Body monitoring and imaging apparatus and method

• US 5,573,012 A
• Filed: 08/09/1994
• Issued: 11/12/1996
• Est. Priority Date: 08/09/1994
• Status: Expired due to Term

• Current Assignee: Lawrence Livermore National Security LLC (Government of the United States of America)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: McEwan, Thomas E.
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): LAYNO, CARL HERNANDZ
• Application Number:
  US08/287,746
• Time in Patent Office: 826 Days
• Field of Search: 128/782, 128/774, 128/721, 128/653.1, 128/782, 128/721, 128/774, 128/653.1
• US Class Current: 600/595
• CPC Class Codes: A61B 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• CPC Class Codes: A61B 5/0507 using microwaves or terahertz waves
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/0809 by impedance pneumography
• CPC Class Codes: A61B 8/4416 related to combined acquisition of different diagnostic modalities, e.g. combination of ultrasound and X-ray acquisitions
• CPC Class Codes: A61B 8/488 involving Doppler signals
• CPC Class Codes: G01S 13/0209 Systems with very large relative bandwidth, i.e. larger than 10 %, e.g. baseband, pulse, carrier-free, ultrawideband
• CPC Class Codes: G01S 13/18 wherein range gates are used
• CPC Class Codes: G01S 13/581 using transmission of interrupted pulse modulated waves and based upon the Doppler effect resulting from movement of targets

Abstract

A non-acoustic pulse-echo radar monitor is employed in the repetitive mode, whereby a large number of reflected pulses are averaged to produce a voltage that modulates an audio oscillator to produce a tone that corresponds to the heart motion. The antenna used in this monitor generally comprises two flat copper foils, thus permitting the antenna to be housed in a substantially flat housing. The monitor converts the detected voltage to an audible signal with both amplitude modulation and Doppler effect. It further uses a dual time constant to reduce the effect of gross sensor-to-surface movement. The monitor detects the movement of one or more internal body parts, such as the heart, lungs, arteries, and vocal chords, and includes a pulse generator for simultaneously inputting a sequence of pulses to a transmit path and a gating path. The pulses transmitted along the transmit path drive an impulse generator and provide corresponding transmit pulses that are applied to a transmit antenna. The gating path includes a range delay generator which generates timed gating pulses. The timed gating pulses cause the receive path to selectively conduct pulses reflected from the body parts and received by a receive antenna. The monitor output potential can be separated into a cardiac output indicative of the physical movement of the heart, and a pulmonary output indicative of the physical movement of the lung.

Claims

1. A monitor for detecting the movement of one or more body parts, comprising;

(a) a pulse generator for producing and simultaneously inputting a sequence of pulses to a transmit path and a gating path;

(b) an impulse generator connected to said pulse generator for producing corresponding transmit pulses;

(c) a transmit antenna connected to impulse generator to transmit said transmit pulses toward the one or more body parts;

(d) a range delay generator connected to said pulse generator for generating timed gating pulses;

(e) a receive antenna;

(f) a sampling receiver connected to said receive antenna in a receive path;

(g) said range delay generator being connected to said sampling receiver and producing timed gating pulses at a fixed range corresponding to the location of the one or more body parts so that said timed gating pulses cause said sampling receiver to selectively sample pulses reflected from the one or more body parts and received by said receive antenna to produce an averaged sampled signal;

(h) a signal processor connected to said sampling receiver for detecting changes in the averaged sampled signal and providing an output signal indicative of motion of said one or more body parts.

2. The monitor according to claim 1, for detecting movement of a heart;

wherein said signal processor includes means for producing non-acoustic indications of the movement of the heart.

3. The monitor according to claim 2, for detecting movement of a lung;

wherein said signal processor includes means for producing non-acoustic indications of the movement of the lung.

4. The monitor according to claim 2, for detecting movement of both a heart and a lung;

wherein the output signal corresponds to the physical movement of the heart and lung; and

wherein said signal processor includes means for separating the output signal into a cardiac output indicative of the physical movement of the heart, and a pulmonary output indicative of the physical movement of the lung.

5. The monitor according to claim 4, wherein the separating means comprises a bandpass filter for separating said output signal into said cardiac output.

6. The monitor according to claim 4, wherein the separating means comprises a bandpass filter for separating said output signal into said pulmonary output.

7. The monitor according to claim 1, wherein said sampling receiver comprises a sample and hold circuit that is gated by said gating pulses from said gating path.

8. The monitor according to claim 7, wherein said range delay generator produces a gating pulse which is delayed by approximately 2 nanoseconds (2 ns) from the time that said transmit antenna radiates a transmit pulse;

and

further comprising an impulse generator connected between the range delay generator and the sample and hold circuit which produces a 200 ps gating pulse for gating said sample and hold circuit.

9. The monitor according to claim 1, wherein said range delay generator comprises an adjustable fixed delay so that the timed gating pulses determine the range gating of the monitor to the one or more body parts.

10. The monitor according to claim 9, wherein said sampling receiver comprises a sample and hold circuit that is gated by said gating pulses from said gating path;

and

wherein said sample and hold circuit samples the pulses along said receive path at least 1,000 times and produces an averaged sample signal with a peak value substantially equal to that of a reflected pulse.

11. The monitor according to claim 9, wherein said signal processor further includes a summation element connected to the sample and hold circuit which subtracts background reflections, and an amplifier connected to the summation element for amplifying the output of said summation element.

12. The monitor according to claim 11, further comprising an audio oscillator which has its output multiplied by the output from said amplifier;

and

wherein the output of said audio oscillator is frequency modulated by the rate of change of the signal from said amplifier for generating a Doppler effect that is related to the velocity of the movement of said body parts.

13. The monitor according to claim 11 further comprising a differentiation circuit connected to said amplifier for deriving the rate of change of the signal from said amplifier.

14. The monitor according to claim 11, wherein said signal processor further includes a feedback path comprising an integrator which servo'"'"'s the output of said amplifier until an equilibrium is reached, such that the output of said amplifier is forced to equal a reference voltage applied to said integrator.

15. The monitor according to claim 11, further including a dual time constant circuit such that for large signals related to gross sensor motion relative to pulmonary motion, there is a fast AC coupling time constant, and for normal signal levels related to heart motion there is a much slower AC coupling time constant.

16. The monitor according to claim 15, wherein said dual time constant circuit includes two oppositely oriented diodes shunted by a resistor.

17. The monitor according to claim 1, wherein said range delay generator produces alternating delays so that the timed gating pulses determine at least a first and second range gates.

18. The monitor according to claim 1, further comprising a homodyne oscillator connected to the impulse generator which generates homodyne signals to modulate the transmit pulses, and a demodulator connected to the sampling receiver and the homodyne oscillator to remove said modulation from the sampled reflected pulses.

19. The monitor according to claim 18, wherein said homodyne signals are fed to said impulse generator for selectively switching ON and OFF said impulse generator at a predetermined homodyne frequency.

20. The monitor according to claim 18 wherein said demodulator comprises a synchronous rectifier.

21. The monitor according to claim 1 for detecting movement of the vocal chords wherein the signal processor includes means for passing output signals in a bandwidth range of about 20 Hz-3 KHz.

22. Method for monitoring the movement of one or more internal body parts, comprising:

(a) simultaneously inputting a sequence of pulses to a transmit path and a gating path;

(b) producing transmit pulses in said transmit path from said input sequence of pulse and launching said transmit pulses toward the one or more internal body parts;

(c) generating timed gating pulses in said gating path from said input sequence of pulses, said gating pulses defining a fixed range gate at the position of the one or more body parts;

(d) selectively receiving pulses reflected from the one or more body parts by receiving reflected signals coincident with the timed gating pulses;

(e) sampling and storing said selected reflected pulses to produce an averaged sampled signal;

(f) detecting changes in the averaged sampled signal to detect movement of the one or more body parts.

23. The method of claim 22 further comprising directing said transmit pulses towards any of the heart, lungs, and vocal chords;

selecting said fixed range gate to receive signals reflected therefrom; and

producing an output signal indicative of movement thereof.