Method of broad band electromagnetic holographic imaging

• US 6,253,100 B1
• Filed: 12/23/1998
• Issued: 06/26/2001
• Est. Priority Date: 06/26/1996
• Status: Expired due to Term

• Current Assignee: University of Utah (State of Utah)
• Original Assignee: University of Utah Research Foundation (State of Utah)
• Inventors: Zhdanov, Michael S.
• Primary Examiner(s): Lateef, Marvin M.
• Assistant Examiner(s): SHAW, SHAWNA JEANNINE
• Application Number:
  US09/214,217
• Time in Patent Office: 916 Days
• Field of Search: 600/407, 600/547, 600/430, 600/476, 324/600, 324/693, 736/03, 342/22, 356/347
• US Class Current: 600/407
• 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 5/417 the bone marrow
• 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, 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 harmonic (frequency domain) or pulse (time domain) primary electromagnetic field (EM) which propagates through the medium. The primary field 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 target located in a nontransparent examined medium, said method comprising the steps of:

a. placing an electromagnetic transmitter source in transmission contact with said examined medium;

b. placing electromagnetic receivers at various receiving positions with respect to said examined medium, spaced from said transmitter source;

c. operating said transmitter source to generate a broad band electromagnetic field comprising an harmonic (frequency domain) and/or pulse (time domain) electromagnetic field, whereby said generated electromagnetic field propagates through said examined medium to interact with said target, 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 consisting of said examined medium without the presence of said anomalous target;

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 positions of said receivers; and

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

2. A method according to claim 1, wherein said transmitter source comprises a plurality of transmitters arranged in an array on the surface of said examined medium.

3. A method according to claim 2, wherein said transmitters include both galvanic and induction transmitters.

4. A method according to claim 1, wherein said receivers include both galvanic and induction receivers.

5. A method according to claim 4, wherein said receivers are arranged in an array on the surface of said examined medium.

6. A method according to claim 1, wherein said scattered electromagnetic field measured by said step d. is input to a computer, and said computer is operated to:

analyze said scattered electromagnetic field;

numerically simulate illumination of the background medium by the original transmitter source;

compute the backscattering anomalous field {E^as,H^as} by simulating illumination of the background medium with electric and magnetic currents equivalent to those of said scattered electromagnetic field transmitted from the locations of said receivers; and

constructing a volume image of electrical conductivity and/or dielectric permittivity by calculating cross power spectra of said background and backscattering fields.

7. A method according to claim 6, wherein said computer is operated iteratively through the steps of:

h. updating the background medium of step e. of a previous iteration by adding the volume image constructed by step g. of said previous iteration;

i. repeating at least steps d through g, whereby to obtain a next generation iteration of a volume image; and

j. repeating steps h. and i. until said background medium approximates said volume image.

8. A method for imaging an anomalous region located within an organism, said method comprising the steps of:

a. placing an electromagnetic transmitter source on the surface of said organism;

b. placing electromagnetic receivers at various positions on the surface of said organism, spaced from said transmitter source;

c. operating said transmitter source to generate a broad band electromagnetic field comprising an harmonic (frequency domain) and/or pulse (time domain) electromagnetic field, whereby said generated electromagnetic field propagates through said organism 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 reference organism equivalent to said organism without the presence of said anomalous region;

f. obtaining a backscattering anomalous field {E^as,H^as} equivalent to that obtained by illuminating said reference organism by transmitting said scattered electromagnetic field from the 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 cross correlation functions between said background and said backscattering fields.