MRI safe actuator for implantable floating mass transducer
An implantable hearing prosthesis for a recipient patient is described. An implantable signal transducer includes one or more electromagnetic drive coils for receiving an electrical stimulation signal and a cylindrical transducer magnet arrangement including an inner disk magnet having a first magnetic field direction, and an outer annular magnet surrounding the inner rod magnet and having a second magnetic field direction opposite to the first magnetic field direction. Current flow through the one or more electromagnetic drive coils from the electrical stimulation signal creates a coil magnetic field that interacts with the magnetic fields of the transducer magnet arrangement to create vibration in the transducer magnet which is developed by the signal transducer as a mechanical stimulation signal for audio perception by the patient.
1. An implantable hearing prosthesis for a recipient patient, the prosthesis comprising:
a receiving coil for transcutaneous receiving of an externally generated communication signal;
an implantable signal processor in communication with the receiving coil for converting the communication signal into an electrical stimulation signal;
an implantable inertial mass signal transducer in communication with the signal processor and including:
i. one or more electromagnetic drive coils for receiving the electrical stimulation signal;
ii. a cylindrical transducer magnet arrangement operating as an inertial mass and including an inner disk magnet having a first magnetic field direction, and an outer annular magnet surrounding the inner disk magnet and having a second magnetic field direction opposite to the first magnetic field direction;
wherein the one or more electromagnetic drive coils is arranged in a central structure over the inner disk magnet so that current flow through the one or more electromagnetic drive coils from the electrical stimulation signal creates a coil magnetic field that interacts mainly with the magnetic field of the inner disk magnet so as to create vibration in the transducer magnet arrangement which is developed by the signal transducer in response to the inertial mass of the transducer magnet arrangement as a mechanical stimulation signal for audio perception by the patient.
2. A prosthesis according to claim 1 , wherein the signal transducer includes a hermetically sealed transducer housing.
3. A prosthesis according to claim 2 , wherein the transducer housing is sealed by a silicone elastomer.
4. A prosthesis according to claim 2 , wherein the transducer housing is made of titanium.
5. A prosthesis according to claim 1 , wherein the prosthesis is a middle ear implant device.