On CT, ischemic tissue is typically described as which of the following?

On CT, ischemic tissue is typically described as which of the following?

• A. Hyperdense (brighter)
• B. Isointense
• C. Hypodense (darker)
• D. Hyperdense rim

Answer: (C)

Ischemia causes cytotoxic edema, which increases water content in the affected brain tissue and lowers its X‑ray attenuation on CT. That swelling makes the tissue look darker than the surrounding normal brain, so ischemic areas are described as hypodense. Early on, CT can be normal, but as edema develops, the hypodensity becomes more evident. By contrast, acute hemorrhage appears hyperdense (bright) because of fresh blood, and a hyperdense rim or other hyperdense findings point to different processes rather than simple ischemia.

Ischemia causes cytotoxic edema, which increases water content in the affected brain tissue and lowers its X‑ray attenuation on CT. That swelling makes the tissue look darker than the surrounding normal brain, so ischemic areas are described as hypodense. Early on, CT can be normal, but as edema develops, the hypodensity becomes more evident. By contrast, acute hemorrhage appears hyperdense (bright) because of fresh blood, and a hyperdense rim or other hyperdense findings point to different processes rather than simple ischemia.