Susceptibility artifact
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
A dark, distorted patch on an MRI caused by metal or by a boundary between air and tissue — a dental filling, a surgical clip, a joint replacement. The area it covers cannot be assessed, which is why the report names it.
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Where you'll see this
MRI findings, particularly of the spine, head and joints after surgery.
Your report may word it “Metallic artifact”, “Blooming artifact” or “Susceptibility effect”. These mean the same thing.
Questions worth asking your doctor
- Was any part of the scan unreadable because of this?
- Does it need to be repeated, and if so how soon?
- Could this have hidden something, or only made the pictures look odd?
How often does this turn up?
Susceptibility artefact is common on MRI and is entirely a property of the physics rather than of the patient. It happens where materials that disturb the magnetic field sit next to tissue — metal above all, but also the boundaries between air and tissue. The result is a local area of distortion or signal loss, often larger than the object causing it.
Does it mean something is wrong?
It is a limitation, not a finding, and the important question is what it obscured. Metal from surgery, dental work, or a fragment produces a blank or distorted zone, and anything inside that zone cannot be assessed. A report noting susceptibility artefact near a previously operated area is telling the referring doctor that the region was not readable, which is different from saying it was normal. On some brain sequences the same effect is used deliberately, because it makes small deposits of blood or calcium show up that would otherwise be invisible.
What to do with it
Where the artefact did not sit over anything important, nothing follows. Where it obscured the area in question, the options are a modified MRI protocol designed to reduce metal artefact, or a different test — CT is much less affected by metal, which is often why it is used after orthopaedic surgery. Telling the department about implants beforehand lets them plan the protocol rather than discover the problem afterwards.
Frequently asked questions
- Is susceptibility artefact caused by something in my body?
- Usually yes, and usually something you know about: surgical metal, dental work, a joint replacement, or occasionally a retained fragment. Air–tissue boundaries such as the sinuses produce it too, which is why it is common at the base of the brain.
- Does metal make an MRI useless?
- Not usually. The distortion is local, so the rest of the study reads normally, and specific protocols exist to reduce metal artefact when the area of interest is close to an implant. It becomes a real problem only when the artefact sits exactly over what needs to be seen.
- Is it ever useful?
- Yes. Some brain sequences are deliberately built to be sensitive to it, because blood products and calcium disturb the field in a characteristic way. On those sequences the artefact is the signal — it reveals small old bleeds that other sequences miss entirely.
Picture problems, not body problems
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