A method for automatically detecting the systole and diastole phases in sequences of angiographic images

This paper deals with a robust technique for automatically detecting the systole and the diastole phases in sequences of angiographic images. First of all, an optical flow method is used to process a field of displacement vectors between a set of couples of successive images. Then, the calculation of an histogram based on the directions of the vectors of each of the whole optical flow images yields an index, that the authors call the polarization index. It indicates the main motion of the ventricle walls detected between two corresponding initial images: a dilation or a contraction movement. However, some undetermined cases appear: the study of the histogram is not enough for determining the main motion of the ventricle. An interpolation of the values of the polarization index along the sequence is necessary; it gives an accurate measure of the systole and the diastole moments along the sequence. This robust and relatively simple to implement method may be used in lot of applications, and it could be simply integrated as a link of the chain of processes in a system of digital angiography.