Method and apparatus for screening or sensing bodily conditions using DC biopotentials

• US 5,678,547 A
• Filed: 04/26/1995
• Issued: 10/21/1997
• Est. Priority Date: 12/22/1988
• Status: Expired due to Fees

• Current Assignee: Biofield Corporation, Sea Med Corporation
• Original Assignee: Biofield Corporation
• Inventors: Doe, Kenneth E., Gordon, Charles Leonard, Hagstrom, Steven Erik, Faupel, Mark L., Stephens, John D., Nathanson, Seth D.
• Primary Examiner(s): Casler, Brian L.
• Application Number:
  US08/429,138
• Time in Patent Office: 909 Days
• Field of Search: 128/653.1, 128/733, 128/734, 128/639, 128/731, 364/413.02
• US Class Current: 600/409
• CPC Class Codes: A61B 2562/046 in a matrix array
• CPC Class Codes: A61B 5/05 Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves impedance plethysmography A61B5/0295; measuring movement of the entire body or parts thereof A61B5/11; detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof A61B5/24
• CPC Class Codes: A61B 5/0531 Measuring skin impedance
• CPC Class Codes: A61B 5/24 Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
• CPC Class Codes: A61B 5/2415 Measuring direct current [DC] or slowly varying biopotentials
• CPC Class Codes: A61B 5/282 Holders for multiple electrodes for introduction into the body A61B5/287
• CPC Class Codes: A61B 5/7264 Classification of physiological signals or data, e.g. using neural networks, statistical classifiers, expert systems or fuzzy systems neural networks per se G06N3/00; expert systems per se G06N5/00
• CPC Class Codes: A61B 5/7267 involving training the classification device
• CPC Class Codes: G06N 3/045 Combinations of networks
• CPC Class Codes: G16H 50/20 for computer-aided diagnosis, e.g. based on medical expert systems

Abstract

A method and apparatus for screening or sensing disease states, injury sites or bodily conditions in a human or animal subject by separately detecting the DC biopotential of the electromagnetic field at a plurality of test points in a test area. The DC biopotentials are converted by analog to digital converters connected to DC biopotential test sensors at the test points into digital test signals, and the DC biopotential test sensors and analog to digital converters form a biopotential sensing section which is separate from a processing section that receives and processes the digital test signals. Signals between the processing section and the bopotential sensing section are transmitted by a transmission network which electrically isolates the two sections. The conversions performed by the analog to digital converters are synchronized with the AC line frequency of the apparatus power supply, and the digital test signals are filtered in the processing section by digital filters, each of which is dedicated to an individual DC biopotential test sensor.

Claims

1. An apparatus for sensing a condition at a test site on a human or animal subject by detecting DC biopotentials during a test period which are a function of the electromagnetic field present in the subject at the test site, said apparatus being powered by an AC power supply having an AC line frequency and comprising:

at least one DC biopotential reference sensor for contacting the subject at a reference location,

a plurality of DC biopotential test sensors for contacting the subject at spaced locations at the test site, each said test sensor operating with a reference sensor to detect DC biopotentials which are present in the area of said test site and to provide DC test potentials as a function thereof,

an analog to digital converter operably connected to said test sensors for receiving said DC test potentials and for converting said analog DC test potentials to digital test signals,

a timing circuit for sensing said AC line frequency and controlling said analog to digital converter to synchronize the conversion operations of said analog to digital converter with said AC line frequency.

2. The apparatus of claim 1 wherein said timing circuit causes said analog to digital converter to provide two conversion operations for each half cycle of AC line frequency.

3. The apparatus of claim 2 wherein said timing circuit causes said analog to digital converter to provide a conversion operation at points on each half cycle of AC line frequency which are substantially equidistant from a peak 90 degree point of such half cycle and are on opposite sides of said peak point.

4. The apparatus of claim 1 which includes a digital processor connected to receive said digital test signals from said analog to digital converter, said processor operating during a test period to sample a plurality of digital test signals which are a function of a plurality of DC test potentials from each test sensor and to identify potential relationships therebetween.

5. The apparatus of claim 4 wherein said processor provides control signals to control a sampling of DC test potentials during a test period, said processor including said timing circuit for providing conversion timing signals to control the conversion operations of said analog to digital converter.

6. An apparatus for sensing a condition at a test site on a human or animal subject by detecting DC biopotentials during a test period at the test site, said apparatus being powered by an AC power supply having an AC line frequency and comprising:

a biopotential sensing section including at least one DC biopotential reference sensor for contacting the subject at a reference location, a plurality of DC biopotential test sensors for contacting the subject at spaced locations at the test site, each said test sensor operating with a reference sensor to detect DC biopotentials and to provide DC test potentials as a function thereof, and an analog to digital converter connected to said test sensors for receiving said DC test potentials and for performing conversion operations for converting said DC test potentials to digital test signals,

a processing section connected to said AC power supply and including a digital processor operative during a test period to sample digital test signals which are a function of a plurality of DC test potentials from each test sensor and to identify potential relationships therebetween, said processor operating to provide control signals to said biopotential sensing section during said test period, the processor sensing said AC line frequency and providing control signals to said analog to digital converter to synchronize the conversion operations of said analog to digital converter with said AC line frequency, and

an isolation circuit connected between said biopotential sensing section and said processing section to transmit control signals to said biopotential sensing section and digital test signals to said processing section, said isolation circuit operating to electrically isolate said biopotential sensing section from said processing section and including test signal conversion means to convert digital test signals from said analog to digital converter to test optical signals and reconvert said test optical signals to electrical digital test signals at said processing section and control conversion means to convert said control signals from said processing section to optical control signals and reconvert said optical control signals to electrical signals at said biopotential sensing section.

7. An apparatus for sensing a condition at a test site on a human or animal subject by detecting DC biopotentials during a test period at the test site, said apparatus being powered by an AC power supply having an AC line frequency and comprising:

a biopotential sensing section including at least one DC biopotential reference sensor for contacting the subject at a reference location, a plurality of DC biopotential test sensors for contacting the subject at spaced locations at the test site, each said test sensor operating with a reference sensor to detect DC biopotentials which are present at said test site and to provide DC test potentials as a function thereof, and an analog to digital converter connected to said test sensors for receiving said analog DC test potentials and for performing conversion operations for converting said DC test potentials to digital test signals,

a processing section connected to said AC power supply and including a digital processor operative during a test period to sample digital test signals which are a function of a plurality of DC test potentials from each test sensor and to identify potential relationships therebetween, said processor operating to provide control signals to said biopotential sensing section during said test period, and operating to sense said AC line frequency and synchronize the conversion operations of said analog to digital converter with said AC line frequency, and

an isolation circuit connected between said biopotential sensing section and said processing section to transmit control signals to said biopotential sensing section and digital test signals to said processing section, said isolation circuit operating to electrically isolate said biopotential sensing section from said processing section.

8. An apparatus for sensing a condition at a test site on a human or animal subject by detecting DC biopotentials during a test period, said apparatus being powered by an AC power supply having an AC line frequency and comprising:

at least one DC biopotential reference sensor for contacting the subject at a reference location,

a plurality of DC biopotential test sensors for contacting the subject at spaced locations at the test site, each said test sensor having a signal output and operating with a reference sensor to detect DC biopotentials which are present in the area of said test site and to provide DC test potentials as a function thereof,

an analog to digital converter connected to said test sensors for converting DC test potentials to digital test signals,

a multiplexor connected between said test sensors and said analog to digital converter for sequentially switching among said test sensors during a test period and performing a parallel to serial conversion,

a de-multiplexor connected to the output of said analog to digital converter for decommutating said digital test signals and performing a serial to parallel conversion, and

a plurality of separate digital filters connected to said de-multiplexor for receiving said digital test signals from said analog to digital converter, said de-multiplexor providing digital test signals from each of said test sensors to one of said plurality of separate digital filters dedicated to receiving digital test signals from DC test potentials received from only that test sensor.

9. The apparatus of claim 8 which includes a signal ranging circuit connected to said digital filters for passing test signals within a predetermined millivolt range and rejecting test signals outside such predetermined range.

10. The apparatus of claim 8 which includes at least first and second separate sensor arrays, each of said sensor arrays including a plurality of said DC biopotential test sensors, said multiplexer operating during a test period to simultaneously provide DC test potentials from individual test sensors in said first and second sensor arrays, at least one analog to digital converter for each sensor array, each analog to digital converter operating during a test period to receive DC test potentials from its associated sensor array.

11. The apparatus of claim 8 which includes a digital processor operating during a test period to sample a plurality of said digital test signals which are a function of a plurality of DC test potentials from each test sensor, said processor including said digital filters and operating to demultiplex the serial test signals from the analog to digital converter and connect the decommutated digital test signals to said separate digital filters.

12. The apparatus of claim 11 wherein said digital processor senses said AC line frequency and synchronizes the conversion operations of said analog to digital converters with said AC line frequency.

13. An apparatus for sensing a condition at a test site on a human or animal subject by detecting DC biopotentials during a test period which are a function of the electromagnetic field present in the subject at the test site comprising:

a biopotential section including at least one reference electrode for contacting the subject at a reference location and a plurality of test electrodes for contacting the subject at spaced locations in the area of the test site, each test electrode having a signal output and operating with a reference electrode to detect DC biopotentials which are present at the test site and to provide DC test potentials as a function thereof, an analog to digital converter for converting said analog DC test potentials to digital test signals, and a multiplexer connected between said test electrodes and said analog to digital converter for providing serial analog DC test potentials to said analog to digital converter by switching between individual test electrodes during a test period and

a processing section including a digital processor operating during a test period to sample and process only digital test signals which are within a range of from -30 mv to +100 mv and to identify potential relationships therebetween while rejecting other test signals.

14. The apparatus of claim 13 wherein said biopotential sensing section includes at least first and second separate electrode arrays, each of said electrode arrays including a plurality of test electrodes, said multiplexer operating during a test period to simultaneously provide DC test potentials from individual test electrodes in said first and second electrode arrays, at least one analog to digital converter for each electrode array, each analog to digital converter operating during a test period to receive DC test potentials from its associated electrode array.

15. The apparatus of claim 14 wherein said processor provides control signals to said biopotential sensing section during said test period, said apparatus including an isolation circuit connected between said biopotential sensing section and said processing section to transmit control signals to said biopotential sensing section and digital test signals to said processing section, said isolation circuit operating to electrically isolate said biopotential sensing section from said processing section.

16. The apparatus of claim 15 wherein said isolation circuit (1) converts digital test signals from said analog to digital converter to optical signals and reconverts said digital test signals to electrical signals at said processing section and (2) converts said control signals from said processing section to optical signals and reconverts said control signals to electrical signals at said biopotential sensing section.

17. The apparatus of claim 16 wherein said processing section is connected to an AC power supply having an AC line frequency.

18. The apparatus of claim 17 wherein said processor senses said AC line frequency and synchronizes the conversion operations of said analog to digital converter with said AC line frequency.

19. The apparatus of claim 18 wherein said processing section includes a de-multiplexer for decommutating the serial digital test signals received from said analog to digital converter for performing a serial parallel conversion and separate digital filters being connected to the separate parallel outputs from said de-multiplexer for filtering said individual digital test signals.

20. A method for sensing and processing DC biopotentials from one or more test sites on a human or animal subject as a function of DC biopotentials present at the test site by using a plurality of spaced DC biopotential sensors in contact with the skin surface of the subject to take DC biopotential measurements, said DC biopotential sensors including one or more DC biopotential reference sensors and a plurality of DC biopotential test sensors which includes:

selecting during a test period a plurality of first and second pairs of DC biopotential sensors from said plurality of spaced DC biopotential sensors, each said first and second selected pair of DC biopotential sensors including a reference and a test sensor,

during a test period, taking a plurality of DC biopotential measurements with each said first and second pair of DC biopotential sensors to obtain a plurality of individual DC biopotential test values for each said first pair of DC biopotential sensors and a plurality of individual DC biopotential test values for each said second pair of DC biopotential sensors in each of said plurality of selected first and second pairs of DC biopotential sensors,

comparing each DC biopotential test value obtained by a first of each said selected first and second pairs of DC biopotential sensors with a DC biopotential test value obtained by a second of each said selected first and second pairs of DC biopotential sensors to obtain a difference value therebetween and to thereby obtain a plurality of difference values for each selected first and second pair of DC biopotential sensors, and

at the end of the test period averaging the plurality of differential values for each selected first and second pair of DC biopotential sensors to obtain a single average differential value for each selected first and second pair of DC biopotential sensors.

21. The method of claim 20 which includes comparing the single average differential values for all of said selected pairs of first and second DC biopotential sensors to identify the highest and the lowest single average differential value for the test period and obtaining maximum differential value for the test period indicative of the difference between the highest and lowest single average differential values.

22. A method for simulating the DC biopotentials for points of a test area on a human or animal subject which are not directly contacted by DC biopotential sensors applied to the skin surface of subject in the test area which includes:

applying one or more DC biopotential reference sensors to the subject,

applying a plurality of spaced DC biopotential test sensors to the skin surface of the subject in the test area with each test sensor at a known separate one of a plurality of measurement points,

taking a plurality of DC biopotential measurements with a reference DC biopotential sensor and each of the DC biopotential sensors at each measurement point during a test period to obtain a plurality of DC biopotential test values for each measurement point,

averaging the DC biopotential test values for each measurement point to obtain an average DC biopotential value for each measurement point, and

inferring a DC biopotential value for an interpolation point in the test area not contacted by a DC biopotential test sensor by vector summing wherein the sum of the average DC biopotential values for the measurement points relative to the vector distance from the interpolated point to each measurement point is used to infer said interpolation point DC biopotential value.

23. The method of claim 22 which includes inferring a DC biopotential value for a plurality of interpolation points and subsequently generating an image using the average DC biopotential values for each measurement point and the DC biopotential inferred for each interpolation point.