Abstract: Two components of the velocity of blood or similar liquids and the true flow vector are derived by a linear transducer array cross-beam configuration. Ultrasound pulses are transmitted from the center elements and backscattered echoes are received by left and right receiver sub-arrays whose locations depend on the observation point. A duplex imaging system with a sector scanner incorporates a Doppler modality with little added complexity and provides components of flow velocity parallel to and transverse to the acoustic beam direction from which the true velocity vector is computed.

Abstract: A technique particularly suitable for measuring volume flow rate in the ascending aorta employs real time sector-scan imaging to locate the cross section of interest and align the Doppler beam with the vessel axis. The number of active transmit and receive array transducer elements is varied to electronically tailor the acoustic beam cross section at the required range to be approximately equal to the vessel cross section, which is the sample volume. Mean flow velocity is computed by averaging the spectral components extracted from the sample volume by a Fourier transform processor. Volume flow rate is calculated by multiplying mean flow velocity and estimated area.

Abstract: A duplex imaging system with a common transducer array for both modes of operation satisfies the conflicting bandwidth requirements by single impulse excitation of the transducer in B-scan imaging operation to generate a wide bandwidth ultrasound pulse and multiple impulse excitation at the emission frequency in Doppler mode operation to generate a narrow bandwidth ultrasound phase. The multiple impulse excitation has a variable repetition frequency depending on range to a sample volume and velocity of blood flow. A Doppler modality, in which the frequency shift of echoes caused by flow of blood is measured to derive the flow velocity, is incorporated into a sector scanner with little additional complexity.