Method and device for non-invasively monitoring the instantaneous fluctuations in the viscoelastic-related properties of a living tissue

• US 4,580,574 A
• Filed: 07/30/1984
• Issued: 04/08/1986
• Est. Priority Date: 08/12/1983
• Status: Expired due to Term

• Current Assignee: Benjamin Gavish
• Original Assignee: Benjamin Gavish
• Inventors: Gavish, Benjamin
• Primary Examiner(s): Howell, Kyle L.
• Assistant Examiner(s): Jaworski, Francis J.
• Application Number:
  US06/636,010
• Time in Patent Office: 617 Days
• Field of Search: 128/774-778, 128/660-661, 128/663, 73/586, 73/589, 73/597-600
• US Class Current: 600/449
• 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: G01N 2291/02475 Tissue characterisation
• CPC Class Codes: G01N 2291/0421 Longitudinal waves
• CPC Class Codes: G01N 29/12 by measuring frequency or resonance of acoustic waves measuring frequency or resonant frequency of mechanical vibrations or acoustic waves in general G01H1/06, G01H3/04, G01H13/00; acoustic resonators G10K11/04; vibration or shock testing of structures G01M7/00

Abstract

The invention provides an ultrasonic device for continuously and noninvasively monitoring instantaneous fluctuations in viscoelastic-related properties of tissue comprising a pair of substantially parallel spaced-apart piezoelectric transducers having a gap therebetween and adapted to bracket and come in direct contact with living tissue inserted in the gap between the transducers, at least one of the transducers being adjustable with respect to the other transducer whereby the distance between the transducers is adjustable to enable insertion and clamping of a segment of living tissue therein. The invention also provides a method for continuously and noninvasively monitoring instantaneous fluctuations in viscoelastic-related properties of a tissue with high resolution utilizing such a device.

Claims

1. An ultrasonic device for continuously and noninvasively monitoring instantaneous fluctuations in visoelastic-related properties of a tissue, comprising a pair of substantially parallel, spaced-apart piezoelectric transducers having front and rear surfaces and adapted to bracket and, with their respective front surfaces come in direct ultrasonic contact with living tissue inserted in a gap between said front surfaces, said transducers, constituting together with said tissue an oscillating system, at least one of said transducers being adjustable with respect to the other transducer whereby the distance between said transducers is adjustable to enable insertion and clamping of a segment of living tissue therein, further comprising a continuous wave frequency generator producing a wave signal, an input electrode connected at one end thereof to the rear surface of one of said transducers and connected at the other end thereof to a frequency generator, and an output electrode connected at one end thereof to the rear surface of the other one of said transducers, and connectable at the other end thereof via an amplifier and demodulator to a signal analyzer, wherein said wave signal is applied continuously and is subjected, via said living tissue, to multiple reflections between said pair of transducers, and wherein said signal, when demodulated, possesses a frequency-dependent peak structure in which the peaks are located at the resonance frequencies of said oscillating system, the parameters of which peaks are a function of the instantaneous viscoelastic properties of said tissue.

2. The device as claimed in claim 1, wherein said transducers are affixed in a mount, at least one of said transducers being mounted in an insert slidingly held in said mount.

3. A method for continuously and noninvasively monitoring instantaneous fluctuations in viscoelastic-related properties of a tissue with high resolution, comprising the steps of:

providing a pair of substantially parallel, spaced-apart piezoelectric transducers having front and rear surfaces, at least one of said transducers being adjustable with respect to the other transducer;

inserting a segment of living tissue into a gap between said spaced-apart transducers;

adjusting the distance between said transducers so as to bring the front surfaces of both transducers in direct ultrasonic contact with said living tissue to form together with said transducers, an oscillating system;

producing a wave signal by means of a frequency generator connectable to one of said transducers;

continuously applying said wave signal and subjecting it, via said living tissue, to multiple reflections between said pair of transducers at resonance conditions of said oscillating system;

demodulating said signal with the aid of a demodulator, and

analyzing said signal as demodulated to obtain the instantaneous fluctuations in the propagation velocity and/or absorption of said wave signal, being a function of the instantaneous viscoelastic properties of said tissue.

4. An ultrasonic device for continuously and noninvasively monitoring instantaneous fluctuations in viscoelastic-related properties of a tissue, said device comprising:

a first piezoelectric ultrasonic transducer;

a second piezoelectric ultrasonic transducer;

means for mounting said tissue in direct tissue contact with said first and second transducers, said tissue sandwiched between said two transducers, said mounting means further including means for adjusting the position of at least one of said transducers to insure direct tissue contact between said transducers and said tissue, said first transducer, said second transducer and said tissue all comprising an oscillating system;

generator means, connected to said first transducer, for producing a periodic signal; and

analyzer means responsive to a signal received at said second transducer, for demodulating said received signal and for establishing fluctuations in the frequencies at which said oscillating system resonates, and the absorption of said signal at said frequencies, which frequencies and absorptions are functions of the instantaneous viscoelastic properties of said tissue.

5. A method for continuously and noninvasively monitoring instantaneous fluctuations in viscoelastic properties of a tissue, said method comprising the steps of:

providing an oscillating system comprised of said living tissue and two piezoelectric ultrasonic transducers, wherein said tissue is in direct contact with and located between said transducers forming a first transducer/tissue interface and a second transducer/tissue interface;

applying a periodic electrical signal to said first transducer, thereby generating a sound wave at said first transducer/tissue interface;

receiving sound waves at said second transducer/tissue interface and thereby providing an electrical signal at said second transducer;

demodulating said second transducer electrical signal; and

analyzing said demodulated signal to determine the fluctuations in the frequencies at which said oscillating system resonates and the absorption of said signal at said frequencies, which frequencies and absorptions are functions of the instantaneous viscoelastic properties of said tissue.