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Figure 2 Determination of regional fractional area change (RFAC). (A) A pie-shaped sector is drawn from the centroid of each contour to 15° arcs on the contour. Sector area is determined and referenced to its value at end-diastole (corresponding to QRS peak) to derive RFAC. (B) Example of RFAC versus time from end-diastole to end-systole, for an example sector.