Figure 5a. Sagittal power Doppler US images show the effects of filter stepwise changes on both feeding and stenotic vessels with the low-frequency transducer. Baseline settings are as follows: longitudinal view; insonation angle, 60°; peak systolic velocity, 2 m/sec; gain, 60%, pulse repetition frequency, 1,500 Hz; and color versus echo priority, 100%. The filter is increased from (a) low to (b) medium and (c) maximum, which results in considerable reduction in signal in the feeding vessel.