In CT imaging, the Hounsfield unit (HU) value of fresh blood (acute hematoma) on unenhanced CT is approximately:

• A +0 to +20 HU (isodense with brain)
• B +150 to +300 HU (dense like cortical bone)
• C -10 to +10 HU (near-water density)
• D +55 to +80 HU (hyperdense relative to brain) ✓

Explanation

Acute (fresh) blood on unenhanced CT appears hyperdense with HU values of approximately +55 to +80, due to the high protein content of clotted blood (specifically globin in hemoglobin). This hyperdensity is the basis for identifying acute intracranial hemorrhage on plain CT. As the hematoma evolves, it becomes isodense (subacute, 1-3 weeks) and then hypodense (chronic, >3 weeks) as proteins are lysed. In anemic patients (Hb <10 g/dL), acute blood may appear isodense or hypodense even acutely. Cortical bone is +700 to +1000 HU; air is -1000 HU; fat is -50 to -100 HU.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.