Magnetic field detectors, implantable medical devices, and related methods that utilize a suspended proof mass and magnetically sensitive material

An implantable medical device, comprising:

• a housing;
• stimulation circuitry within the housing that produces electrical stimulation signals;
• a processor within the housing that controls the operation of the stimulation circuitry, the processor having multiple modes of operation, wherein the processor implements at least one of the modes when a magnetic field of interest is present;
• and
• a magnetic field detector within the housing and in communication with the processor to provide a signal to the processor regarding a magnetic field, the magnetic field detector comprising:
• a proof mass;
• a chassis;
• a plurality of deformable arms connected on one end to the proof mass and on the other end to the chassis to suspend the proof mass relative to the chassis, the deformable arms having an electrical characteristic that varies depending upon a degree of deformation;
• and
• a magnetically sensitive material located on at least one of the proof mass and the deformable arms, the magnetically sensitive material being responsive to the presence of the magnetic field by imposing a force on the deformable arms to cause deformation.

A method of detecting that an implantable medical device is in proximity to a magnetic resonance image (MRI) scanner, comprising:

• providing the implantable medical device with a magnetic field detector that comprises:
• a proof mass;
• a chassis;
• a plurality of deformable arms connected on one end to the proof mass and on the other end to the chassis to suspend the proof mass relative to the chassis, the deformable arms having an electrical characteristic that varies depending upon a degree of deformation;
• and
• a magnetically sensitive material located on at least one of the proof mass and the deformable arms, the magnetically sensitive material being responsive to the presence of a magnetic field by imposing a force on the deformable arms to cause deformation;
• upon placing the implantable medical device in proximity to the MRI scanner such that the magnetic field of the MRI scanner causes deformation of the deformable arms, generating an electrical signal that relates to the magnetic field of the MRI scanner;
• and
• detecting from the electrical signal that the implantable medical device is in proximity to the MRI scanner.

A method of constructing a magnetic field detector, comprising:

• providing a structure that comprises:
• a proof mass;
• a chassis;
• and
• a plurality of deformable arms connected on one end to the proof mass and on the other end to the chassis to suspend the proof mass relative to the chassis, the deformable arms having an electrical characteristic that varies depending upon a degree of deformation;
• and
• applying a magnetically sensitive material onto at least one of the proof mass and the deformable arms, the magnetically sensitive material being responsive to the presence of a magnetic field by imposing a force on the deformable arms to cause deformation.