A method for detecting the blood flow in animals, particularly in the brain, is provided wherein a detectable amount of a novel radioactive compound of the formula I is administered to one animal: <IMAGE> (I) wherein R1 and R2 are independently alkyl of 1 to 6 carbon atoms or benzyl; R3 is alkyl of 1 to 6 carbon atoms, benzyl, cyclopropylalkyl of 4 to 6 carbon atoms, or cyanoalkyl of 2 to 6 carbon atoms; R4 is hydrogen, benzyl or alkyl of 1 to 6 carbon atoms; with the provisos that R4 is not isopropyl and when R4 is methyl, R3 is not benzyl; and X is a radioactive halogen.
Rapid brain scanning radiopharmaceutical