MRI Terminology

What It Is

MRI creates images by detecting signals from hydrogen atoms, mostly in water and fat, after they are disturbed by radio wave pulses inside a strong magnetic field. By changing the timing of these pulses, technologists produce different image types, called sequences, that highlight different tissue properties.

For example, on T1-weighted images, fat usually appears bright and fluid dark, while on T2-weighted images fluid usually appears bright. Specialized sequences can suppress fat or fluid, measure the movement of water molecules, or show blood flow.

Many MRI terms also describe the scanner hardware, the orientation of images, and the use of contrast. This guide covers common terms but cannot explain what any particular image or report means for an individual.

Common Terminology

Tesla (T)

The unit for magnetic field strength. Most clinical scanners are 1.5T or 3T.

T1-weighted

A sequence type in which fat typically looks bright and fluid looks dark; often used for anatomy and with contrast.

T2-weighted

A sequence type in which fluid typically looks bright; useful for showing swelling and many abnormalities.

FLAIR

Fluid-attenuated inversion recovery; a T2-type sequence that darkens normal fluid, often used in brain imaging.

DWI

Diffusion-weighted imaging; measures how freely water molecules move, often used when evaluating stroke.

STIR / fat suppression

Techniques that darken fat so fluid or swelling stands out more clearly.

MRA

Magnetic resonance angiography; MRI focused on blood vessels, with or without contrast.

Axial, sagittal, coronal

Slice directions: axial is horizontal (top-to-bottom slices), sagittal divides left and right, and coronal divides front and back.

Where You May See These Terms

MRI terms commonly appear in places such as:

• The technique section of a radiology report.
• The findings and impression sections of a report.
• Order forms and scheduling information, such as "MRI brain with and without contrast."
• Online patient portals that display reports and image series names.
• Discussions with clinicians, technologists, and specialists.
• Patient education materials from imaging centers.

Key Concepts

A few core ideas help make sense of MRI terminology:

• Signal: how bright or dark a tissue appears, described as hyperintense, hypointense, or isointense.
• Weighting: which tissue property a sequence emphasizes, such as T1 or T2.
• Contrast: a gadolinium-based agent that can make some tissues brighter, called enhancement.
• Orientation: images can be viewed in axial, sagittal, and coronal planes.
• Artifact: something in the image that does not reflect real anatomy, often caused by motion or metal.
• Field strength: higher-tesla scanners can produce more signal but have their own trade-offs.

Examples

Here are general examples of how these terms might appear:

• "MRI of the lumbar spine without contrast" describes the body area and indicates no contrast was used.
• "Sagittal T1 and T2, axial T2 images were obtained" lists the sequences and slice directions in the technique section.
• "Focal T2 hyperintensity" describes a small area that looks bright on T2-weighted images, without naming a cause.
• "No restricted diffusion" refers to DWI findings, a term often used in brain imaging reports.
• "Motion artifact limits evaluation" means movement during the scan reduced image quality.

Tips for Reading

General tips for reading MRI-related documents:

• Descriptive terms about brightness are not diagnoses on their own.
• The Impression section usually summarizes the most important points.
• Abbreviations can mean different things in different contexts; a medical glossary or the care team can help.
• Writing down unfamiliar terms can help when results are discussed.
• Online searches of single terms without context may cause unnecessary worry.

Getting Clarification

Clinicians and imaging staff can help explain terms. People often ask about:

• What a specific term or abbreviation means in their report.
• Why certain sequences or contrast were used.
• Whether an "artifact" affected the results and if a repeat scan is suggested.
• How a finding described in technical terms relates to their symptoms.
• Where to find reliable patient education resources about MRI.

Questions to Ask a Healthcare Professional

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

• What does this abbreviation in my report mean?
• Why were these particular sequences used?
• What is the difference between T1 and T2 images?
• Did any artifact affect the quality of the scan?
• What does "enhancement" mean in this report?
• Is there a plain-language summary of these results?

Sources

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

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

Related Guides

• TestsCommon Terms in MRI ReportsA general glossary of terms often seen in MRI reports, such as hyperintense, enhancement, and incidental finding. Educational only, not interpretation.
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• TestsMRI Contrast (Gadolinium)General information about gadolinium-based contrast agents used in MRI: why they are used, how they are given, and known safety considerations.
• Medical TermsCommon Medical AbbreviationsA plain-English guide to common medical abbreviations seen in visit notes, lab reports, prescriptions, and hospital records, such as BP, CBC, and PRN.
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