1. An apparatus for determining partition coefficients and blood flow rates in a tissue region of interest of a subject, the apparatus comprising: an enhancement agent means for introducing an enhancement agent into a patient's blood; a means for providing an indication of a concentration of the enhancement agent within the blood over time; an absorption curve projecting means for projecting an absorption curve designation indicative of one of a plurality of preselected absorption curves representing enhancement agent absorption by the blood from the provided indications of the enhancement agent concentration in the blood over time; a look-up table means preprogrammed with blood flow and partition coefficient values which have a previously calculated relationship to preselected sampling intervals, image pixel values, and blood enhancement agent absorption curve designations, the look-up table means being addressable at least by the image pixel values and the absorption curve designations to retrieve the corresponding precalculated blood flow and partition coefficient values; an imaging means for generating electronic image representations of at least the tissue region of interest, each image representation including a plurality of image pixel values, each pixel value being indicative of enhancement agent concentration in a corresponding subregion of the tissue region of interest; an image representation storing means for storing a plurality of image representations of the selected region of interest, the stored image representations being generated at selected sampling intervals; and, a look-up table access means for selectively accessing the look-up table means with at least the projected absorption curve designation and the image pixel values to retrieve the corresponding preprogrammed partition coefficient and blood flow values.