Fig. 1
Strain Method. a Registration of cine images is used to calculate pixel-wise displacement fields between each image frame and the reference frames. b The process of registration yields displacement images (∆xi, ∆yi) that contain the translation of each pixel from the reference frame to the target ith image frame. c The user specifies endocardial (red) and epicardial (green) points on the end-diastolic frame. A uniform grid of points is generated at end-diastole consisting of 20 equally spaced contours between the user-specified endocardial and epicardial tracings from, with 100 equally spaced points along each contour. d Each point, or equivalently, each series of points in a contour, is propagated to all other cardiac phases using the previously calculated displacement fields. Four sample contours are shown. Strain for each contour is calculated as the fraction change in the contour length to end-systole. For regions that contain multiple contours, as shown here for GLS_AVE and GRS, average strains are calculated as the average of the strains from the individual contours. GLS_AVE, average global longitudinal strain; GRS, global radial strain