Magnet locating apparatus and method of locating a magnet using such apparatus

• US 7,561,051 B1
• Filed: 04/18/2006
• Issued: 07/14/2009
• Est. Priority Date: 04/20/2005
• Status: Expired due to Fees

• Current Assignee: Creare Incorporated
• Original Assignee: Creare Incorporated
• Inventors: Kynor, David B., Kenton, Marc A.
• Primary Examiner(s): TRIEU, VAN THANH
• Application Number:
  US11/406,113
• Time in Patent Office: 1,183 Days
• Field of Search: 340/572.1, 340/572.2, 340/572.4, 340/572.5, 340/572.8, 340/686.1, 340/691.1, 340/573.1, 600/117, 600/424, 600/407, 600/420, 128/898, 128/899, 128/653.1
• US Class Current: 340/572.6
• CPC Class Codes: A61B 2034/2051 Electromagnetic tracking systems
• CPC Class Codes: A61B 2090/3958 emitting a signal
• 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

Abstract

An apparatus for locating a magnet and/or determining the orientation of the apparatus relative to the magnet. In one embodiment, the apparatus includes a multi-axis magnetic field sensor movable in a reciprocating manner so as to permit sensor readings at multiple spaced locations. In another embodiment, the apparatus includes a plurality of multi-axis magnetic field sensors arrayed along a straight line. The apparatus may be used in a number of medical and other applications, including tissue resection, tracking movement of a medical device in a body cavity and tracking movement of an internal organ.

Claims

1. An apparatus for locating a margin located within a living body an offset distance from a magnetic marker located in the living body and having a magnetic field, the apparatus comprising:

a probe that includes;

(a) a structure having a reference point positionable at the margin;

(b) at least one magnetic field sensor configured to generate an output signal as a function of the magnetic field of the magnetic marker;

(c) a selector for presetting the offset distance between the margin and the magnetic marker;

(d) a central processor configured to calculate a location of the margin relative to said reference point as a function of said output signal and the offset distance; and

(e) a display operatively coupled to said central processor and configured to display information about said location.

2. An apparatus according to claim 1, wherein said display is a visual display.

3. An apparatus according to claim 2, wherein said visual display comprises a portion that indicates when said reference is at the margin.

4. An apparatus according to claim 1, wherein said display is an aural display.

5. An apparatus according to claim 4, wherein said aural display comprises a sound having a volume modulation frequency that varies as a function of said location.

6. A method of determining the location of a magnet using a plurality of magnetic field sensors, comprising:

(a) determining whether any one or more of the plurality of magnetic field sensors has saturated;

(b) calculating the location of the magnet using only ones of the plurality of magnetic field sensors that are not saturated;

(c) determining whether a sufficient number of the plurality of magnetic field sensors remain unsaturated so as to permit a solution; and

(d) if an insufficient number of the plurality of magnetic field sensors remain to permit a solution, calculate the location of the magnet using the ones of the plurality of magnetic field sensors that are not saturated and assuming a magnetic gradient does not exist.