[Laboratory experimental studies on quantitative blood flow measurement with the c.w. ultrasound Doppler procedure: II. Flow measurements].

The reliability of Doppler blood flow measurement was examined by testing a cw Doppler flowmeter on a flow-rig. Comparing the Doppler measurements with those simultaneously obtained by means of EFM, the correlation coefficient was found to be 0.989 for continuous, and 0.985 for pulsatile streaming. With velocities up to 40 cm/sec there was a systemic overestimation of flow velocity which was attributed to the effects of the high pass filter used. Unequal distribution of intensity within the sound field is discussed. Systemic underestimation of velocities over 45 cm/sec is due to the interaction of the low pass filter. Identification of the 90 degrees reference angle using the cw Doppler technique seems to be appropriate. Within zones of turbulence caused by eccentric stenoses no reliable flow values could be determined.