Regional Blood Flow of the Cerebral Cortex Determined by Krypton85

Abstract A new method for determining regional blood flow in tissue by means of the inert radioactive gas Krypton 85 is presented. The method has been applied on the exposed cerebral cortex of anesthetized rabbits, cats and dogs. The radioisotope Kr 85 , a weak beta emitter, was dissolved in saline which was then injected into the carotid artery of the hemisphere to be studied. The rapid uptake and slower clearance of the isotope was recorded from a small area of the exposed cortical surface, about 1 mm in depth. The theory of analyzing the clearance curves and of calculating the average regional cortical blood flow in ml per gram per minute is described. The method requires constant blood flow in the tissue during the measurement (about 5 min). It may, however, to some extent be used for studies of acute changes in perfusion. It is also possible to use it in a continuous fashion. It has been possible to confirm and to study in quantitative terms the correlation between arterial carbon dioxide tension or cortical functional activity, and the regional cortical blood flow. The method is simple to use and permits repeated measurements in the same experiment with minimal interference with the functional activity of the brain. The method may readily be adapted for studies in man