1. A method for automatically determining a contour of an internal organ based upon digital image data of a region in which the organ is disposed, said image data representing a sequence of image frames of the region made over an interval of time during which a wall of the organ has completed at least one cycle of movement, the wall of the organ undergoing repetitive cycles of movement as part of the organ's physiological function, each image frame of said sequence of image frames comprising a plurality of pixels, said method comprising the steps of: (a) developing an initial estimate of a region bounded by the contour of the organ in each image frame of the sequence, based upon a comparison of the image data with parameters derived from training data that were previously produced through manual evaluation of a plurality of image frames over a corresponding cycle for each of a plurality of corresponding organs in other individuals, said parameters derived from the training data being used to assign classes to the pixels comprising each of the image frames of the sequence, said classes indicating pixels that are most likely inside the contour of the organ in each image frame; and (b) using boundary motion data that were previously developed through manual evaluation of the corresponding organs in other individuals, refining the initial estimate of the region in each image frame of the sequence to determine the contour, said boundary motion data establishing an allowed range of motion of the contour between subsequent image frames of the sequence.