Quantitative Doppler flowmetry. II. Reliability of a duplex scanning system under in vitro conditions

A duplex scanning system especially intended for abdominal vessel flowmetry was constructed and tested in vitro. An effort was made to mimic the special conditions encountered in the in vivo examination of abdominal vessels. The accuracy of flow estimation in blood-filled plastic tubes was studied with varying blood velocity, flow pattern, diameter of blood-filled tube and placement of sample volume in relation to tube. The influence on flow estimation by flow in a second nearby tube was also tested. The flow estimates performed in a single tube with the Doppler sample volume covering the entire cross-sectional area of the tube, were all within +/- 10 per cent of true flow as long as the velocities were within the working range of the Doppler velocity meter. The error in flow estimation due to a discrepancy in size and placement of sample volume in relation to tube, and the unfavourable influence of flow in a nearby tube, is quantified and discussed.