Distortion-immune position tracking using redundant magnetic field measurements

• US 8,082,020 B2
• Filed: 08/07/2006
• Issued: 12/20/2011
• Est. Priority Date: 08/07/2006
• Status: Active Grant

• Current Assignee: Biosense Webster Incorporated (Johnson & Johnson)
• Original Assignee: Biosense Webster Incorporated (Johnson & Johnson)
• Inventors: Bar-Tal, Meir, Govari, Assaf
• Primary Examiner(s): Ahmed, Samir
• Assistant Examiner(s): Li, Ruiping
• Application Number:
  US11/462,733
• Publication Number:
  US 20080033282A1
• Time in Patent Office: 1,961 Days
• Field of Search: 600/424, 324/207.17, 324/207.12, 324/244, 702/150, 702/152
• US Class Current: 600/424
• CPC Class Codes: A61B 2017/00725 Calibration or performance testing
• CPC Class Codes: A61B 2034/105 Modelling of the patient, e.g. for ligaments or bones
• CPC Class Codes: A61B 2034/2051 Electromagnetic tracking systems
• CPC Class Codes: A61B 2034/2072 Reference field transducer attached to an instrument or patient
• CPC Class Codes: A61B 2090/0818 Redundant systems, e.g. using two independent measuring systems and comparing the signals
• CPC Class Codes: A61B 34/20 Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis
• CPC Class Codes: A61B 5/062 using magnetic field
• CPC Class Codes: G01D 5/2086 by movement of two or more coils with respect to two or more other coils
• CPC Class Codes: G01R 33/025 Compensating stray fields G01R33/0017 takes precedence
• CPC Class Codes: G01V 3/081 the magnetic field is produced by the objects or geological structures characterised by the method of magnetic field measurement G01R33/00

Abstract

A method for tracking a position of an object includes using a field sensor associated with the object to measure field strengths of magnetic fields generated by two or more field generators, wherein a measurement of at least one of the field strengths is subject to a distortion. Rotation-invariant location coordinates of the object are calculated responsively to the measured field strengths. Corrected location coordinates of the object are determined by applying to the rotation-invariant location coordinates a coordinate correcting function so as to adjust a relative contribution of each of the measured field strengths to the corrected location coordinates responsively to the distortion in the measured field strengths.

Claims

1. A method for tracking a position of an object in a working volume, comprising:

using a field sensor associated with the object to perform redundant field measurements of field strengths of magnetic fields generated by two or more field generators so as to provide redundant location information, wherein at least some of the field strength measurements are subject to a distortion; and

determining location coordinates of the object relative to the two or more field generators by applying to the redundant field measurements a coordinate correcting function according to a plurality of sub-volumes of the working volume that exploits the redundant location information so as to reduce an impact of the distortion on the location coordinates.

2. A system for tracking a position of an object in a working volume, comprising:

two or more field generators, which are arranged to generate respective magnetic fields in a vicinity of the object, the respective magnetic fields generated by two or more field generators defining a working volume;

a field sensor associated with the object, which is arranged to perform redundant field measurements of field strengths of the magnetic fields so as to provide redundant location information, wherein at least some of the field strength measurements are subject to a distortion; and

a processor, which is arranged to determine location coordinates of the object relative to the two or more field generators by applying to the redundant field measurements a coordinate correcting function according to a plurality of sub-volumes of the working volume that exploits the redundant location information so as to reduce an impact of the distortion on the location coordinates.

3. A computer software product used in a system for tracking a position of an object in a working volume, the product comprising a non-transitory computer-readable storage medium, in which program instructions are stored, which instructions, when read by the computer, cause the computer to control two or more field generators so as to generate magnetic fields in a vicinity of the object, the respective magnetic fields generated by two or more field generators defining a working volume, to accept redundant field measurements of field strengths of the magnetic fields performed by a field sensor associated with the object, the redundant field measurements comprising redundant location information, wherein at least some of the redundant field measurements are subject to a distortion, and to determine location coordinates of the object relative to the two or more field generators by applying to the redundant field measurements a coordinate correcting function according to a plurality of sub-volumes of the working volume that exploits the redundant location information so as to reduce an impact of the distortion on the location coordinates.