Apparatus and method for magnetic resonance measurement and mapping of electrical impedance, complex permittivity and complex conductivity as applied to detection and evaluation of sample pathology

• US 20050052182A1
• Filed: 07/30/2004
• Published: 03/10/2005
• Est. Priority Date: 08/30/2002
• Status: Active Grant

• Current Assignee: Wollin Ventures, Inc.
• Original Assignee: Wollin Ventures, Inc.
• Inventors: Wollin, Ernest
• Granted Patent: US 8,200,309 B2
• Time in Patent Office: Days
• US Class Current: 324/307
• CPC Class Codes: A61B 5/0035 adapted for acquisition of images from more than one imaging mode, e.g. combining MRI and optical tomography
• CPC Class Codes: A61B 5/0536 Impedance imaging, e.g. by tomography
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61B 5/708 Breast positioning means
• CPC Class Codes: G01R 33/28 Details of apparatus provided for in groups G01R33/44 - G01R33/64
• CPC Class Codes: G01R 33/30 Sample handling arrangements, e.g. sample cells, spinning mechanisms
• CPC Class Codes: G01R 33/422 of the radio frequency field
• CPC Class Codes: G01R 33/4808 Multimodal MR, e.g. MR combined with positron emission tomography [PET], MR combined with ultrasound or MR combined with computed tomography [CT]

Abstract

A method of measurement of or mapping the distribution of complex permittivity, complex conductivity, complex impedance, or electric loss angle during magnetic resonance imaging or analysis. The method includes applying a time-varying electric field of a Faraday shield to a sample and cross-correlating the line spectrum signal so produced with the voltage applied to the Faraday shield in a detection circuit. The method permits non-contrast magnetic resonance screening for breast cancer in vivo and/or continuous measurement of electrical characteristics of materials at variable frequencies in vitro. A system of detecting and evaluating sample pathology includes a Faraday shield device that includes parallel electrodes oriented orthogonal to the static magnetic field of a MRI device to produce a time varying electric field. A detector is coupled to the MRI device to detect at least one of a complex permittivity, a complex conductivity, and an electrical impedance of the sample.

Claims

1. A method of detecting and evaluating sample spatially ordered pathology, comprising:

placing a sample to be measured in a Faraday shield device having electrodes;

applying a time varying potential distribution across the electrodes, so as to create a time varying electric field in the sample, so as to create a local time varying current field in the sample, so as to create a periodic aberration in a local magnetic field that periodically varies a phase of spins within the sample; and

measuring at least one of a complex permittivity, a complex conductivity, and an electrical impedance of the sample.

2. The method according to claim 1, wherein the sample is a human breast, and wherein the Faraday shield device comprises a pair of compression paddles and the electrodes are oriented in parallel to each other, and wherein the electrodes are embedded in an insulating material.

3. The method according to claim 2, wherein the electrodes are further oriented substantially perpendicular to a main magnetic field of a magnetic resonance imaging device.

4. The method according to claim 2, wherein the compression paddles are non-conductive, the insulating material has a high dielectric constant, and the electrodes are coupled to a voltage source that applies the time varying potential distribution across the electrodes.

5. The method according to claim 4, wherein the insulating material comprises one or more ferroelectric materials.

6. The method according to claim 1, wherein the electrodes are arranged to make electrical conductivity contact with the sample and are coupled to a voltage source that applies the time varying potential distribution across the electrodes.

7. The method according to claim 1, wherein the wherein the Faraday shield device comprises a pair of compression paddles, the method further comprising:

placing the Faraday shield within an imaging region of a magnetic resonance imaging device; and

placing one of a receiver coil and a transmitter-receiver coil of the magnetic resonance imaging device on or near a surface of the compression paddles.

8. The method according to claim 7, further comprising detecting orthogonal components of each sideband of a line spectrum resolved with respect to the phase of a voltage applied to the electrodes.

9. The method according to claim 8, further comprising determining a ratio of the resolved real and imaginary components of the sidebands.

10. The method according to claim 7, further comprising detecting orthogonal components of each sideband of a line spectrum resolved with respect to the phase of a voltage applied to the electrodes at a frequency Ω

<

<

ω

₀, the Larmor frequency of the magnetic resonance imaging device.

11. The method according to claim 10, further comprising identifying focal aberrations contained in an image produced by the magnetic resonance imaging device so as to locate pathology.

12. The method according to claim 7, further comprising detecting orthogonal components of each sideband of a line spectrum resolved with respect to the phase of a voltage applied to the electrodes at variable frequencies Ω

<

<

ω

₀, the Larmor frequency of the magnetic resonance imaging device.

13. The method according to claim 1, further comprising determining an electric loss angle of the sample.

14. The method according to claim 1, wherein the sample is a portion of a human breast.

15. A method of measuring electrical impedance by the application of time-varying electric fields in a sample, comprising:

placing the sample in a magnetic resonance device;

providing a detector to the magnetic resonance device;

providing an electrode attachment about the sample, wherein the electrode attachment includes a pair of electrode arrays oriented parallel to each other;

applying a periodic potential distribution across the sample so as to create a time varying electric field in the sample, so as to create a local time varying current field in the sample, so as to create a periodic aberration in a local magnetic field that periodically varies a phase of spins within the sample; and

measuring an electrical impedance of the sample with the detector.

16. The method of claim 15, wherein the periodic potential distribution across the sample is a variable frequency Ω

<

<

ω

₀, the Larmor frequency of the magnetic resonance imaging device, so as to measure the electrical impedance of the sample at variable frequencies Ω

<

<

ω

₀.

17. The method according to claim 15, wherein the sample is a portion of a human breast.

18. A system for detecting and evaluating sample pathology, comprising:

a magnetic resonance imaging device configured to produce an image of a sample, the magnetic resonance imaging device generating a static magnetic field and including one of receiving coils and transmitter-receiver coils;

a Faraday shield device that includes parallel electrodes oriented orthogonal to the static magnetic field to produce a time varying electric field;

a voltage source configured to generate a periodic voltage at a frequency Ω

; and

a detector configured to detect one of a complex permittivity, a complex conductivity, and an electrical impedance of the sample.

19. The system according to claim 18, wherein the detector comprises:

first demodulators supplied with a quadrature output at a Larmor frequency ω

₀′

from a magnetic resonance master radio frequency oscillator;

a first amplifier configured to sum first output signals from the first demodulators;

a second amplifier configured to receive a second output signal from the first amplifier; and

second demodulators coupled to the second amplifier configured to provide cross-correlated outputs corresponding to at least one of real and imaginary components that correspond to a signal received by the one of receiver and transmitter-receiver coils from a location x in the sample, and corresponding to the frequency ω

₀′

resolved with respect to a phase of the periodic voltage.

20. The system according to claim 19, wherein the second demodulators comprise a series n of double-balanced demodulator pairs, each double balanced demodulator pair coupled to the second amplifier, configured to provide cross-correlated outputs corresponding to at least one of real and imaginary components of the signal received by the one of receiver coils and transmitter-receiver coils from the location x in the sample.

21. The system according to claim 19, wherein the second demodulators are supplied with frequency sources sin (nΩ

t) and cos (nΩ

t).

22. The system according to claim 19, further comprising a processor configured to analyze the cross-correlated outputs of the second demodulators and to provide the complex permittivity at the location x at frequency Ω

.

23. The system according to claim 18, wherein the Faraday shield includes a pair of non-conductive compression paddles, each compression paddle comprising an electrode array contained in an insulating portion thereof and coupled to the voltage source.

24. The system according to claim 23, wherein the at least one of receiving coils and transmitter-receiver coils is disposed on or near at least one of the compression paddles.

25. The system according to claim 18, wherein the periodic voltage is continuously applied.

26. The system according to claim 18, wherein the voltage source is pulsed.

27. The system according to claim 18, wherein the voltage source is timed to the event sequence of the magnetic resonance imaging device.

28. The system according to claim 18, wherein the sample is a portion of a human breast.

29. A system for measuring the electrical impedance of a sample, comprising:

a magnetic resonance device;

an electrode attachment disposed about the sample, wherein the electrode attachment includes a pair of electrode arrays oriented substantially parallel to each other and substantially orthogonal to the static magnetic field of the magnetic resonance device;

a voltage source configured to apply a periodic potential distribution across the sample so as to create a time varying electric field in the sample, so as to create a local time varying current field in the sample, so as to create a periodic aberration in a local magnetic field that periodically varies a phase of spins within the sample; and

a detector coupled to the magnetic resonance device to measure a value corresponding to an electrical impedance of the sample.

30. The system according to claim 29, wherein the sample is a portion of a human breast.

31. A method of detecting and evaluating sample spatially ordered pathology, comprising:

placing a human breast to be measured in a Faraday shield device having electrodes;

applying across the electrodes a time varying potential distribution having a phase modulating frequency, so as to create a time varying electric field in the breast, so as to create a time varying current field in the breast that periodically varies a phase of spins within the breast; and

measuring the distribution of at least one of a complex permittivity and an electrical impedance of the breast at the phase modulating frequency.

32. The method according to claim 31, comprising measuring the distribution of the complex permittivity of the breast at the phase modulating frequency.

33. The method according to claim 32, comprising measuring the distribution of the complex permittivity at a phase modulating frequency of the time varying potential distribution.

34. The method according to claim 31, wherein the sample is a portion of a human breast.

35. A system for detecting and evaluating sample spatially ordered pathology, comprising:

means for placing a sample to be measured in a Faraday shield device having electrodes;

means for applying a time varying potential distribution across the electrodes, so as to create a time varying electric field in the sample, so as to create a local time varying current field in the sample, so as to create a periodic aberration in a local magnetic field that periodically varies a phase of spins within the sample; and

means for measuring at least one of a complex permittivity, a complex conductivity, and an electrical impedance of the sample.

36. A system for measuring electrical impedance by the application of time-varying electric fields in a sample, comprising:

means for placing the sample in a magnetic resonance device;

means for providing a detector to the magnetic resonance device;

means for providing an electrode attachment about the sample, wherein the electrode attachment includes a pair of electrode arrays oriented parallel to each other;

means for applying a periodic potential distribution across the sample so as to create a time varying electric field in the sample, so as to create a local time varying current field in the sample, so as to create a periodic aberration in a local magnetic field that periodically varies a phase of spins within the sample; and

means for measuring an electrical impedance of the sample with the detector.

37. A system for detecting and evaluating sample spatially ordered pathology, comprising:

means for placing a human breast to be measured in a Faraday shield device having electrodes;

means for applying across the electrodes a time varying potential distribution having a phase modulating frequency, so as to create a time varying electric field in the breast, so as to create a time varying current field in the breast that periodically varies a phase of spins within the breast; and

means for measuring the distribution of at least one of a complex permittivity and an electrical impedance of the breast at the phase modulating frequency.