A Fully Automatic Mid-Diastole Frame Detection in 2D Echocardiography Sequences

Mitral valve stenosis (MS) is one of the most prevalent heart valve diseases. The mitral valve orifice area (MVA) is a reliable measure for evaluating the MS severity. This measure is typically obtained by applying planimetry methods to the echocardiography video frames in a parasternal short axis view (PSAX). From the diagnostic perspective, the most proper frame for measuring the MVA is the mid-diastole frame. Since manual methods for localizing this frame within a sequence of recorded echocardiography frames are time-consuming and user-dependent, a novel three-stage approach is proposed. Firstly, the mitral valve orifice (MVO) region is detected automatically for each frame using the Circular Hough transform (CHT) leading to a lower computational cost and an increased accuracy. Secondly, for each of the detected MVO regions, a data dimensionality reduction (DR) method is applied to map it into a single point in a two-dimensional (2D) space. Finally, a curve is generated based on Euclidean distances between consecutive points in the 2D space. The curve analysis allows for the detection of the location of the mid-diastole frame. The proposed algorithm was validated using echocardiographic video sequences collected from 11 different participants including 7 individuals diagnosed with mitral valve stenosis and 4 control non-stenosis individuals. The mid-diastole frame location estimated by an expert cardiologist was used as the gold standard for assessing the evaluation results. The performance of different DR methods including the linear principal component analysis (LPCA) and the kernel PCA (with a polynomial or a Gaussian kernel) was evaluated. The PCA with Gaussian kernel produced the best results with the average difference between the proposed method and the gold standard equal to 0.57 frames in MS and 0.50 frames in non-MS cases.