NON-INVASIVE ELECTROMAGNETIC BLOODFLOW MEASURING SYSTEM WITH REJECTION OF NOISES

• US 3,809,070 A
• Filed: 10/11/1972
• Issued: 05/07/1974
• Est. Priority Date: 07/01/1971
• Status: Expired due to Term

• Current Assignee: Hans J. Broner, Henri Georges Doll
• Original Assignee: Hans J. Broner, Henri Georges Doll
• Inventors: Doll, Henri Georges, Broner, Hans J.
• Primary Examiner(s): Howell, Kyle L.
• Application Number:
  US05/296,677
• Time in Patent Office: 573 Days
• Field of Search: 128/2.5F,2.5R 73/194EM
• US Class Current: 600/409
• CPC Class Codes: A61B 5/0265 using electromagnetic means, e.g. electromagnetic flowmeter
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: G01F 1/58 by electromagnetic flowmeters

Abstract

A non-invasive measuring system adapted to measure arterial blood flow in human beings is provided. A stable, strong magnetic field is produced in the region of the artery under measurement by a magnet suitably positioned near the human being. A mechanical means moves the magnet away from its normal position or back to such position. The blood flow induced signals, which are pulsatile, are sensed by electrodes placed on the skin adjacent to the artery. Mixed with the blood flow signals are the local electrocardiogram signals. In addition, the electrodes also pick up random noises which are not synchronized with the heart. The signals are amplified and processsed by a repetitive waveform averager which is synchronized by a cardiogram signal obtained from auxiliary electrodes. The waveform averager accumulates a first predetermined number of composite pulsatile signals from said measuring electrodes during a first series of heart cycles occurring when the magnetic field is produced in the region of the artery, and accumulates an equal number of composite pulsatile signals from said measuring electrodes during a second series of heart cycles occurring when the magnetic field in the region is suppressed. A signal selector includes a comparator connected at the input of the waveform averager for comparing each incoming pulsatile signal with predetermined acceptable signal characteristics, so that the incoming pulsatile signal will be accumulated by the waveform averager only if it is accepted by the signal selector. The waveforms registered in the waveform averager respectively during the first and the second series of heart cycles are subtracted from each other to obtain the blood flow pulse substantially free from electrocardiogram and random noise influence.

Claims

1. A blood flow measuring system comprising:

first sensory means adapted to be positioned on the skin of a living being at such locations that a strong and sharp cardiogram can be repeatedly obtained to use as a synchronizing signal and as a clock;

means for producing in the region of a blood vessel a stable and sufficiently homogeneous magnetic field having an intensity large enough to generate measurable blood flow signals in said region;

second sensory means adapted to be placed on the skin or in the subcutaneous tissue of said living being at locations adjacent to said vessel;

amplifying means for amplifying the composite pulsatile signals sensed by said second sensory means during successive heart cycles, said composite pulsatile signals generally including a blood flow waveform component which is proportional not only to the blood flow but also to the intensity of the magnetic field, and a random noise component;

measuring means synchronized by said synchronizing signal derived from said first sensory means to average, in waveform, a predetermined number of composite pulsatile signals from said second sensory means accumulated during a series of heart cycles, said measuring means including a waveform averager having individual storage elements which accumulate voltage samples of said pulsatile signals taken at corresponding time intervals of all successive heart cycles of said series;

signal selector means including comparator means connected at the input to said waveform averager for comparing each incoming pulsatile signal with predetermined acceptable signal characteristics, and gating means for enabling said incoming pulsatile signal to be accumulated by said waveform averager only if said pulsatile signal is within said acceptable signal characteristics; and

means for indicating the waveform averaged blood flow signal.

2. System as recited in claim 1, wherein said signal selector means includes reference means for providing maximum and/or minimum acceptable amplitude for each pulsatile signal to be accumulated by said waveform averager, said reference means being connected to said comparator means.

3. System as recited in claim 1, wherein said signal selector means includes a reference means for providing an acceptable pulsatile signal duration defined by the time duration between successive pulsatile signals as characterized by the synchronizing signal in each cycle, said reference means being connected to said comparator means.

4. A method for measuring the blood flow waveform in a blood vessel of a living being comprising:

producing a strong and homogeneous magnetic field of an intensity sufficient to produce measurable blood flow signals in the region of said blood vessel;

sensing a plurality of successive composite pulsatile signals by measuring electrodes placed on the skin or in the tissue of said living being at a location adjacent said blood vessel, said composite pulsatile signals generally comprising a blood flow waveform component, and a random noise component;

deriving a synchronizing signal from a cardiogram signal sensed by auxiliary electrodes positioned on the skin of the living being;

comparing each composite pulsatile signal with predetermined acceptable waveform characteristics to determine which signals are acceptable for waveform averaging;

selecting only those composite pulsatile signals which have been determined to be acceptable for waveform averaging;

waveform averaging a predetermined number of successive acceptable composite pulsatile signals sensed by said measuring electrodes during a series of heart cycles occurring while said magnetic field is in said region, said waveform averaging being accomplished by accumulating voltage samples of said pulsatile signals taken at corresponding time intervals of all successive heart cycles of said series; and

indicating the waveform averaged blood flow signal.

5. A blood flow measuring system comprising:

first sensory means adapted to be positioned on the skin of a living being at such locations that a strong and sharp cardiogram can be repeatedly obtained to be used as a synchronziing signal and as a clock;

means for producing in the region of a blood vessel a stable and sufficiently homogeneous magnetic field having an intensity large enough to produce measurable blood flow signals for said region;

second sensory means adapted to be placed on the skin or in the subcutaneous tissues of said living being at locations adjacent to said vessel;

amplifying means for amplifying the composite pulsatile signals sensed by said second sensory means during successive heart cycles, said composite pulsatile signals generally comprising a blood flow waveform component proportional not only to the blood flow but also to the intensity of the magnetic field, a local electrocardiogram component and random noise components;

measuring means synchronized by said synchronizing signal derived from said first sensory means to average, in waveform, a predetermined number of composite pulsatile signals from said second sensory means accumulated during a series of heart cycles;

to eliminate the random noise signals, said measuring means including a waveform averager having individual storage elements which accumulate voltage samples of said pulsatile signals taken at corresponding time intervals of all successive heart cycles;

means for producing a cardiogram signal of said living being for use as a bucking signal, said means including subtraction means for subtracting said bucking cardiogram signal from said composite pulsatile signals provided at said second sensory means, whereby the relative amplitude of said local electrocardiogram component with respect to said blood flow waveform amplitude is reduced, either continuously during each cycle of said series of heart cycles, or on the averaged waveform of said series, so that the reduced amplitude of said local cardiogram component is made small and practically negligible with respect to said blood flow waveform amplitude; and

means for indicating the waveform averaged signal.

6. System as recited in claim 5, wherein said second sensory means comprise more than two measuring electrodes, two of said measuring electrodes being adapted to be located near to the blood vessel, and the other said electrode or electrodes being adapted to be in such a position that, by combination with the first said electrodes through amplifying and adding circuits, said other electrode or electrodes provide the bucking cardiogram waveform which essentially cancels the local cardiogram waveform component which would otherwise be be mixed with the blood flow waveform in the composite signal measured between the two said measuring electrodes that are near the blood vessel.

7. System as recited in claim 5, wherein said means for producing a cardiogram signal for use as a bucking signal comprises additional sensory means adapted to be placed on the skin of the said living being.

8. System as recited in claim 7, wherein said subtraction means includes differential amplifier means connected at its inputs, respectively, to said second sensory means and said additional sensory means, resistive means connected at an output of sad differential amplifier means for matching the amplitudes of said bucking cardiogram and said local cardiogram component, whereby the outputs of said differential amplifier means are substantially matched by means of said resistive means.

9. System as recited in claim 8, further comprising adder means for adding the outputs of said differential amplifier means.

10. System as recited in claim 5, wherein said measuring means includes counter means for counting said predetermined number of incoming pulsatile signals which are received in said waveform averager, said counter means providing a control output signal when said predetermined number of pulsatile signals has been counted.

11. System as recited in claim 10, wherein the output of said counter means is used to terminate the accumulation in said waveform averager of a predetermined number of pulsatile signals.

12. System as recited in claim 10, wherein the output of said counter means is connected to a means for changing said magnetic field to thereby activate the same.

13. A method for measuring the blood flow waveform in a blood vessel of a living being, comprising:

producing a strong and homogeneous magnetic field of a first intensity value in the region of said blood vessel;

sensing a purality of successive composite pulsatile signals by measuring electrodes placed on the skin or in the tissue of said living being at a location adjacent said blood vessel, said composite pulsatile signals generally comprising a blood flow waveform component, a local cardiogram component and a random noise component;

deriving a synchronizing signal from a cardiogram signal sensed by auxiliary electrodes positioned on the skin of the living being;

comparing each composite pulsatile signal with predetermined acceptable waveform characeristics to determine which signals are acceptable for waveform averaging;

selecting only those composite pulsatile signals which have been determined to be acceptable for waveform averaging;

waveform averaging a predetermined number of successive acceptable composite pulsatile signals sensed by said measuring electrodes during a first series of heart cycles occurring while said magnetic field in said region is of said first intensity value, said waveform averaging being accomplisheD by accumulating voltage samples of said pulsatile signals taken at corresponding time intervals of all successive heart cycles of said first series;

changing said magnetic field from said first intensity value to a second intensity value in the region of said blood vessel and thereafter waveform averaging a predetermined number of composite pulsatile signals sensed by said measuring electrodes during a second series of herat cycles;

combining said averaged first series of composite pulsatile signals with said averaged second series of composite pulsatile signals in a manner whereby the local cardiogram component is eliminated to thereby derive a blood flow waveform which is substantially free from the local cardiogram; and

indicating the waveform averaged blood flow signal.

14. Method as recited in claim 13, further comprising:

prior to the step of waveform averaging each of said composite pulsatile signals, temporarily storing each of said composite pulsatile signals until it has been determined which signals are accepted or rejected for waveform averaging.

15. Method as recited in claim 13, wherein said composite pulsatile signals are compared with a reference means providing a maximum and/or minimum acceptable amplitude for each pulsatile signal.

16. Method as recited in claim 13, wherein said composite pulsatile signals are compared with a reference means providing an acceptable pulsatile signal duration defined by the time duration between successive pulsatile signals as characterized by the synchronizing signal in each cycle.

17. Method as recited in claim 13, further comprising:

producing a cardiogram signal of said living being for use as a bucking signal, and subtracting said bucking cardiogram signal from said composite pulsatile signals provided at said measuring electrodes, whereby the relative amplitude of said local cardiogram component with respect to said blood flow waveform amplitude is reduced.

18. Method as recited in claim 17, further comprising:

adjusting the amplitude of said bucking cardiogram signal so that it is the same amplitude as the local cardiogram component of the composite pulsatile signals, whereby subtraction of said adjusted bucking cardiogram signal from said composite pulsatile signal will substantially reduce or cancel the local cardiogram component of said composite pulsatile signal.

19. A method as recited in claim 13, wherein said magnetic field during one of said series of heart cycles is of sufficient intensity to generate measurable blood flow signals in the region of the blood vessel, and the magnetic field intensity during the other of said series of heart cycles is essentially suppressed.

20. A method as recited in claim 19, wherein said magnetic field is suppressed by moving said magnetic field to a location remote from the region of said blood vessel.

21. Method as recited in claim 13 wherein said waveform averaging of said first series of successive composite pulsatile signals occurs while said magnetic field in said region is suppressed to produce a waveform averaged local cardiogram of said first series of heart cycles, said waveform averaging of of said second series of successive composite pulsatile signals occurs while said magnetic field in said region is active, and further comprising the steps of waveform averaging a third series of heart cycles occurring while said magnetic field in said region is suppressed to produce a local cardiogram average of said third series of heart cycles, comparing the local cardiogram averaged during said first series with the local cardiogram averaged during said third series, to determine the stability of the local cardiogram whereby the composite pulsatile signals sensed during said second series of heart cycles can be prevented from being processed or recorded if the waveform difference between said first and third series of averaged local cardiogram signals is in excess of prescribed limits.

22. Method as recited in claim 13, wherein said step of changing said magnetic field from said first intensity value to a second intensity value in the region of said blood vessel is preceeded by deactivating and reversing the polarity of the circuits used to obtain said composite pulsatile signals after said first series of heart cycles are waveform averaged, suppressing said magnetic field while said circuits are deactivated, and then reactivating said circuits for sensing and waveform averaging said second series of heart cycles, whereby the local cardiogram signals sensed during said first series of heart cycles will be substantially cancelled by the local cardiogram signals sensed during said second series of heart cycles, making available the blood flow waveform without the local cardiogram component.

23. Method as recited in claim 13, wherein the magnetic field intensity during one of said series of heart cycles remains essentially suppressed so that a local cardiogram is waveform averaged during said series of heart cycles, and further comprising the step of storing said averaged local cardiogram as a source for subsequent series of herat cycles, until such time as said stored local cardiogram needs to be updated.

24. Method as recited in claim 23, wherein said step of combining said averaged first series of signals with said averaged second series of signals is carried out by subtracting the averaged local cardiogram which has been averaged and stored, during a series of heart cycles, from the composite pulsatile signals measured in subsequent series of heart cycles taken while said magnetic field remains applied in the region of said blood vessel, whereby the local cardiogram component is essentially cancelled out from said composite pulsatile signals.

25. Method as recited in claim 13, wherein one or more of said auxiliary electrodes is the same as one or more of said measuring electrodes.

26. A blood flow measuring system comprising:

1 first sensory means adapted to be positioned on the skin of a living being at such locations that a strong and sharp cardiogram can be repeatedly obtained to be used as a synchronizing signal and as a clock;

means for producing in the region of a blood vessel a stable and sufficiently homogeneous magnetic field of a first intensity value;

means for changing said magnetic field in said region from said first intensity value to a second and substantially different intensity value, at least one the two said magnetic field intensity values being large enough to generate measurable blood flow signals in said region;

second sensory means adapted to be placed on the skin or in the subcutaneous tissues of said living being at locations adjacent to said vessel;

amplifying means for amplifying the composite pulsatile signals sensed by said second sensory means during successive heart cycles, said composite pulsatile signals generally comprising a blood flow waveform component proportional not only to the blood flow but also to the intensity of the magnetic field, a local electrocardiogram component and random noise components;

measuring means synchronized by said synchronizing signal derived from said first sensory means to average, in waveform, a first predetermined number of composite pulsatile signals from said second sensory means accumulated during a first series of heart cycles occurring when the magnetic field in said region is of said first intensity value, and to average a second predetermined number of composite pulsatile signals from said second sensory means accumulated during a second series of heart cycles occurring when the magnetic field in said region is of said second intensity value, said measuring means including a waveform averager having individual storage elements which accumulate voltage samples of said pulsatile signals taken at corresponding time intervals of all successive heart cycles of said first series and said second series;

signal selector means including comparator means connected at the input to said waveform averAger for comparing each incoming pulsatile signal with predetermined acceptable signal values, and gating means for enabling said incoming pulsatile signal to be accumulated by said waveform averager only if said pulsatile signal is within said acceptable values;

means to subtract from each other the waveforms registered in said waveform averager respectively during the first and the second series of heart cycles to obtain the blood flow waveform substantially free from electrocardiogram and random noise influence; and

means for indicating the waveform averaged blood flow signal.

27. System as recited in claim 26, wherein said signal selector means includes reference means for providing maximum and/or minimum acceptable amplitude for each pulsatile signal to be accumulated by said waveform averager, said reference means being connected to said comparator means.

28. System as recited in claim 26, wherein said signal selector means includes a reference means for providing an acceptable pulsatile signal duration defined by the time duration between successive pulsatile signals, as characterized by the synchronizing signal in each cycle, said reference means being connected to said comparator means.

29. System as recited in claim 26, further comprising a temporary memory connected at the input to said signal selector means, said temporary memory being connected to receive and store the composite pulsatile signals after they are amplified by said amplifier means, said temporary memory being connected to said comparator means for enabling said signal selector means to pass on to said averager means the selected pulsatile signal stored in said temporary memory.

30. System as recited in claim 26, wherein said measuring means includes counter means connected to said signal selector means for counting a predetermined number of incoming pulsatile signals which are accepted by said signal selector means, said counter means providing a control output signal when said predetermined number of pulsatile signals has been counted.

31. System as recited in claim 30, wherein the output of said counter means is used to terminate the accumulation in said waveform averager of a predetermined number of pulsatile signals.

32. System as recited in claim 30, wherein the output of said counter means is connected to said means for changing said magnetic field to thereby activate the same.

33. System as recited in claim 32, wherein said means for producing a strong and homogeneous magnetic field comprises a permanent magnet system.

34. System as recited in claim 33, wherein said permanent magnet system includes motorized means for moving said system from a first position such that the strong and homogeneous field is applied to the region of the blood vessel, to a second position such that the magnetic field in the region of the blood vessel is essentially suppressed.

35. System as recited in claim 33, wherein said permanent magnet system includes motorized means for moving said system from a first position such that the magnetic field is applied to the blood vessel with a first polarity, to a second position such that the magnetic field is applied to the region of the blood vessel with the opposite polarity.

36. System as recited in claim 26, wherein said second sensory means comprise more than two measuring electrodes, two of said measuring electrodes being adapted to be located near the blood vessel, and the other said electrode or electrodes being adapted to be in such a position that, by combination with the first said electrodes through amplifying and adding circuits, said other electrode or electrodes provide a cardiogram waveform which essentially cancels the local cardiogram waveform component which would otherwise be mixed with the blood flow waveform in the composite signal measured between the two said measuring electrodes that are near the blood vessel.

37. System as recited in claim 26, further comprising additional sensory means adapted to be placed on thE skin of said living being to produce a bucking cardiogram waveform, and subtraction means for subtracting said bucking cardiogram waveform from said composite pulsatile signals provided at said second sensory means to thereby essentially cancel the local electrocardiogram component of said composite pulsatile signals.

38. System as recited in claim 37, wherein said subtraction means includes differential amplifier means connected respectively to said second sensory means and said additional sensory means, resistive means connected at an output of said differential amplifier means for matching the amplitudes of said bucking cardiogram produced by said additional sensory means and said local cardiogram component produced by said second sensory means, whereby the outputs of said differential amplifier means are substantially matched by means of said resistive means.

39. System as recited in claim 38, further comprising adder means for adding the outputs of said differential amplifier means.