you lie on goes into the tube during the test.
- There are different types of MRI scanners. The conventional MRI is a closed machine where the patient passes into the hollow tube. The newer open or shorter MRI machines allow more room for patients. These types of MRI machines are better for people who need more space like children and larger patients. They also work better for patients who are claustrophobic (klaws-troh-FOH-bik) or anxious in closed spaces. Ask your caregiver for medicine to help you relax and lie still during the test if you are anxious. The pictures made by the open MRI may not be quite as good as those from the closed MRI. Talk with your caregiver to decide which type of MRI is best for you.
- The machine is usually in a room by itself. Your caregiver sits behind a window on one side of the room during the MRI. From this spot, the caregiver can talk to you during your scan. The MRI machine aims magnetic and radio waves at the part of your body being tested. These waves pass through your body to create pictures that show up on a computer screen. The pictures can be made into hard (paper) copies once the computer is finished taking pictures. These hard copies can then be taken or sent to your caregiver.
What happens during the MRI?
You may be asked to put on a gown, and then caregivers will help you lie down on the MRI table. The body part being tested may be kept in place with a cradle or straps to hold it very still. You are not able to see anything once you are inside the machine. There may be mirrors in the machine so you can see out of it. You may speak to your caregiver at all times during your test. You are also given an "emergency" call button. Caregivers stop the test and move your bed out of the MRI machine immediately if you press the button.
- The bed slides into the round tube in the center of the machine. You hear very loud banging noises during a series of scans. The noise is caused by the magnets moving. You are given earplugs or ear muffs to help soften the noise of the MRI machine. You may be allowed to wear music headphones to help you relax and soften the noise of the machine.
- Each MRI is made up of a number of sets of image scans (pictures). You must lie very still during the actual scans, for a few seconds to a few minutes at a time. You may be able to move a little in between the scan sets. Your caregiver may put padding or cushions around and under you for comfort.
- Some MRI tests need dye medicine to help make your body part show up better in the pictures. The dye is put through an IV started in a vein in your hand or arm. Your skin around the IV may feel warm or cold as the dye is put into the IV. Tell your caregiver if you feel any unusual things as the dye is given. People who are allergic to shellfish (lobster, crab, or shrimp) may be allergic to this dye. Tell your caregiver if you are allergic to any of these.
You have the right to help plan your care. To help with this plan, you must learn about your health condition and how it may be treated. You can then discuss treatment options with your caregivers. Work with them to decide what care may be used to treat you. You always have the right to refuse treatment.
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The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.