MRI Scan (Magnetic Resonance Imaging) Definition

A magnetic resonance imaging scan (MRI) produces an image of the body using a strong magnet and radio waves. Unlike other diagnostic imaging tests, an MRI scan can show the muscles, ligaments and tendons, nerve roots, and cartilage with precision. Additionally, an MRI does not have the radiation risks associated with other tests such as x-ray and CT scans.

How an MRI Works

When exposed to the magnet in an MRI machine, the hydrogen protons in the body align along the magnetic field to face the same direction. (Because the human body is mostly water, the hydrogen protons that respond to the magnetic field are found in all types of tissue.) A radio wave is then sent through the body, flipping the protons at either 90 or 180 degrees away from the magnetic field.

When this radio wave is turned off, the protons gradually realign to the MRI’s magnetic field, releasing energy in the process. Based on the amount of energy released and the time it takes protons to realign, the MRI can differentiate between types of tissues to create a detailed image.

When an MRI Is Considered for the Spine

MRI scans are used to confirm a suspected diagnosis of spinal conditions, such as a herniated disc or pinched nerve. They are also commonly used to visualize the spine in order to plan for surgery. An MRI scan is generally considered to be the single best imaging study of the spine to help plan treatment for back pain. Due to the strength of the magnet, an MRI may not be recommended for patients with pacemakers. Additionally, some metallic implants such as rods, screws, or plates, may become heated or moved during an MRI.