System and method for detection of metal disturbance based on orthogonal field components

A method for detecting metal objects during an invasive medical procedure, comprising:

• providing an apparatus, the apparatus comprising:
• a probe configured to generate X-Y position signals indicative of a position of the distal end of the probe, and force signals indicative of force exerted on the distal end of the probe, the probe comprising:
• an insertion tube having a longitudinal axis and having a distal end;
• a distal tip disposed at the distal end of the insertion tube;
• at least one X-Y sensor within the probe, said at least one X-Y sensor providing the X-Y position signals indicative of the position of the distal end of the probe, wherein said at least one X-Y sensor is oriented for receiving magnetic fields along a respective X axis or Y axis;
• a joint, which couples the distal tip to the distal end of the insertion tube;
• a joint sensor within the probe for sensing a position of the distal tip relative to the distal end of the insertion tube, the joint sensor comprising a first subassembly and a second subassembly, which are disposed within the probe on opposite, respective sides of the joint and comprising magnetic transducers for generating the signals indicative of force exerted on the distal end of the probe;
• the first subassembly comprising a field coil, the field coil being configured to generate a magnetic field along an axial Z-axis, the magnetic field having a first driving frequency when driven by an electrical current;
• the second subassembly comprising a plurality of receiving transducers fixed at different radial locations within the probe, the receiving transducers adapted to emit respective electric signals in response to said Z-axis magnetic field generated by the field coil;
• wherein the electrical signals emitted by respective receiving transducers are force signals, and vary in response to movement of the distal tip with respect to the distal end of the insertion tube;
• a display for displaying an electroanatomical map;
• and
• a processor adapted for generating the electroanatomical map based on the X-Y position signals from the at least one X-Y sensor of the probe, and for determining a force measurement based on the force signals from the second subassembly of the joint sensor,
• the processor having a threshold field value stored therein, the threshold field value being based on signals output by the field coil;
• the method comprising:
• inserting the probe into a patient, and moving the probe to a first position within the patient in contact with a tissue surface;
• applying a current to the field coil of the first assembly, and the field coil generating a magnetic field having a first driving frequency along an axial Z-axis;
• the receiving transducers of the second assembly receiving the magnetic field generated by the first assembly, and the receiving transducers generating respective electric force signals;
• the processor detecting at least one of a compression and a deflection of the distal tip based on the electrical force signals from the receiving transducers;
• the processor receiving X-Y position signals from the at least one X-Y sensor, determining and displaying on the electroanatomical map a first position of the distal end of the probe based on the X-Y position signals;
• and thereafter:
• moving the probe to a second position within the patient in a vicinity of a metal object, with the field coil generating the magnetic field having the first driving frequency along the axial Z-axis;
• the metal object interfering with the magnetic field having the first driving frequency along the axial Z-axis;
• the at least one X-Y sensor receiving the magnetic field at the first driving frequency and in response thereto generating an X-Y position signal having a first driving frequency component;
• using the processor, comparing the first driving frequency component of the X-Y position signal to the threshold field value, determining that the first driving frequency component of the X-Y position signal is greater than the threshold field value and, in response to said determination, marking the electroanatomical map with a visual indicator indicating the metal object,
• and initiating an audible alarm accompanied by distinct tactile feedback upon identifying the presence of the metal object near the distal end of the probe based on said determination that the first driving frequency component of the X-Y position signal is greater than the threshold field value,
• wherein the X-Y sensor comprises a first X-Y sensor coil and a second X-Y sensor coil, wherein the first X-Y sensor coil and the second X-Y sensor coil are adapted and oriented to receive force signals,
• wherein the coils of the second subassembly and the coils of the X-Y sensor are adapted and oriented so that all measurements received from the coils of the second subassembly and the coils of the X-Y sensor relate linearly to a force vector,
• wherein the coils of the second subassembly and the coils of the X-Y sensor are adapted and oriented so that there is linear relation between readings from the coils of the second subassembly and readings from the coils of the X-Y sensor,
• wherein the coils of the second subassembly and the coils of the X-Y sensor are oriented relative to one another such that a distortion in the magnetic field caused by the metal object, causes a different distortion in the coils of the second subassembly than in the coils of the X-Y sensor, and
• wherein the relation between second subassembly signal readings and X-Y sensor readings is measurably altered.

A method for detecting metal objects during an invasive medical procedure, comprising:

• providing an apparatus, the apparatus comprising:
• a probe configured to generate X-Y position signals indicative of a position of the distal end of the probe, and force signals indicative of force exerted on the distal end of the probe, the probe comprising:
• an insertion tube having a longitudinal axis and having a distal end;
• a distal tip disposed at the distal end of the insertion tube;
• at least one X-Y sensor within the probe, said at least one X-Y sensor providing the X-Y position signals indicative of the position of the distal end of the probe;
• a joint, which couples the distal tip to the distal end of the insertion tube;
• a joint sensor within the probe for sensing a position of the distal tip relative to the distal end of the insertion tube, the joint sensor comprising a first subassembly and a second subassembly, which are disposed within the probe on opposite, respective sides of the joint and comprising magnetic transducers for generating the signals indicative of force exerted on the distal end of the probe;
• the first subassembly comprising a field coil, the field coil being configured to generate a magnetic field having a first driving frequency when driven by an electrical current;
• the second subassembly comprising a plurality of receiving transducers within the probe, the receiving transducers adapted to emit respective electric signals in response to said magnetic field generated by the field coil which vary in response to movement of the distal tip with respect to the distal end of the insertion tube;
• and
• a processor, the processor having a threshold field value stored therein, the threshold field value being based on signals output by the field coil;
• the method comprising:
• inserting the probe into a patient, and moving the probe to a first position within the patient in contact with a tissue surface;
• the field coil of the first subassembly generating the magnetic field having the first driving frequency;
• the metal object interfering with the magnetic field having the first driving frequency;
• the at least one X-Y sensor receiving the magnetic field at the first driving frequency and in response thereto generating an X-Y position signal having a first driving frequency component;
• using the processor, comparing the first driving frequency component of the X-Y position signal to the threshold field value, determining that the first driving frequency component of the X-Y position signal is greater than the threshold field value and, in response to said determination, identifying a metal object,
• and initiating an audible alarm accompanied by distinct tactile feedback upon identifying the presence of the metal object near the distal end of the probe based on said determination that the first driving frequency component of the X-Y position signal is greater than the threshold field value,
• wherein the X-Y sensor comprises a first X-Y sensor coil and a second X-Y sensor coil, wherein the first X-Y sensor coil and the second X-Y sensor coil are adapted and oriented to receive force signals,
• wherein the coils of the second subassembly and the coils of the X-Y sensor are adapted and oriented so that all measurements received from the coils of the second subassembly and the coils of the X-Y sensor relate linearly to a force vector,
• wherein the coils of the second subassembly and the coils of the X-Y sensor are adapted and oriented so that there is linear relation between readings from the coils of the second subassembly and readings from the coils of the X-Y sensor,
• wherein the coils of the second subassembly and the coils of the X-Y sensor are oriented relative to one another such that a distortion in the magnetic field caused by the metal object, causes a different distortion in the coils of the second subassembly than in the coils of the X-Y sensor, and
• wherein the relation between second subassembly signal readings and X-Y sensor readings is measurably altered.