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Figure 1 Calculation of two-dimensional WT and strain on short-axis cine MR images (A) and tagged images (B), respectively. The end-diastolic images are shown on the left and the end-systolic images on the right. For calculation of WT, the centerline method was used. The white arrow (a) is one of the 100 chords, representing the end-diastolic WT. The other white arrow (a') represents the end-systolic WT at that point. According the formula (a' – a) x 100/a, the percent change in WT between end-diastole and end-systole can be calculated. On the tagged images, the white diamonds indicate the intersection points of the tagging grid. By using groups of three intersection points, multiple triangular elements of the myocardium can be created (C). The variables r and c both represent a line segment in the undeformed state, in the radial and circumferential directions, respectively. The variables r' and c' represent the same line segment in the deformed state. (For the two-dimensional strain computation of a triangle, see Appendix.) MR = magnetic resonance; WT = wall thickness.