1. In a medical diagnostic imaging system, a method for positively identifying target tissue in a target subject comprising: generating at least two test images of the same location in the target subject that contains known target tissue, each one of the at least two images are generated using a different imaging modality and storing the at least two test images; identifying a color value in each of the at least two stored test images that corresponds to the known target tissue and storing the color value as the known target tissue color value; selecting a vector magnitude for the known target tissue color value identified in each of the at least two test images; using the stored known target tissue color values and the selected vector magnitudes to derive a plurality of diagnostic functions; generating at least two diagnostic images of the same location in the target subject, each of the at least two diagnostic images are generated using a different imaging modality and storing the at least two diagnostic images; utilizing the plurality of diagnostic functions to assign at least first, second and third pre-selected vector magnitudes to locations in each of the at least two stored diagnostic images if any of the stored diagnostic images include a color value that is the same as the stored known target tissue color value and storing the location of the assigned first, second and third pre-selected vector magnitudes in each of the at least two diagnostic images; registering the at least two stored diagnostic images; summing the at least first, second and third stored, pre-selected vector magnitudes that are assigned to the same location in each of the at least two stored diagnostic images to arrive at corresponding first, second and third total vector values for each location, and storing the values as a set of total vector values; employing the set of total vector values to form a diagnostic mathematical relationship; and using the diagnostic mathematical relationship to positively identify the target tissue.