Bubble measuring instrument and method

• US 6,463,785 B1
• Filed: 03/26/2002
• Issued: 10/15/2002
• Est. Priority Date: 02/04/2000
• Status: Expired due to Fees

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: The United States of America As Represented By The Secretary of Agriculture
• Inventors: Magari, Patrick J., Kline-Schoder, Robert
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): Wiggins, David J.
• Application Number:
  US10/113,647
• Time in Patent Office: 203 Days
• Field of Search: 73/190.3, 73/191, 73/645.3, 73/647.9, 73/614.9, 73/617.1, 735/92, 736/03, 324/71.4, 324/76.41, 128/443-444, 128/425, 128/463
• US Class Current: 73/19.03
• CPC Class Codes: A61B 8/08 Detecting organic movements or changes, e.g. tumours, cysts, swellings A61B8/02 - A61B8/06 take precedence
• CPC Class Codes: A61B 8/4209 by using holders, e.g. positioning frames
• CPC Class Codes: A61B 8/488 involving Doppler signals
• CPC Class Codes: G01N 2291/014 Resonance or resonant frequency
• CPC Class Codes: G01N 2291/02433 Gases in liquids, e.g. bubbles, foams
• CPC Class Codes: G01N 2291/0421 Longitudinal waves
• CPC Class Codes: G01N 29/036 by measuring frequency or resonance of acoustic waves
• CPC Class Codes: G01N 29/348 with frequency characteristics, e.g. single frequency signals, chirp signals measuring frequency of mechanical vibrations or acoustic waves in general G01H1/06, G01H3/04; measuring frequency or analysing frequency spectra G01R23/00
• CPC Class Codes: G01N 29/42 by frequency filtering or by tuning to resonant frequency
• CPC Class Codes: G01N 29/46 by spectral analysis, e.g. Fourier analysis or wavelet analysis spectral signal processing per se G06F17/14
• CPC Class Codes: G01S 7/52026 Extracting wanted echo signals Doppler systems G01S15/50; Doppler short range imaging systems G01S15/8979
• CPC Class Codes: G01S 7/52036 using analysis of echo signal for target characterisation
• CPC Class Codes: Y10S 128/916 Ultrasound 3-D imaging

Abstract

Method and apparatus are provided for a non-invasive bubble measuring instrument operable for detecting, distinguishing, and counting gaseous embolisms such as bubbles over a selectable range of bubble sizes of interest. A selected measurement volume in which bubbles may be detected is insonified by two distinct frequencies from a pump transducer and an image transducer, respectively. The image transducer frequency is much higher than the pump transducer frequency. The relatively low-frequency pump signal is used to excite bubbles to resonate at a frequency related to their diameter. The image transducer is operated in a pulse-echo mode at a controllable repetition rate that transmits bursts of high-frequency ultrasonic signal to the measurement volume in which bubbles may be detected and then receives the echo. From the echo or received signal, a beat signal related to the repetition rate may be extracted and used to indicate the presence or absence of a resonant bubble. In a preferred embodiment, software control maintains the beat signal at a preselected frequency while varying the pump transducer frequency to excite bubbles of different diameters to resonate depending on the range of bubble diameters selected for investigation.

Claims

1. An apparatus for monitoring bubbles in a selected volume, comprising:

a pump transducer;

a controller for said pump transducer operable for producing a signal at a first frequency from said pump transducer, said first frequency being selectable over a range of frequencies;

an image transducer;

a reference signal generator for producing a reference signal at a second frequency higher than said first frequency;

a pulser for producing a pulsed signal output from said image transducer at said second frequency;

a receiver for detecting a return signal from said image transducer; and

a multiplier for multiplying said return signal with said reference signal to produce a multiplier output signal.

2. The apparatus of claim 1, further comprising:

a first lowpass filter for filtering said multiplier output signal to produce a first filtered signal.

3. The apparatus of claim 1, further comprising:

a sample and hold circuit for receiving said first filtered signal to produce a beat signal.

4. The apparatus of claim 3, further comprising:

a second lowpass filter for producing said beat signal.

5. The apparatus of claim 3, further comprising:

a highpass filter for producing said beat signal.

6. The apparatus of claim 3, further comprising:

a level detector for detecting a bubble from said beat signal.

7. The apparatus of claim 1, further comprising:

a pulser controller for said pulser for controlling a repetition frequency of said pulsed signal output.

8. The apparatus of claim 7, wherein said pulser controller is software operable for selecting of said repetition frequency.

9. The apparatus of claim 7, wherein said pulser controller varies said repetition frequency based on said first frequency.

10. The apparatus of claim 7, wherein said pulser controller is programmable for varying said repetition frequency to maintain a constant frequency of a beat signal contained in said return signal.

11. An apparatus for monitoring bubbles in a selected volume, comprising:

a pump transducer;

a controller for said pump transducer operable for producing a signal at a first frequency from said pump transducer, said first frequency being selectable over a range of frequencies;

an image transducer;

a reference signal generator for producing a reference signal at a second frequency higher than said first frequency;

a pulser for producing a pulsed signal output from said image transducer at said second frequency;

a pulser controller for controlling a repetition frequency of said pulsed signal output produced by said pulser, said pulser controller operating to vary said repetition frequency as a function of said first frequency; and

a receiver for detecting a return signal from said image transducer.

12. The apparatus of claim 11, further comprising:

a multiplier for multiplying said return signal with said reference signal to produce a multiplier output signal.

13. The apparatus of claim 11, further comprising:

a sample and hold circuit for detecting a beat signal.

14. The apparatus of claim 11, further comprising:

at least one filter for detecting a beat signal with a beat signal frequency.

15. The apparatus of claim 14, said pulser controller being operable for varying said repetition frequency to maintain said beat signal frequency at a selected frequency.