Assessment of regional cerebral blood flow by continuous carotid infusion of krypton-81m.

In order to obtain functional images of brain perfusion, we exploited a new concept, which is to take advantage of the short half-life of a radioactive tracer. Under continuous intracarotid infusion of a solution of Kr-81m (T1/2 = 13 sec; produced from its parent, 4.6-hr Rb-81), this tracer will never reach equilibrium within the brain because of the rapid radioactive decay. Its distribution will therefore reflect regional arrival of the nuclide, indicating regional cerebral blood flow rather than volume. During continuous infusion of Kr-81m, perfusion images can be obtained by simply collecting counts with a gamma camera and recording on Polaroid film. The procedure is readily repeatable in order to get images in multiple veiws or to follow minute-by-minute changes of cerebral perfusion.