[en] The tracer kinetics of 4-Fluoro(₁₈F)-, 4-Bromo(₈₂Br)- and 4-Iodo(₁₂₅I)-antipyrine and ₁₅O-water were compared in a cat or baboon animal model. First-pass cerebral extraction and clearance with alterations in PaCO² were measured for whole brain. The Renkin/Crone model was used to evaluate brain capillary permeability-surface area product for 4-₁₈FAP in cats. Positron-emission-tomographic measurements required development of an instrument and technique for control of the arterial concentration of the radiotracer as a ramp function, so that tracer concentration changes due to radioactive decay or altered physiological processes could be accurately described with PET. Pharmacokinetic and tissue-distribution studies in cats were used to determine dosimetry for 4-₁₈FAP. 4-Bromoantipyrine labeled with ₇₈Br (t = 6.5 m) is suggested as a tracer for determination of rCBF with PET