How the map of mass centers of the first order absolute moment can be used to track contours in image sequences [cardiovascular application]

The problem of contour tracking in sequences of images is considered when an approximate contour is given on the first frame. The approach is to enhance the gray level discontinuities of the images with ridges and subsequently to locate the top of the ridges. Ridges at discontinuities are obtained with the first order absolute moment (FOAM) operator. If the FOAM is used, discontinuities can be located without making use of the purely local strategy which takes every point of the approximate contour to the top of the ridge profile. The FOAM mass center approaches the discontinuity regardless of the distance between the discontinuity and the starting point. Therefore, the center of mass is used, in turn, as the starting point of subsequent iterations until the discontinuity is located. Methods derived from standard regularization theory are also used to cope with real noise conditions. Contours are located by choosing between the curves which interpolate N knots, which are those that best approximate the line of FOAM mass centers.