A magnetic resonance imaging scan (MRI) is an imaging test that creates pictures of internal body structures (bones and soft tissues) with the help of magnetic fields and radio waves.The scan is often used to clarify findings from previous X-rays or CT scans, and can be combined with other imaging techniques to provide a more definitive diagnosis.


Before the procedure, you will be asked to remove any metallic devices such as hearing aids, hairpins, removable dental work or other objects that may interfere with the procedure.

The MRI machine consists of a large strong magnet and a table that moves into the opening of the scanner. During the procedure, you will be asked to lie on the table that is advanced into the scanner. The machine creates a magnetic field that causes loud noises. A radio wave antenna directs signals to the body and receives them back to create images by a computer attached to the scanner. You need to keep very still throughout the scan as movement may blur the resulting images. The entire procedure may take up to an hour to complete.

Advantages and disadvantages

The advantages of MRI include:

  • Does not use harmful ionizing radiation
  • Is noninvasive
  • Can take images of any part of the body from almost any direction and orientation
  • Produces better images of soft-tissue structures compared to other imaging techniques
  • Can differentiate between tissues based on their biochemical properties such as water, fat and iron
  • Can scan large regions of the body

The disadvantages of MRI include:

  • Certain patients who get nervous in small spaces (claustrophobic) may not be able to have an MRI.
  • Elderly or ill patients may find it difficult to cooperate, which may result in blurred images.
  • An MRI cannot be performed on patients with implanted medical devices such as aneurysm clips in the brain, heart pacemakers and cochlear (inner ear) implants.
  • The MRI is an expensive procedure.

Risks and complications

Since an MRI scan is a noninvasive test, it is a very safe procedure. Any metal or electronic devices in your body are a safety threat and you should not undergo an MRI in those circumstances. Before your MRI test, make sure you notify your doctor and the MRI technologist if you:

  • are pregnant, as the effects of magnetic fields on the baby are not yet known
  • have had any recent surgeries, such as new or removable hardware in the body.