3-DIMENSIONAL VECTOR FLOW ESTIMATION USING 2 TRANSDUCERS AND SPECTRALWIDTH

Current ultrasonic blood flow measurement systems estimate only that c omponent of flow which is parallel to the incident ultrasound beam. Th is is done by relating the mean backscattered frequency shift to the a xial velocity component through the classical Doppler equation. A numb er of ultrasonic techniques for estimating the two-dimensional (2-D) b lood velocity vector have been published, both Doppler and non-Doppler . Several three-dimensional (3-D) blood velocity vector techniques hav e also been proposed, all of which require a multiplicity of transduce rs or lines of sight. Here a technique is described for estimating the total velocity vector, using only two transducers. This is achieved b y measuring not only the frequency shifts but also the bandwidths of t he back-scattered spectra, making use of the fact that the bandwidth o f a Doppler spectrum has been shown to be proportional to the velocity component normal to the sound beam. Partial experimental verification of the proposed vector flow estimation scheme is demonstrated by usin g a constant velocity thread phantom.