Pharmacokinetic Models and Positron Emission Tomography: Studies of Physiologic and Pathophysiologic Conditions

Because of the structurally and functionally heterogeneous nature of the brain, it is necessary to measure changes in physiologic and biochemical parameters in the human brain on a regional basis. Such information is important in furthering our understanding of the normal function of the brain and the derangements that occur in various pathologic conditions. The development of the Kety-Schmidt technique for the quantitative measurement of cerebral blood flow in man, made it possible to determine the average rates of glucose and oxygen utilization and blood flow in the brain as a whole (1). Using these same principles a method to measure hemispheric changes in these parameters has been developed (2). Regional methods for the determination of cerebral blood flow using diffusable tracers have also been developed (3–5). These methods, however, do not provide 3-dimensional resolution by which it is possible to determine the physiologic and metabolic parameters in specific structural and functional subunits of the brain. With the development of the 18F-fluorodeoxyglucose technique it became possible to do this in terms of glucose metabolism in the human brain (6).