The Cerebral Blood Flow in Man Determined by the Use of Radioactive Krypton

Summary. A method for the determination of cerebral blood flow in man using the radioactive isotope krypton 85 is described. The standard deviation of cerebal blood flow was esperimentally determined to he 1.6 cc/100 g/min. Repeateil determinations of cerebral oxygen consumption at an interval of 30 minutes showed insignificant variations in 10 normal subjects and significant variations in 1 subject with slight hypertension. Repeat ect deteminations of cerebral oxygen consumption at all interval of 3 to 8 days showed significant variations in 3 out of 4 normal individuals and in none out of 5 arteriosclerotic individuals. In a group of 10 normal males and 10 normal females, mean age 38 years, the mean value for cerebral blood flow was 52 (S. D. = 8.6) cc/100 g/min., the mean value for cerebral oxygen consumption was 3.4 (S. D. = 0.58) cc/100 g/min., and the mean value for cerebral vascular resistance was 1.8 (S. D. = 0.38) mm Hg/cc/100 g/min. The method described is compared to the nitrous oxide method as described by K ety and S chmidt . The results of the two methods agree, but the krypton 85 method is more accurate, secures more normal physiological conditions during the examination. and demands less manual work.