Adaptive electromagnet for high performance magnetic resonance imaging

Patent metadata

Field	Value
Publication number	US-9523751-B2
Application number	US-201514898545-A
Country	US
Kind code	B2
Filing date	Apr 27, 2015
Priority date	Apr 27, 2015
Publication date	Dec 20, 2016
Grant date	Dec 20, 2016

Abstract

A method of configuring a conducting grid of elements interconnected at intersecting nodes by switches is described. The method includes: constructing a background grid by connection of centroids of the cell shape of the conducting grid; identifying a subset of elements in the background grid that intersect the smooth pattern of loops; identifying a subset of elements in the conducting grid that intersect the subset of elements in the background grid; the subset of elements in the conducting grid forming a discretized pattern of loops representing the smooth pattern of loops; for each of the discretized pattern of loops identifying current-in and current-out nodes; altering the on-off state of individual switches in accordance with the discretized pattern of loops; opening the switch between each respective pair of current-in and current out nodes; and applying power to the conducting grid via at least one pair of the input and output current nodes such that the current flow through the elements generates the magnetic field profile.

First claim

We claim:

1. A method of configuring a conducting grid of elements interconnected at intersecting nodes by switches, for generating a dynamically changeable current distribution represented in two dimensions on said conducting grid by a smooth pattern of loops, to create a time varying magnetic field profile within a region of interest in an MRI system, comprising:
constructing a background grid to said conducting grid by connection of centroids of the cell shape of the conducting grid;
identifying a subset of elements in said background grid that intersect said smooth pattern of loops;
identifying a subset of elements in said conducting grid that intersect said subset of elements in the background grid, wherein said subset of elements in said conducting grid forms a discretized pattern of loops representing said smooth pattern of loops;
for each of said discretized pattern of loops identifying input and output current nodes;
altering the on-off state of individual switches in accordance with said discretized pattern of loops;
opening the switch between each respective pair of input and output current nodes; and
applying power to said conducting grid via at least one pair of said input and output current nodes such that the current flow through said elements generates said magnetic field profile.

2. The method of claim 1 , further comprising interconnecting respective ones of said discretized pattern of loops via said input and output current nodes.

3. The method of claim 1 , wherein identifying input and output current nodes further comprises:
identifying an initial current-in node for receiving said power;
ordering said discretized pattern of loops based on distance from said initial current-in node; and
identifying a current-in and current-out node for each successive loop in said ordering.

4. An adaptive electromagnet, comprising:
an array of conducting grid elements for generating a time varying magnetic field profile within a region of interest in an MRI system;
a plurality of switches interconnecting said conducting grid of elements at intersecting nodes for generating a dynamically changeable current distribution represented in two dimensions on said array of conducting grid elements by a smooth pattern of loops;
a background grid constructed to said array of conducting grid elements by connection of centroids of the cell shape of the array of conducting grid elements, wherein a subset of elements in said background grid intersect said smooth pattern of loops and a subset of elements in said array of conducting grid elements intersect said subset of elements in the background grid such that said subset of elements in said conducting grid forms a discretized pattern of loops representing said smooth pattern of loops; and
input and output current nodes for each of said discretized pattern of loops;
wherein upon (i) altering the on-off state of individual switches in accordance with said discretized pattern of loops, (ii) opening the switch between each respective pair of input and output current nodes, and (iii) applying power to said conducting grid via at least one pair of said input and output current nodes, current flows through said elements to generate said magnetic field profile, and wherein said switches are transistor switches.

5. The adaptive electromagnet of claim 4 , wherein said elements are arranged in a rectangular grid comprising a plurality of horizontal and vertical wire conductors that intersect at said plurality of nodes.

6. The adaptive electromagnet of claim 4 , wherein the input input current node of at least one loop is connected to a corresponding output current node of a next loop via a second conductive grid.

7. The method of claim 1 , wherein applying power to said array further comprises:
assigning each loop a combined current-in and current-out element; and
connecting a separate source of power to each respective combined current-in and current-out element.

8. An adaptive electromagnet, comprising:
an array of conducting grid elements for generating a time varying magnetic field profile within a region of interest in an MRI system;
a plurality of switches interconnecting said conducting grid of elements at intersecting nodes for generating a dynamically changeable current distribution represented in two dimensions on said array of conducting grid elements by a smooth pattern of loops;
a background grid constructed to said array of conducting grid elements by connection of centroids of the cell shape of the array of conducting grid elements, wherein a subset of elements in said background grid intersect said smooth pattern of loops and a subset of elements in said array of conducting grid elements intersect said subset of elements in the background grid such that said subset of elements in said conducting grid forms a discretized pattern of loops representing said smooth pattern of loops;
a combined current-in and current-out element for each of said discretized pattern of loops;
a separate source of power to each respective combined current-in and current-out element;
wherein upon (i) altering the on-off state of individual switches in accordance with said discretized pattern of loops, (ii) opening the switch between each respective combined current-in and current-out element, and (iii) applying power to said conducting grid via one said respective combined current-in and current-out element, current flows through said grid elements to generate said magnetic field profile, and, wherein the source of power comprises a power supply.

9. An adaptive electromagnet, comprising:
an array of conducting grid elements for generating a time varying magnetic field profile within a region of interest in an MRI system;
a plurality of switches interconnecting said conducting grid of elements at intersecting nodes for generating a dynamically changeable current distribution represented in two dimensions on said array of conducting grid elements by a smooth pattern of loops;
a background grid constructed to said array of conducting grid elements by connection of centroids of the cell shape of the array of conducting grid elements, wherein a subset of elements in said background grid intersect said smooth pattern of loops and a subset of elements in said array of conducting grid elements intersect said subset of elements in the background grid such that said subset of elements in said conducting grid forms a discretized pattern of loops representing said smooth pattern of loops;
a combined current-in and current-out element for each of said discretized pattern of loops;
a separate source of power to each respective combined current-in and current-out element;
wherein upon (i) altering the on-off state of individual switches in accordance with said discretized pattern of loops, (ii) opening the switch between each respective combined current-in and current-out element, and (iii) applying power to said conducting grid via one said respective combined current-in and current-out element, current flows through said grid elements to generate said magnetic field profile, and wherein the source of power comprises a single power supply and a circuit to divide the current from the power supply to each loop via each combined current-in and current-out element.

10. The adaptive electromagnet of claim 9 , wherein the amount of current to each loop is equal.

11. The adaptive electromagnet of claim 9 , wherein the amount of current to each loop is unequal.

12. The adaptive electromagnet of claim 8 , further comprising:
first and second strips of conducting material distributed in the azimuthal direction on a surface adjacent said conductive gri

Assignees

• Harris Chad Tyler
• Panther Alexander Gyles
• Mcfadyen Stephen B E
• Synaptive Medical Barbados Inc

Inventors

• Harris Chad Tyler
• Panther Alexander Gyles
• Mcfadyen Stephen B E

Classifications

• G01R33/385

  using gradient magnetic field coils · CPC title

• G01R33/3875

  using correction coil assemblies, e.g. active shimming · CPC title

• G01R33/4833

  using spatially selective excitation of the volume of interest, e.g. selecting non-orthogonal or inclined slices · CPC title

• G01R33/381 Primary

  using electromagnets · CPC title

• G01R33/3664

  Switching for purposes other than coil coupling or decoupling, e.g. switching between a phased array mode and a quadrature mode, switching between surface coil modes of different geometrical shapes, switching from a whole body reception coil to a local reception coil or switching for automatic coil selection in moving table MR or for changing the field-of-view (G01R33/3671 takes precedence) · CPC title