How can T1-weighted perfusion techniques be used to evaluate brain tumors?
There are two reasons that gadolinium contrast enhancement can be seen in a tissue. First, the tissue may contain a large number of blood vessels. Because initially intravenous gadolinium is distributed in these blood vessels, tissues containing a large number of vessels will densely enhance. In normal brain, the existence of a blood-brain barrier does not allow gadolinium to leak out of the brain and into the interstitial tissues (the extravascular extracellular space) around blood vessels. In many brain tumors, blood vessels are abnormally leaky, and because of this increasing contrast enhancement can be seen over time. T1-weighted perfusion imaging is a technique used to rapidly obtain (every 5 to 7 seconds) a series of images of the brain. Using this technique, we can start to determine whether the contrast enhancement we are seeing at a particular location in the brain is due to increased blood volume in vessels, due to increased leakiness (or permeability) of the cerebral blood v
