Apparatus and techniques for electric tomography

• US 4,486,835 A
• Filed: 07/24/1981
• Issued: 12/04/1984
• Est. Priority Date: 05/13/1981
• Status: Expired due to Fees

• Current Assignee: Yeda Research and Development Co. Ltd. (Weizmann Institute of Science)
• Original Assignee: Yeda Research and Development Co. Ltd. (Weizmann Institute of Science)
• Inventors: Sollish, Bruce D., Brandt, Achi E., Bai, Dov
• Primary Examiner(s): Krass, Errol A.
• Assistant Examiner(s): Teska, Kevin J.
• Application Number:
  US06/286,538
• Time in Patent Office: 1,229 Days
• Field of Search: 364/414, 364/415, 364/480-483, 250/428, 250/436, 378/21, 378/37, 378/901, 128/630, 128/734
• US Class Current: 378/21
• 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 5/4312 Breast evaluation or disorder diagnosis A61B5/0091 takes precedence
• CPC Class Codes: G06T 11/006 Inverse problem, transformation from projection-space into object-space, e.g. transform methods, back-projection, algebraic methods
• CPC Class Codes: G06T 2211/424 Iterative
• CPC Class Codes: Y10S 378/901 Computer tomography program or processor

Abstract

Apparatus for electric tomography comprising a coupling medium for receiving an object to be examined, a plurality of electrodes disposed in the coupling medium and arranged in a three dimensional array; multiplexing apparatus for applying electric voltages at selected first pluralities of electrodes and simultaneously measuring electric currents at corresponding selected second pluralities of electrodes in a desired sequence; and computation apparatus coupled to the multiplexing apparatus for originally estimating the electrical properties at a multiplicity of locations in the object to be examined, these locations being arranged in a three dimensional imaginary grid defined in the object to be examined and subsequently correcting the conductivity estimates at each of the multiplicity of locations on the basis of the measured currents by an iterative process.

Claims

1. Apparatus for use in electric tomography comprising:

a coupling medium for receiving an object to be examined;

a plurality of electrodes disposed in communication with said coupling medium and arranged in a three dimensional array generally surrounding the object to be examined;

multiplexing and measuring means for applying electric voltages at selected first pluralities of electrodes and simultaneously measuring electric currents including non-straight line currents at corresponding selected second pluralities of electrodes in a desired sequence;

computation means coupled to said multiplexing means for initially estimating the values of the electrical properties at a multiplicity of locations in the object to be examined, said locations being arranged in a three dimensional imaginary grid defined in the object to be examined and subsequently correcting the initially estimated values of the electrical properties at each of said multiplicity of locations by solving an inverse Laplace equation using the applied electric voltages and electrical current measurements provided by said multiplexing and measuring means by an iterative process; and

means for providing a visible tomographic representation of the values of the electrical properties at each of said multiplicity of locations as determined by said computation means.

2. Apparatus according to claim 1 and wherein said first pluralities of electrodes are arranged to provide non-parallel currents flowing through the object to be examined in response to application of electric voltages thereto by said multiplexing means.

3. Apparatus according to claim 2 and wherein said plurality of electrodes is arranged to substantially surround the object to be examined.

4. Apparatus according to claim 3 and wherein said plurality of electrodes are arranged to lie along surfaces which include surfaces which are mutually perpendicular.

5. Apparatus according to claim 2 and wherein said plurality of electrodes are arranged to lie along surfaces which include surfaces which are mutually perpendicular.

6. Apparatus according to claim 1 and wherein said plurality of electrodes is arranged to substantially surround the object to be examined.

7. Apparatus according to claim 6 and wherein said plurality of electrodes are arranged to lie along surfaces which include surfaces which are mutually perpendicular.

8. Apparatus according to claim 1 and wherein said plurality of electrodes are arranged to lie along surfaces which include surfaces which are mutually perpendicular.

9. A method for carrying out electric tomography comprising the steps of:

providing a coupling medium for receiving an object to be examined;

arranging a plurality of electrodes in electrical contact with said coupling medium in a three dimensional array generally surrounding said object to be examined;

selectably energizing various combinations of said electrodes in a desired sequence and measuring the currents including non-straight line currents between various combinations of said electrodes as the result of such energization;

computing the values of the electrical properties of the interior of the object from the measured currents; and

providing a visible tomographic representation of the computed values of the electrical properties of the interior of the object.

10. A method according to claim 9 and wherein said selectably energizing step comprises energizing combinations of electrodes to produce non parallel currents flowing through said object.