Design of a continuous-wave Doppler ultrasonic flowmeter for perivascular application

The paper details the specification of an ultrasonic Doppler flowmeter intended for perivascular application and describes the elements of the design of an ultrasonic blood flow transducer. An optimised design is outlined for probes to be used on vessels in the range 5–12 mm. The design is based on the use of continuous-wave Doppler techniques and incorporates a novel polymer ultrasonic couplant. A constrained jet technique is used to test the performance of the probe in vitro and the results indicate that in use velocity profile effects are likely to lead to sensitivity changes of only 3 per cent. A companion paper details the design and performance of the electronic processing system needed for the complete flowmeter.