Straight-Line Approximation for the Boundary of the Left Ventricular Chamber from a Cardiac Cineangiogram

A cardiac cineangiogram is an X-ray motion picture of the heart. Boundary detection is an essential task to compute valuable quantitative information such as the temporal volume change and the wall velocity. Previously, boundary detection methods treated frames independent of each other. Consecutive frames of a motion picture are, however, highly correlated and therefore this property can be exploited. The method described takes advantage of the known location of the boundary on previous frames. The previous boundary is divided into a set of segments along which local rectangular regions are set up on the present frame. This boundary is approximated by a set of straight lines which minimize the square error in each rectangular region with the spatial derivative as its weight. The method is a fast computing algorithm and relatively insensitive to white noise because the resultant positive and negative weights tend to cancel this effect. An experiment was carried out, and good agreement with boundaries detected by humans was obtained.