Automatic segmentation of mitral leaflet movement in Doppler tissue M-Mode ultrasound

Introduction: Doppler Tissue M-Mode ultrasound facilitates a method for measuring both mitral and aortic valve opening and closing. These measures can be used when assessing global information about the cardiac cycle. The method depends on an operator to manually setting points in the ultrasound image to obtain the timing intervals. We developed an automatic segmentation algorithm that segmented the mitral leaflet movement line, to guide the clinician in this work. Methods: The algorithm used a series of steps to reduce noise in the image, leaving only the region of interest left with the mitral leaflet movement line. Next the gradient of the image was calculated with a the Sobel method, creating a high gradient on the edge of the mitral leaflet movement line. Using a multidimensional weight matrix the mitral leaflet movement was tracked in the image. The automatic algorithm is validated against three human operators. Results: In 19 of 29 images the correlation coefficients are larger than 0.8 between the algorithm and the mean of the operators. The median operator standard deviation within the 95% CI was 5 pixels. The median rms error for the algorithm was 4 pixels. Conclusion: The novel method of automated segmentation the mitral leaflet movement line has a high accuracy but depends on the quality of the image.