Tracking Contrast in Echocardiography by a Combined Snake and Optical Flow Technique

Contrast-echocardiography in conjunction with realtime video-densiometry can be an effective means of studying right ventricular (RV) structural changes, e.g. in patients diagnosed with Arrhythmogenic Right Ventricular Dysplasia (ARVD). In order to characterize RV flow pattern it may be necessary to track the front of the contrast agent as it enters the RV. Active contour models (ACM) is a standard image analysis method, which can be applied to time-dynamic tracking problem. To improve tracking speed we extended the formulation of ACM by including an additional force, derived from the optical flow field, another standard image analysis algorithm. This reduced the number of iterations needed to find the front of the contrast agent significantly. Also the changes in intensity of the contrast agent over time were studied. Two groups were compared, one with 30 patients diagnosed with ARVD and one with 18 healthy volunteers. Our study shows that that using our suggested method (calculating wash-in and wash-out time indices) it is possible to discriminate between the two groups.