Impedance measurement process

• US 20110046505A1
• Filed: 08/07/2008
• Published: 02/24/2011
• Est. Priority Date: 08/09/2007
• Status: Abandoned Application

• Current Assignee: ImpediMed Limited
• Original Assignee: ImpediMed Limited
• Inventors: Smith, Jye Geoffrey, Thomas, Brian John, Cornish, Bruce Herbert
• Application Number:
  US12/672,893
• Publication Number:
  US 20110046505A1
• Time in Patent Office: Days
• US Class Current: 600/547
• CPC Class Codes: A61B 2562/0214 Capacitive electrodes
• CPC Class Codes: A61B 2562/046 in a matrix array
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/0537 Measuring body composition by impedance, e.g. tissue hydration or fat content
• CPC Class Codes: A61B 5/4331 of the cervix A61B5/435 takes precedence
• CPC Class Codes: A61B 5/444 Evaluating skin marks, e.g. mole, nevi, tumour, scar
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7282 Event detection, e.g. detecting unique waveforms indicative of a medical condition A61B5/4094, A61B5/4818, A61B5/349, A61B5/0823 take precedence

Abstract

A method for use in performing impedance measurements on a subject. The method includes, in a processing system, determining at least one first impedance value, measured at a site using a first electrode configuration, determining at least one second impedance value, measured at the site using a second electrode configuration, and determining the presence, absence or degree of an anomaly using the first and second impedance values.

Claims

1. ) A method for use in performing impedance measurements on a subject, the method including, in a processing system:

a) determining at least one first impedance value, measured at a site using a first electrode configuration;

b) determining at least one second impedance value, measured at the site using a second electrode configuration; and

,

c) determining the presence, absence or degree of an anomaly using the first and second impedance values.

2. ) A method according to claim 1, wherein the method includes using a tetrapolar electrode arrangement, the first and second electrode configurations using a different configuration of drive and measurement electrodes.

3. ) A method according to claim 2, wherein the method includes, in the processing system, determining an impedance value for each of four electrode configurations.

4. ) A′

method according to any one of claims 1 to 3, wherein the method uses apparatus including a signal generator, a sensor, a switching device and an electrode array having a number of electrodes, and wherein the method includes in the processing system, controlling the electrode configuration by;

a) selectively interconnecting the signal generator and electrodes using the switching device; and

,

b) selectively interconnecting the sensor and electrodes using the switching device.

5. ) A method according to any one of claims 1 to 4, wherein the method includes, in the processing system:

a) causing at least one drive signals to be applied to the subject;

b) measuring at least one induced signal across the subject; and

,

c) determining at least one impedance value using an indication of the excitation signal and the induced signal.

6. ) A method according to any one of claims 1 to 5, wherein the method includes, in the processing system:

a) determining impedance values at a number of different sites; and

,

b) determining an impedance map using the impedance values at each site.

7. ) A method according to claim 6, wherein the method includes, in the processing system:

a) determining the presence of an anomaly at any one of the sites; and

,

b) determining the impedance map taking the anomaly into account.

8. ) A method according to claim 7, wherein the method includes, in the processing system, for a site having an anomaly, at least one of:

a) excluding the site from the impedance map;

b) modifying the impedance value determined for the site.

9. ) A method according to any one of claims 1 to 8, wherein the method includes, in the processing system:

a) determining a difference between the first and second impedance values; and

,

b) determining the presence, absence or degree of an anomaly using the determined difference.

10. ) A method according to any one of claims 1 to 9, wherein the method includes, in the processing system:

a) determining a difference between the first and second impedance values;

b) comparing the difference to a reference; and

,

c) determining an anomaly depending on the result of the comparison.

11. ) A method according to any one of claims 1 to 10, wherein the method includes, in the processing system:

a) comparing first and second impedance values; and

,

b) determining the presence, absence or degree of a biological anomaly using the results of the comparison.

12. ) A method according to any one of claims 1 to 11, wherein the reference in a previously measured difference value for the subject.

13. ) A method according to any one of claims 1 to 12, wherein the impedance values are at least one of:

a) measured impedance values; and

,

b) impedance parameter values derived from measured impedance values.

14. ) A method according to claim 12, wherein the impedance parameter values include at least one of:

a) an impedance at infinite applied frequency (R_∞

);

b) an impedance at zero applied frequency (R₀); and

,

c) an impedance at a characteristic frequency (Z_c).

15. ) A method according to claim 13, wherein the method includes, in the processing system, determining the impedance parameter values at least in part using the equation:

16. ) A method according to any one of claims 1 to 15, wherein the method includes, in the processing system:

a) causing at least one first impedance value to be measured at a site using a first electrode configuration; and

,

b) causing at least one second impedance value to be measured at the site using a second electrode configuration.

17. ) A method according to any one of claims 1 to 16, wherein the processing system forms part of a measuring device for performing impedance measurements.

18. ) A method according to any one of claims 1 to 17, wherein the anomaly includes any one or a combination of:

a) a tissue anomaly; and

,

b) an erroneous measurement.

19. ) A method according to claim 18, wherein the tissue anomaly is a tissue lesion.

20. ) A method according to claims 1 to 19, wherein the impedance measurements are performed using apparatus including an electrode array having a number of electrodes provided thereon, and wherein the method includes, in the processing system, causing impedance measurements to be performed using different ones of the electrodes in the array.

21. ) A method according to claim 20, wherein the method includes:

a) causing a first measurement to be performed at a site using first and second electrodes as drive electrodes and using third and fourth electrodes as measurement electrodes; and

,

b) causing a second measurement to be performed at the site using first and third electrodes as drive electrodes and using second and fourth electrodes as measurement electrodes.

22. ) A method according to claim 20 or claim 21, wherein the method includes:

a) causing a measurement to be performed at a site using first and second electrodes as drive electrodes and using third and fourth electrodes as measurement electrodes; and

,

b) causing a measurement to be performed at a second site using at least two of the first, second, third and fourth electrodes.

23. ) A method according to claim 20, wherein the method includes:

a) causing a first measurement to be performed at a first site using first and second electrodes as drive electrodes and using third and fourth electrodes as measurement electrodes;

b) causing a second measurement to be performed at the first site using first and third electrodes as drive electrodes and using second and fourth electrodes as measurement electrodes.

c) causing a first measurement to be performed at a second site using third and fifth electrodes as drive electrodes and using fourth and sixth electrodes as measurement electrodes; and

,

d) causing a second measurement to be performed at the second site using third and fourth electrodes as drive electrodes and using fifth and sixth electrodes as measurement electrodes.

24. ) A method according to any one of the claims 20 to 23, wherein the apparatus includes a signal generator for generating drive signals, a sensor for sensing measured signals, and a multiplexer, and wherein the method includes, in the processing system selectively interconnecting the signal generator and the sensor to electrodes in the array using the multiplexer.

34. ) Apparatus according to any one of the claims 25 to 33, wherein the apparatus is for performing the method of any one of the claims 1 to 24.

25. ) Apparatus for use in analysing impedance measurements performed on a subject, the apparatus including a processing system for:

a) determining at least one first impedance value, measured at a site using a first electrode configuration;

b) determining at least one second impedance value, measured at the site using a second electrode configuration; and

,

c) determining the presence, absence or degree of an anomaly using the first and second impedance values.

26. ) Apparatus according to claim 25, wherein the apparatus includes:

a) a signal generator for applying drive signals to the subject using drive electrodes; and

,

b) a sensor for determining measured signals using measurement electrodes.

27. ) Apparatus according to claim 26, wherein the processing system is for:

a) causing the signal generator to apply one or more drive signals to the subject; and

,

b) determining an indication of the measured signals measured using the sensor.

28. ) Apparatus according to any one of the claims 25 to 27, wherein the processing system is for:

a) determining an indication of drive signals applied to the subject;

b) determining an indication of measured signals determined using the sensor; and

,

c) using the indications to determine an impedance.

29. ) Apparatus according to any one of the claims 25 to 28, wherein the apparatus includes an electrode array having a number of electrodes provided thereon, and wherein in use, selected ones of the electrodes are used as drive and measurement electrodes.

30. ) Apparatus according to claim 29, wherein the processing system is for:

a) causing a first measurement to be performed at a site using first and second electrodes as drive electrodes and using third and fourth electrodes as measurement electrodes; and

,

b) causing a second measurement to be performed at the site using first and third electrodes as drive electrodes and using second and fourth electrodes as measurement electrodes.

31. ) Apparatus according to claim 29 or claim 30, wherein the method includes:

a) causing a measurement to be performed at a site using first and second electrodes as drive electrodes and using third and fourth electrodes as measurement electrodes; and

,

b) causing a measurement to be performed at a second site using at least two of the first, second, third and fourth electrodes.

32. ) Apparatus according to claim 29, wherein the method includes:

a) causing a first measurement to be performed at a first site using first and second electrodes as drive electrodes and using third and fourth electrodes as measurement electrodes;

b) causing a second measurement to be performed at the first site using first and third electrodes as drive electrodes and using second and fourth electrodes as measurement electrodes.

c) causing a first measurement to be performed at a second site using third and fifth electrodes as drive electrodes and using fourth and sixth electrodes as measurement electrodes; and

,

d) causing a second measurement to be performed at the second site using third and fourth electrodes as drive electrodes and using fifth and sixth electrodes as measurement electrodes.

33. ) Apparatus according to any one of the claims 25 to 32, wherein the apparatus includes:

a) a signal generator for generating drive signals;

b) a sensor for sensing measured signals; and

,

c) a multiplexer, and wherein the processing system is for selectively interconnecting the signal generator and the sensor to electrodes in the array using the multiplexer.

35. ) A method for use diagnosing the presence, absence or degree of a biological anomaly in a subject by using impedance measurements performed on the subject, the method including, in a processing system:

a) determining at least one first impedance value, measured at a site using a first electrode configuration;

b) determining at least one second impedance value, measured at the site using a second electrode configuration; and

,

c) determining the presence, absence or degree of an anomaly using the first and second impedance values.