The intact blood brain barrier prevents that contrast agents penetrate in the normal brain tissue. If the blood brain barrier is damaged by a malignant tumor, the contrast medium can accumulate within the interstitial tumor tissue due to the alterations in the blood brain barrier permeability. Adjacent normal brain tissue does not contain the contrast agent.

Ischemia refers to a lack of adequate blood flow to an organ, such as the heart or the brain, which may be the result of a blood clot, blood vessel constriction or a hemorrhage.

See also Regional Cerebral Blood Flow, Blood Brain Barrier, Cerebral Blood Pool Imaging and Hematoma.