FREQUENCY MODULATED ULTRASOUND TECHNIQUE FOR MEASUREMENT OF FLUID VELOCITY

• US 3,568,661 A
• Filed: 10/02/1968
• Issued: 03/09/1971
• Est. Priority Date: 10/02/1968
• Status: Expired due to Term

• Current Assignee: Dean L. Franklin
• Original Assignee: Dean L. Franklin
• Inventors: Franklin, Dean L.
• Application Number:
  US04/764,515
• Time in Patent Office: 888 Days
• US Class Current: 600/454
• CPC Class Codes: A61B 8/06 Measuring blood flow measuring volume flow in general G01F, e.g. G01F1/66, G01F1/72; measuring speed of fluids in general G01P5/00
• CPC Class Codes: A61B 8/12 in body cavities or body tracts, e.g. by using catheters catheters per se A61M25/00
• CPC Class Codes: G01F 1/66 by measuring frequency, phase shift or propagation time of electromagnetic or other waves, e.g. using ultrasonic flowmeters

Abstract

A device for measuring fluid velocity of the blood stream utilizing frequency modulated ultrasound transmitted through the moving blood with a composite signal detected, difference frequency signal extracted, phases across each of a pair of transducers compared, and the difference in phase being a measure of blood stream velocity.

Claims

1. An ultrasonic apparatus for measurement of fluid flow especially of the blood stream through a blood vessel comprising:

a repetitive voltage ramp generator;

a frequency modulated oscillator connected to and modulated by said ramp generator;

first and second buffer stages coupled to said frequency modulated oscillator;

first and second transducers spaced apart upstream and downstream of the fluid flow and defining a transmission path for ultrasonic waves therebetween through said fluid, said first and second transducers connected respectively to said first and second buffer stages;

detection, mixing and band-pass filtering means connected to each of said first and second transducers;

amplifying means connected to each of said filtering means;

a phase comparator connected for comparison of outputs from each of said amplifying means; and

indicating means connected to said phase comparator and responsive to the difference of the outputs from each of said amplifying means.

2. The ultrasonic apparatus of claim 1 further characterized by:

a mounting means for holding said first and second transducers in a spaced apart relationship including;

a pair of fitted longitudinal portions of a substantially cylindrical form; and

said first transducer mounted on one of said longitudinal portions and said second transducer mounted on the other of said longitudinal portions, said first and second transducers spaced diagonally across from each other when said pair of longitudinal portions are in position fitted to each other.

3. The ultrasonic apparatus of claim 2 further characterized by:

said longitudinal portions shaped and adapted for fitting around a blood vessel surgically exposed; and

said transducers adapted to be positioned against and on opposite sides of the blood vessel.

4. The ultrasonic apparatus of claim 1 wherein said transducers include crystals of lead zirconate-titanate.

5. A method of measuring the velocity of fluid flow in a blood vessel which comprises:

surgically exposing a blood vessel;

mounting a pair of crystal transducers spaced apart upstream and downstream of the fluid flow and defining a transmission path for ultrasonic waves therebetween through said fluid, with the crystals of said transducers in contact with the wall of the blood vessel;

generating an electric signal by modulating a frequency modulated oscillator with a repetitive voltage ramp which is then fed to each of said transducers;

detecting, mixing, and filtering the signal from each of said transducers and combining the signals from each of said transducers for phase comparison; and

calibrating and indicating the phase difference in terms of velocity of the fluid flow in the blood vessel.

6. The method of claim 5 further characterized by mounting said pair of transducers by clamping them to the blood vessel in diagonally opposite positions against opposite sides of the blood vessel.