1. A non-transitory computer readable medium embodying a computer program that when executed by a processing unit, at least causes the processing unit to quantify contrast agent behavior of an administrated contrast agent within a region of interest of a subject, said computer program comprising: computer program code for processing image data of an acquired time sequence of images including two tissue locations, one of said tissue locations (I) being outside of said region of interest and the other of said tissue locations (J) being within said region of interest, to yield a time sequence of measurements, I(t), at the tissue location (I) outside of the region of interest that detect contrast agent concentration before the contrast agent enters the region of interest and to yield a time sequence of measurements, J(t), at the tissue location (J) within the region of interest that detect the contrast agent concentration as the contrast agent perfuses the region of interest; computer program code for deconvolving I(t) from J(t) to determine a vector describing the time estimate of the impulse response function, R′(t), for the region of interest, where the shape of the vector is constrained such that the vector comprises a single local maximum and such that first and last elements of said vector have values no less than zero; and computer program code for determining the behaviour of the contrast agent in the region of interest based on the determined vector, wherein the two tissue location (I) and (J) are in close proximity to avoid spatial dispersion of the contrast agent prior to entry into the region of interest and wherein tissue location (I) is small to avoid smoothing of the time sequence of measurements I(t).