Methods and system for performing magnetic induction tomography

Patent metadata

Field	Value
Publication number	US-2016305910-A1
Application number	US-201514689871-A
Country	US
Kind code	A1
Filing date	Apr 17, 2015
Priority date	Apr 17, 2015
Publication date	Oct 20, 2016
Grant date	—

Abstract

Methods and system for performing magnetic induction tomography imaging of an object are provided. An apparatus includes an array of unit cells and a control circuit coupled to the array of unit cells. The array of unit cells can generate a first magnetic field using an excitation pattern in the direction of a target object and sense a second magnetic field induced in the target object by the first magnetic field. The control circuit can determine a minimum of the first magnetic field. The minimum may correspond to a higher conductivity region of the target object. The control circuit can adjust the excitation pattern based on the higher conductivity region of the target object.

First claim

1 . An apparatus for performing magnetic induction tomography of a target object, comprising:
an array of unit cells, wherein each unit cell includes a pattern of conducting lines, and wherein the array of unit cells is configured to generate a first magnetic field based on an excitation pattern and sense a second magnetic field induced in a target object by the first magnetic field; and a control circuit coupled to the array of unit cells, wherein the control circuit is configured to provide the excitation pattern that minimizes a condition number of a sensitivity matrix and consequently increases accuracy of conductivity estimates.

2 . The apparatus of claim 1 , where the condition number is reduced by generating a magnetic field whose intensity pattern has a minimum at the location of the estimated higher-conductivity region of the target object, wherein the minimum is an intensity null.

3 .- 5 . (canceled)

6 . The apparatus of claim 1 , wherein the target object is at least one of: a human body, a portion of a human body, a piece of baggage or another transported good, an assembly of manufactured parts at a production factory, a geological formation, or a volume adjacent to a borehole.

7 . The apparatus of claim 1 , wherein the unit cells include a first set of unit cells configured to generate the first magnetic field and a second set of unit cells configured to sense the second magnetic field.

8 . The apparatus of claim 1 , wherein the array of unit cells is arranged in at least one of a planar formation, a curved formation, or a random formation.

9 .- 14 . (canceled)

15 . The apparatus of claim 1 , wherein the array of unit cells includes two layers of unit cells, wherein a first layer of unit cells is stacked on top of a second layer of unit cells.

16 . The apparatus of claim 15 , wherein the first layer of unit cells is configured to generate a first portion of the first magnetic field perpendicular to a plane of the array of unit cells, and wherein the second layer of unit cells is configured to generate a second portion of the first magnetic field orthogonal to a plane of the array of unit cells.

17 . The apparatus of claim 1 , wherein the array of unit cells includes three or more layers of unit cells, wherein the three or more layers of unit cells is configured to generate the first magnetic field having a predefined magnitude, direction, and phase.

18 . The apparatus of claim 1 , wherein the pattern of conducting lines forms at least one inductor in each unit cell in the array of unit cells.

19 . (canceled)

20 . The apparatus of claim 1 , wherein a spatial resolution of the array of unit cells is based on a spacing between centroids of adjacent unit cells and dimensions of the unit cells, wherein the width of each of the conducting lines is greater than a skin depth of a corresponding conducting line at an operational frequency.

21 .- 27 . (canceled)

28 . The apparatus of claim 1 , further comprising a housing, wherein the array of unit cells is coupled to a surface of the housing, wherein the housing includes a metamaterial that includes at least one of: an active metamaterial, a powered metamaterial, a current-driven metamaterial, or a voltage-controlled metamaterial, and wherein the array of unit cells is coupled to an inner portion of the spherical structure and is configured to generate the first magnetic field towards a bore of the spherical structure.

29 .- 37 . (canceled)

38 . The apparatus of claim 1 , wherein the array of unit cells are at least one of: broadband unit cells configured to generate a range of frequencies or narrow band unit cells configured to generate a narrow band excitations.

39 .- 54 . (canceled)

55 . An apparatus for performing magnetic induction tomography enhanced with relaxation contrast imaging of a target object, comprising:
an array of unit cells, wherein each unit cell includes a pattern of conducting lines, and wherein the array of unit cells is configured to generate a first magnetic field at a first time t and then sense a second magnetic field induced in a target object by the first magnetic field at the at least one second time t+Δt; and a control circuit coupled to the array of unit cells, wherein the control circuit is configured to provide the excitation pattern to the array of unit cells such that the first magnetic field has a minimum corresponding to an estimated higher conductivity region of the target object.

56 . The apparatus of claim 55 , wherein the array of unit senses the second magnetic field at two or more times after the target object is excited by the first magnetic field.

57 . The apparatus of claim 55 , wherein the array of unit cells is configured to continuously generate magnetic field and continuously sense magnetic fields induced in the target object.

58 .- 61 . (canceled)

62 . The apparatus of claim 55 , wherein the unit cells include a first set of unit cells configured to generate the first magnetic field and a second set of unit cells configured to sense the second magnetic field.

63 . The apparatus of claim 55 , wherein the array of unit cells is arranged in at least one of a planar formation, a curved formation, or a random formation.

64 .- 69 . (canceled)

70 . The apparatus of claim 55 , wherein the array of unit cells includes two layers of unit cells, wherein a first layer of unit cells is stacked on top of a second layer of unit cells.

71 . The apparatus of claim 70 , wherein the first layer of unit cells is configured to generate a first portion of the first magnetic field perpendicular to a plane of the array of unit cells, and wherein the second layer of unit cells is configured to generate a second portion of the first magnetic field orthogonal to a plane of the array of unit cells.

72 . The apparatus of claim 55 , wherein the array of unit cells includes three or more layers of unit cells, wherein the three or more layers of unit cells is configured to generate the first magnetic field having a predefined magnitude, direction, and phase.

73 .- 74 . (canceled)

75 . The apparatus of claim 55 , wherein a spatial resolution of the array of unit cells is based on a spacing between centroids of adjacent unit cells and dimensions of the unit cells.

76 . The apparatus of claim 75 , wherein the width of each of the conducting lines is greater than a skin depth of a corresponding conducting line at an operational frequency.

77 .- 157 . (canceled)

158 . A method for performing magnetic induction tomography of a target object, comprising;
generating, by an array of unit cells, a first magnetic field at a location of a target object using a predetermined excitation pattern; sensing, by the array of unit cells, a second magnetic field induced in the target object by the first magnetic field; determining, by the control circuit, an approximate conductivity map based on the second magnetic field and characteristics of the first magnetic field; comparing a difference between the conductivity map and a previous estimate of the conductivity map to a threshold value, wherein a current estimate of the conductivity map is generated when the difference is below the threshold; and adjusting, by the control circuit, the excitation pattern based on the

Assignees

• Elwha Llc

Inventors

• Driscoll Tom
• Smith David R
• Urzhumov Yaroslav A

Classifications

• G01V3/081

  the magnetic field is produced by the objects or geological structures (characterised by the method of magnetic field measurement G01R33/00) · CPC title

• A61B5/0522 Primary

  Magnetic induction tomography · CPC title

• A61B5/0037

  Performing a preliminary scan, e.g. a prescan for identifying a region of interest · CPC title

• G01V3/08

  operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices (with electromagnetic waves G01V3/12) · CPC title

• G01N27/72 Primary

  by investigating magnetic variables · CPC title