Method and apparatus for dynamic magnetic field control using multiple magnets

• US 7,772,950 B2
• Filed: 02/24/2009
• Issued: 08/10/2010
• Est. Priority Date: 08/10/2005
• Status: Active Grant

• Current Assignee: Stereotaxis, Inc.
• Original Assignee: Stereotaxis, Inc.
• Inventors: Tunay, Ilker
• Primary Examiner(s): Enad; Elvin G
• Assistant Examiner(s): TALPALATSKI, ALEXANDER
• Application Number:
  US12/391,302
• Publication Number:
  US 20090206972A1
• Time in Patent Office: 532 Days
• Field of Search: 335/306, 335/219
• US Class Current: 335/306
• CPC Class Codes: A61B 5/06 Devices, other than using radiation, for detecting or locating foreign bodies for removing same A61B17/50 ; determining position of probes within or on the body of the patient
• CPC Class Codes: A61B 5/062 using magnetic field

Abstract

A method and apparatus for dynamic magnetic field control using multiple magnets. Control methods and system means are described that allow dynamically changing the magnetic field generated at a point in space by a multiplicity of magnets.

Claims

1. A method of generating a specific target magnetic field at an operating point in space, the method comprising the steps of:

(a) representing magnet and application related constraints;

(b) defining a series of intermediate field vectors at the operating point;

(c) using an inversion procedure to find a series of magnets control parameters for a multiplicity of magnets associated with the series of field vectors of step (b);

(d) finding a time sequence of control parameters for the multiplicity of magnets of step (c) subject to the constraints of step (a) to approximate the series of control parameters of step (c); and

(e) performing the time sequence of step (d), whereby the target magnetic field at the operating point is achieved at a given level of accuracy and within a specific time interval,

wherein the magnets are permanent magnets.

2. The method of claim 1, wherein the permanent magnets are focusing permanent magnets.

3. A magnetic field apportionment method of distributing a target magnetic field at an operating point in space among a multiplicity of magnets, the method comprising:

determining a magnetic field angle as a representation of a magnetic field magnitude and a pivot angle;

determining one or more translational coordinates, rotational angles and pivotal angles for orienting each of the multiplicity of magnets to a final state, subject to design and application related constraints, and determining a field apportionment for contributing to a target magnetic field at an operating point for each of the multiplicity of magnets, wherein the sum of the magnetic fields contributed by the multiplicity of magnets at the operating point is equal to the target magnetic field at the operating point, wherein the fields generated by each of the multiplicity of magnets are constrained to be aligned within a predetermined angle of the target magnetic field such that the target field magnitude is distributed in equal parts to the multiplicity of magnets, and wherein adjustments are made to the field apportionments to account for each magnet'"'"'s lower and upper field magnitudes at the operating point, wherein the field magnitude apportionment adjustments are made by using methods of linear mathematics and linear programming.

4. A magnetic field apportionment method of distributing a target magnetic field at an operating point in space among a multiplicity of magnets, the method comprising:

determining a magnetic field angle as a representation of a magnetic field magnitude and a pivot angle;

determining one or more translational coordinates, rotational angles and pivotal angles, subject to design and application related constraints, for orienting each of the multiplicity of magnets to a state that provides a target magnetic field at the operating region, and determining an apportionment of the target magnetic field to be contributed by each of the multiplicity of magnets, wherein the sum of the magnetic fields contributed by the multiplicity of magnets at the operating point is equal to the target magnetic field at the operating point, whereby the magnet field apportionment to a multiplicity of N magnets is formulated as a constrained optimization problem.

5. The method of claim 4, wherein the constraints include a representation of magnet field magnitude upper and lower bounds for each of the multiplicity of magnets, and limits for reducing the amount of magnet pivoting, minimizing field gradients, and magnet field magnitudes.