Circle detection in pulsative medical video sequence

The article deals with a new method for the detection of pulsative circular objects in a medical video sequence. The motivation for investigating this method consists in the fact that a circular object is not very apparent and its detection in such a frame is inaccurate. In some cases of medical images, the pulsative character of the circular area being searched can be used for its localisation. The proposed method starts from an analysis of movement, using optical flow estimation. The compensation of global movement is necessary because only local pulsative movement during the video sequence is assumed. The optical flow estimation is followed by another main processing step: the Hough Transform for the circle position estimation. Circles with expected properties are selected using the Bayes classifier. Finally, the circle position in a single frame is adapted using the analysis of average pixel intensity in the directions starting from the circle centre.