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Figure 3 Automated regurgitant flow analysis software at work in the calibration stage (left) and measurement stage (right). (Top) Touch-screen panel with control keys. (Bottom) In vitro example of a narrow-spectrum Doppler signal from laminar flow at the vena contracta with the automatic border detection algorithm in operation. The measurement bars—S(ystole) and D(iastole)—specify a cardiac cycle of interest and the limits of integration over time. In the calibration stage (left), the software displays mean power and mean pixel intensity within the specified cardiac cycle. In the measurement stage (right), total flow volume (47.8 ml) and average flow cross-sectional area (average cross-sectional area 0.31 cm²) are displayed.