The crescent sign refers to the high signal crescent seen in the wall of a vessel when dissected. This may be seen both on T1 or T2 sequences depending on the age of the blood (see ageing blood on MRI). It is classically referred to in internal carotid artery dissection.
It should not be confused with other radiological crescents, including:
- calyceal crescent sign
- air crescent sign
- crescent in a doughnut sign
- crescent sign of femoral avascular necrosis