1. A computer implemented method of evaluating the quality of a match between two digitized images, said method performed by the computer comprising the steps of: providing a pair of digitized images, each image comprising a plurality of intensities corresponding to a domain of points on an 3-dimensional grid, wherein said images depict the same object at different times, and wherein a contrast enhancing agent was applied to said object before the acquisition of at least one of said images, calculating a subtraction image I Δ as I Δ (x,y,z)=I 2 (x,y,z)−I 1 (x,y,z), wherein (x,y,z) represents a point in the domain, I 1 (x,y,z) is a first image of said pair of images and I 2 (x,y,z) is a second image of said pair of images; and calculating a motion quantification measure | I Δ − | from said difference of said pair of images as  〈 I Δ - 〉  = β N - ⁢ ∑ x , y , z ⁢ [ f ⁡ ( I Δ ⁡ ( x , y , z ) ) ❘ I Δ ⁡ ( x , y , z ) < 0 ] , wherein the sum is restricted to those I Δ <0, ƒ is a function, β is a constant, and N − is the number of domain points with negative subtraction image values, wherein said motion quantification measure quantifies motion artifacts in said pair of images.