Advanced implanted magnet management in the face of external magnetic fields
A method, including subjecting a subcutaneous medical device containing a first magnet to a magnetic field of an MRI machine, thereby imparting a torque onto the first magnet and resisting the imparted torque via an external device that includes a second magnet, wherein the second magnet is movable relative to another component of the external device.
1 . An MRI compatibility assembly, comprising:
a first component configured to interface with skin of a recipient at a location overlying an implanted magnet of an implantable component; and
a magnet including, for a given orientation relative to the first component, a first surface area facing the first component and a second surface area opposite the first surface area; and
a casing assembly, wherein
the magnet is supported by the first component and the casing assembly,
the casing assembly includes a plurality of pieces including a first piece and a second piece, the first piece extending between the first surface area of the magnet and the first component, the second piece extending over the second surface area of the magnet, the casing assembly establishing a cavity when the plurality of pieces are assembled,
the magnet is housed in the cavity and movable relative to the first component and the casing assembly, and
the MRI compatibility assembly is configured to be exposed to at least a 1T magnetic field of an MRI machine.
2 . The MRI compatibility assembly of claim 1 , wherein:
the magnet supported by the first component is a disk magnet, and the disk magnet is rotatable about an axis thereof.
3 . The MRI compatibility assembly of claim 1 , wherein:
the MRI compatibility assembly is configured to be placed against the recipient such that the MRI compatibility assembly at least generally aligns with the implanted magnet.
4 . The MRI compatibility assembly of claim 1 , wherein:
the MRI compatibility assembly is configured to be exposed to at least a 3T magnetic field of an MRI machine for at least 30 minutes.
5 . The MRI compatibility assembly of claim 1 , wherein:
the MRI compatibility assembly is configured such that the magnet supported by the first component automatically aligns the first component over the implanted magnet.
6 . The MRI compatibility assembly of claim 1 , wherein:
the MRI compatibility assembly is configured so that the magnet always experiences little to no torque thereon as a result of the at least 1T magnetic field acting directly thereon.
7 . The MRI compatibility assembly of claim 1 , wherein:
the MRI compatibility assembly is configured to be exposed to at least a 3T magnetic field of an MRI machine.
8 . The MRI compatibility assembly of claim 1 , wherein:
the MRI compatibility assembly is configured to be exposed to at least a 3 T magnetic field of an MRI machine for at least 15 minutes.
9 . The MRI compatibility assembly of claim 1 , wherein:
a height of the MRI compatibility assembly is at least about half of a maximum diameter thereof.
10 . The MRI compatibility assembly of claim 1 , wherein:
the MRI compatibility assembly is configured to resist a torque imparted onto the implanted magnet of the implantable component.
11 . The MRI compatibility assembly of claim 1 , wherein:
the magnet supported by the first component is magnetically coupled to the implanted magnet; and
the magnet supported by the first component generates a magnetic force that is at least about 2 times as strong as a magnetic force generated by the implanted magnet of the implantable component.
12 . The MRI compatibility assembly of claim 1 , wherein:
a height of the MRI compatibility assembly is more than a maximum diameter of the magnet supported by the first component.
13 . The MRI compatibility assembly of claim 1 , wherein:
the MRI compatibility apparatus interfaces with no more than about 4,000 mm 2 of recipient body surface when the magnet supported by the first component interacts with the implanted magnet of the implantable component.
14 . The MRI compatibility assembly of claim 1 , wherein:
the first component indirectly supports the magnet.
15 . The MRI compatibility assembly of claim 1 , wherein:
the magnet supported by the first component is a magnet that produces a magnetic field of at least about a half of a tesla.
16 . The MRI compatibility assembly of claim 1 , wherein:
the magnet supported by the first component is a spherical magnet, and the spherical magnet rotates when it interacts with the magnetic field of the MRI machine.
17 . The MRI compatibility assembly of claim 1 , wherein:
the MRI compatibility assembly has a skin interfacing side surface that is between 30 mm and 60 mm at its maximum diameter.
18 . The MRI compatibility assembly of claim 1 , wherein:
a maximum diameter of the MRI compatibility assembly at a location away from a skin interfacing portion is larger than a maximum diameter of the MRI compatibility assembly at a location proximate the skin interfacing portion.
19 . The MRI compatibility assembly of claim 1 , wherein:
the MRI compatibility assembly is a puck.
20 . The MRI compatibility assembly of claim 1 , wherein:
the MRI compatibility assembly is configured to be exposed to at least a 1T magnetic field of an MRI machine for at least 15 minutes.
21 . The MRI compatibility assembly of claim 20 , wherein:
the magnet supported by the first component is a spherical magnet, and the spherical magnet rotates when it interacts with the magnetic field of the MRI machine.
22 . The MRI compatibility assembly of claim 20 , wherein:
the magnet supported by the first component is a magnet that produces a magnetic field of at least about a half of a tesla.
23 . The MRI compatibility assembly of claim 20 , wherein:
the MRI compatibility assembly has a skin interfacing side surface that is between 30 mm and 60 mm at its maximum diameter.
24 . The MRI compatibility assembly of claim 20 , wherein:
a maximum diameter of the MRI compatibility assembly at a location away from a skin interfacing portion is larger than a maximum diameter of the MRI compatibility assembly at a location proximate the skin interfacing portion.
25 . The MRI compatibility assembly of claim 20 , wherein:
the MRI compatibility assembly is configured to be exposed to at least a 1T magnetic field of an MRI machine for at least 60 minutes.
26 . The MRI compatibility assembly of claim 20 , wherein:
the MRI compatibility assembly is a puck.
27 . A method, comprising:
placing an MRI compatibility apparatus including a second magnet and a first component configured to interface with a skin of a recipient at a location overlaying a first magnet, implanted beneath the skin of the recipient, of an implanted medical device implanted in the recipient, against the recipient such that the MRI compatibility apparatus at least generally aligns with the first magnet of the implanted medical device implanted in the recipient via magnetic interaction with the first magnet;
subjecting the medical device containing the first magnet to a magnetic field of an MRI machine, thereby imparting a torque onto the first magnet; and
resisting the imparted torque via the MRI compatibility apparatus that includes the second magnet, wherein
the second magnet includes, for a given orientation relative to the first component, a first surface area facing the first component and a second surface area opposite the first surface area,
the MRI compatibility apparatus further includes a casing assembly,
the second magnet is supported by the first component and the casing assembly,
the casing assembly includes a plurality of pieces including a first piece and a second piece, the first piece extending between the first surface area of the second magnet and the first component, the second piece extending over the second surface area of the second magnet, the casing assembly establishing a cavity when the plurality of pieces are assembled, and
the second magnet is housed in the cavity and movable relative to the first component and the casing assembly.
28 . The method of claim 1 , wherein the action of placing the MRI compatibility apparatus against the recipient includes placing the MRI compatibility apparatus against a head of the recipient over the first magnet so that the second magnet moves relative to the first component of the MRI compatibility apparatus when the second magnet interacts with the magnetic field of the first magnet.
29 . A method, comprising:
placing an MRI compatibility apparatus, including a magnet, against a recipient such that the MRI compatibility apparatus at least generally aligns with an implanted magnet in the recipient due to magnetic attraction between the magnet of the MRI compatibility apparatus and the implanted magnet, wherein the magnet of the MRI compatibility apparatus generates a magnetic force that is at least about 2 times as strong as a magnetic force generated by the implanted magnet as measured at a surface of the skin of the recipient closest to the implanted magnet; and
subjecting the recipient and the MRI compatibility apparatus to an MRI field with the two magnets being subjected to the field, wherein
the MRI compatibility apparatus includes:
a first component configured to interface with skin of a recipient at a location overlying an implanted magnet of an implantable component; and
a casing assembly, wherein
the magnet of the MRI compatibility apparatus includes, for a given orientation relative to the first component, a first surface area facing the first component and a second surface area opposite the first surface area,
the magnet of the MRI compatibility apparatus is supported by the first component and the casing assembly,
the casing assembly includes a plurality of pieces including a first piece and a second piece, the first piece extending between the first surface area of the magnet MRI compatibility apparatus and the first component, the second piece extending over the second surface area of the magnet, the casing assembly establishing a cavity when the plurality of pieces are assembled, and
the magnet MRI compatibility apparatus is housed in the cavity and movable relative to the first component and the casing assembly.
30 . The method of claim 29 , further comprising:
wrapping a fabric around a head of the recipient with the MRI compatibility apparatus interposed between the fabric and the head of the recipient, wherein the magnetic attraction between the two magnets maintains the general position of the MRI compatibility apparatus over the implanted magnet during the action of wrapping.