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doctors looking at MRI scan

What is an MRI (magnetic resonance imaging)?

Magnetic Resonance Imaging (MRI) is a safe diagnostic imaging technique which uses a magnetic field and radio waves to produce pictures of your body. X-rays are not used. The MRI scanner sends out radio signals to the hydrogen atoms found in the water molecules in your body. The hydrogen atoms then send back radio signals which are recorded by the MRI scanner. A computer then compiles this information and produces cross-sectional images of your body, very much like slices from a loaf of bread. Doctors are able to see many of your body's internal structures better on MRI than with other techniques. The procedure provides excellent images of soft tissue structures like the brain, spinal cord, muscle and certain internal organs, as well as joint anatomy. 

How to prepare for an MRI

When scheduling your appointment, you will be asked if you have any metal objects in your body, since the metal may interfere with the magnetic field. MRI cannot be performed on people with:

  • Cardiac pacemakers or defibrillators
  • Neurostimulators
  • Some brain aneurysm clips
  • Metal fragments in the eye (plain film X-rays will be done of the orbits if there is prior history of a metallic foreign body)

If you are having a scan of the head, we recommend that you do not wear heavy eye makeup as the metal particles in the makeup may interfere with your exam. You may follow your normal diet and take any medications in your usual fashion. As with any medical procedure, be sure to inform your physician or the technologist if there is any possibility that you are pregnant or if you have a history of allergies.

What you can expect during your MRI

Before the MRI

When you arrive, you may need to change into a gown or pajamas and will be asked to remove all metal objects before going into the scanning room. You may wish to leave your jewelry and valuables at home or we have secured lockers where you can store these items. The technologist will help position you on a padded table in front of the magnet. Depending on the type of exam you are having, you will then enter the scanner head first or feet first. The technologist will begin by moving the table into the magnet.

During the MRI

During the exam, the technologist will be inside the control room watching you at all times. An intercom system allows you to talk freely with the technologist. As the exam starts, you may hear a variety of thumping noises, similar to light hammering. Some people find this noise relaxing, but we also have earplugs and stereo headsets available for your comfort. While the scanner is working, you may feel a slight vibration; but other than this vibration, you should not experience any other sensations. The procedure takes between 30 and 60 minutes depending on the exam and the scanner used.

Get scheduled

With locations across Northern California, a Dignity Health Advanced Imaging location is just right around the corner. Call our centralized scheduling department to schedule an appointment today.


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