COCHLEAR IMPLANTS HAVING MRI-COMPATIBLE MAGNET APPARATUS AND ASSOCIATED METHODS
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.
The present disclosure relates generally to the implantable portion of implantable cochlear stimulation (or “ICS”) systems.
2. Description of the Related ArtICS systems are used to help the profoundly deaf perceive a sensation of sound by directly exciting the intact auditory nerve with controlled impulses of electrical current. Ambient sound pressure waves are picked up by an externally worn microphone and converted to electrical signals. The electrical signals, in turn, are processed by a sound processor, converted to a pulse sequence having varying pulse widths and/or amplitudes, and transmitted to an implanted receiver circuit of the ICS system. The implanted receiver circuit is connected to an implantable electrode array that has been inserted into the cochlea of the inner ear, and electrical stimulation current is applied to varying electrode combinations to create a perception of sound. The electrode array may, alternatively, be directly inserted into the cochlear nerve without residing in the cochlea. A representative ICS system is disclosed in U.S. Pat. No. 5,824,022, which is entitled “Cochlear Stimulation System Employing Behind-The-Ear Sound processor With Remote Control” and incorporated herein by reference in its entirety. Examples of commercially available ICS sound processors include, but are not limited to, the Advanced Bionics™ Harmony™ BTE sound processor, the Advanced Bionics™ Naida™ BTE sound processor and the Advanced Bionics™ Neptune™ body worn sound processor.
As alluded to above, some ICS systems include an implantable cochlear stimulator (or “cochlear implant”), a sound processor unit (e.g., a body worn processor or behind-the-ear processor), and a microphone that is part of, or is in communication with, the sound processor unit. The cochlear implant communicates with the sound processor unit and, some ICS systems include a headpiece that is in communication with both the sound processor unit and the cochlear implant. The headpiece communicates with the cochlear implant by way of a transmitter (e.g., an antenna) on the headpiece and a receiver (e.g., an antenna) on the implant. Optimum communication is achieved when the transmitter and the receiver are aligned with one another. To that end, the headpiece and the cochlear implant may include respective positioning magnets that are attracted to one another, and that maintain the position of the headpiece transmitter over the implant receiver. The implant magnet may, for example, be located within a pocket in the cochlear implant housing.
The present inventors have determined that conventional cochlear implants are susceptible to improvement. For example, the magnets in many conventional cochlear implants are disk-shaped and have north and south magnetic dipoles that are aligned in the axial direction of the disk. Such magnets are not compatible with magnetic resonance imaging (“MRI”) systems. In particular, the cochlear implant 10 illustrated in
The implant magnet produces a magnetic field M in a direction that is perpendicular to the patient's skin and parallel to the axis A, and this magnetic field direction is not aligned with, and may be perpendicular to (as shown), the direction of the MRI magnetic field B. The misalignment of the interacting magnetic fields M and B is problematic for a number of reasons. The dominant MRI magnetic field B (typically 1.5 Tesla or more) may demagnetize the implant magnet 14 or generate a significant amount of torque T on the implant magnet 14. The torque T may dislodge the implant magnet 14 from the pocket within the housing 12, reverse the magnet 14 and/or dislocate the cochlear implant 10, all of which may also induce tissue damage. One proposed solution involves surgically removing the implant magnet 14 prior to the MRI procedure and then surgically replacing the implant magnet thereafter. The present inventors have determined that a solution which does not involve surgery would be desirable.
SUMMARYA cochlear implant in accordance with one of the present inventions includes 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 in contact with one another and are movable relative to one another.
A method in accordance with one of the present inventions may be practice in conjunction with 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 within the case that are in contact with one another. In response to the application of a magnetic field defining a magnetic field direction to the implantable cochlear stimulator, the magnetic field is allowed to rotate the magnetic material particles in any direction, relative to the case, into magnetic alignment with the magnetic field.
A system in accordance with one of the present inventions includes cochlear implant, with 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 in contact with one another and movable relative to one another, and headpiece.
There are a number of advantages associated with such apparatus and methods. For example, a strong magnetic field, such as an MRI magnetic field, will not demagnetize the magnet apparatus. Nor will it generate a significant amount of torque on the magnet apparatus and associated cochlear implant. As a result, surgical removal of the cochlear implant magnet prior to an MRI procedure, and then surgically replacement thereafter, is not required.
The above described and many other features of the present inventions will become apparent as the inventions become better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings.
Detailed descriptions of the exemplary embodiments will be made with reference to the accompanying drawings.
The following is a detailed description of the best presently known modes of carrying out the inventions. This description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the inventions.
As illustrated for example in
The case 24 is not limited to any particular configuration, size or shape. In the illustrated implementation, the case 24 includes a base 26 and a cover 28 that may be secured to base after the magnetic material particles 22 have been dispensed into the base. The cover 28 may be secured to the base 26 in such a manner that a hermetic seal is formed between the cover and the base. Suitable techniques for securing the cover 28 to the base 26 include, for example, seam welding with a laser welder. With respect to materials, the case 24 may be formed from biocompatible paramagnetic metals, such as titanium or titanium alloys, and/or biocompatible non-magnetic plastics such as polyether ether ketone (PEEK), low-density polyethylene (LDPE), high-density polyethylene (HDPE) and polyamide. In particular, exemplary metals include commercially pure titanium (e.g., Grade 2) and the titanium alloy Ti-6Al-4V (Grade 5), while exemplary metal thicknesses may range from 0.20 mm to 0.25 mm. With respect to size and shape, the case 24 may have an overall size and shape similar to that of conventional cochlear implant magnets so that the magnet apparatus 20 can be substituted for a conventional magnet in an otherwise conventional cochlear implant. The exemplary case 24 is disk-shaped and defines a central axis A. In some implementations, the diameter that may range from 9 mm to 16 mm and the thickness may range from 1.5 mm to 3.0 mm. The diameter of the case 24 is 12.9 mm, and the thickness is 2.4 mm, in the illustrated embodiment.
The magnet apparatus 20 includes an inner surface 30 which, in this embodiment, is formed by the inner surface of the case 24, i.e., the inner surfaces of the base 26 and cover 28. A lubricious layer may be added to the inner surface to improve the movement of the particles 22 that are adjacent to the inner surface 30. To that end, and referring to the magnet apparatus 20a illustrated in
The exemplary magnet apparatus 20b illustrated in
Referring to
The exemplary magnet apparatus 20d illustrated in
Turning to
The magnetic material density ratio within the case 24, i.e. the ratio of the total volume of magnetic material particles to the total volume within the case 24, may be at least 70%, i.e., there is no more than 30% free space within the case. This ratio allows the present magnet apparatuses 20-20d to be essentially the same size and shape as a conventional disk-shaped permanent magnet in a cochlear implant when combined with an appropriate headpiece. With respect to the density of the magnetic material particles, the density may range, in the exemplary context of neodymium-iron-boron, from 2.75 g/cm3 (30% free space) to 3.94 g/cm3 (fully packed and pressed with a force of 100 kPa). Free space percentages that are larger than 30% may be employed in those instances where the magnet apparatus is larger. The magnetic strength of the of the exemplary magnet apparatus 20b, which includes the particles 22 within the case 24 and a shim 34, is about 60-70 gauss measured at a distance of 1 mm from the case on the axis A. The pull force between a cochlear implant including the magnet apparatus 20 and a cochlear implant headpiece (e.g., headpiece 300 in
It should also be noted that the use of significantly larger magnetic elements within the case in place of the magnetic material particles will decrease the magnetic material density (due to air gaps between the magnetic elements) and prevent magnet apparatus which have cases of the sizes and shapes disclosed herein from achieving the desired level of magnetic strength. Similarly, the use of ferrofluids, which include nano-sized particles dispersed and suspended within a fluid, in place of the magnetic material particles would also necessitate the use of a case that is larger than a conventional cochlear implant magnet to achieve the desired level of magnetic strength.
For ease of illustration purposes on only, the non-spherical particles may be represented in the manner shown in
An external magnetic field may be used to reorient the magnetic material particles 22 within the case 24 to establish the desired N-S orientation of magnet apparatuses 20-20d. Such reorientation may be performed before or after the magnet apparatuses 20-20d are incorporated into a cochlear implant. To that end, and referring to
The magnet apparatus 20 (or 20a-20d) may form part of a cochlear implant in a cochlear implant system that also includes a sound processor and a headpiece. One example of such a cochlear implant system is the system 50, which is described in greater detail below with reference to
There are a variety of advantages associated with such magnetic field reorientation. For example, the MRI magnetic field B (typically 1.5 Tesla or more) will not demagnetize the magnet apparatus 20 or generate a significant amount of torque T on the magnet apparatus and associated cochlear implant. As a result, surgical removal of the cochlear implant magnet prior to an MRI procedure, and then surgically replacement thereafter, is not required.
It should also be noted that movement of the patient relative to the MRI magnetic field B while in the MRI magnetic field B will also result in reorientation of the magnetic material particles 22 within the case 24, as is illustrated in
After the MRI procedure has been completed, the implanted magnet apparatus may be exposed to a magnetic field (e.g., with the magnet 32) to return the particles 22 to their intended N-S orientation.
One example of a cochlear implant (or “implantable cochlear stimulator”) including the present magnet apparatus 20 is the cochlear implant 100 illustrated in
Turning to
The exemplary body worn sound processor 200 in the exemplary ICS system 50 includes a housing 202 in which and/or on which various components are supported. Such components may include, but are not limited to, sound processor circuitry 204, a headpiece port 206, an auxiliary device port 208 for an auxiliary device such as a mobile phone or a music player, a control panel 210, one or microphones 212, and a power supply receptacle 214 for a removable battery or other removable power supply 216 (e.g., rechargeable and disposable batteries or other electrochemical cells). The sound processor circuitry 204 converts electrical signals from the microphone 212 into stimulation data. The exemplary headpiece 300 includes a housing 302 and various components, e.g., a RF connector 304, a microphone 306, an antenna (or other transmitter) 308 and a positioning magnet apparatus 310, that are carried by the housing. The magnet apparatus 310 may consist of a single magnet or, as is discussed below with reference to
In at least some implementations, the cable 312 will be configured for forward telemetry and power signals at 49 MHz and back telemetry signals at 10.7 MHz. It should be noted that, in other implementations, communication between a sound processor and a headpiece and/or auxiliary device may be accomplished through wireless communication techniques. Additionally, given the presence of the microphone(s) 212 on the sound processor 200, the microphone 306 may be also be omitted in some instances. The functionality of the sound processor 200 and headpiece 300 may also be combined into a single head wearable sound processor. Examples of head wearable sound processors are illustrated and described in U.S. Pat. Nos. 8,811,643 and 8,983,102, which are incorporated herein by reference in their entirety.
Turning to
The exemplary magnet apparatus 308 illustrated in
By way of example, but not limitation, the following are specific examples of the magnet apparatus 308 that will, in combination with an implant 100 having the internal magnet apparatus 20c and isotropic neodymium particles 22 with a mesh size that ranges from 300 μm to 500 μm, provide a pull force of about 2.2±0.1 N when there is a spacing of about 3 mm between the external magnet apparatus 308 and the internal magnet apparatus 20c. A magnet apparatus 308 with the shim 311 and three N52 magnets that are 12.7 mm in diameter and 1.5 mm thick is one example. Another example is a magnet apparatus 308 with the shim 311 and a single N52 magnet that is 10.0 mm in diameter and 5.0 mm thick. In those instances where even more pull force is required, e.g., where a patient has a relatively thick skin flap, a magnet apparatus 308 with the shim 311 and a single N52 magnet that is 12.7 mm in diameter and 5.0 mm thick may be employed. It should also be noted that particles 22 having a mesh size that ranges from 100 μm to 300 μm may be used when the headpiece includes such a magnet apparatus. In another otherwise identical example, which instead employs anisotropic neodymium particles 22 with a mesh size that ranges from 50 μm to 200 μm, the pull force is about 2.4±0.1 N when there is a spacing of about 3 mm and the magnet apparatus 308 includes two N52 magnets that are 12.7 mm in diameter and 1.5 mm thick. The pull force at about 3 mm increases to about 3.0±0.1 N when a third N52 magnet (12.7 mm in diameter and 1.5 mm thick) is added to the magnet apparatus 308.
Although the inventions disclosed herein have been described in terms of the preferred embodiments above, numerous modifications and/or additions to the above-described preferred embodiments would be readily apparent to one skilled in the art. By way of example, but not limitation, the inventions include any combination of the elements from the various species and embodiments disclosed in the specification that are not already described. In some instances, a lubricant such as vegetable oil may be applied to the particles 22 to reduce friction and improvement movement of the particles relative to one another. It is intended that the scope of the present inventions extend to all such modifications and/or additions and that the scope of the present inventions is limited solely by the claims set forth below.
Claims
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.
Type: Application
Filed: May 28, 2015
Publication Date: Apr 26, 2018
Inventors: Jeryle L. Walter (Valencia, CA), Sung Jin Lee (Valencia, CA)
Application Number: 15/568,469