Yin Yang Sign

A term referring to the morphology of a blood vessel with a pseudoaneurysm (communicating haematoma) or partially thrombosed aneurysm, when transversely ‘sliced’ by ultrasound or contrast CT. The yin yang sign may occur anywhere, but appears to be more common in abdominal and cerebral vessels. It is due to differences in attenuation; the lower attenuation half corresponds to the (swirling) contrast and the higher attenuation half to the round or oval mural thrombus
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