Ultrasonic doppler flowmeters

Details Ultrasonic doppler flowmeters Ultrasonic doppler flowmeters

1980-06-24

1982-04-13

Michell, Robert W.

Surgery

Truss

Pad

7386125, A61B 1000

Patent

active

043242588

ABSTRACT:
In an ultrasonic Doppler flowmeter system for the measurement, imaging and mapping of blood flow, a transducer coupled to a patient's skin is caused to emit pulses of high frequency ultrasound waves. The resulting echo signals are received by the transducer, demodulated into quadrature components, sampled into a large plurality of channels, and digitized. An improved stationary filter circuit utilizing a finite iteration then suppresses unwanted masking "clutter", i.e., low frequency but large amplitude signals from stationary tissue interfaces, with significantly improved response time and dynamic range, while providing good resolution. The Doppler frequency period of the moving acoustic scatterers is obtained by passing the remaining signal through a zero crossing detector. A sign detector circuit separates the multiplexed quadrature components and compares them to each other to determine the direction of the flow, while extending the Doppler bandwidth to assure compliance with the Nyquist criteria for sampled systems. A frequency to velocity converter then generates a voltage proportional to the Doppler velocity for each sample channel. These velocity values enable outputs in various forms, for example, blood flow profiles.

REFERENCES:
Brandestini, M. "Topoflow-A Digital Full Range Doppler Velocity Meter", IEEE Trans. on Sonics & UTS, vol. SU-25, #5, Sep. 1978, pp. 287-293.
Brandestini, M. et al., "Blood Flow Imaging Using a Discrete-Time Frequency Meter", 1978 UTS Symp. Proc., Cherry Hill, N.J., 25-27 Sep. 1978.
Brandestini, M., "A Digital 128-Channel Transcutaneous Blood Flowmeter", Biomedizinische Technik, vol. 21, pp. 291-292, Jun. 1976.

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