Correction of Measured Values for a Magnetic Localization Device

• US 20080157755A1
• Filed: 02/11/2005
• Published: 07/03/2008
• Est. Priority Date: 02/18/2004
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Timinger, Holger, Wischmann, Hans-Aloys, Borgert, Jorn, Kruger, Sascha, Sabczynski, Jorg
• Granted Patent: US 7,652,468 B2
• Time in Patent Office: Days
• US Class Current: 324/207.12
• CPC Class Codes: A61B 2034/2051 Electromagnetic tracking systems
• 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 5/06 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
• CPC Class Codes: A61B 90/36 Image-producing devices or illumination devices not otherwise provided for

Abstract

The invention relates to a device and a method for correction of the position (x) of a field sensor (4) measured by means of a magnetic localization device. External field distortions, such as caused for example by the rotating components (1a, 1b) of a computer tomograph (1), are then determined with the help of reference sensor (3) placed at a known position. It is possible to deduce, for example, the current angle of rotation (Φ) of the computer tomograph (1) from the measurement signals of the reference sensor (3). Based on an empirically determined correction (δ(x, Φ)), the uncorrected determined positions (x) of the field sensor (4) can then be converted to corrected positions (x′) in relation to the field distortions. The field generator (2) and the reference sensor (3) are preferably fastened to the gantry in order to eliminate the dependency of the field distortions on an inclination of the gantry.

Claims

1. A magnetic localization device, comprising:

a) a field generator for generating a magnetic field;

b) a field sensor for measuring the magnetic field;

c) a reference sensor for measuring the magnetic field at a known reference position;

d) a control unit, which is arranged for determining the position of the field sensor relative to the field generator and thereby for compensating external field distortions by taking the reference sensor into consideration.

2. A localization device as claimed in claim 1, wherein the spatial position of the field generator is known.

3. A localization device was claimed in claim 1, wherein the field generator and/or the reference sensor are fastened to the gantry of a computer tomograph.

4. A localization device as claimed in claim 1, wherein the control unit contains a memory with a calibration function, which provides a correction shift for the uncorrected determined position of the field sensor based on measured signals of the reference sensor and the field sensor.

5. An examination device, comprising:

an imaging device, in particular a computer tomograph;

a magnetic localization device as claimed in claim 1.

6. A method for position measurement with a magnetic localization device, comprising the steps of:

a) collecting the signals of a field sensor and/or a field generator;

b) collecting the signals of a magnetic reference sensor, which is placed at a known spatial position relative to the field generator or to the field sensor;

c) determining the position of the field sensor relative to the field generator, where external field distortions are compensated by taking the signals of the reference sensor into consideration.

7. A method as claimed in claim 6, wherein a correction function is determined, which indicates a correction shift for the uncorrected determined position of the field sensor in dependence on the signal of the reference sensor and the uncorrected determined position of the field sensor.

8. A method as claimed in claim 7, wherein the correction function for support points in a volume of interest is empirically determined and extended by extrapolation or interpolation respectively on the whole volume.

9. A method as claimed in claim 6, wherein a parameter is determined from the signal of the reference sensor, which parameter characterizes the external field distortion.

10. A method as claimed in claim 9, wherein the parameter describes the angle of rotation of a computer tomograph situated in the vicinity of the localization device.