APPARATUS AND METHODS THAT USE MAGNETIC INDUCTION SPECTROSCOPY TO MONITOR TISSUE FLUID CONTENT

• US 20180143150A1
• Filed: 05/27/2015
• Published: 05/24/2018
• Est. Priority Date: 06/03/2014
• Status: Active Application

• Current Assignee: Koninklijke Philips N.V.
• Original Assignee: Rick Bezemer
• Inventors: Bezemer, Rick, Bongers, Edwin Gerardus Johannus
• Application Number:
  US15/316,317
• Publication Number:
  US 20180143150A1
• Time in Patent Office: Days
• CPC Class Codes: A61B 2562/0223 Magnetic field sensors
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02108 from analysis of pulse wave characteristics
• 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 5/02444 Details of sensor A61B5/02427 takes precedence
• 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 5/0537 Measuring body composition by impedance, e.g. tissue hydration or fat content
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/11 Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb for measuring pulse A61B5/02 ;A61B5/1038 takes precedence; motion detection to correct for motion artifacts in physiological signals A61B5/721
• CPC Class Codes: A61B 5/4875 Hydration status, fluid retention of the body
• CPC Class Codes: A61B 5/721 using a separate sensor to detect motion or using motion information derived from signals other than the physiological signal to be measured
• CPC Class Codes: A61B 5/7214 using signal cancellation, e.g. based on input of two identical physiological sensors spaced apart, or based on two signals derived from the same sensor, for different optical wavelengths
• CPC Class Codes: G01N 27/025 a current being generated within the material by induction
• CPC Class Codes: G01N 27/74 of fluids G01N24/00 takes precedence

Abstract

There is provided an apparatus for using magnetic induction spectroscopy, MIS, to determine a measure of the fluid content of a tissue sample of a subject, the apparatus comprising a first excitation coil that is to be placed near to the tissue sample for inducing a current in the tissue sample; a reference coil; a second excitation coil that is arranged close to the reference coil and that is for inducing a current in the reference coil; and a control unit that is configured to apply an alternating current to the first excitation coil and the second excitation coil; obtain a measure of the current induced in the tissue sample; and determine a measure of the fluid content of the tissue sample from the measure of the current induced in the tissue sample.

Claims

1. An apparatus for using magnetic induction spectroscopy, MIS, to determine a measure of fluid content of a tissue sample of a subject, the apparatus comprising:

a first excitation coil that is to be placed near to the tissue sample for inducing a current in the tissue sample;

a receiver coil that is to be placed near to the tissue sample so that the first excitation coil and the current in the tissue sample induce a current in the receiver coil;

a reference coil;

a second excitation coil that is arranged close to the reference coil for inducing a current in the reference coil; and

a control unit that is configured to;

apply an alternating current to the first excitation coil and the second excitation coil;

obtain a measure of the current induced in the tissue sample from a first signal and a second signal, the first signal representing the current induced in the reference coil by the second excitation coil and the second signal representing the current induced in the receiver coil by the first excitation coil and the current in the tissue sample; and

determine a measure of the fluid content of the tissue sample from the measure of the current induced in the tissue sample.

2. An apparatus as claimed in claim 1, wherein the control unit is configured to apply the same alternating current to each of the first excitation coil and the second excitation coil.

3. An apparatus as claimed in claim 1, wherein the receiver coil is connected to the reference coil such that the current induced in the receiver coil by the first excitation coil and the current in the tissue sample flows in the opposite direction to the current induced in the reference coil by the second excitation coil;

and

wherein the control unit is configured to obtain the measure of the current induced in the tissue sample and to determine the measure of the fluid content of the tissue sample using the output of the interconnected receiver coil and reference coil and a third signal, the third signal representing the alternating current applied to the first excitation coil and the second excitation coil.

4. An apparatus as claimed in claim 1, wherein the first excitation coil and the receiver coil are configured to be placed around the tissue sample to be measured.

5. An apparatus as claimed in claim 1, wherein the control unit is configured to apply an alternating current having a first magnitude to the first excitation coil and the second excitation coil in order to measure the fluid content of the tissue sample at a first depth in the tissue sample, and wherein the control unit is further configured to:

apply a further alternating current having a second magnitude to the first excitation coil and the second excitation coil in order to measure the fluid content of the tissue sample at a second depth in the tissue sample;

obtain a measure of the current induced in the tissue sample at the second depth; and

determine a measure of the fluid content of the tissue sample at the second depth from the potential measured in the tissue sample at the second depth.

6. An apparatus as claimed in claim 1, wherein the control unit is further configured to:

control the apparatus to determine a plurality of measures of the fluid content of the tissue sample over time; and

analyse the plurality of measures of the fluid content of the tissue sample over time to determine a measure of at least one of a heart rate, a breathing rate or a pulse pressure variations of the subject.

7. An apparatus as claimed in claim 1, the apparatus further comprising a motion sensor configred to be attached to the subject for measuring movement of the subject;

wherein the control unit is further configured to;

analyse the measurements of the movement of the subject from the motion sensor to determine if the amount of movement exceeds a threshold value; and

discard the measure of the fluid content if the amount of movement exceeds the threshold value.

8. An apparatus as claimed in claim 1, the apparatus further comprising a motion sensor configred to be attached to the subject for measuring movement of the subject;

wherein the control unit is further configured to;

analyse the measurements of the movement of the subject from the motion sensor to determine if the amount of movement exceeds a threshold value; and

only apply the alternating current to the first excitation coil and the second excitation coil if the amount of movement is below the threshold value.

9. A method of using magnetic induction spectroscopy, MIS, to determine a measure of the fluid content of a tissue sample of a subject, the method comprising:

applying an alternating current to a first excitation coil configured to be placed near to the tissue sample to induce a current in the tissue sample and a receiver coil configured to be placed near to the tissue sample and to a second excitation coil arranged close to a reference coil to induce a current in the reference coil;

obtaining a measure of the current induced in the tissue sample from a first signal and a second signal, the first signal representing the current induced in the reference coil by the second excitation coil and the second signal representing the current induced in the receiver coil by the first excitation coil and the current in the tissue sample; and

determining a measure of the fluid content of the tissue sample from the measure of the current induced in the tissue sample.

10. A method as claimed in claim 9, wherein the step of applying an alternating current comprises applying the same alternating current to each of the first excitation coil and the second excitation coil.

11. A method as claimed in claim 9, the method further comprising the step of:

connecting the receiver coil to the reference coil such that the current induced in the receiver coil by the current in the tissue sample flows in the opposite direction to the current induced in the reference coil by the second excitation coil;

wherein the steps of obtaining the measure of the current induced in the tissue sample and determining the measure of the fluid content of the tissue sample use the output from the connected receiver coil and reference coil and a third signal, the third signal representing the alternating current applied to the first excitation coil and the second excitation coil.

12. A method as claimed in claim 9, the method further comprising the step of placing the first excitation coil and the receiver coil around the tissue sample to be measured.

13. A method as claimed in claim 9, wherein the step of applying an alternating current to the first excitation coil and the second excitation coil comprises applying an alternating current having a first magnitude in order to measure the fluid content of the tissue sample at a first depth in the tissue sample;

the method further comprising the steps of;

applying a further alternating current having a second magnitude to the first excitation coil and the second excitation coil in order to measure the fluid content of the tissue sample at a second depth in the tissue sample; and

obtaining a measure of the current induced in the tissue sample at the second depth; and

determining a measure of the fluid content of the tissue sample at the second depth from the measure of the current induced in the tissue sample at the second depth.

14. A method as claimed in claim 9, the method further comprising the steps of:

determining a plurality of measures of the fluid content of the tissue sample over time; and

analysing the plurality of measures of the fluid content of the tissue sample over time to determine a measure of the heart rate, breathing rate and/or pulse pressure variations of the subject.

15. A method as claimed in claim 9, the method further comprising the steps of:

measuring movement of the subject;

analysing the measurements of the movement of the subject to determine if the amount of movement exceeds a threshold value; and

one of the steps of;

discarding the measure of the fluid content if the amount of the movement exceeds the threshold value;

or

applying the alternating current to the first excitation coil and the second excitation coil only if the amount of the movement is below the threshold value.