Magnetic Resonance Imaging (MRI): About This Test

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Magnetic resonance imaging (MRI) is a test that uses a magnetic field and pulses of radio wave energy to make pictures of organs and structures inside the body. When you have an MRI, you lie on a table and your body is moved into the MRI machine, where an image is taken of the area of the body being studied.

Why is this test done?

You may have an MRI for many reasons. This test can find problems such as tumours, bleeding, injury, blood vessel disease, and infection. An MRI also may provide more information about a problem seen on an X-ray, ultrasound scan, CT scan, or nuclear medicine examination.

How can you prepare for the test?

Talk to your doctor about all your health conditions before the test. For example, tell your doctor if:

  • You are allergic to any medicines.
  • You are or might be pregnant.
  • You have a pacemaker, an artificial limb, any metal pins or metal parts in your body, metal heart valves, metal clips in your brain, metal implants in your ears, or any other implanted or prosthetic medical device.
  • You have an intrauterine device (IUD) in place.
  • You get nervous in confined spaces. You may need medicine to help you relax.
  • You wear any patches that contain medicine.
  • You have kidney disease.

What happens before the test?

  • You will remove all metal objects from your body. These include hearing aids, dentures, jewellery, watches, and hairpins.
  • You will take off all or most of your clothes and then change into a gown.
  • If you do leave some clothes on, make sure you take everything out of your pockets.
  • You may have contrast materials (dye) put into your arm through a tube called an IV. Contrast material helps doctors see specific organs, blood vessels, and most tumours.

What happens during the test?

  • You will lie on your back on a table that is part of the MRI scanner.
  • The table will slide into the space that contains the magnet.
  • Inside the scanner you will hear a fan and feel air moving. You may hear tapping, thumping, or snapping noises. You may be given earplugs or headphones to reduce the noise.
  • You will be asked to hold still during the scan. You may be asked to hold your breath for short periods.
  • You may be alone in the scanning room, but a technologist will be watching you through a window and talking with you during the test.

What else should you know about the test?

  • An MRI does not hurt.
  • If a dye is used, you may feel a quick sting or pinch and some coolness when the IV is started. The dye may give you a metallic taste in your mouth. Some people feel sick to their stomach or get a headache.
  • If you breastfeed and are concerned about whether the dye used in this test is safe, talk to your doctor. Most experts believe that very little dye passes into breast milk and even less is passed on to the baby. But if you prefer, you can store some of your breast milk ahead of time and use it for a day or two after the test.
  • You may feel warmth in the area being examined. This is normal.

How long does the test take?

  • The test usually takes 30 to 60 minutes but can take as long as 2 hours.

What happens after the test?

  • You will probably be able to go home right away, depending on the reason for the test.

Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor or nurse call line if you are having problems. It's also a good idea to keep a list of the medicines you take. Ask your doctor when you can expect to have your test results.

Where can you learn more?

Go to https://www.healthwise.net/patientEd

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