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FIG 1. Plot of mean normalized PSV for the aggregate patient data as a function of time. Time "zero" on the horizontal axis denotes baseline PSV before the administration of contrast material. Vertical lines at data points are error bars denoting ± 1 SD. Note that the mean PSV increases fairly rapidly, reaching a maximum within approximately 1 min of injection. Mean PSV remains elevated to approximately 5% above baseline until approximately 4 min after injection. FIG 2. Representative waveforms at the onset of contrast effect and at peak enhancement. Note the marked enhancement of the Doppler spectrum after the administration of contrast material and the apparent increase in PSV after the administration of contrast material compared with before
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