What Is an MRI and How Does It Work?

Doctor and patient using Magnetic Resonance Imaging (MRI) scanner
Getty Images/Monty Rakusen

Why You Might Have an MRI:

Unlike an X-ray, an MRI can provide clear pictures of soft-tissue structures. An MRI can detect soft tissue and nerve damage, and can show differences between healthy and unhealthy tissues. Your doctor may use an MRI if he suspects vertebral disc problems, nerve damage or even to get a closer look at joint structures.

How an MRI Works:

MRI stands for magnetic resonance imaging, because an MRI uses strong magnets to scan your body and create an image.

When you have an MRI, you lie down on a table that moves into the scanner. Traditional scanners were cylindrical tubes that often struck fear into the hearts of the claustrophobic. Today, however, technological advances have provided us with MRIs that are more open and less restrictive.

Safety and Your MRI:

Before you have an MRI, let your doctor know if you have a pacemaker, any type of metal implant, or tattoos. Certain types of implants such as pain pumps or defibrillators may also be affected by the magnet. You will also need to remove any jewelry, pain-relief patches (which sometimes contain foil), hearing aids or hair clips. And if you are pregnant or suspect you may be pregnant, inform your doctor before you arrive for your scan.

What to Expect During Your MRI:

Once you are inside the MRI machine, you will need to lie still and occasionally may be asked to hold your breath for a few seconds at a time.

The machine often makes loud thumping noises as it scans, but it won’t hurt you. You can expect your exam to be over within 45 minutes unless your doctor is having more than the usual amount of scans taken. Your MRI tech will let you know ahead of time how long you will be in the machine.


International Society for Magnetic Resonance in Medicine.

Magnetic Resonance Imaging Information for Patients. http://www.ismrm.org/public/