Magnetic resonance imaging (MRI) is a technique using magnets, radio waves, and a computer that produces images of soft tissues in the body, like muscles and organs. Unlike some other imaging tests, this type of scan does not use radiation.

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An MRI scan is a noninvasive medical test that provides images of the soft tissues, like organs and muscles, within the body. The images are created using a magnetic field along with radio waves and a computer.

Unlike X-ray or CT scans, MRI does not use radiation. As a result, it is a safe choice for imaging – especially for people who need frequent imaging tests for chronic health concerns.

An MRI machine is big enough to fit around your entire body. Its tube-shaped magnets create a magnetic field that realigns the protons found in all the water molecules in your tissues.

Radio waves transmitted by the machine are what help create 3D images. They appear as slices, called cross-sections, and allow doctors to visualize each layer of tissue.

Open MRI

An open MRI machine has two magnets. One is above the body, while the other is below. As the name implies, the sides of the machine are open, which can help prevent feelings of claustrophobia that some people experience inside closed MRI machines.

The open design also helps with noise and can accommodate people whose height or weight makes traditional MRI machines uncomfortable.

Closed MRI

A closed MRI is the more traditional design of an MRI machine. It has a ring of magnets that go around the entire body. Unlike an open MRI, a person must undergo a closed MRI in a tube-like tunnel that is open on only one end.

Closed MRIs are associated with clearer, more detailed images. However, newer open MRI machines produce high quality images as well and can be used for many diagnostic purposes.

Your doctor may order an MRI with contrast. This means that prior to the scan, you will be given a contrast agent (sometimes called a “dye”) intravenously. This agent typically contains a metal called gadolinium.

When a contrast agent is in your body, it speeds up the proton activity and produces brighter, clearer images.

MRI is not used to diagnose things like broken bones. This is because bones do not contain much water, so the magnetic field and radio waves cannot make clear images.

Instead, MRI is used to visualize organs and other soft tissues. It can help diagnose a variety of health conditions throughout the body.

MRI of the brain and spinal cord can detect:

MRI of the cardiovascular system can evaluate:

Other uses for MRI include:

  • detecting tumors and cancer throughout the body, including breast cancer
  • identifying other issues with organs (brain, heart, lungs, digestive organs)
  • visualizing soft tissue injuries (ligaments, tendons, muscles)
  • revealing joint disease and injury

In general, you can expect your MRI to go something like this:

  1. You will arrive at your appointment, change into a cotton or paper gown, and remove any metal objects (like jewelry or watches) from your body.
  2. You will lie on the scanning table and be moved into the MRI machine. The hospital staff will be able to communicate with you through an intercom.
  3. The machine will make beeping and clicking noises. They may be quite loud — up to 120 decibels, or louder than a chainsaw. The hospital staff may provide you with earplugs or other protection from the noise.
  4. You will need to lay still for the duration of the scan. You may notice that the area of your body being scanned feels warm.
  5. The scan will last between 20 and 90 minutes. The length of time depends on what part of the body is being scanned.

There isn’t much preparation involved with getting an MRI. You may take your medications and continue eating and drinking as you usually do.

If you are having an abdominal or pelvic MRI, you may need to fast for 5 or more hours before your scan.

Young children may be given an MRI under sedation. Your doctor will provide instructions for eating, drinking, and other special considerations with regard to anesthesia.

Following your scan, you may wait to ensure the images are clear. If the radiographer needs additional images, you may need to go back into the MRI machine.

If everything looks good, you can get dressed and go home to wait for your results. MRIs are noninvasive, so there isn’t any necessary recovery time or aftercare.

Again, MRI machines do not emit radiation like X-ray or CT scans. That said, the magnets are extremely powerful in and around the machine.

It’s important to inform the hospital staff about any medical implants you have that contain metal. Likewise, you’ll need to remove any jewelry or other metal objects (steel, iron, etc.) from your body and clothing before entering the room with the machine.

Implants that may be affected include:

If you have any of these implants, a doctor can advise whether a different type of scan would be better for you than an MRI.

MRI scans are generally safe.

Experts advise that pregnant people may need to avoid scans, particularly in the first trimester when a baby’s organs are forming.

People who are experiencing kidney failure and need dialysis should speak with their doctor or healthcare professional before getting an MRI with contrast. The contrast agent gadolinium may lead to a rare and potentially fatal condition called nephrogenic systemic fibrosis.

Your images will be read by a radiologist or other doctor who is trained to interpret MRI scans. The report of that specialist’s findings will be forwarded to your doctor.

You will likely have a follow-up appointment with your doctor to discuss these results and any next steps.

An MRI scan can be a useful tool for diagnosing soft tissue injuries, tumors, and diseases. This test does not hurt or involve any recovery time. It is also safe to have done if you need multiple scans over time.

Open MRI is an option for people who have concerns about tight spaces, noise, and comfort. If you have questions about an upcoming MRI, speak with your doctor to find out more about the machines and procedures at your health center.