External measurement of regional cerebral blood flow in man by common carotid arterial injection of radioactive krypton-85 saline solution.

1) External recording of cerebral clearance was performed after Kr85 saline solution injection into the common carotid artery. Clearance curve thus obtained was divided into 3 exponentials. The 3rd phase represents mainly clearance of the area perfused with external carotid artery and the rest of the curve after subtraction of the 3rd phase can be treated in the similar way to that of reported by Lassen et al. 2) The method was applied on the 43 cases. Cerebral blood flow was decreased in cases with cerebrovascular diseases. This is proved to be the result of decrease of both blood flow and relative weight of grey matter. Blood flow of slow phase (representing white matter) is insignificantly decreased. Whereas blood flow of grey and white matter shows increase during 4% carbon dioxide inhalation. 3) Advantage of this simplified method was discussed.