concentric ring sign

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The concentric ring sign is a pathognomonic sign for a subacute hematoma on MRI. A subacute hematoma may show three characteristic layers of signal intensity:

  • a thin peripheral rim of low signal intensity on all pulse sequences corresponding to hemosiderin
  • an inner peripheral high-signal intensity zone on T1-weighted imaging due to methemoglobin
  • the central component of the hematoma has variable signal intensity based on the amounts of seroma, deoxyhemoglobin, and methemoglobin present

See also