Probe for determining magnetic marker locations

Abstract

A probe including a first sensor having a first magnetometer and a first accelerometer and a second sensor having a second magnetometer and a second accelerometer is configured for determining the distance and direction to a marker. The marker may be magnetic and may be surgically inserted into a patient's body to mark a specific location. The probe may be used to locate the marker, thus identifying the location. The probe may include a microprocessor that receives an output from the first sensor and an output from the second sensor and determines the distance and direction to the marker.

What is claimed is: 
     
         1 . A method for determining a distance and direction between a probe and a magnetic marker implanted in a patient, the method comprising:
 providing the probe, wherein the probe comprises
 a first sensor including a first magnetometer and a first accelerometer, and 
 a second sensor including a second magnetometer and a second accelerometer, 
 wherein the probe is configured to determine a position, in three-dimensional space, of the magnetic marker; 
   balancing the probe while away from the magnetic marker;   moving the balanced probe so that the magnetic marker is within range of the first magnetometer;   determining the distance and direction between the probe and the magnetic marker by comparing an output of the first sensor with an output of the second sensor;   aligning the probe with the magnetic marker based on the determined distance and direction between the probe and the magnetic marker; and   inserting a portion of the aligned probe into an incision in the patient and directing the probe toward the magnetic marker.   
     
     
         2 . The method of  claim 1 , further comprising continuously indicating the alignment of the probe with the magnetic marker through visual or audio feedback. 
     
     
         3 . A probe for detecting a magnetic marker, the probe comprising:
 a first sensor including a first magnetometer and a first accelerometer located in a handheld housing;   a second sensor including a second magnetometer and a second accelerometer, the second sensor located in the housing and separated from the first sensor; and   a processor located in the housing and electrically connected to the first sensor and the second sensor, the processor configured to receive an output from the first sensor and an output from the second sensor and determine a distance and direction between one of the first sensor and the second sensor and a magnetic marker.   
     
     
         4 . The probe of  claim 3 , wherein each of the first and the second magnetometers are configured to detect the field strength of the magnetic field of a magnetic maker within a range measured from each of the first and second magnetometers, and wherein the first and second sensors are separated by a distance greater than the range. 
     
     
         5 . The probe of  claim 4 , wherein the distance separating the first and second sensors is at least twice the range of the first and second magnetometers, such that the field strength of the magnetic field of a magnetic marker can only be substantially detected by either the first magnetometer or the second magnetometer. 
     
     
         6 . The probe of  claim 4 , wherein the processor is configured to determine the distance between one of the first sensor and the second sensor and a magnetic marker by calculating a difference between the output of the first sensor and the output of the second sensor. 
     
     
         7 . The probe of  claim 6 , wherein the difference represents the field strength of the magnetic marker. 
     
     
         8 . The probe of  claim 7 , further comprising a memory configured to store a lookup table containing data relating the magnetic field strength of a magnetic marker to a distance from the magnetic marker. 
     
     
         9 . The probe of  claim 3 , wherein the handheld housing is configured as a wand comprising:
 a base, wherein the first sensor is located in the base;   an extension member extending from the base, the extension member defining the distance; and   a tip, wherein the second sensor is located in the tip, and wherein the processor determines the distance and direction between the tip and a magnetic marker.   
     
     
         10 . The probe of  claim 1 , wherein the first and second sensors are located with a sensing portion which is configured to be removable from the housing. 
     
     
         11 . The probe of  claim 10 , wherein the sensing portion is disposable.