A method is provided for estimating a parameter of physiological significance. One or more images are provided of a tissue in a subject to whom a dose of a contrast agent (CA) has been administered, using a computer equipped with image processing software, the concentration or relative concentration of the agent in a region or regions of interest in the tissue is determined, thus generating concentration data. The time-based behavior of concentrations of CA within the tissue is determined using a pharmacokinetic model that is based on a set of pharmacokinetic model parameters. Using computer code, the pharmacokinetic model is fit to the concentration data, varying one or more parameters, such that a best fit estimate of a parameter of physiological significance is provided.