MRI-Safe and Force-Optimized Implantable Ring Magnet System with an Enhanced Inductive Link

Abstract

A magnetic system for a medical implant system is described. A planar implant receiver coil is configured to lie underneath and parallel to overlying skin of an implanted patient for transcutaneous communication of an implant communications signal. A planar ring-shaped attachment magnet also is configured to lie underneath and parallel to the overlying skin and radially surrounds the receiver coil. The attachment magnet is characterized by a magnetic field configured to avoid creating torque on the attachment magnet in the presence of an external magnetic field.

1 . A magnetic system for a medical hearing implant system for a patient user, the system comprising:
 an implant housing having:   a ring-shaped implant receiver coil configured to lie underneath and parallel to overlying skin of an implanted patient for transcutaneous communication of an implant communications signal; and   a ring-shaped attachment magnet configured to lie underneath and parallel to the overlying skin and radially surrounding the receiver coil,   
     
     
         2 . The system according to  claim 1 , wherein the implant receiver coil is planar. 
     
     
         3 . The system according to  claim 1 , wherein the ring-shaped attachment magnet is planar. 
     
     
         4 . The system according to any of  claims 1 , wherein the attachment magnet and receiver coil is circular or oval ring-shaped. 
     
     
         5 . The system according to  claim 4 , wherein the ratio of the inner diameter of the ring-shaped attachment magnet to the outer diameter of the ring-shaped receiver coil is in the range from 0.74 to 0.76. 
     
     
         6 . The system according to any of  claims 1 , wherein the attachment magnet is characterized by a single magnetic dipole moment. 
     
     
         7 . The system according to  claim 6 , wherein the dipole moment is oriented across the ring diameter parallel to the overlying skin or parallel to the center axis of the ring-shaped attachment magnet and perpendicular to the overlying skin. 
     
     
         8 . The system according to  claim 1 , wherein the attachment magnet comprises a plurality of local magnetic sections, wherein each local magnetic section has an independent local magnetic dipole and an independent local magnetic dipole orientation. 
     
     
         9 . The system according to  claim 8 , wherein the combined magnetic dipole for all the local magnetic sections has a zero overall magnetic dipole moment. 
     
     
         10 . The system according to  claim 8 , wherein the independent local magnetic dipoles are oriented such, that the exerted attractive holding force to an external part comprising a ring-shaped external attachment magnet where the attachment magnet and the external attachment magnet are aligned about a common center axis, has at least one distinguished maximum at one rotational angle about the common center axis relative to the attachment magnet. 
     
     
         11 . The system according to any  claim 8 , wherein each local magnetic section is a physically distinct ring segment, whereby the attachment magnet comprises a plurality of ring segments connected together to form a ring-shape. 
     
     
         12 . The system according to  claim 1 , wherein the implant housing and the attachment magnet are configured to prevent rotation of the attachment magnet within the implant housing. 
     
     
         13 . The system according to  claim 1 , wherein the implant housing and the attachment magnet are configured to enable rotation of the attachment magnet within the implant housing in the presence of an external magnetic field. 
     
     
         14 . The system according  claim 13 , wherein the implant housing further comprising a sensor adapted for determining the relative angle of rotation between the implant housing and the attachment magnet. 
     
     
         15 . (canceled)