Tests guide

MRI Scan

An MRI (magnetic resonance imaging) scan is an imaging test that uses a strong magnet and radio waves to create detailed pictures of the inside of the body. It does not use ionizing radiation (x-rays).

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At a Glance

  • MRI uses a powerful magnetic field, radio waves, and a computer to make detailed images.
  • It is especially good at showing soft tissues such as the brain, spinal cord, muscles, ligaments, and many organs.
  • MRI does not use x-rays or other ionizing radiation.
  • A typical scan takes roughly 15 to 60 minutes or more, depending on the body part and the images needed.
  • Metal and electronic devices in or on the body are an important safety consideration and are screened for before the scan.
  • A radiologist reviews the images and writes a report for the ordering clinician.

What It Is

During an MRI, a person lies on a table that slides into a large machine containing a strong magnet. The magnet temporarily lines up hydrogen atoms in the body, and radio wave pulses briefly disturb that alignment. As the atoms return to their resting state, they give off signals that a computer turns into cross-sectional images.

Different tissues give off different signals, which is why MRI can show contrast between, for example, fat, water, muscle, and nerve tissue. The images can be viewed as thin slices in several directions and sometimes reconstructed in three dimensions.

Some MRI exams use a contrast agent, usually a gadolinium-based material given through a vein, to make certain tissues or blood vessels show up more clearly. Many MRI exams are done without contrast.

Common Terminology

Magnetic field
The invisible force produced by the MRI magnet. MRI magnet strength is measured in tesla (T); common clinical scanners are 1.5T or 3T.
Radiologist
A physician who specializes in performing and interpreting medical imaging tests such as MRI, CT, and x-ray.
MRI technologist
A trained professional who positions the person, operates the scanner, and communicates with them during the exam.
Coil
A device placed around or near the body part being scanned that helps send and receive radio signals to improve image quality.
Sequence
One set of images acquired with specific scanner settings. An MRI exam usually includes several sequences.
Contrast agent
A substance, usually gadolinium-based for MRI, given to help certain tissues or blood vessels stand out on the images.

Why the Test Is Done

Clinicians may order an MRI for many different reasons. Common general uses include:

  • Looking at the brain and spinal cord, for example when evaluating headaches, seizures, nerve symptoms, or suspected stroke.
  • Evaluating joints, ligaments, tendons, cartilage, and muscles, such as in the knee, shoulder, or hip.
  • Examining organs in the abdomen and pelvis, such as the liver, pancreas, kidneys, uterus, and prostate.
  • Studying the heart and blood vessels with specialized cardiac MRI or MR angiography (MRA).
  • Characterizing a lump, mass, or abnormal finding seen on another imaging test.
  • Monitoring a known condition over time to look for changes.

What the Results Generally Describe

MRI results come as a written report from a radiologist. In general terms, a report may describe:

  • The type of exam, the body part scanned, and whether contrast was used.
  • The size, shape, location, and signal characteristics of structures and any areas that look different from expected.
  • Comparison with earlier imaging, when available, noting whether findings appear new, stable, or changed.
  • An "Impression" or "Conclusion" section that summarizes the most important findings.
  • Results are interpreted by the radiologist and the ordering clinician in the context of the person's history; there is no single "normal range" for an MRI.

How the Test Is Done

Although details vary by facility and body part, an MRI generally follows these steps:

  • The person completes a safety screening form about implants, devices, metal fragments, pregnancy, allergies, and kidney health.
  • Metal items such as jewelry, watches, hairpins, and cards with magnetic strips are removed, and a gown may be provided.
  • The person lies on a padded table, and a coil is placed over or around the area being imaged.
  • The table moves into the scanner, which makes loud knocking or buzzing sounds; earplugs or headphones are typically offered.
  • Staying still is important because movement can blur the images; the technologist can speak with the person through an intercom.
  • If contrast is needed, it is usually given through an IV partway through the exam.

Preparation and What to Expect

Preparation instructions come from the imaging facility and vary by exam. In general:

  • Some exams, especially of the abdomen, may involve fasting for a few hours beforehand, while many require no special preparation.
  • People with implanted devices are usually asked to bring device information cards so staff can check MRI safety.
  • People who feel anxious in enclosed spaces may discuss options with their care team, such as open or wide-bore scanners or medication for relaxation.
  • Most people can resume normal activities right after the scan unless they received sedation.
  • The radiologist's report is usually sent to the ordering clinician, who shares the results.

When Results Are Discussed With a Clinician

MRI results are generally reviewed with the clinician who ordered the test. Topics often discussed include:

  • What the main findings in the report mean in the context of the person's symptoms and history.
  • Whether any findings are incidental, meaning unrelated to the reason the scan was ordered.
  • Whether follow-up imaging, other tests, or a referral to a specialist is being considered.
  • How the results compare to any previous imaging.
  • Any questions about medical terms used in the report.

Questions to Ask a Healthcare Professional

General questions people often find useful to bring to an appointment:

  • Why is an MRI being recommended instead of another imaging test?
  • Will this MRI use contrast, and why?
  • How long is the scan expected to take?
  • Are there any safety concerns with my implants or devices?
  • Is any special preparation needed before this exam?
  • When and how will the results be shared?

Sources

This guide was written in plain language from the following authoritative references.

  1. MRI Scans — MedlinePlus (U.S. National Library of Medicine)
  2. Magnetic Resonance Imaging (MRI) - Body — RadiologyInfo.org (RSNA and ACR)
  3. MRI (Magnetic Resonance Imaging): Benefits and Risks — U.S. Food and Drug Administration (FDA)

Last updated October 8, 2026. FreeDoc guides are general educational information and are not a substitute for care from a qualified professional.