What Is an MRI?

Types of MRI Machines

• Wide-bore MRI, which is a slightly wider version of the traditional machine, making it more suitable for larger bodies or those with claustrophobia
• High-field open MRI, which resembles hamburger buns rather than the traditional MRI machine’s “pig in a blanket” design, allowing the patient more visibility and movement
• Open upright MRI, in which you can stand or sit between the machine’s two parts (best for people who have trouble lying down or staying still for a long time)

Types of MRI Scans

Some common specific or specialized types of MRI include:

• Functional MRI (fMRI) Measures and maps brain activity by detecting changes in blood flow
• Diffusion MRI (dMRI) and Diffusion Tensor Imaging (DTI) Measures the movement of water molecules within tissues and is especially useful for imaging white matter tracts in the brain

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• Breast MRI Provides detailed images of breast tissue to detect and evaluate breast diseases and reveal abnormalities other imaging techniques cannot (though it doesn’t replace, and is often used along with, mammography and ultrasound)
• Cardiac (or cardiovascular) MRI Images the heart, valves, and blood vessels to detect abnormalities and assess how well your heart is functioning
• Magnetic Resonance Angiography (MRA) Focuses on blood vessels and helps identify issues like aneurysms or blockages
• Magnetic Resonance Enterography Images the intestines to diagnose and monitor issues like inflammatory bowel disease (IBD)

MRI is incredibly versatile and used to investigate, diagnose, or monitor a wide range of medical issues throughout the body, such as:

• Neurological issues including brain tumors, conditions affecting the eyes or ears, multiple sclerosis, stroke, and spinal cord injuries
• Musculoskeletal issues including torn ligaments, cartilage damage, herniated discs, bone infections, and joint disease
• Cardiovascular abnormalities including narrowed or blocked blood vessels, thickened heart walls, and heart attack impacts

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• Gastrointestinal diseases including IBD and bowel tumors

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• Tumors and other irregularities of other organs, including the liver, kidneys, uterus, and prostate

MRI scans work by combining strong magnetic fields and radio waves. When subjected to the MRI’s powerful magnetic field, the protons in your body’s molecules align in the same direction like tiny magnets. When hit with bursts of radio waves from the machine, these protons fall out of alignment; they line back up when the radio waves are turned off, releasing radio waves in the process that the MRI analyzes.

Preparation for an MRI is generally simple, but it's important.

When setting up your appointment, let your provider know if you:

• Have claustrophobia
• Are unable to lie still on your back for up to 60 minutes

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• Are pregnant
• Have allergies

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• Have severe kidney failure and require dialysis, which carries risk of a serious illness if you receive a gadolinium contrast

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• Heart pacemaker or defibrillator
• Implanted stimulators or devices, including deep brain stimulators, vagus nerve stimulators, and implanted electrodes or wires
• Metallic protheses
• Cochlear or ear implants
• Stents
• Insulin pumps
• Metallic shrapnel
• Body piercings

An MRI is painless, but it can be a strange experience. Expect:

• Loud thumping and humming noises from the MRI machine (you’ll be given earplugs or headphones to reduce the noise)
• Remaining still for up to an hour or more
• Cold from the scanning bed and air-conditioned room (you should be able to request a blanket)
• Mild warmth in the area of the body being scanned

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• Communicating with the technologist through an intercom system and having a call button to use if you have any problems or concerns
• An IV line if you are receiving a contrast agent

• Injury from small projectile metals if they are not removed from the room when the MRI is activated
• Burns from transdermal patches like nicotine patches if not removed
• Burns from tattoos, permanent cosmetic products, and synthetic clothing that contain metallic components
• Psychological distress from being in a confined space for a prolonged time
• Hearing damage if earplugs or headset are not used properly

Though rare, side effects and complications of MRI include:

• Nephrogenic systemic fibrosis, a rare but serious condition linked to gadolinium contrast in people with severe kidney dysfunction
• Allergic reaction to the contrast, which may cause a rash, nausea, headache, and pain at the injection site

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• Headache, fatigue, irritability, and high blood pressure from the strong magnetic field

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• Temporary hearing loss or tinnitus (ringing in the ears)

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• Anxiety

• An MRI is a safe, noninvasive imaging test that uses magnetic fields and radio waves to create detailed pictures of the body’s internal structures.
• It is used to diagnose and monitor a wide range of health issues throughout the body, including stroke, soft tissue damage, narrowed or blocked blood vessels, and tumors.
• The procedure typically takes less than an hour and may require you to lie still inside a cylindrical machine that can feel noisy and confined (other, more open MRI machines may be available).
• Side effects and complications are rare, and the test requires no follow-up care.