Quantitative Doppler flowmetry. I. Construction and testing of a duplex scanning system.

With the aim of designing a duplex scanner especially suited for flow estimation in abdominal vessels, a mechanical coupling device was constructed, combining a real time sector scanner and a pulsed Doppler velocity meter. The possible error in estimation of vessel cross-sectional area by means of ultrasound measured diameters, was studied through diameter measurements of blood-filled plastic tubes. In conclusion, the ultrasound measured outer-inner diameter seemed to be the most accurate estimation of true inner diameter. The accuracy and reproducibility of flow estimation was tested under optimum in vitro conditions, with special reference to the ability of the mechanical coupling device in giving the correct angle between Doppler beam and blood-filled tube. Ninety blood flow estimates with varying angle of insonation were all within +/- 10 per cent of true flow.