STIR
Read Your Scan Editorial Team·Last updated
Written from published radiology references and reviewed for plain language. Not written or signed by a physician, and not a diagnosis. How we write these pages →
In plain language
An MRI sequence that switches the brightness of fat off so that fluid stands out unmistakably. It is how a radiologist tells swelling inside a bone from the normal fatty marrow around it.
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Where you'll see this
The technique section of spine, joint and bone MRI reports.
Your report may word it “Short tau inversion recovery” or “Fat-suppressed T2”. These mean the same thing.
Questions worth asking your doctor
- Did this scan use the right technique to answer my question?
- Would contrast, or a different sequence, show something this one could not?
- Do I need another scan, or is this one enough?
How often does this turn up?
STIR is an MRI sequence used routinely on spine and musculoskeletal studies and named in the technique section. Like FLAIR it suppresses a signal deliberately — in this case fat, which is bright on ordinary sequences and can mask what sits next to it.
Does it mean something is wrong?
The name itself means nothing clinically. What STIR does is make fluid stand out unmistakably against a background where fat has been removed, which is why it is the sequence that reveals bone marrow oedema — the fluid inside bone that follows a fracture, a bruise, inflammation or wear at a joint surface. Findings frequently invisible on other sequences appear obviously on STIR, which is why a spine or joint protocol without it would be considered incomplete.
What to do with it
Nothing follows from the sequence being run. Where it found something, the finding is described separately — most often marrow oedema, which is a description of fluid rather than a diagnosis and has a long list of ordinary causes. A report naming STIR in the technique and describing nothing on it means the sequence looked and found nothing, which is useful information rather than an absence.
Frequently asked questions
- What does STIR show that other sequences do not?
- Fluid hidden against fat. By suppressing the fat signal it makes bone marrow oedema and soft tissue swelling obvious, and those are frequently invisible or subtle on standard sequences.
- What is bone marrow oedema?
- Fluid within the bone itself, seen brightly on STIR. It follows fractures, bruising, inflammation and wear at a joint surface. It is a description rather than a diagnosis, and its meaning depends on the context and the clinical picture.
- Is STIR the same as FLAIR?
- They work on a similar principle but suppress different things. STIR suppresses fat and is used mainly on the spine and joints; FLAIR suppresses free fluid and is used mainly on the brain.
How the scan was taken
Where this word comes up
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