Accuracy and Reproducibility of a Novel Dynamic Volume Flow Measurement Method

In clinical practice, the blood volume flow (BVF) is typically calculated assuming a perfect parabolic and axisymmetric velocity distribution. This simple approach cannot account for the complex flow configurations that are produced by vessel curvatures, pulsatility and diameter changes, thereby resulting in a poor estimation. The application of the Womesley model allows compensating the flow distortion due to pulsatility, and, with some adjustment, the effects of slight curvatures, but several problems remain unanswered. 2D/3D approaches can acquire the actual velocity field over the whole vessel section, but they are typically affected by a limited temporal resolution. The multigate technique allows the acquisition of the actual velocity profile over a line intersecting the vessel lumen, and, when coupled to a suitable wall-tracking method, can offer the ideal tradeoff among attainable accuracy, temporal resolution, and required calculation power. In this work we present a BVF measurement method based on the multigate spectral Doppler and a B-mode edge detector algorithm for wall-position tracking. The method has been extensively tested on the research platform ULA-OP with more than 1700 phantom measurements at flow rates between 60 and 750 ml/min, steering angles between 10° and 22° and constant, sinusoidal or pulsed flow trends. In the averaged BVF measurement we found an underestimation of about -5% and a coefficient of variability (CV) less than 6%. In instantaneous measurements (e.g. the systolic peak) the CV was in the range 2% - 8.5%. These results were confirmed by a preliminary test on the common carotid artery of 10 volunteers (CV 2% - 11%).