The time course of gadolinium concentration for the frontal, temporal, occipital, and parietal lobes. CSF concentration, cortical gray matter, and juxtacortical white matter curves are shown. Juxtacortical white matter is within 3 mm of the cortex. In each case, the CSF tracer concentration is fitted to a γ-variate distribution, while the tissue concentrations are fitted by 2-compartment pharmacokinetic models.