Holding magnet and magnet system for implantable systems optimized for MRI

Abstract

Embodiments of the invention relate to implantable hearing implants, such as cochlear implants. The implantable hearing implant includes an implant device that contains signal processing circuitry configured to receive an implant communication signal transmitted from an external transmitting coil. The implantable hearing implant also includes an implant magnet configured to cooperate with a corresponding external stationary magnet in an external device located above the skin to magnetically hold the external device against the overlying skin with magnetic force. The implant magnet has a north magnetic pole, a south magnetic pole, and an overall magnetic dipole moment that is parallel to or at an angle of 30° or less from the outermost surface. The implant magnet has a north end and a south end, each having a separate magnetic dipole moment that is tilted relative to the overall magnetic dipole moment.

Description

Technical Field

[0001] The present invention relates to at least partially implantable devices, such as partially implantable auditory devices, such as cochlear implants, and more particularly to implantable magnets for interacting with external magnets in such devices. Background Technology

[0002] Some hearing implants (such as middle ear implants (MEI) and cochlear implants (CI)) employ cooperative attachment magnets located in both the implant and the external component to magnetically hold the external component in place above the implant. For example, as Figure 1 As shown, a typical cochlear implant system may include an external transmitter device 101 comprising a transmitter coil 102 and an external attachment magnet 103. The external attachment magnet 103 has a conventional cylindrical disk shape and north-south magnetic dipoles whose axes are perpendicular to the patient's skin to generate external magnetic field lines 104 as shown. A corresponding receiver assembly 105 is implanted beneath the patient's skin, having a similar receiver coil 106 and an implanted magnet 107. The implanted magnet 107 also has a cylindrical disk shape and north-south magnetic dipoles whose magnetic axes are perpendicular to the patient's skin to generate internal magnetic field lines 108 as shown. The internal receiver device 105 is surgically implanted and fixed in a suitable position within the patient's body. The external transmitter device 101 is positioned above the skin covering the internal receiver assembly 105 and is held in place by the interaction between the internal magnetic field lines 108 and the external magnetic field lines 104. The RF signal from transmitter coil 102 couples data and / or power to receiver coil 106, which communicates with the implanted processor module (not shown).

[0003] A problem arises when a patient undergoes a magnetic resonance imaging (MRI) examination. An interaction occurs between the implanted magnet and the external magnetic field applied for the MRI. For example... Figure 2 As shown, the magnetization direction of the implanted magnet 202 It is essentially perpendicular to the patient's skin. In this example, the strong static magnetic field from the MRI... Torque is generated on the internal magnet 202 This torque can displace the internal magnet 202 or the entire implantable device 201 from its proper position. This could, in particular, damage adjacent tissues within the patient's body. Additionally, external magnetic fields from MRI... It can reduce or eliminate the magnetization of the implanted magnet 202 This may render it no longer strong enough to hold the external transmitter device in place. The implanted magnet 202 may also cause imaging artifacts in the MRI images, induced voltages may exist in the receiving coil, and due to the external magnetic field of the MRI... Interactions with the implanted device can lead to auditory artifacts. The torque and force acting on the implanted magnet, as well as the demagnetization of the implanted magnet, are particularly problematic for MRI fields of 1.5 Tesla or higher. Therefore, for many existing implanted systems with magnet devices, MRI is often not permitted, or its use is limited to reduce the field strength. Other existing solutions include the use of surgically demagnetizable magnets, spherical implanted magnets (e.g., U.S. Patent 7,566,296, the entire contents of which are incorporated herein by reference), and various toroidal magnet designs (e.g., U.S. Patent Publication 2011 / 0022120, the entire contents of which are incorporated herein by reference).

[0004] U.S. Patent 8,634,909 (the entire contents of which are incorporated herein by reference) discloses an implantable magnet whose magnetic dipole moment direction is parallel to the end face of a disk-shaped implantable magnet, i.e., perpendicular to the conventional magnetic dipole moment direction of a disk-shaped implantable magnet. The magnet is then held in a magnet container that allows the magnet to rotate about its central axis in response to an external magnetic field (such as from an MRI) to realign and minimize the formation of torque. However, this rotation can only occur about a single axis.

[0005] It is also suggested to use a set of multiple cylindrical magnets, magnetized perpendicular to their cylindrical axis and rotatable about their cylindrical axis, embedded in a magnet frame and housing, so that they can rotate about the central axis of the housing (see, for example, WO2017 / 105510, the entire contents of which are incorporated herein by reference). In this method, two or more radially magnetized cylindrical magnets are always aligned with one north pole oriented close to the adjacent south pole (and vice versa). One disadvantage of this configuration is that the cylindrical magnets together behave like a single disk magnet disclosed in the '909 patent, where the magnetization direction is parallel to the skin surface unless a very strong external magnetic field is applied, but due to the relatively poor fill factor, the combined magnet volume is very small, thus requiring a very large or very strong external magnet. On the other hand, using two or more cylindrical magnets does allow for relatively thin implantable magnet designs. Summary of the Invention

[0006] Embodiments of the present invention relate to a magnetic device for an auditory implantation device. An implantation device includes signal processing circuitry configured to receive implantation communication signals transmitted from an external transmitting coil through the overlying skin of an implanted patient, and the implantation device includes an outermost surface adapted to be located between the overlying skin and the lower skull of the implanted patient. A magnetic housing is provided within the implantation device and is configured to be rotatable about a housing rotation axis at least approximately perpendicular to the outermost surface of the implantation device. The implanted magnetic device is located within the magnetic housing and is configured to cooperate with a corresponding external holding magnet in an external device located above the overlying skin to magnetically hold the external device against the overlying skin. The implanted magnetic device includes one or more cylindrical magnets, each having a central cylindrical axis perpendicular to the axis of the housing, and each cylindrical magnet is configured to be rotatable about its central cylindrical axis. Each cylindrical magnet has a cylindrical outer surface with a north magnetic pole and a south magnetic pole. The north magnetic direction is defined by a radial vector extending from the central cylindrical axis to the north magnetic pole, and the south magnetic direction is defined by a radial vector extending from the south magnetic pole to the central cylindrical axis. The north and south magnetic poles are arranged relative to each other such that they are not located on a common diameter passing through the central cylindrical axis, such that the north and south magnetic directions form a magnetic angle of less than 180 degrees with the vertex at the central cylindrical axis.

[0007] In other specific embodiments, the implanted magnet device may be configured to magnetically align the plurality of cylindrical magnets relative to each other to form a common magnetic flux line passing through the cylindrical magnets, the magnet housing, and the overlying skin, to maintain magnet cooperation with the external environment. One or more radially magnetized auxiliary cylindrical magnets may also be located between the cylindrical magnets and configured to couple the common magnetic flux line between the cylindrical magnets. Alternatively, a soft magnetic material may be located between the cylindrical magnets and configured to couple the common magnetic flux line between the plurality of cylindrical magnets.

[0008] The implantable magnet device can be configured to respond to a strong external magnetic field by rotating the magnet housing about its rotational axis and rotating the cylindrical magnets about their respective central cylindrical axes, thereby minimizing the net torque applied to the implantable device. The magnetic angle can be between 90 and 140 degrees. Each cylindrical magnet can be configured to rotate fully about its central cylindrical axis within a complete 360-degree rotational range. Alternatively, each cylindrical magnet can be configured to rotate within a limited range of rotation about its central cylindrical axis, less than 180 degrees. For example, the limited rotational range could be 90 degrees.

[0009] A second aspect of the invention relates to an implantable device comprising signal processing circuitry configured to receive (e.g., from an external transmitting coil) implantation communication signals transmitted through the overlying skin of an implanted patient, wherein the implantable device includes an outermost surface adapted to be located between the overlying skin and the underlying skull and at least approximately parallel to the patient's skin; and an implantable magnet configured to cooperate with an external holding magnet in an external device located above the overlying skin to magnetically hold the external device against the overlying skin. According to the second aspect of the invention, the implantable magnet has a north pole, a south pole, and an overall total magnetic dipole moment parallel to or at an angle of 30° or less, preferably 20° or less, to the outermost surface. Furthermore, the implanted magnet has a north end including the north magnetic pole and a south end including the south magnetic pole, each end being formed of a permanent magnet material and each having an individual magnetic dipole moment tilted relative to the total magnetic dipole moment. The individual magnetic dipole moment in the north end is tilted relative to the total magnetic dipole moment to have a component pointing towards the outermost surface, and the individual magnetic dipole moment in the south end is tilted relative to the total magnetic dipole moment to have a component away from the outermost surface. The north and south ends of the implanted magnet can be directly and fixedly attached to each other, or each can be fixedly attached to the middle portion of the implanted magnet.

[0010] According to a second aspect of the invention, the implanted magnet, "as a whole," has a "total magnetic dipole moment" that is at least approximately parallel to the outermost surface, or in other words, approximately parallel to the skin in the implanted state. Those skilled in the art will understand that the magnetic dipole moment m of the magnetic body as a whole is a macroscopic quantity defining the "strength" of the magnetic dipole. When placed in an external magnetic field having a magnetic flux density B, a torque τ is generated, which corresponds to the vector product of the magnetic dipole moment m and the magnetic flux density B, i.e., τ = m x B. Therefore, when placed in an external magnetic field, the total magnetic dipole moment m of the implanted magnet can be easily determined: the implanted magnet orients itself to align the dipole moment m with the magnetic flux density B of the external magnetic field, thereby revealing the direction of the magnetic dipole moment m, the magnitude of which is defined by the magnitude of the torque required to rotate the implanted magnet out of alignment.

[0011] The magnetic dipole moment of the implanted magnet as a whole determines how the internal magnet responds to the external magnetic field in the MRI device.

[0012] However, according to the present invention, the implanted magnet has a north end and a south end, each comprising a north magnetic pole and a south magnetic pole, respectively, each magnetic pole having an individual magnetic dipole moment tilted relative to the total magnetic dipole moment. In these north and south ends, the corresponding magnetization is therefore misaligned with the total magnetic dipole moment of the implanted magnet as a whole. The magnetization of the material is designated as a vector field M, which expresses the density of magnetic dipole moments in the magnetic material, i.e., Where dm is the fundamental magnetic moment, and dV is the corresponding volume element. In other words, the magnetic moment m associated with a magnet is the spatial integral of magnetization M over the volume of the magnet, i.e., m = ∫∫∫MdV. As used in this paper, a “vector” is simply understood as a physical object with magnitude and direction. This paper does not distinguish between vectors and pseudovectors based on their transformation properties. Vectors are typically represented by bold symbols.

[0013] In this invention, the north and south ends are each formed of a permanent magnet material. The term "permanent magnet material" as understood herein has a broad meaning, but in any case differs from soft magnetic materials, such as soft iron, which are used in the art for pole shoes, etc. Specifically, the permanent magnet material in the north and south ends should have an intrinsic magnetic coercivity HCI greater than 200 A / m, preferably greater than 500 A / m, more preferably greater than 800 A / m, and most preferably greater than 1000 A / m. The individual magnetic dipole moment in the north end has a component pointing towards the outermost surface, and the individual magnetic dipole moment in the south end has a component away from the outermost surface. The inventors have found that this significantly increases the magnetic attraction or holding force of the external magnet applied to the external device compared to prior art implanted magnets of the same size and material that are uniformly magnetized throughout the entire volume in a direction parallel to the skin, while still allowing the total magnetic moment to be parallel to the skin.

[0014] In a preferred embodiment, the implanted magnet can rotate about a rotation axis that is perpendicular to the outermost surface or deviates from the vertical by less than 30°, preferably less than 20°, wherein in each available rotational position when the implanted magnet rotates about its rotation axis, the total magnetic dipole moment is parallel to the outermost surface or at an angle of 30° or less, preferably 20° or less.

[0015] Preferably, the implanted magnet has a shape that is rotationally symmetrical about the axis of rotation. In a preferred embodiment, the implanted magnet has an outer end face facing the outermost surface of the implantation device and an inner end face facing away from the outermost surface, wherein one or both of the inner and outer end faces are perpendicular to the axis of rotation. For example, the implanted magnet may have a disk shape.

[0016] In a preferred embodiment, the implanted magnet has a flat outer end face to make optimal use of the limited space in the implantation device.

[0017] In a preferred embodiment, the tilt angle between each individual magnetic dipole moment in the north and south ends relative to the total magnetic dipole moment is ≤50°. This allows for the safe avoidance of situations where the implanted magnet may be unintentionally weakened or demagnetized in a strong external MRI field, in case the patient does not keep his or her head straight during the MRI procedure, but tilts to one side, for example, up to 30°.

[0018]

[0019] In a preferred embodiment, the implanted magnet has an average diameter d in a direction parallel to the total magnetic dipole moment. I And has an average thickness h in the direction perpendicular to the outermost surface. I In one or both of the northern and southern ends, the individual magnetic dipole moment is tilted by an angle α relative to the total magnetic dipole moment, wherein

[0020] arctan(h I / (d I / 2))-15°≤α≤arctan(h I / (d I / 2))+7°, preferentially

[0021] arctan(h I / (d I / 2))-10°≤α≤arctan(h I / (d I / 2))+5°.

[0022] In this paper, angle α is measured in a plane perpendicular to the outermost surface. This range of angles has been found to allow for particularly good increases in adhesion force. For larger angles α, the distance between the north and south poles decreases, which in turn leads to an excessive decrease in holding force with distance from the implanted magnet.

[0023] In some embodiments, the north and south ends are directly adjacent to each other, and in particular, each forms one of the two halves of the implanted magnet. This embodiment results in excellent retention force while allowing for relatively easy manufacturing.

[0024] However, in an alternative embodiment, the north and south ends of the implanted magnet can be separated from each other by a middle portion having individual magnetic dipole moments parallel to or deviating from the total magnetic dipole moment by less than 10°, preferably less than 5°. This embodiment allows for a considerable tilt in the magnetization of the north and south ends while avoiding magnetic short circuits at the outer surfaces, thereby resulting in excellent retention force.

[0025] Alternatively, one or both of the north and south ends of the implanted magnet may have an outer section closer to the outermost surface and an inner section further away from the outermost surface, wherein the tilt angle of the individual magnetic dipole moment relative to the total magnetic dipole moment in the outer section is smaller than the tilt angle in the inner section. This embodiment allows for improved magnetic flux within the implanted magnet while avoiding a reduction in the distance between the north and south poles.

[0026] In a preferred embodiment, the implanted magnet has an outer end face facing the outermost surface of the implantation device and an inner end face facing away from the outermost surface. Furthermore, an intermediate plane is defined as being located at equidistant from the outer and inner end faces, and the external magnet preferably satisfies one or both of the following criteria (i) and (ii):

[0027] (i) When placed alone in air or a vacuum, at least 55%, preferably at least 65%, of the total magnetic flux of the magnetic field generated outside the implanted magnet is located on the side of the outermost surface of the intermediate plane in the assembled state.

[0028] (ii) More than 50%, preferably more than 55%, of the mass of the magnet is located on the side of the outermost surface of the intermediate plane, wherein in particular the edge of the magnet at the inner end face is chamfered.

[0029] Standard (i) defines the distribution of magnetic flux generated by the implanted magnet itself, i.e., the distribution of magnetic flux generated when placed alone in air or a vacuum. According to this standard, the majority of the magnetic flux is located on one side of the intermediate plane, and this side is the side where the outermost layer of the implanted device will be located in the "assembled state" (i.e., when the implanted magnet is arranged in the implanted device). In other words, the implanted magnet is designed such that it already generates most of its flux alone in the area where it needs to establish an attractive retention force with the external device, i.e., more towards the outside than towards the inside.

[0030] Standard (ii) specifies that more than half of the mass of the implanted magnet is located on the side where the outermost surface of the midplane lies. This again helps to generate magnetic flux closer to the outer region than the inner region of the implanted magnet. One way to reduce the mass of the implanted magnet toward the interior of the midplane is to provide a chamfered edge at the inner end face of the implanted magnet. This shape also allows for more favorable magnetic flux.

[0031] In a preferred embodiment, the north and south ends are formed of anisotropic magnetic elements, each having a preferred magnetization direction, wherein the anisotropic magnetic elements are coupled to each other or to an intermediate portion disposed therebetween. The preferred magnetization direction is angularly arranged relative to the total dipole moment of the implanted magnet as a whole. The anisotropic magnetic elements can be manufactured, for example, by applying an external magnetic field during magnet formation, which may involve, for example, sintering. Anisotropic magnets have the advantage of allowing for higher magnetization in their final state. Anisotropic magnets do not reach their final magnetic strength after manufacturing, but only after final magnetization using a strong magnetic pulse. While isotropic magnets can be magnetized by strong magnetic pulses in any direction, anisotropic magnets can only be magnetized along the preferred magnetization direction established during manufacturing. This is actually an advantage in the manufacturing process of the magnet as a whole, because the magnet can be assembled from anisotropic magnet elements with preferred magnetization directions that are tilted relative to the overall magnetization direction at the north and south ends, but beforehand, the anisotropic magnet elements are fully magnetized. This allows for processing of the anisotropic magnet elements before assembly and facilitates the combination of the magnet elements. The combined anisotropic magnet elements can then be fully magnetized by applying an external magnetic pulse aligned with the direction of the final total magnetic dipole moment. During this magnetization process, the magnetization direction of the anisotropic magnet elements, as part of the entire implanted magnet, is preserved, while their strength is increased.

[0032] In a preferred embodiment, the implanted magnet may have a layer of soft magnetic material, such as soft iron, applied to at least a portion of the inner end face (913). This can help shield the magnetic field generated by the implanted magnet itself toward the interior of the body, thereby reducing artifacts during MRI scans.

[0033] In a preferred embodiment, the implanted magnet is a rare earth magnet, especially a rare earth magnet including neodymium, samarium, terbium, dysprosium or holmium.

[0034] Another embodiment of the present invention relates to an implantation system comprising an implantation device or magnet device according to any of the foregoing embodiments and an external device, the external device including signal processing circuitry configured to transmit implantation communication signals to the implantation device, the external device including an innermost surface adapted to be located near the skin; and an external magnet or magnet assembly located in the external device above the overlying skin and magnetically configured to cooperate with the implantation magnet or magnet device according to any of the foregoing embodiments, such as to hold the external device against the skin.

[0035] External magnets can be similar to implanted magnets, but can also have different designs. Specifically, since the external device can be removed before the MRI procedure, the external magnet does not need to be specifically designed to withstand strong external MRI magnetic fields. Therefore, the external magnet can be a device of two magnets with magnetic dipole moments perpendicular to the innermost surface of the external device and thus perpendicular to the skin, with their north and south poles arranged adjacent to the south and north poles of the implanted magnet, respectively.

[0036] However, in some embodiments of the implantation system, the external magnet or magnet device may have a north magnetic pole, a south magnetic pole, and may also have a total magnetic dipole moment that is parallel to or at an angle of 30° or less to the innermost surface of the external device.

[0037] Furthermore, the external magnet may have a design similar to that disclosed regarding the internal magnet in one of the embodiments. Specifically, the external magnet may have a north end including the north magnetic pole and a south end including the south magnetic pole, the north end and the south end each being formed of a permanent magnet material and each having an individual magnetic dipole moment tilted relative to the total magnetic dipole moment of the external magnet, wherein the individual magnetic dipole moment in the north end has a component pointing towards the innermost surface of the external device, and the individual magnetic dipole moment in the south end has a component away from the innermost surface of the external device.

[0038] In a preferred embodiment of the implantation system, the external magnet is rotatable about the innermost surface of the external device or about 30° away from the vertical axis of rotation, wherein in each available rotational position of the external magnet about its axis of rotation, the total magnetic dipole moment is parallel to or at an angle of 30° or less to the innermost surface, and wherein the external magnet preferably has a shape that is rotationally symmetrical about its axis of rotation.

[0039] In a preferred embodiment, the external magnet has a flat inner end surface facing the innermost surface of the external device.

[0040] In a preferred embodiment of the implantation system, the external magnet has an average diameter d in a direction parallel to the total magnetic dipole moment. E And has an average thickness h in the direction perpendicular to the innermost surface of the external device. E In one or both of the northern and southern ends, the individual magnetic dipole moment is tilted by an angle α relative to the total magnetic dipole moment, wherein

[0041] arctan(h E / (d E / 2))-15°≤α≤arctan(h E / (dE / 2))+7°, preferentially

[0042] arctan(h E / (d I / 2))-10°≤α≤arctan(h E / (d E / 2))+5°.

[0043] The advantages of these angular ranges are similar to those explained above regarding implanted magnets. Similar to the case of implanted magnets, angle α is measured in a plane perpendicular to the innermost surface of the external device, or in other words, in a plane at least approximately perpendicular to the skin.

[0044] In some embodiments, the north and south ends of the external magnet are directly adjacent to each other, and in particular, each forms one of the two halves of the external magnet. In an alternative embodiment, the north and south ends of the external magnet are separated from each other by a middle portion having individual magnetic dipole moments parallel to or deviating from the total magnetic dipole moment of the external magnet by less than 10°, preferably less than 5°.

[0045] In a preferred embodiment of the implantation system, one or both of the north and south ends of the implanted magnet have an inner section closer to the innermost surface of the external device and an outer section further away from the innermost surface of the external device, wherein the tilt angle of the individual magnetic dipole moment relative to the total magnetic dipole moment in the inner section is smaller than the tilt angle in the outer section.

[0046] In a preferred embodiment, the external magnet has an inner end face facing the innermost surface of the external device and an outer end face facing away from the innermost surface of the external device, wherein an intermediate plane is defined at equidistant distances from the outer end face and the inner end face of the external device, and wherein the external magnet satisfies one or both of the following criteria (i) and (ii): (i) when placed alone in air or a vacuum, at least 55%, preferably at least 65%, of the total magnetic flux of the magnetic field generated outside the external magnet is located on the side of the intermediate plane where the innermost surface of the external device is located in the assembled state.

[0047] (ii) More than 50%, preferably more than 55%, of the mass of the outer magnet is located on the side of the innermost surface of the intermediate plane, wherein in particular the edge of the magnet at the inner end face is chamfered.

[0048] In a preferred embodiment, the north and south ends of the external magnet are formed by anisotropic magnet elements each having a preferred magnetization direction, wherein the anisotropic magnet elements are combined with each other or with an intermediate portion disposed therebetween, wherein the preferred magnetization direction is angularly arranged relative to the total dipole moment of the external magnet as a whole.

[0049] In a preferred embodiment, the external magnet is a rare earth magnet, particularly including neodymium (such as neodymium-ion-boron magnets) or samarium (such as samarium-cobalt magnets) or rare earth magnets including terbium or dysprosium or holmium or combinations thereof.

[0050] Embodiments of the present invention also include an auditory implantation system comprising a magnet device according to any one of the foregoing descriptions. Attached Figure Description

[0051] Figure 1 A portion of a typical cochlear implant system is shown, along with the magnetic interaction between the implanted magnet and the external implanted magnet.

[0052] Figure 2 This illustrates the possible force interactions between the implanted magnet and the magnetic field applied to the MRI system.

[0053] Figure 3A An example of a cylindrical implanted magnet with a V-shaped magnetic angle according to an embodiment of the present invention is shown.

[0054] Figure 3B It shows having Figure 3A An example of a cochlear implant device of the type shown, with two implanted magnets.

[0055] Figure 4A and Figure 4B This demonstrates how the magnetic field of an implanted magnet aligns to maintain cooperation with an external magnet.

[0056] Figure 5A and Figure 5B This illustrates how the magnetic field of the implanted magnet aligns when it is present.

[0057] Figure 6A and Figure 6B An example of an embodiment is shown where radially magnetized auxiliary cylindrical magnets are located between cylindrical magnets.

[0058] Figure 7A and Figure 7B An example of an embodiment in which a soft magnetic material is located between cylindrical magnets is shown.

[0059] Figure 8 An embodiment of a cylindrical implantable magnet according to an embodiment of the present invention is shown, the cylindrical implantable magnet being configured to rotate finitely within a limited range of rotation.

[0060] Figures 9A to 9C The different orientations of the cylindrical implanted magnet in response to the external MRI magnetic field are shown.

[0061] Figures 10A to 10C The orientation of a reverse-magnetized cylindrical implanted magnet is shown in an embodiment of the invention with reduced rotational properties.

[0062] Figure 11 Another example of a cochlear implant device using an implanted magnet is shown, wherein the north and south ends of the implanted magnet have separate magnetic dipole moments tilted relative to the total magnetic dipole moment of the implanted magnet.

[0063] Figure 12 yes Figure 11 A perspective view of the type of implanted magnet used in the device.

[0064] Figure 13 yes Figure 11 A side view of the device.

[0065] Figure 14 This is a schematic cross-sectional view showing the implanted device and the external device with a corresponding magnet.

[0066] Figure 15 This is a schematic cross-sectional view showing the magnets of the implant and external device.

[0067] Figure 16 The direction of the magnetic flux generated by a uniformly magnetized conventional implanted magnet is shown.

[0068] Figure 17 The direction of the magnetic flux generated by the implanted magnet of the present invention is shown. The implanted magnet has a north end and a south end, which have individual magnetic dipole moments tilted relative to the total magnetic moment of the implanted magnet.

[0069] Figure 18 It shows Figure 16 The magnetic flux density of a typical implanted magnet.

[0070] Figure 19 The present invention is shown according to Figure 17 The magnetic flux density of the implanted magnet.

[0071] Figure 20 This shows the effect of a uniformly magnetized external magnet and... Figure 16 The magnetic flux density generated when ordinary implanted magnets interact.

[0072] Figure 21 The invention is illustrated by a uniformly magnetized external magnet and the basis of the invention. Figure 17 The magnetic flux density generated when the implanted magnets interact.

[0073] Figure 22 This is a schematic cross-sectional view of an implanted magnet and an external magnet according to another embodiment of the present invention.

[0074] Figure 23 This is a schematic diagram illustrating the torque applied by an external magnetic field to a conventional implantable magnet and the implantable magnet of the present invention. Detailed Implementation

[0075] The advantage of a larger distance between the two magnetic poles is that the attractive force of the external magnet does not decrease drastically as the distance between the magnets increases. Embodiments of the invention relate to an improved implantable magnet device using two cylindrical implantable magnets with V-shaped magnetic angles in their magnetization directions. These magnets are mounted in the implantable device such that the "strong" side (i.e., the side with high magnetic flux) is at least partially ground-up over the skin. Both magnets are mounted within a magnet housing, which can also rotate about the housing's axis of rotation.

[0076] Figure 3A An example of a cylindrical implanted magnet 300 with a V-shaped magnetic angle α according to an embodiment of the present invention is shown, while Figure 3B It shows having Figure 3A An example of a cochlear implantation device 305 of the type shown, comprising two implanted magnets 300. The cochlear implantation device 305 includes: a signal processing circuit (not shown) configured to receive implantation communication signals transmitted from an external transmitting coil through the overlying skin of the implanted patient; and an outermost surface 308 adapted to be located between the overlying skin and the lower skull of the implanted patient.

[0077] The implantable device 305 contains a magnet housing 306, whose housing rotation axis 307 is perpendicular to the outermost surface 308 of the implantable device 305. The magnet housing 306 is configured to rotate about the housing rotation axis 307. Typically, the magnet housing 306 is surrounded by the receiver coil of the implantable device 305. The magnet housing 306 may be metallic (e.g., made of titanium), or it may be made of a biocompatible non-metallic material (e.g., PEEK, FEP, PTFE, PSU, etc.) and may be coated (e.g., coated with parylene). The magnet housing 306 may be adapted to facilitate long-term hermetic encapsulation, and / or it may be adapted to be surgically eliminated to minimize sensitivity to MRI artifacts.

[0078] The implantable magnet device includes one or more cylindrical magnets 300 located within a magnet housing 306 and configured to cooperate with a corresponding external holding magnet in an external device located above the overlying skin to magnetically hold the external device against the overlying skin. Each cylindrical implantable magnet 300 has a central cylindrical axis 301 perpendicular to the housing rotation axis 307, and each cylindrical magnet 300 is configured to rotate about its central cylindrical axis 301.

[0079] Each cylindrical magnet 300 has a cylindrical outer surface 302 with a north magnetic pole and a south magnetic pole. In the most general sense, a "cylindrical surface" is a surface composed of all points on all lines parallel to a reference line and passing through a fixed planar curve in a plane not parallel to the given line. In this disclosure, the cylinder is a so-called right-angled cylinder, where the "fixed planar curve" is a circle, and the reference line is a line perpendicular to the plane of the circle, such as the central axis 301 of the cylinder. The north magnetic direction 303 is defined by a radial vector extending from the central cylindrical axis 301 to the north magnetic pole. Similarly, the south magnetic direction 304 is defined by a radial vector extending from the south magnetic pole to the central cylindrical axis 301. The north and south magnetic poles are arranged relative to each other such that they are not located on a common diameter passing through the central cylindrical axis 301, such that the north magnetic direction 303 and the south magnetic direction 304 form a magnetic angle α of less than 180 degrees with the vertex at the central cylindrical axis 301. For example, the magnetic angle α can specifically be between 90° and 140° (or some other defined range). This magnetic angle α can be established, for example, by forming a cylindrical magnet 300 from two preformed portions 309 and 310, which are magnetized according to the aforementioned north magnetic direction 303 and south magnetic direction 304 in a manner explained with reference to another embodiment described in more detail below. In the embodiment shown in FIG3, the preformed portions 309 and 310 each correspond to the direction along which the magnetic angle α is formed by forming a cylindrical magnet 300 from two preformed portions 309 and 310. Figure 3A The dashed line 311 indicates the longitudinal half of the fully cylindrical magnet 300 whose interfaces are attached to each other.

[0080] Figure 4A and Figure 4BThe diagram illustrates how the magnetic fields of cylindrical magnets 300 are aligned to cooperate with one or more external retaining magnets 403 in an external device 402, wherein the cylindrical magnets 300 are magnetically aligned relative to each other to form a common magnetic flux line passing through the magnet, the magnet housing, and the overlying skin to cooperate with the external retaining magnet 403. Because the two cylindrical magnets 300 are arranged close together (e.g., the distance between their cylindrical outer surfaces 302 is less than 2 mm), the two adjacent magnetic poles form an attractive magnetic connection with a common magnetic direction parallel to the outer surface 308 of the magnet device 305 and the overlying skin 401. Due to the V-shaped magnetic angle, the magnetic direction of the non-adjacent halves of the two cylindrical magnets 300 directs the magnetic flux toward the outer surface 308 of the implant device 305 and the overlying skin 401, thereby allowing a strong magnetic attraction with the external retaining magnet 403, almost as strong as that of a vintage axially magnetized implanted magnet with a magnetization direction also normal to the skin 401.

[0081] Figure 5A and Figure 5B This illustrates how the cylindrical magnets 300 are arranged in the presence of an MRI magnetic field 501. It can be seen that the two cylindrical magnets 300 are immediately aligned relative to the external magnetic field 501, such that the torques generated by the interaction of the corresponding magnetizations of the different halves of each magnet 300 with the external magnetic field 501 cancel each other out. Figures 5B to 7B In the diagram, magnetization is schematically represented by the shaded lines.

[0082] Figure 6A and Figure 6B An example embodiment is shown where a radially magnetized auxiliary cylindrical magnet 601 is located between cylindrical magnets 300. The auxiliary cylindrical magnet 601 is configured to couple a common magnetic flux line between the cylindrical magnets 300. This provides an increased distance between the two local maxima of the magnetic flux through the skin 401, thus improving the magnetic attraction to the outer magnet 403.

[0083] Figure 7A and Figure 7B An example of an embodiment is shown in which a soft magnetic material 701 is located between cylindrical magnets 300 to couple a common magnetic flux line between the cylindrical magnets 300.

[0084] In the above embodiment, the cylindrical magnet 300 is configured to rotate fully around a central cylindrical axis 301 within a complete 360-degree rotational range, and the magnet housing 306 containing the cylindrical magnet 300 can rotate around its housing axis 307. Otherwise, when the central cylindrical axis 301 is fixed and the orientation of the strong external magnetic field 501 is antiparallel to the cylindrical magnet 300, the magnet will flip 180°, and the strong magnetic side of the magnet will face the lower skull in the medial direction instead of the skin in the lateral direction. Note that the orientation of the external magnetic field 501 in a given MRI scanner is different when the head of the implanted user is scanned first compared to when the legs of the implanted user are scanned first. Therefore, it is advantageous if the magnet device can handle both orientations of the external magnetic field 501. Furthermore, there is no general convention for the orientation of the external magnetic field 501 in an MRI scanner, and in some cases where two MRI scanners are arranged adjacent to each other in the same facility, the orientations of the corresponding external magnetic fields 501 are even deliberately chosen to be opposite.

[0085] However, another design variant with two cylindrical magnets in V-shaped magnetization is also applicable when the magnet has only one degree of freedom and the rotation angle is limited to about 90°. Figure 8 An embodiment of a cylindrical implantable magnet 800 according to another embodiment of the invention is shown, the cylindrical implantable magnet being configured to rotate within a limited rotation range 801 of less than 180 degrees. For example, the cylindrical implantable magnet may have V-shaped magnetization with a magnetic angle between 100° and 140°, and the limited rotation range 801 may be 90°.

[0086] Figures 9A to 9C The limited rotational range of the cylindrical implanted magnet 800 is shown with respect to different orientations of the external MRI magnetic field 501. As long as the component orientation of the strong external magnetic field 501 is parallel to the total magnetization of the cylindrical implanted magnet 800, the magnet behaves the same as in the other embodiments described above.

[0087] Figures 10A to 10C This illustrates a limited range of orientations for the reverse-magnetized cylindrical implanted magnets in an embodiment of the invention with reduced rotationality. When the orientation of a strong external magnetic field is antiparallel to the total magnetization of the cylindrical implanted magnets 800, they cannot rotate approximately 180° to the point of not being able to align parallel to the external magnetic field. Instead, each implanted magnet 800 reverses its magnetic polarity.

[0088] In the above embodiments, although some individual components of the implanted magnet are oriented perpendicular to the skin surface, the magnets do not weaken in the MRI environment because they immediately become safely oriented relative to the strong static magnetic field of the MRI scanner. The component of each individual magnet is always parallel to the strong static magnetic field of the MRI scanner. And therefore, each individual magnet is always aligned such that there is no external torque. The magnetic flux points towards the skin side and decreases in the medial direction. Therefore, MRI artifacts reach less in the medial direction and more towards the skin side.

[0089] Figure 11 The image shows an example of another implantable device, which in a particular embodiment is a cochlear implant device 905, which is generally similar to... Figure 3B The cochlear implant device 305. The cochlear implant device 905 includes signal processing circuitry (not shown), which is configured to receive signals from an external device (such as...) Figure 4B and 6A The external device (shown below element symbol 402) transmits implantation communication signals through the overlying skin 401 of the patient to which it is implanted.

[0090] The implantable device 905 includes an outermost surface 908 adapted to be located between the overlying skin 401 and the underlying skull and at least approximately parallel to the skin 401 of the patient to whom it is implanted. The implantable device 905 also includes an implantable magnet 900 configured to cooperate with an external holding magnet in an external device 402 located above the overlying skin 401 to magnetically hold the external device against the overlying skin 401.

[0091] like Figures 11 to 13 The instructions state that the implanted magnet 900 has a north pole and a south pole, and that the entire structure is parallel to the outermost surface 908 and therefore parallel to the skin 401. Figures 11 to 13 The total magnetic dipole moment m (not shown in the figure) does not need to be exactly parallel to the outermost surface 908 (skin 401), but should be at least approximately parallel to it, for example, forming an angle of 30° or less, preferably 20° or less, relative to the outermost surface 908.

[0092] The implanted magnet 900 is rotatable about a rotation axis 907, which in the illustrated embodiment is perpendicular to the outermost surface 908, such that in each available rotational position when the implanted magnet 900 rotates about its rotation axis 907, the total magnetic dipole moment m is parallel to the outermost surface 908.

[0093] like Figure 12 and Figure 13As can be seen, the implanted magnet 900 has an outer end face 912 facing the outermost surface 908 of the implantation device 905 (i.e., facing the skin 401 in the implanted state) and an inner end face 913 facing away from the outermost surface 908 (i.e., facing the inside of the patient's head in the implanted state). Both the outer end face 912 and the inner end face 913 are flat surfaces and perpendicular to the axis of rotation 907. For example, the implanted magnet 900 may have a cylindrical disk shape, wherein the sides are formed by cylindrical surfaces, such as... Figure 12 As shown. However, the sides do not need to be precisely cylindrical, but can be slightly tapered, as... Figure 13 As shown. However, it is preferred that the implanted magnet 900 has a shape that is rotationally symmetrical about the rotation axis 907.

[0094] Furthermore, the implanted magnet 900 has a north end portion 914 including the north magnetic pole and a south end portion 915 including the south magnetic pole. Both the north end portion 914 and the south end portion 915 are formed of permanent magnet material and each has a separate magnetic dipole moment 916, 917 tilted relative to the total magnetic dipole moment m, as referenced. Figure 14 To explain in more detail.

[0095] Figure 14 The implantation device 905, including the implanted magnet 900, and the external device 955, including the external magnet 950, are schematically shown again in cross-sectional view. The external device 955 can be attached to the patient's skin 401 through the magnetic interaction between the internal magnet 905 and the external magnet 950. The internal magnet 900 consists of two halves, one formed by a north end 914 and the other by a south end 915. The shading lines with arrows indicate local magnetization M. It can be seen that the local magnetization in the north end 914 and the south end 915 has a deviated direction, thereby producing the so-called "magnetic angle" with reference to the first aspect of the invention described above. Each of the north end 914 and the south end 915 has a separate magnetic dipole moment 916, 917, which corresponds to the spatial integral of the magnetization M in the respective portion. It can then be seen that although the total dipole moment m of the implanted magnet 900 as a whole points parallel to the outermost surface 908 of the implantation device 905, each of the individual magnetic dipole moments 916 and 917 is tilted relative to the total dipole moment m.

[0096] More precisely, it can be seen that the magnetic dipole moment 916 in the northern end 914 is tilted in a plane perpendicular to the outermost surface 908 / skin 401, having a component pointing towards the outermost surface 908, and the individual magnetic dipole moment in the southern end 915 is tilted to have a component away from the outermost surface. This results in a situation where most of the magnetic flux B generated by the implanted magnet 901 is located externally, requiring a holding force to maintain the external magnet 950.

[0097] Specifically, in a preferred embodiment, when simply considering the internal magnet 900 alone (i.e., without the external magnet 950) and when placed in air or a vacuum, at least 55%, preferably at least 65%, or even 70% or more of the total magnetic flux B generated outside the implanted magnet 900 lies “outside” the intermediate plane, which is arranged at equidistant from the outer end face 912 and the inner end face 913. In this document, “outside the intermediate plane” means the side where the outermost surface 908 is located in the assembled state. This significantly increases the holding force and allows for the implantation of magnets of the same size and material, which will be uniformly magnetized parallel to the skin 401.

[0098] exist Figure 14 In one embodiment, the implanted magnet 900 has a diameter d in a direction parallel to the total magnetic dipole moment. I And has a thickness h in the direction perpendicular to the outermost surface. I Given this geometry, in both the north end 914 and the south end 915, the individual magnetic dipole moments 916 and 917 are tilted relative to the total magnetic dipole moment m by a certain angle α = arctan(h). I / (d I / 2)). In this document, angle α is measured in a plane perpendicular to the outermost surface 908. This choice of angle α is sufficiently large to provide a significant improvement in the attraction of the external magnet 950 compared to prior art implanted magnets of the same size and material that are uniformly magnetized parallel to the skin 401. Significantly larger angles α have been found to be less advantageous for two reasons. First, with larger angles α, the distance between the north and south poles decreases, which in turn leads to an excessive decrease in holding force with increasing distance from the implanted magnet 900. Second, the tilt angle α between each individual magnetic dipole moment 916, 917 in the north end 914 and the south end 915 relative to the total magnetic dipole moment m should generally not exceed 60°, with a certain safety margin, preferably not exceeding 50°, such as to avoid situations where the implanted magnet 900 may inadvertently weaken or demagnetize in a strong external MRI field, in case the patient does not keep his or her head straight during the MRI procedure, but tilts to one side, for example, up to 30°. The preferred range for angle α is arctan(h I / (d I / 2))-15°≤α≤arctan(h I / (d I / 2))+7°, more preferably arctan(h I / (d I / 2))-10°≤α≤arctan(h I / (d I / 2))+5°, provided that in each case, preferably α≤50°.

[0099] Notice, Figure 14 The external magnet 950 in the external device 955 of the embodiment has a structure similar to that of the internal magnet 905. That is, the total magnetic dipole moment m of the external magnet 950 is parallel to the innermost surface 958 of the external device 955 located near the skin 401. The external magnet 950 also has a north end 964 and a south end 965, wherein the corresponding individual magnetic dipole moments 966, 967 are inclined relative to the total dipole moment m, such that the individual magnetic dipole moment 966 in the north end 964 has a component pointing towards the innermost surface 958 of the external device 955, and the individual magnetic dipole moment 967 in the south end 965 has a component away from the innermost surface 958 of the external device 955. However, although the implanted magnet 905 has been specifically designed to be compatible with the external magnetic field of MRI, the external device 955 can be removed from the cochlear implant user before the MRI procedure, making such a design unnecessary. Specifically, the outer magnet 950 need not be rotatable, and its total magnetic dipole moment m need not be parallel to the innermost surface 958 (skin 401). However, in a preferred embodiment, the outer magnet 950 is designed similarly to the inner magnet 905, incorporating some or all of the features described in the above summary of the invention.

[0100] Figure 15 It shows the relationship with Figure 14 Similar embodiments to the previous one, the main difference being that the edge of the implanted magnet 905 at the inner end surface 913 is chamfered. This allows for improved magnetic flux and further allows more than half of the magnet mass to be concentrated outside the intermediate plane, i.e., concentrated on the side where the outermost surface 908 of the intermediate plane is located.

[0101] Figure 16 This shows the direction of the magnetic flux generated by a uniformly magnetized ordinary implanted magnet. Conversely, Figure 17 It shows the result of Figures 11 to 14 The implanted magnet 900 of the type shown generates a magnetic flux direction having a north end 914 and a south end 915, which have individual magnetic dipole moments 916 and 917 tilted relative to the total magnetic moment of the implanted magnet 900.

[0102] Figure 18 It shows Figure 16 The magnetic flux density of a typical implanted magnet. In other words, Figure 16 Only the direction of the magnetic flux is shown. Figure 18The magnetic flux density is indicated by the size of the arrow shown in the diagram. It can be seen that both the direction and density of the magnetic flux are mirror-symmetric about the midplane of the magnet, a result of uniform magnetization. Figure 19 The present invention is shown Figure 17 The magnetic flux density of the implanted magnet 900. It can be seen that in the implanted magnet 900 of the present invention, the magnetic poles are... Figure 19 The "upward" shift in the representation places them above the mid-plane. In fact, as a technician will understand, the magnetic poles correspond to the regions of highest flux density on the surface where the magnet 900 is implanted, and these locations are found in... Figure 19 The top left and top right corners in the representation, therefore with Figure 14 and Figure 15 The contents are consistent with those shown schematically. Furthermore, it can be seen that, when considered in isolation, a larger portion of the total magnetic flux of the magnetic field generated outside the implanted magnet 900 lies above the mid-plane. Therefore, the magnetic field generated by the implanted magnet 900 of the present invention is indeed suitable for producing a higher attractive force when working in conjunction with an external magnet.

[0103] Figure 20 This shows the effect of a uniformly magnetized external magnet and... Figure 16 and Figure 18 The magnetic flux density generated when ordinary implanted magnets interact. For comparison, Figure 21 It shows that in relation to Figure 20 The same uniformly magnetized external magnet and Figure 17 and Figure 19 The magnetic flux density generated when the implanted magnet 900 interacts with the magnetic flux density. It can be seen that, using the implanted magnet 900 of the present invention, the attractive force per unit volume of the implanted magnet 900 can be increased by 15%. If using... Figure 14 and Figure 15 An external magnet of the type shown under reference numeral 950 in the attached figure can further increase this attraction gain.

[0104] In the illustrated embodiment, both the implanted magnet 900 and the external magnet 950 are made from two separate anisotropic magnet sheets forming the north ends 914, 964 and south ends 915, 965 of the finished magnets 900, 950. Each anisotropic magnet sheet has a preferred magnetization direction corresponding to the direction of the individual magnetic dipole moments 916, 917; 966, 967 in the finished magnets 900, 950. The preferred magnetization direction can be imprinted onto the magnet material by applying a corresponding magnetic field during magnet manufacturing (e.g., during the corresponding sintering process). The respective magnet sheets can be combined, for example, by bonding them together, and only after they are combined can final magnetization be established by applying a strong magnetization pulse parallel to the direction of the total dipole moment of the finished magnets 900, 950. Due to the anisotropic nature of the magnet sheets, the magnetization pulse does not magnetize the two magnet sheets along the magnetic field direction of the strong magnetization pulse, but rather according to their preferred magnetization directions. In a preferred embodiment, the implanted magnet 900 and / or the external magnet 950 are rare earth magnets, especially rare earth magnets including neodymium, samarium, terbium, dysprosium or holmium.

[0105] exist Figure 14 and Figure 15 In one embodiment, the north ends 914, 964 and the south ends 915, 965 are directly adjacent to each other, each forming one of the two halves of the implanted magnet 900 and the external magnet 950.

[0106] However, in an alternative embodiment, the north and south ends of the implanted magnet can be separated from each other by a middle portion having a separate magnetic dipole moment (at least approximately) parallel to the total magnetic dipole moment. Figure 22 In the figure, an example of such an external magnet 950 is shown, wherein such an intermediate portion is indicated by reference numeral 970. This intermediate portion 970 allows for a considerable angle of magnetization of the north end 964 and the south end 965, while avoiding magnetic short circuits at the outer surface, thereby resulting in very good holding force.

[0107] Alternatively, one or both of the north end portion 914 and the south end portion 915 of the implanted magnet 900 may have a portion closer to the outermost surface 908. Figure 22 Not shown in the image, see [link / reference]. Figure 14 The outer segments 914a and 915a and the inner segments 914b and 915b further away from the outermost surface 908, and the separate magnetic dipole moments (by...) in the outer segments 914a and 915a. Figure 22 The tilt angle of the magnetization indicator (in the inner section) relative to the total magnetic dipole moment is smaller than the tilt angle in the inner sections 914b and 915b. This embodiment allows for improved magnetic flux within the implanted magnet 900 while avoiding a reduction in the distance between the north and south poles. Figure 22The external magnet 950 in the design also indicates a similar design.

[0108] Figure 23 The lower half shows a conventional implanted magnet with uniform magnetization and a dipole moment m parallel to the skin 401 and rotatable about an axis perpendicular to the skin 401. When the implanted person is placed in the external magnetic field B of an MRI device, it is generally assumed that the magnetic field B is parallel to the skin 401, and under this assumption, the implanted magnet can be rotated, such as to align its dipole moment m with the external magnetic field B, so that no torque acts on the implanted magnet. However, this is an idealized assumption, because the implanted magnet may not be perfectly parallel to the skin covering the magnet, and in reality, due to the patient's individual anatomy and the fact that the patient may tilt his or her head to the side, the skin covering the magnet will not be precisely parallel to the external magnetic field B. Therefore, in practice, as shown... Figure 23 The upper part indicates the case where the magnetic dipole moment m of a conventional implanted magnet is tilted at a certain angle ε relative to the external magnetic field B. In this case, a torque τ is applied to the implanted magnet, the magnitude of which is |τ|=|m|·|B|·sin(ε).

[0109] Figure 23 The upper part shows the same case for an implantable magnet 900 according to an embodiment of the invention, which has a north end 914 and a south end 915, which form half of the implantable magnet 900 and have corresponding individual magnetic dipole moments 916 and 917, each of which is tilted at an angle α relative to the total magnetic dipole moment of the implantable magnet 900. This means that in each of the two halves forming the north end 914 and the south end 915, even if the external magnetic field B is parallel to the total magnetic dipole moment of the implantable magnet 900, a local torque will be applied, but these two local torques cancel each other out. Assume that the amplitude of the individual dipole moments 916 and 917 in each of the north end 914 and the south end 916 is m. O If so Figure 23 The magnitude of the total torque shown in the lower part, under the condition of an inclined external magnetic field B, can be calculated as follows:

[0110] |τ|=m O ·|B|·sin(α+ε)-m O ·|B|·sin(α-ε)=2·m O ·|B|·sin(ε)·cos(α).

[0111] By comparing this torque with the torque experienced by a conventional uniformly magnetized implanted magnet of the same size, we can assume 2·m. O≈|m|, where |m| is again the amplitude of the magnetic dipole moment of a conventional uniformly magnetized implanted magnet. Therefore, it can be seen that, compared to a conventional magnet of the same size, the torque experienced by the implanted magnet 900 of the present invention in an inclined external magnetic field B is actually reduced by a factor of cos(α), thus making the implanted magnet 900 of the present invention less sensitive to deviations from the ideal assumption that the external magnetic field is parallel to the skin.

[0112] Although various exemplary embodiments of the present invention have been disclosed, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the true scope of the invention to achieve some of its advantages.

Claims

1. An implantable device (305), characterized in that, The implantable device (305) includes: A signal processing circuit configured to receive implantation communication signals transmitted from an external transmitting coil through the skin (401) of the implanted patient, wherein the implantation device (305) includes an outermost surface (308) adapted to be located between the skin (401) and the lower skull of the implanted patient; A magnet housing (306) within the implantation device (305), wherein the magnet housing (306) is configured to rotate about a housing rotation axis (307), the housing rotation axis being at least approximately perpendicular to the outermost surface (308) of the implantation device (305); and The implanted magnet device is located within the magnet housing (306) and is configured to cooperate with an external holding magnet (403) in an external device (402) located above the skin (401) to magnetically hold the external device (402) against the skin (401). The implanted magnet device includes a plurality of cylindrical magnets (300), each cylindrical magnet having a central cylindrical axis (301) perpendicular to the rotation axis of the housing, and each cylindrical magnet (300) is configured to rotate about the central cylindrical axis; Each of the plurality of cylindrical magnets has a cylindrical outer surface with a north magnetic pole and a south magnetic pole; The north magnetic direction (303) is defined by a radial vector extending from the central cylindrical axis to the north magnetic pole; The south magnetic direction (304) is defined by a radial vector extending from the south magnetic pole to the central cylindrical axis (301); and The north magnetic pole and the south magnetic pole are arranged relative to each other such that they are not located on a common diameter passing through the central cylindrical axis (301), such that the north magnetic direction (303) and the south magnetic direction (304) form a magnetic angle of less than 180 degrees with the vertex at the central cylindrical axis (301).

2. The implantation device according to claim 1, characterized in that, The implanted magnet device is configured to magnetically align the plurality of cylindrical magnets (300) relative to each other to form a common magnetic flux line passing through the cylindrical magnets (300), the magnet housing (306), and the skin (401) to cooperate with the external retaining magnet (403).

3. The implantation device according to claim 2, characterized in that, Also includes: One or more radially magnetized auxiliary cylindrical magnets (601) among the plurality of cylindrical magnets (300), the radially magnetized auxiliary cylindrical magnets being configured to couple the common magnetic flux line among the plurality of cylindrical magnets (300).

4. The implantation device according to claim 2, characterized in that, It also includes a soft magnetic material (701) between the plurality of cylindrical magnets (300), the soft magnetic material being configured to couple the common magnetic flux line between the plurality of cylindrical magnets (300).

5. The implantation device according to claim 1, characterized in that, The implanted magnet device is configured to respond to a strong external magnetic field by the rotation of the magnet housing (306) about the housing rotation axis (307) and the rotation of the cylindrical magnets (300) about their respective central cylindrical axes (301) to minimize the net torque applied to the implanted device (305).

6. The implantation device according to claim 1, characterized in that, The magnetic angle is between 90 and 140 degrees.

7. The implantation device according to claim 1, characterized in that, Each cylindrical magnet (300) is configured to be fully rotatable around the central cylindrical axis (301) within a full 360-degree rotation range.

8. The implantation device according to claim 1, characterized in that, Each cylindrical magnet (300) is configured to rotate within a limited range of rotation of less than 180 degrees around the central cylindrical axis (301).

9. The implantation device according to claim 8, characterized in that, The finite rotation range is 90 degrees.

10. An implantable device (905), characterized in that, Includes signal processing circuitry configured to receive implantation communication signals transmitted through the skin (401) of the implanted patient, wherein the implantation device (905) includes an outermost surface (908) adapted to be located between the skin (401) and the underlying skull and at least approximately parallel to the skin (401) of the implanted patient. as well as An implanted magnet (900) is configured to cooperate with an external holding magnet (950) in an external device (955) located above the skin (401) to magnetically hold the external device (955) against the skin (401). The implanted magnet (900) has a north magnetic pole and a south magnetic pole, and has a total magnetic dipole moment that is parallel to or at an angle of 30° or less to the outermost surface (908). The implanted magnet (900) has a north end (914) including the north magnetic pole and a south end (915) including the south magnetic pole, the north end (914) and the south end (915) being formed of permanent magnet material and each having a separate magnetic dipole moment (916, 917) tilted relative to the total magnetic dipole moment. The individual magnetic dipole moment (916) in the northern end (914) is tilted relative to the total magnetic dipole moment so as to have a component pointing towards the outermost surface (908), and the individual magnetic dipole moment (917) in the southern end (915) is tilted relative to the total magnetic dipole moment so as to have a component away from the outermost surface (908). The implanted magnet (900) is rotatable about an axis of rotation (907) perpendicular to the outermost surface (908) or deviating from the perpendicular by less than 30°. Wherein, the tilt angle between each individual magnetic dipole moment in the north end and the south end relative to the total magnetic dipole moment is ≤60°, and / or the individual magnetic dipole moment in the north end is tilted and not parallel relative to the individual magnetic dipole moment in the south end.

11. The implantation device (905) according to claim 10, characterized in that, In each available rotational position as the implanted magnet (900) rotates about the rotation axis (907), the total magnetic dipole moment is parallel to or at an angle of 30° or less to the outermost surface (908).

12. The implantation device (905) according to claim 11, characterized in that, The implanted magnet (900) has a shape that is rotationally symmetrical about the axis of rotation (907).

13. The implantation device (905) according to claim 11, characterized in that, The implanted magnet (900) has an outer end face (912) facing the outermost surface (908) of the implantation device (905) and an inner end face (913) facing away from the outermost surface (908), wherein one or both of the inner end face (913) and the outer end face (912) are perpendicular to the axis of rotation (907).

14. The implantation device (905) according to claim 10, characterized in that, The implanted magnet (900) has a flat outer end face (912).

15. The implantation device (905) according to claim 10, characterized in that, The tilt angle between each individual magnetic dipole moment (916, 917) in the north end (914) and the south end (915) relative to the total magnetic dipole moment is ≤50°.

16. The implantation device (905) according to claim 10, characterized in that, The implanted magnet (900) has an average diameter d in a direction parallel to the total magnetic dipole moment. I And has an average thickness h in the direction perpendicular to the outermost surface (908). I In one or both of the northern end (914) and the southern end (915), the individual magnetic dipole moment (916, 917) is tilted by an angle α relative to the total magnetic dipole moment, wherein arctan (h I / (d I / 2)) -15° ≤ α ≤ arctan (h I / (d I / 2)) + 7°。 17. The implantation device (905) according to claim 10, characterized in that, The northern end (914) and the southern end (915) are directly adjacent to each other and each forms one of the two halves of the implanted magnet (900).

18. The implantation device (905) according to claim 10, characterized in that, The north end (914) and south end (915) of the implanted magnet (900) are separated from each other by a middle portion having individual magnetic dipole moments that are parallel to the total magnetic dipole moment or deviate from parallel by less than 10°.

19. The implantation device (905) according to claim 10, characterized in that, The implanted magnet (900) has one or both of its northern end (914) and southern end (915) having an outer segment (914a, 915a) closer to the outermost surface (908) and an inner segment (914b, 915b) further away from the outermost surface (908), wherein the tilt angle of the individual magnetic dipole moment relative to the total magnetic dipole moment in the outer segment (914a, 915a) is smaller than the tilt angle in the inner segment (914b, 915b).

20. The implantation device (905) according to claim 10, characterized in that, The implanted magnet (900) has an outer end face (912) facing the outermost surface (908) of the implantation device (905) and an inner end face (913) facing away from the outermost surface (908), wherein an intermediate plane is defined at an equal distance from the outer end face (912) and the inner end face (913), and wherein the implanted magnet (900) satisfies one or both of the following criteria (i) and (ii): (i) When placed alone in air or a vacuum, at least 55% of the total magnetic flux of the magnetic field generated outside the implanted magnet (900) is located on the side of the outermost surface (908) of the intermediate plane in the assembled state. (ii) More than 50% of the mass of the implanted magnet (900) is located on one side of the outermost surface (908) of the intermediate plane, wherein the implanted magnet (900) has a chamfered edge at the inner end face (913).

21. The implantation device (905) according to claim 10, characterized in that, The north end (914) and south end (915) are formed by anisotropic magnet elements each having a preferred magnetization direction, wherein the anisotropic magnet elements are combined with each other or with an intermediate portion disposed therebetween, wherein the preferred magnetization direction is angularly arranged relative to the total dipole moment of the implanted magnet (900) as a whole.

22. The implantation device (905) according to claim 13, characterized in that, A layer of soft magnetic material is applied to at least a portion of the inner end face (913).

23. The implantation device (905) according to claim 10, characterized in that, The implanted magnet (900) is a rare earth magnet, including neodymium, samarium, terbium, dysprosium or holmium.

24. An implantation system, characterized in that, The device includes an implantable device (305) according to claim 1 or an implantable device (905) according to claim 10, and an external device (402, 955), the external device (402, 955) including a signal processing circuit configured to transmit implantation communication signals to the implantable device (305, 905), the external device (402, 955) including an innermost surface (958) adapted to be located near the skin (401); and an external holding magnet (403, 950) or magnet assembly located in the external device (955) above the skin (401) and magnetically configured to cooperate with the implantation magnet (900) of the implantable device (905) or the implantation magnet device of the implantable device (305) to hold the external device (402, 955) against the skin (401).

25. The implantation system according to claim 24, characterized in that, The external holding magnet (403, 950) or magnet device has a north magnetic pole, a south magnetic pole, and an overall total magnetic dipole moment that is parallel to or at an angle of 30° or less to the innermost surface (958) of the external device (402, 955).

26. The implantation system according to claim 25, characterized in that, The external retaining magnets (403, 950) have a north end (964) including the north magnetic pole and a south end (965) including the south magnetic pole, the north end (964) and the south end (965) being formed of permanent magnet material and each having an individual magnetic dipole moment tilted relative to the total magnetic dipole moment of the external retaining magnets (403, 950). The individual magnetic dipole moment (966) in the northern end (964) has a component pointing toward the innermost surface (958) of the external device (955), and the individual magnetic dipole moment (967) in the southern end (965) has a component away from the innermost surface (958) of the external device (955).

27. The implantation system according to claim 24, characterized in that, The external holding magnets (403, 950) are rotatable about the innermost surface (958) of the external device (955) or about 30° away from the vertical axis of rotation. In each available rotational position of the external holding magnets (403, 950) about the axis of rotation, the total magnetic dipole moment is parallel to or at an angle of 30° or less to the innermost surface (958). The external holding magnets (403, 950) have a shape that is rotationally symmetrical about their axis of rotation.

28. The implantation system according to claim 24, characterized in that, The external holding magnet (403, 950) has a flat inner end face (962) facing the innermost surface (958) of the external device (402, 955).

29. The implantation system according to claim 26, characterized in that, The external retaining magnets (403, 950) have an average diameter d in a direction parallel to the total magnetic dipole moment. E And has an average thickness h in the direction perpendicular to the innermost surface (958) of the external device (955). E In one or both of the northern end (964) and the southern end (965), the individual magnetic dipole moment (966, 967) is tilted by an angle α relative to the total magnetic dipole moment, wherein arctan (h E / (d E / 2))-15° ≤ α ≤ arctan (h E / (d E / 2))+ 7°。 30. The implantation system according to claim 24, characterized in that, The northern end (964) and southern end (965) of the external retaining magnet (403, 950) are directly adjacent to each other and each forms one of the two halves of the external retaining magnet (403, 950).

31. The implantation system according to claim 26, characterized in that, The north end (964) and south end (965) of the external holding magnet (403, 950) are separated from each other by a middle portion (970) having individual magnetic dipole moments that are parallel to or deviate from the parallelism of the total magnetic dipole moment of the external holding magnet (403, 950) by less than 10°.

32. The implantation system according to claim 26, characterized in that, The northern end (964) and southern end (965) of the external retaining magnet (403, 950) have an inner section (964a, 965a) closer to the innermost surface (958) of the external device (955) and an outer section (964b, 965b) further away from the innermost surface (958) of the external device (955), wherein the tilt angle of the individual magnetic dipole moment relative to the total magnetic dipole moment in the inner section (964a, 965a) is smaller than the tilt angle in the outer section (964b, 965b).

33. The implantation system according to claim 26, characterized in that, The external holding magnet (403, 950) has an inner end face (962) facing the innermost surface (958) of the external device (955) and an outer end face (963) facing away from the innermost surface (958) of the external device (955). The intermediate plane is defined as being located at an equal distance from the outer end face (963) and inner end face (962) of the external device (955), and wherein the external retaining magnets (403, 950) satisfy one or both of the following criteria (i) and (ii): (i) When placed alone in air or a vacuum, at least 55% of the total magnetic flux of the magnetic field generated outside the external magnet (403, 950) lies on the side of the innermost surface of the external device in the assembled state, on the intermediate plane. (ii) More than 50% of the mass of the external retaining magnets (403, 950) is located on the side of the innermost surface (958) of the intermediate plane, wherein the edge of the external retaining magnets (403, 950) at the outer end face is chamfered.

34. The implantation system according to claim 26, characterized in that, The north end (964) and south end (965) of the external holding magnet (403, 950) are formed by anisotropic magnet elements each having a preferred magnetization direction, wherein the anisotropic magnet elements are combined with each other or with an intermediate portion arranged therebetween, wherein the preferred magnetization direction is angularly arranged relative to the total dipole moment of the external holding magnet (403, 950) as a whole.

35. The implantation system according to claim 24, characterized in that, The external holding magnet (403, 950) is a rare earth magnet, including neodymium, samarium, terbium, dysprosium or holmium.

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