25 + 1 channel pulsed ultrasound Doppler velocity meter for quantitative flow measurements and turbulence analysis.

A multichannel pulsed ultrasound Doppler instrument designed to measure velocity and volume flow rate quantitatively has been applied for turbulence detection. A 7-MHz transmitting frequency and a phase locked loop technique for the frequency to velocity conversion have been used to obtain high temporal resolution in the single channel mode. To provide for reliable positioning of the single gate within the arterial lumen the device could first be operated in the multichannel mode measuring the velocity profiles with zero crossing detection methods. Measurements of the velocity in the center of the lumen of the common and internal carotid arteries have been recorded on a beat to beat basis. An ensemble average of 16 consecutive pulses was determined. Thereafter, the root mean square of the differences between ensemble average and individual velocity pulses was computed, and a disturbance index was defined by dividing the disturbance velocity by the mean velocity. First clinical results show that the method presented is a valuable complement to the analysis of flow pulse patterns in the transcutaneous examination of carotid arteries.