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