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Figure 3 The method of transmitral Doppler (TMD) signal power analysis. Two TMD velocity profiles are shown. (Left panel): Immediately before contrast injection (baseline), (right panel): three beats after RA opacification. Individual bubble signals are indicated by the arrows in the postcontrast profile. An envelope was traced around each TMD profile (illustrated for the baseline profile) allowing exclusion of the valve opening signal present at baseline. The distribution of signal power within the envelope for each profile is plotted in the lower panels. Note that single bubbles in the TMD envelopes correspond to spikes in the power display. The signal power within each envelope was then integrated to give the power time integral (PTI). The postcontrast PTI is normalized by dividing by the baseline power. In this patient the normalized power is 6.
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