During the last decade, neuroimaging has advanced elegantly in the medical and research arenas. Positron emission tomography (PET), with its superior sensitivity and spatial resolution, appears uniquely suited to take the lead in this promising fie ld of functional and molecular imaging. Advances in quantification of brain function (blood flow, metabolism and receptor characteristics) with PET rely on two improvements: (1) hardware improvements to enhance spatial resolution and sensitivity, and addition of components to correct for physical degrading factors; and (2) software improvements to attain better image quality and achieve more accurate quantification of relevant parameters. The latter constitutes the objective of the present work.