Hyperdense on CT Appears White
Hyperdense structures on CT imaging appear white (bright), representing areas of increased attenuation compared to surrounding tissues. 1
Understanding CT Density Terminology
- Hyperdense = white/bright appearance on CT images, with attenuation values typically measured in Hounsfield Units (HU) 1
- Hypodense = black/dark appearance on CT images, representing lower attenuation 2
- Isodense = similar gray appearance to surrounding reference tissue 2
Clinical Examples of Hyperdense Structures
Acute Hemorrhage
- Acute blood appears as homogeneous hyperdensity (white) that is brighter than surrounding brain tissue, with attenuation values typically ranging from 50-90 HU 1
- The hyperdense middle cerebral artery (MCA) sign represents acute thrombus appearing as increased density (white) within the vessel 2
- Acutely thrombosed cerebral veins and sinuses appear as homogeneous hyperdensity (white), best visualized when CT slices are perpendicular to the vessel 3, 1
Other Hyperdense Lesions
- Hypercellular brain tumors (malignant lymphomas, germinomas, medulloblastomas) show homogeneous hyperdensity (white appearance) on CT images 4
- Calcifications within tumors or other structures appear hyperdense (white) 4
- Metal foreign bodies are radiodense and appear hyperdense (white) on CT 5
Evolution of Hemorrhage Density Over Time
- Acute phase (hours to days): High attenuation/hyperdensity (white) due to clot formation and retraction 1
- Subacute phase (days to weeks): Mixed attenuation as clot begins to lyse; may become isodense (gray) to brain tissue 1
- Chronic phase (weeks to months): Low attenuation/hypodensity (dark) as tissue breakdown occurs and hemosiderin deposits form 1
Common Clinical Pitfall
The key error is confusing terminology: When radiologists describe something as "hyperdense," they are referring to the white/bright appearance on CT, not the dark appearance. This is the opposite of what some clinicians might intuitively expect from the prefix "hyper-" 2, 1