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System and method to determine the location and orientation of an indwelling medical device

  • US 5,879,297 A
  • Filed: 05/08/1997
  • Issued: 03/09/1999
  • Est. Priority Date: 05/08/1997
  • Status: Expired due to Term
First Claim
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1. A system for detecting a position of a magnet associated with an indwelling medical device from a measurement location on the surface of a patient and in the presence of a magnetic field of the Earth, the system comprising:

  • a housing;

    first, second, and third magnetic sensors mounted in the housing, the first sensor positioned at a first distance from a magnet and generating a first set of electrical signals as a function of a first magnetic field strength and direction due to the magnet, the second sensor positioned at a second distance from the magnet and generating a second set of electrical signals as a function of a second magnetic field strength and direction due to the magnet, and the third sensor positioned at a third distance from the magnet and generating a third set of electrical signals as a function of a third magnetic field strength and direction due to the magnet;

    a processor to calculate an estimated position of the magnet in a three-dimensional space and to calculate a predicted magnetic field strength for the first, second and third sensors based on the estimated position and to calculate a measured magnetic field strength using the first, second, and third sets of electrical signals wherein the processor generates the measured magnetic field strength by subtracting a first selected one of the first, second, and third sets of electrical signals from a second selected one of the first, second, and third sets of electrical signals different from the first selected one of the first, second, and third sets of electrical signals to cancel the effects of the Earth'"'"'s magnetic field, the processor generating an error function based on a difference between the predicted magnetic field strength and the measured magnetic field strength; and

    a display providing a visual display of the three-dimensional position of the magnet using the error function.

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