The goal of this research is to produce an ultrasonic device to assist in the diagnosis of venous thrombosis in humans. The ultrasound time-domain correlation technique can accurately and precisely estimate the volumetric fluid flow through a circular vessel without prior knowledge of the vessel diameter, flow velocity profile, or transducer measurement angle. This technique estimates the change in arrival time (instead of frequency) of ultrasound reflected from scatterers. A system based on this technique has been constructed and the technique has been verified in a blood-flow phantom system with both a blood-mimicking substance and porcine blood. Under in vitro conditions, the measurement angle has been determined within 5%, and continuous and pulsatile volumetric flow has been measured to 150 beats/min with an accuracy better than 18%. The effects of tissue attenuation have also been examined in vitro by surrounding the vessel with tissues. In vivo measurements with canine subjects indicate that blood-flow velocity measurements (the 1-D problem) have an accuracy of better than 20%.
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