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How Does an MRI Work?

Posted by Johnson Memorial Health on Jan 1, 2019

Magnetic resonance imaging (MRI) is the best way for doctors to see inside your body without doing so invasively. It uses a magnetic field and radio waves to create detailed images of your organs, tissues, and skeletal system.

MRI machines are large and they can be intimidating, especially if you've never had one of these tests before. But we want to help put your anxiety to rest because you have nothing to fear. If you have been scheduled for an MRI exam, you might be curious about what you can expect and how it works.

What to expect

As you prepare for your MRI, you will be asked to change into a gown and remove any jewelry, glasses, watches, hearing aids, underwire bras (essentially anything with metal that might skew your results). Be sure to notify the technologist if you have metal in your body that cannot be removed, such as shrapnel or cochlear implants.

The MRI machine looks like a tube that is open on both ends. You will lie down on a table that slides into the opening, and you will be asked to hold very still so the technician can get clear images. There are no moving parts around you, and the procedure is painless.

During the MRI scan, you’ll hear repetitive tapping, thumping and other noises. You may be provided with earplugs or headphones in some cases. You will be able to talk through a microphone to the technician running the test throughout the procedure. If you are worried about feeling claustrophobic in the machine, your doctor may be able to give you a sedative before your procedure.

How it works

The MRI machine creates a strong magnetic field around you, which is why you have to remove anything metal. The magnetic field causes most of the atoms in your body to line up. Some atoms don’t line up, and when radio waves are applied these extra atoms go back to their normal position causing energy. This energy sends a signal to the computer which converts the signal into an image.

In some cases, a contrast material that helps enhance image details, may be injected through an IV into a vein in your hand or arm.

Why it's done

MRIs produce high­quality images that help diagnose a variety of problems. You might have an MRI of your:

  • Brain and spinal cord to diagnose tumors, stroke, spinal cord injuries, MS, aneurysms
  • Heart and blood vessels to assess the size and function of the heart chambers, damage caused by a heart attack or heart disease, inflammation or blockages in blood vessels
  • Bones and joints to evaluate arthritis, bone infections, tumors of the bones and soft tissues, disk abnormalities
  • Breasts to detect breast cancer in women who have dense breast tissue or are considered high risk
  • Internal organs to check for tumors or abnormalities in the liver, kidneys, spleen, pancreas, ovaries, prostate
After your MRI is finished, a radiologist will analyze the images from your scan and report the findings to your doctor, who will then follow up with you.

Overall, MRIs are painless and helpful in diagnosing medical conditions. If you have one in your future, you can rest easy knowing that you are in good hands with Johnson Memorial Health

Topics: MRI