Principles for 4D Auto LAQ
For volume computation, a semi-automated segmentation approach was applied. At the annular level, a mark was inserted in the center of the mitral valve (MV) to initiate the algorithm. Using an extended Kalman filter that incorporates the LA motion model, geometry, and edge detection techniques, the segmentation procedure determines the deformation of the three-dimensional model. Using differences in the lengths of several lines perpendicular to each anatomical direction, strain was assessed. Using a triangular mesh, eight longitudinal lines, each connecting two opposing LA base points, were used to calculate longitudinal strain. Seven circumferential lines are uniformly positioned between the LA base and LA apex in order to compute the circumferential strain. The strain duration for each frame was then determined using the formula s(t) = (L(t) L(tr))/L(tr) x 100 percent, where L(t) is the line length at time t and tr is the end diastolic time of the left ventricle. To determine the global strain, the strains of all significant directional lines were averaged. [9, 12, 13]