Cochlear implants having mri-compatible magnet apparatus and associated methods

Abstract

A cochlear implant is disclosed, including a cochlear lead, an antenna, a stimulation processor, a magnet apparatus, associated with the antenna, including a case and a plurality of magnetic material particles within the case that are movable relative to one another.

1 . A cochlear implant, comprising:
 a cochlear lead including a plurality of electrodes;   an antenna;   a stimulation processor operably connected to the antenna and to the cochlear lead; and   a magnet apparatus, associated with the antenna, including a case and a plurality of magnetic material particles packed within the case in such a manner that adjacent magnetic material particles are in contact with one another and are also movable relative to one another.   
     
     
         2 . A cochlear implant as claimed in  claim 1 , wherein
 the magnetic material particles are rotatable relative to one another.   
     
     
         3 . A cochlear implant as claimed in  claim 1 , wherein
 the magnetic material particles are each are free to move from one X-Y-Z coordinate to another and to rotate in any direction.   
     
     
         4 . A cochlear implant as claimed in  claim 1 , wherein
 the magnetic material particles are at least substantially polyhedral in shape.   
     
     
         5 . A cochlear implant as claimed in  claim 1 , wherein
 the magnetic material particles define mesh sizes that range from 50 μm to 500 μm, or from 100 μm to 300 μm, or from 300 μm to 500 μm.   
     
     
         6 . A cochlear implant as claimed in  claim 1 , wherein
 the magnetic material particles are formed from a material selected from the group consisting of neodymium-iron-boron, magnetic material, isotropic neodymium, anisotropic neodymium, samarium-cobalt.   
     
     
         7 . A cochlear implant as claimed in  claim 1 , wherein
 the case comprises a disk-shaped case.   
     
     
         8 . A cochlear implant as claimed in  claim 1 , wherein
 the case is formed from a material selected from the group consisting of paramagnetic metal and plastic.   
     
     
         9 . A cochlear implant as claimed in  claim 1 , further comprising:
 a magnetic field focusing shim located within the case.   
     
     
         10 . A cochlear implant as claimed in  claim 1 , wherein
 the antenna, the stimulation processor and the magnet apparatus are located within a flexible housing.   
     
     
         11 . A cochlear implant as claimed in  claim 1 , wherein
 the magnet apparatus defines a strength of at least 60-70 gauss measured at a distance of 1 mm from the case.   
     
     
         12 . A cochlear implant as claimed in  claim 1 , wherein
 the case has an internal volume and includes a divider that separates the internal volume into a plurality of sub-volumes.   
     
     
         13 . A method, comprising the step of:
 in response to the application of a magnetic field defining a magnetic field direction to an implantable cochlear stimulator including an antenna and a magnet apparatus, associated with the antenna, having a case and a plurality of magnetic material particles packed within the case in the absence of a carrier and with adjacent magnetic material particles in contact with one another, allowing the magnetic field to rotate the magnetic material particles in any direction, relative to the case, into magnetic alignment with the magnetic field.   
     
     
         14 . A method as claimed in  claim 13 , wherein
 the magnetic field has a magnetic flux density of at least 1.5 Tesla.   
     
     
         15 . A method as claimed in  claim 13 , wherein
 the magnetic field comprises a MRI magnetic field.   
     
     
         16 . A method as claimed in  claim 13 , wherein
 the step of allowing the magnetic field to rotate the magnetic material particles comprises allowing the magnetic field to rotate the magnetic material particles in any direction, relative to the case and relative to one another, into magnetic alignment with the magnetic field.   
     
     
         17 . A method as claimed in  claim 13 , wherein
 the step of allowing the magnetic field to rotate the magnetic material particles comprises allowing the magnetic field to move from one X-Y-Z coordinate to another and to rotate in any direction relative to the case and relative to one another into magnetic alignment with the magnetic field.   
     
     
         18 . A method as claimed in  claim 13 , wherein
 the magnetic material particles are at least substantially polyhedral in shape.   
     
     
         19 . A method as claimed in  claim 13 , wherein
 the magnetic material particles define mesh sizes that range from 50 μm to 500 μm, or from 100 μm to 300 μm, or from 300 μm to 500 μm.   
     
     
         20 . A method as claimed in  claim 13 , further comprising the step of:
 in response to movement of the implantable cochlear stimulator within the magnetic field subsequent to the magnetic material particles having been rotated into alignment with the magnetic field, allowing the magnetic field to further rotate the magnetic material particles in any direction, relative to the case, back into magnetic alignment with the magnetic field.   
     
     
         21 . A method as claimed in  claim 13 , wherein
 the magnet apparatus defines a strength of at least 60-70 gauss measured at a distance of 1 mm from the case.   
     
     
         22 . A system, comprising
 a cochlear implant as claimed in  claim 1 ; and   a headpiece including
 an antenna, and 
 a headpiece magnet apparatus associated with the antenna; 
   wherein the cochlear implant magnet apparatus and the headpiece magnet apparatus are respectively configured such that a pull force is defined there between that is equal to about 2.2±0.1 N when the cochlear implant magnet apparatus and the headpiece magnet apparatus are separated by a distance of 3 mm.   
     
     
         23 . A system as claimed in  claim 22 , wherein
 the headpiece magnet apparatus includes a magnetic field focusing shim.   
     
     
         24 . A system as claimed in  claim 22 , wherein
 the headpiece magnet apparatus includes a plurality of magnets.