Errors and artifacts of Doppler flowmeters and their solution.

Continuous-wave Doppler ultrasound flowmeters are essential instruments for the vascular surgeon. Unfortunately, when used for quantitative purposes, they yield a flow velocity waveform that is substantially in error. Current directional continuous-wave Doppler velocimeters used a O-crossing detector to convert the Doppler signal to a waveform. Unfortunately, there are several inherent problems with this technique, and velocity waveforms are produced that have significant artifacts or errors. In this report, it is shown that a multifilter system is a simple, inexpensive alternative to systems using a O-crossing detector, and furthermore, permits real-time display of the Doppler waveform. The severity of the underlying arterial disease can be quantified by the calculation of pulsatility index. The pulsatility index was calculated from the Doppler waveforms recorded from peripheral arteries in 155 limbs and showed an excellent correlation with the severity of atherosclerosis as assessed by arteriography.