Kinetic Analysis of Glucose Tracer Uptake and Metabolism by Brain in Vivo

This chapter examines the interaction between tracer glucose uptake and phosphor-ylation in brain. It derives the equations for the use of labeled deoxyglucose, fluorodeoxyglucose, or glucose itself to calculate brain glucose phosphorylation. The chapter estimates the value of the “lumped constant” as a function of the glucose phosphorylation rate, the plasma glucose concentration, the maximal transport capacity of the cerebral capillary endothelium, and the plasma flow of the brain. The driving force of the loss of tracer from a compartment is the aqueous concentration of the tracer in the compartment, if the tracer is in aqueous solution. Compartmental analysis of tracer uptake in vivo serves to measure the size of the different compartments of the tracer, that is, the relative abundance of its different states, and the magnitude of the transfer coefficient or relaxation constant of each compartment. The brain has two kinetic compartments, the vascular space and an extra-vascular space, separated by a blood-brain barrier.