-When performing a CT brain perfusion exam, it is common to first do a non-contrast head, a CTA of the head, and then perfusion imaging.
-Brain perfusion evaluates blood flow in and out of the brain tissue. This exam is performed typically as part of a stroke protocol.
The goal of the exam is to determine infarcted brain tissue from potentially viable brain tissue.
-There are several key measurements that are taken during this exam:
Cerebral blood volume
The quantity of blood contained within 100g of brain tissue.
Cerebral blood flow
The quantity of blood that moves within 100g of brain tissue in a min ute.
Mean transit time
The average time it takes for blood to pass through a given area of brain tissue.
-Typical protocols require at least 50mL of contrast media to be injected at a rate of 5-7mL/second.
-Imaging takes place over the specified area of the brain for up to 60 seconds in order to completely image contrast moving through the brain.
-In order to be able to properly calculate the measurements listed above, ROI measurements must be placed on an artery and venous outflow within brain.
-With this, the computer will calculate the measurements during post processing
– Patient radiation dose is very high during this scan due to the continuous scanning, it is crucial that only the area of interest is imaged.
-Xenon (Xe) gas (per department protocol)
-Stroke, vasospasm, cerebrovascular reserve detection, can be used with temporary balloon occlusion.
-The area of brain tissue of interest
– Soft tissue