Electrical impedance tomography using a virtual short measurement technique

• US 20060116599A1
• Filed: 11/10/2005
• Published: 06/01/2006
• Est. Priority Date: 11/13/2004
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Davis, Grant E.
• Granted Patent: US 7,660,617 B2
• Time in Patent Office: Days
• US Class Current: 600/547
• CPC Class Codes: A61B 5/0536 Impedance imaging, e.g. by tomography

Abstract

Typical electrical impedance tomography (“EIT”) systems apply current to a body under test and measure the induced voltages on the surface and then through an inverse process, reconstruct an approximation to the electrical conductivity in the interior. The EIT system described herein employs a new approach to evaluating the interior electrical conductivity by using a virtual short that allows both current and voltages to be measured at various locations on the body under test. The architecture of this system is described, distinguishability of embedded conductive anomalies is evaluated, typical error sources associated with a virtual short measurement is discussed in the context of electrical impedance tomography, and a new imaging system is discussed.

Claims

1. An electrical impedance tomography (“

EIT”

) method for evaluating interior features of a body under test with a plurality of electrodes, said method comprising;

designating a first one of the plurality of electrodes as a source electrode, and a second one of the plurality of electrodes as a sink electrode;

establishing a virtual short between said source electrode and at least one of the plurality of electrodes other than said sink electrode;

applying a test current to said source electrode; and

measuring a sense voltage between said source electrode and said sink electrode.

2. An EIT method according to claim 1, further comprising repeating said designating, establishing, applying, and measuring steps for different source and sink electrodes.

3. An EIT method according to claim 1, further comprising repeating said designating, establishing, applying, and measuring steps for all possible combinations of source and sink electrodes.

4. An EIT method according to claim 1, wherein said establishing step comprises establishing said virtual short between said source electrode and all of the plurality of electrodes other than said sink electrode.

5. An EIT method according to claim 1, wherein said establishing step comprises maintaining said source electrode and said at least one of the plurality of electrodes at an identical voltage.

6. An EIT method according to claim 1, further comprising:

obtaining current data indicative of said test current;

obtaining voltage data indicative of said sense voltage; and

performing a reconstruction procedure, based upon said current data and said voltage data, to obtain electrical characteristics of the interior features of the body under test.

7. An EIT method according to claim 6, further comprising creating, in response to said reconstruction procedure, an image of the interior features of the body under test.

8. An EIT method according to claim 6, wherein said reconstruction procedure determines an impedance for a section of the body under test, said section being located between said source electrode and said sink electrode.

19. An EIT system according to claim 1, wherein said EIT processing unit is configured to:

obtain current data indicative of said test current;

obtain voltage data indicative of said sense voltage; and

perform a reconstruction procedure, based upon said current data and said voltage data, to obtain electrical characteristics of the interior features of the body under test.

20. An EIT system according to claim 19, wherein said reconstruction procedure determines an impedance for a section of the body under test, said section being located between said source electrode and said sink electrode.

9. An electrical impedance tomography (“

EIT”

) method for evaluating interior features of a body under test, said method comprising;

coupling a plurality of electrodes to the body under test;

controlling a switching network to designate, from said plurality of electrodes, a source electrode and a sink electrode;

maintaining all of said plurality of electrodes, other than said sink electrode, at an identical voltage;

applying a test current to said source electrode; and

measuring a sense voltage between said source electrode and said sink electrode.

10. An EIT method according to claim 9, wherein said maintaining step establishes a virtual short between said source electrode and all of said plurality of electrodes other than said sink electrode.

11. An EIT method according to claim 9, further comprising repeating said controlling, maintaining, applying, and measuring steps for different source and sink electrodes.

12. An EIT method according to claim 9, further comprising repeating said controlling, maintaining, applying, and measuring steps for all possible combinations of source and sink electrodes.

13. An EIT method according to claim 9, further comprising:

storing current data indicative of said test current;

storing voltage data indicative of said sense voltage; and

performing a reconstruction procedure, based upon said current data and said voltage data, to obtain electrical characteristics of the interior features of the body under test.

14. An EIT method according to claim 13, further comprising creating, in response to said reconstruction procedure, an image of the interior features of the body under test.

15. An EIT method according to claim 13, wherein said reconstruction procedure determines an impedance for a section of the body under test, said section being located between said source electrode and said sink electrode.

16. An electrical impedance tomography (“

EIT”

) system for evaluating interior features of a body under test, said EIT system comprising;

a plurality of electrodes, each being configured to be placed on the body under test, and each having a voltage lead and a current lead;

a switching network coupled to said plurality of electrodes, said switching network being configured to designate a first one of said plurality of electrodes as a source electrode, to designate a second one of said plurality of electrodes as a sink electrode, and to establish a virtual short between said source electrode and at least one of said plurality of electrodes other than said sink electrode;

a current source coupled to said plurality of electrodes, said current source being configured to provide a test current to said source electrode, said test current producing a sense voltage between said source electrode and said sink electrode; and

an EIT processing unit coupled to said switching unit, said EIT processing unit being configured to process test currents and corresponding sense voltage measurements generated in response to test currents.

17. An EIT system according to claim 16, said switching network being configured to establish said virtual short between said source electrode and all of said plurality of electrodes other than said sink electrode.

18. An EIT system according to claim 16, said switching network being configured to maintain said source electrode and said at least one of said plurality of electrodes at an identical voltage.