The sentinel clot sign is a useful CT finding for the evaluation of probable anatomic sites of haemorrhage.
On CT, acute clotted haemorrhage typically has high attenuation (45 to 80 HU), whereas surrounding areas of acute nonclotted haemorrhage or more chronic haemorrhage have either lower attenuation (25 to 45 HU) or fluid attenuation (0 to 20 HU).
This is the basis for the sentinel clot sign, areas of higher attenuation are likely to represent more acute clotted haemorrhage, and are therefore more likely to indicate the anatomic sites of haemorrhage.
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