Medical broad band electromagnetic holographic imaging

• US 6,876,878 B2
• Filed: 06/06/2001
• Issued: 04/05/2005
• Est. Priority Date: 06/26/1996
• Status: Expired due to Term

• Current Assignee: University of Utah Research Foundation (State of Utah)
• Original Assignee: University of Utah Research Foundation (State of Utah)
• Inventors: Zhdanov, Michael S.
• Primary Examiner(s): Smith, Ruth S.
• Application Number:
  US09/876,262
• Publication Number:
  US 20020062074A1
• Time in Patent Office: 1,399 Days
• Field of Search: 600/407, 600/430, 600/547, 600/425, 324/600, 324/637, 324/693, 324/638, 324/639, 342/22
• US Class Current: 600/407
• CPC Class Codes: A61B 5/004 adapted for image acquisition of a particular organ or body part A61B5/0082 takes precedence; arrangements for optical scanning A61B5/0062
• CPC Class Codes: A61B 5/0044 for the heart
• 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 5/0536 Impedance imaging, e.g. by tomography
• CPC Class Codes: A61B 5/417 the bone marrow
• CPC Class Codes: A61B 5/4509 Bone density determination
• CPC Class Codes: G03H 1/04 Processes or apparatus for producing holograms G03H1/26 takes precedence

Abstract

A method of imaging an object, such as a diseased human heart or bone or malignant tumor, in a nontransparent medium, such as the human body, involves placing an array of transmitters and receivers in operational association with the medium. The transmitters generate a broad band harmonic (frequency domain) or pulse (time domain) primary electromagnetic field (EM) field, including the lower frequency portions of the EM spectrum, whose propagation is typically characterized by the diffusion phenomena, or by the combination of the diffusion and wave phenomena. The primary field propagates through the examined medium and interacts with the object to produce a scattered field, which is recorded by the receivers. The scattered EM field components measured by the receivers are applied as an artificial EM field to generate a backscattering EM field. Cross power spectra of the primary and backscattering fields (in the frequency domain) or cross correlation between these fields (in the time domain) produce a numerical reconstruction of an EM hologram. The desired properties of the medium, such as conductivity or dielectric permittivity, are then derived from this hologram.

Claims

1. A method for imaging an anomalous region located within a nontransparent medium of an organism, said method comprising the steps of:

a. placing one or more electromagnetic transmitters in transmission contact with said medium;

b. placing one or more electromagnetic receivers at receiving positions with respect to said medium;

c. operating said transmitters to generate a broad band electromagnetic field, comprising a frequency domain and/or time domain electromagnetic field, whereby said generated electromagnetic field propagates through said medium to interact with said anomalous region, resulting in a scattered electromagnetic field;

d. measuring said scattered electromagnetic field with said receivers;

e. obtaining a background field {E^b, H^b} representative of a background medium equivalent to said medium without the presence of said anomalous region;

f. obtaining a backscattering anomalous field {E^as, H^as} equivalent to that obtainable by illuminating said background medium with said scattered electromagnetic field transmitted from the receiving positions of said receivers; and

g. producing a broad band holographic image of said anomalous region by calculating cross power spectra of said background and said backscattering fields, or calculating cross correlation functions between said background and said backscattering fields.

2. The method of claim 1, wherein said produced image of said anomalous region identifies a medical condition of said anomalous region.

3. The method of claim 1, wherein said produced image of said anomalous region identifies an abnormal portion of said anomalous region.

4. The method of claim 1, wherein operating said transmitters to generate a broad band electromagnetic field comprises operating said transmitters to generate a broad band electromagnetic field with a frequency between approximately one megahertz and approximately ten megahertz.

5. The method of claim 1, wherein operating said transmitters to generate a broad band electromagnetic field comprises operating said transmitters to generate a broad band electromagnetic field with a frequency between approximately ten megahertz and approximately one hundred megahertz.

6. The method of claim 1, wherein operating said transmitters to generate a broad band electromagnetic field comprises operating said transmitters to generate a broad band electromagnetic field with a frequency of between approximately one megahertz and approximately one hundred megahertz.

7. The method of claim 1, wherein said broad band electromagnetic field comprises a portion of EM spectrum, wherein propagation of said portion is characterized by diffusion phenomena.

8. The method of claim 1, wherein said broad band electromagnetic field comprises a portion of EM spectrum, wherein propagation of said portion is characterized by a combination of diffusion phenomena and wave phenomena.

9. A system of imaging a body part of a human or animal, comprising:

an imaging ring including one or more transmitter coils and one or more receiver coils, said imaging ring configured to accommodate said body part inside said imaging ring, said transmitter coils configured to generate a broad band electromagnetic field comprising a frequency domain and/or time domain electromagnetic field, whereby said generated electromagnetic field propagates through said human or animal and interacts with said body part to result in a scattered electromagnetic field, said receiver coils configured to record said scattered electromagnetic field; and

a computer configured to simulate a background field representing a hypothetical electromagnetic field of said human or animal without said body part, to compute a backscattering field representing another hypothetical electromagnetic field obtainable by transmitting said scattered electromagnetic field from said receivers, and to produce a volume image of electric conductivity and/or dielectric permittivity of said body part.

10. The system of claim 9, wherein the computer is configured to produce said volume image by calculating cross power spectra of said background field and said backscattering field.

11. The system of claim 9, wherein the computer is configured to produce said volume image by calculating cross correlation functions between said background field and said backscattering field.

12. The system of claim 9, further comprising one or more support posts connected to said imaging ring and configured to support said imaging ring.

13. The system of claim 12, wherein said support posts are adjustable in height.

14. The system of claim 12, wherein said imaging ring is adjustable in height along said support posts.

15. The system of claim 9, wherein the computer is configured to produce said volume image iteratively by:

calculating an updated (corrected) background field as electromagnetic response for the updated background medium with the complex conductivity, obtained on the previous iteration;

calculating the updated residual field between this response and observed field;

calculating the updated backscattering field for the updated residual field by simulating illumination of the updated background medium with electric and magnetic currents equivalent to those of the updated residual field recorded at the location of the receivers; and

constructing the updated volume images of anomalous conductivity a(n)(r) and of anomalous permittivity ε

_a(n)(r) on the basis of updated cross power spectrum or cross correlation functions between said background field and said updated backscattering field, using regularization procedures.

16. The system of claim 9, further comprising a converter configured to receive analog signals of said scattered electromagnetic field from said receiver coils, to convert said received analog signals into digital signals of said scattered electromagnetic field, and to transmit said digital signals to said computer.

17. The system of claim 9, wherein said receiver coils are further configured to record said generated electromagnetic field, said system further comprising a filter configured to receive said generated electromagnetic filed and said scattered electromagnetic field from said receiver coils, to filter said generated electromagnetic field from said scattered electromagnetic field, and to transmit said scattered electromagnetic field to said computer.