Time domain ultrasonography – a reliable method of percutaneousvolume flow measurement in large arteries

The estimation of blood flow inarteries is important in the study of the (patho)physiology of the circulatory system. However,non-invasive techniques using pulsed Doppler ultrasound have so far shown potentially largeerrors. The aim of this study was to evaluate the precision and variability of a newly developednon-invasive ultrasonic system based on time domain processing, CVI (Philips). In vitro measurement of blood flow was conducted on a phantom with an elastic silicon tube.Both constant and pulsatile flow were tested at increasing flow levels, and pulsatile flowmeasurements were performed at three different pulse rates at each flow level. Furthermore,fixed and hand-held probes were compared. In vivo measurements of blood flowwere conducted on the common carotid artery of seven volunteers. The intra- and inter-observer variability was evaluated. In vitro measurements with fixed transducer andcontinuous flow showed an inaccuracy of 3·5%. Pulsatile flow showed nodifference between measurements at the three different pulse rates (P=0·69), and the overall inaccuracy of pulsatile measurements was2·5%. Pulsatile flow was more accurately measured than continuous flow (P<0·01). No difference was seen between fixed and hand-heldtransducers (P=0·26). In vivo, the intra-observervariability was 25 ml min−1 (CV 7·8%), and theinterobserver variability was 35 ml min−1 (CV 10·9%).CVI is a promising non-invasive new technique for flow measurements in arteries that givescorrect data with good reproducibility in vitro, as well as in healthy common carotidarteries in vivo.