Magnetic resonance imaging safe magnet structure and cochlear implant including same
The cochlear implant design with a magnet structure having cancelling magnetic fields ensures safety and stability in MRI environments by stabilizing the magnet and enhancing attachment force, thus improving power and data transmission efficiency.
Patent Information
- Authority / Receiving Office
- AU · AU
- Patent Type
- Applications
- Current Assignee / Owner
- TODOC CO LTD
- Filing Date
- 2024-03-25
- Publication Date
- 2026-07-16
Smart Images
Figure 00000000_0000_ABST
Abstract
Description
[Technical Field] A magnet structure safe for magnetic resonance imaging (MRI) and a cochlear implant including the same are provided. [Background Art] A cochlear implant is a medical device used for patients with hearing loss or hearing impairment, and generally consists of a neural stimulator and a sound processor. The sound processor collects sound from the outside, processes it, and transmits it to the neural stimulator. The neural stimulator is a device implanted in the body to stimulate the auditory nerve, and a neural stimulation electrode connected to one end of the implanted neural stimulator is inserted into the cochlea, through which the neural stimulator stimulates the auditory nerve to transmit sound signals. The neural stimulator of the cochlear implant includes an electronic circuit, a coil, and a magnet. The coil of the neural stimulator receives the sound signal and power processed by the sound processor through inductive link communication with the coil of the sound processor to drive the electronic circuit and deliver neural stimulation to the auditory nerve. As such, since the cochlear implant operates by the coil of the neural stimulator receiving signals and power from the coil of the sound processor, magnets are used in both the neural stimulator and the sound processor to align the two coils to face each other and to attach the sound processor to a position close to the neural stimulator. The magnet of the neural stimulator of the cochlear implant generally uses a neodymium magnet. Since the neodymium magnet can generate a strong magnetic field, the neodymium magnet of the neural stimulator attracts the magnet located in the sound processor to fix the sound processor and aligns the coil structure, thereby increasing the efficiency of the inductive link. The coil of the neural stimulator generates a signal for neural stimulation by receiving the inductive link signal transmitted from the sound processor. The signal received by the coil is converted into a neural stimulation signal through the electronic circuit of the neural stimulator, and the generated neural stimulation signal is transmitted to the auditory nerve through the neural stimulation electrode. However, the magnet of the neural stimulator of the cochlear implant implanted in the body may pose a great risk to the patient when the patient undergoes an MRI (Magnetic Resonance Imaging) examination. Since MRI is an examination that uses a strong magnetic field to image the internal structure of the human body, the magnet of the neural stimulator of the cochlear implant implanted in the body may be affected by the MRI magnetic field and move out of the implanted position in the body. For example, the magnet of the cochlear implant neural stimulator may move in the body due to the action of attractive and repulsive forces of electromagnetic force, or it may rotate in the body or stand upright enough to lift the patient's skin due to torque, which is a force to align the N and S poles. Such movement of the magnet may not only cause damage to the neural stimulator but also pose a great risk to the patient, and may reduce the efficiency of the inductive link with the sound processor. Accordingly, making the cochlear implant safe in an MR environment is one of the notable issues in the cochlear implant industry. In order to improve the safety or stability of the cochlear implant in an MR environment, currently marketed cochlear implants use magnets designed to minimize the generation of attractive and repulsive forces or torque to the magnet of the neural stimulator during MRI imaging. Alternatively, MRI imaging is performed by physically compressing and restricting the implanted area of the neural stimulator to take measures so that the magnet does not move. A conventional cochlear implant has a structure fixed by using a magnet magnetized with N / S or S / N poles on the direction surface facing the skin and the opposite surface, respectively. However, according to such a magnet structure, an upright phenomenon of the magnet of the neural stimulator of the cochlear implant may occur due to a characteristic that the magnet tries to align in the magnetic field direction at the center portion of the MR equipment. In order to prevent the upright phenomenon of the magnet, a cochlear implant configured with a rotating type magnet is being developed. However, according to the cochlear implant having such a rotating type magnet, an attachment force between the sound processor and the neural stimulator is lowered, and thus cochlear implant users may feel discomfort in daily life. In addition, according to the conventional cochlear implant, safety of the cochlear implant in an MR environment and an attachment force between the sound processor and the neural stimulator are in a trade-off relationship with each other. In addition, since the magnet of the neural stimulator of the conventional cochlear implant has a structure located only at the center portion of the coil, mutual inductance occurs between the magnet and the coil, and this mutual inductance causes power loss, whereby power efficiency may be reduced. Because of this, electrical energy transmitted from the sound processor to the neural stimulator is partially transmitted not only to the coil of the neural stimulator but also to the magnet of the neural stimulator, and thus power loss may occur. In this regard, Korean Registered Patent No. 10-2195014 discloses an external sound processing device for a cochlear implant system, Korean Registered Patent No. 10-1488480 discloses a cochlear implant device, US Patent Publication No. 2019-0239007 discloses Reversible Magnets, and US Patent Publication No. 2020-0238088 discloses Cochlear Implants and Magnets. [Disclosure] [Technical Problem] An embodiment is intended to maintain patient safety and stability of a cochlear implant even in a magnetic resonance (MR) environment, while simultaneously increasing an attachment force between an external apparatus and a neural stimulator. An embodiment is intended to wirelessly transmit power and data with high efficiency while maintaining patient safety and stability of a cochlear implant even in an MR environment. [Technical Solution] A cochlear implant according to an embodiment includes a neural stimulator for stimulating an auditory nerve connected to a cochlea, and the neural stimulator includes a first coil unit for receiving power, data, or both from an external apparatus, a first magnet unit attached to the external apparatus by magnetic force and including two or more pairs of magnetic poles arranged to have mutually cancelling magnetic fields, a neural stimulation processing unit for processing a neural stimulation signal, and a neural stimulation electrode for stimulating the auditory nerve based on the neural stimulation signal. The first magnet unit may extend in one direction from a center portion to a peripheral portion of the first coil unit. The external apparatus may include a second coil unit connected to the first coil unit in an inductive link manner, and a second magnet unit attached to the first magnet unit. The first coil unit and the second coil unit may be at positions overlapping each other. The second magnet unit may be located at a center portion of the second coil unit. The two or more pairs of magnetic poles may include a first S-N pole in a vertical direction located at the center of the first coil unit, and one or more N-S poles located at the periphery of the first coil unit. Magnetic fields of the first S-N pole and the one or more N-S poles may mutually cancel each other. The one or more N-S poles may be located at the periphery of the first coil unit at intervals of an arbitrary angle, centered on the first S-N pole. The first magnet unit may be separated from or inserted into the neural stimulator. A magnet structure for a cochlear implant according to an embodiment includes a first coil unit located inside a neural stimulator for stimulating an auditory nerve connected to a cochlea and receiving power, data, or both from an external apparatus, and includes a first magnet unit attached to the external apparatus by magnetic force, including two pairs of magnetic poles arranged to have mutually cancelling magnetic fields, and extending in one direction from a center portion to a peripheral portion of the first coil unit. [Advantageous Effects] According to an embodiment, patient safety and stability of the cochlear implant can be maintained even in an MR environment, while an attachment force between the external apparatus and the neural stimulator can be simultaneously increased. In addition, according to an embodiment, power and data can be wirelessly transmitted with high efficiency while maintaining patient safety and stability of the cochlear implant even in an MR environment. [Description of the Drawings] FIG. 1A is a view schematically showing a cochlear implant according to an embodiment, and FIG. 1B is a view schematically showing hardware of a neural stimulation processing unit according to an embodiment. FIG. 2 is a view schematically showing a neural stimulator of a cochlear implant according to an embodiment. FIG. 3A is a perspective view schematically showing the neural stimulator shown in FIG. 2, FIG. 3B is a cross-sectional view schematically showing the neural stimulator shown in FIG. 3A, and FIG. 3C is an exploded perspective view schematically showing the neural stimulator shown in FIG. 3A. 6 FIG. 4A is a perspective view schematically showing a neural stimulator of a cochlear implant according to an embodiment, FIG. 4B is a cross-sectional view schematically showing the neural stimulator shown in FIG. 4A, and FIG. 4C is an exploded perspective view schematically showing the neural stimulator shown in FIG. 4A. FIG. 5A is a perspective view schematically showing a neural stimulator of a cochlear implant according to an embodiment, FIG. 5B is a cross-sectional view schematically showing the neural stimulator shown in FIG. 5A, and FIG. 5C is an exploded perspective view schematically showing the neural stimulator shown in FIG. 5A. FIG. 6A is a view schematically showing a neural stimulator of a cochlear implant according to an embodiment. FIG. 6B is a view schematically showing a neural stimulator of a cochlear implant according to an embodiment, and FIG. 6C is a cross-sectional view schematically showing the neural stimulator shown in FIG. 6B. FIG. 7A is a view schematically showing a subject wearing a cochlear implant according to an embodiment entering an MRI environment, and FIG. 7B is a view schematically showing a subject wearing a cochlear implant according to the prior art entering an MRI environment. FIG. 8 is a view schematically showing a simulation for the MRI environment shown in FIGS. 7A and 7B. FIG. 9A is a graph measuring electromagnetic force according to the position of the subject in the MRI environment by performing a simulation for the MRI environment shown in FIG. 7A, and FIG. 9B is a graph measuring electromagnetic force according to the position of the subject in the MRI environment by performing a simulation for the MRI environment shown in FIG. 7B. FIG. 10A is a graph measuring torque according to the position of the subject in the MRI environment by performing a simulation for the MRI environment shown in FIG. 7A, and FIG. 10B is a graph measuring torque according to the position of the subject in the MRI environment by performing a simulation for the MRI environment shown in FIG. 7B. FIG. 11A is a view measuring an attachment force of the cochlear implant according to the embodiment shown in FIG. 7A, and FIG. 11B is a view measuring an attachment force of the cochlear implant according to the prior art shown in FIG. 7B. [Mode for Invention] With reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those skilled in the art to which the present invention pertains can easily carry out the present invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein. In order to clearly describe the present invention in the drawings, parts irrelevant to the description are omitted, and the same reference numerals are used for the same or similar components throughout the specification. In addition, in the case of widely known technologies, detailed descriptions thereof will be omitted. Throughout the specification, when a part "includes" a certain component, it means that the part may further include other components, rather than 8 excluding other components, unless specifically stated to the contrary. Throughout the specification, singular expressions may be interpreted as singular or plural unless an explicit expression such as "one" or "single" is used. Throughout the specification, terms including ordinal numbers such as first, second, etc. may be used to describe various components, but these components are not limited by the terms including ordinal numbers. Terms including ordinal numbers are used only for the purpose of distinguishing one component from another component. For example, without departing from the scope of the present disclosure, a first component may be named a second component, and similarly, a second component may also be named a first component. Throughout the specification, devices constituting a network may be implemented with hardware, software, or a combination of hardware and software. Throughout the specification, terms such as "... unit", "... device", and "... module" mean a unit that processes at least one function or operation, which may be implemented with hardware, software, or a combination of hardware and software. Throughout the specification, devices are configured with hardware including at least one processor, a memory device, a communication device, and the like, and a program or software that is executed in combination with the hardware is stored in a designated place. The hardware has a configuration and performance capable of executing a method according to an embodiment. The program or software includes instructions implementing the operating method according to an embodiment described with reference to the drawings, and 9 executes an embodiment in combination with hardware such as a processor and a memory device. Throughout the specification, "transmitting or providing" may include not only direct transmitting or providing but also indirect transmitting or providing through another device or using a bypass path. Throughout the specification, in the flowcharts described with reference to the drawings, an operation sequence may be changed, several operations may be merged, any operation may be divided, and a specific operation may not be performed. Now, the magnetic resonance safe magnet structure and the cochlear implant including the same will be described in detail. FIG. 1A is a view schematically showing a cochlear implant according to an embodiment, and FIG. 1B is a view schematically showing hardware of a neural stimulation processing unit according to an embodiment. Referring to FIG. 1A, the cochlear implant includes a neural stimulator 100 for stimulating an auditory nerve and an external apparatus 200 located outside the human body and communicating with the neural stimulator 100. For example, the external apparatus 200 may perform a sound processing function of processing sound from the outside and transmitting it to the neural stimulator 100. In addition, the neural stimulator 100 may include a sound processing function for processing sound from the outside. The neural stimulator 100 may be implanted inside the human body 10 and applies stimulation to the auditory nerve connected to the cochlea 500. The neural stimulator 100 includes a first coil unit 110, a first magnet unit 120, a neural 10 stimulation processing unit 130, and a neural stimulation electrode 140. The external apparatus 200 may be located outside the human body 10. The external apparatus 200 includes a second coil unit 210, a second magnet unit 220, a signal processing unit 230, and a power supply unit 240. In addition, when the neural stimulator 100 includes a sound processing function for processing sound from the outside, the signal processing unit 230 may be embedded in the neural stimulator 100. The first coil unit 110 and the second coil unit 210 are connected to each other in an inductive link manner to wirelessly transmit and receive power, data, or both. In addition, the first magnet unit 120 and the second magnet unit 220 may be attached to each other by magnetic force. The first magnet unit 120 includes one or more magnets, and the one or more magnets include two or more pairs of magnetic poles arranged to have mutually cancelling magnetic fields, and accordingly, movement of the cochlear implant is suppressed even in a magnetic resonance (MR) environment, thereby maximizing patient safety and stability of the cochlear implant. In addition, the first magnet unit 120 may have a structure extending in one direction from the center portion to the peripheral portion of the first coil unit 110. For example, the first magnet unit 120 attached to the second magnet unit 220 is disposed inside the neural stimulator 100 such that the centers of the first coil unit 110 and the second coil unit 210 overlap each other. Accordingly, transmission and reception efficiency of power and data by the inductive link can be maximized. A relative position of each magnet of the one or more magnets in the first magnet unit 120 is fixed, and accordingly, the magnets can be prevented from rotating or moving to a position where magnetic fields are not mutually cancelled. For example, sound collected through a microphone may be converted into a digital signal through the signal processing unit 230, amplified, and transmitted to the second coil unit 210. The power supply unit 240 supplies power for driving the external apparatus 200, and applies power to the signal processing unit 230 and the second coil unit 210. The second coil unit 210 transmits sound data received from the signal processing unit 230 to the first coil unit 110 in an inductive link manner, and transmits power received from the power supply unit 240 to the first coil unit 110 in an inductive link manner. The power received through the first coil unit 110 drives the neural stimulator 100. In addition, the sound data received through the first coil unit 110 is converted into a neural stimulation signal by operation of the neural stimulation processing unit 130 and transmitted to the neural stimulation electrode unit 140. Accordingly, the neural stimulation electrode unit 140 located inside the cochlea 150 applies stimulation to the cochlea 150 based on the neural stimulation signal, whereby the auditory nerve connected to the cochlea is stimulated, and the subject can recognize sound. Referring to FIG. 1B, the neural stimulation processing unit 130 may be implemented as at least one computing device, and may execute a computer program including instructions described to execute operations according to an embodiment. Hardware of the neural stimulation processing unit 130 may include one or more processors 131, one or more memories 133, one or more storages 135, and one or more communication interfaces 137, and these may be connected to each other through a bus. In addition, the hardware of the neural stimulation processing unit 130 may include hardware such as an input device and an output device. In addition, various software including an operating system capable of running a program may be mounted in the neural stimulation processing unit 130. In addition, the neural stimulation processing unit 130 may be implemented as one or more chips. The processor 131 is a device for controlling operations of the neural stimulation processing unit 130, and may be various types of processors processing instructions included in a program. For example, the processor 131 may be a CPU (Central Processing Unit), an MPU (Micro Processor Unit), an MCU (Micro Controller Unit), a GPU (Graphic Processing Unit), or the like. The memory 133 loads a corresponding program such that instructions described to execute operations according to an embodiment are processed by the processor 131. For example, the memory 133 may be a ROM (read only memory), a RAM (random access memory), or the like. The storage 135 stores various data, programs, and the like required to execute operations according to an embodiment. The communication interface 137 is a wired / wireless communication module, and may communicate with an external database through a wired / wireless network. In addition, the signal processing unit 230 of the external apparatus 200 may be implemented as at least one computing device, and may include one or more processors, one or more memories, one or more storages, and one or more communication interfaces, which may be connected to each other through a bus. Accordingly, descriptions of the signal processing unit 230 are applied in the same manner as the above descriptions of the neural stimulation processing unit 13 130. FIG. 2 is a view schematically showing a neural stimulator of a cochlear implant according to an embodiment, FIG. 3A is a perspective view schematically showing the neural stimulator shown in FIG. 2, FIG. 3B is a cross-sectional view schematically showing the neural stimulator shown in FIG. 3A, and FIG. 3C is an exploded perspective view schematically showing the neural stimulator shown in FIG. 3A. Referring to FIGS. 2 and 3A to 3C, the neural stimulator 100 includes a first coil unit 110, a first magnet unit 120, a neural stimulation processing unit 130, a neural stimulation electrode unit 140, and a housing 190 containing these. The descriptions of FIGS. 1A and 1B described above are equally applied to the neural stimulator 100 of FIGS. 2 and 3A to 3C. The first magnet unit 120 may be inserted into or separated from the inside of the housing 190 through a side opening 199 formed on a side surface of the housing 190. The housing 190 may be made of a silicone material. The first magnet unit 120 includes one or more magnets in which two or more pairs of magnetic poles 121, 122, 123, and 124 are arranged to have mutually cancelling magnetic fields. The two pairs of magnetic poles 121, 122, 123, and 124 are composed of a first magnet 121 and 123 and a second magnet 122 and 124. For example, a first pole 121 may be an S pole, a second pole 122 may be an N pole, a third pole 123 may be an N pole, and a fourth pole 124 may be an S pole. In this case, magnetic fields of the first magnets 121 and 123 and magnetic fields of the second magnets 122 and 124 may mutually cancel each other. In addition, magnetic fields of the first pole 121 and the third pole 123 and magnetic fields of the second pole 122 and the fourth pole 124 may mutually cancel each other. The magnet composed of two pairs of magnetic poles 121, 122, 123, and 124 is seated in grooves formed in an upper case 128 and a lower case 129, and the upper case 128 and the lower case 129 are coupled to each other. As such, since the first magnets 121 and 123 and the second magnets 122 and 124 are fixed inside the housing 190, the first magnets 121 and 123 and the second magnets 122 and 124 can be prevented from rotating or moving to a position where magnetic fields are not mutually cancelled. The side protrusion portion 127 formed at one end of the upper case 128 is seated in the side opening 199 of the housing 190, making it possible to easily insert and separate the first magnet unit 120. The first magnets 121 and 123 may be located at the center portion of the first coil unit 110. Accordingly, the first magnets 121 and 123 may be attached by magnetic force to the second magnet unit 220 located at the center portion of the second coil unit 210 of the external apparatus 200. In addition, by the attachment of the first magnets 121 and 123 and the second magnet unit 220, the first coil unit 110 and the second coil unit 210 overlap each other, so that transmission and reception efficiency of power and data can be maximized. Furthermore, referring to FIG. 3B, the first magnet unit 120 is inclined toward an upper center direction of the housing 190 such that the first magnets 121 and 123 are located above the second magnets 122 and 124. Accordingly, a distance between the first magnets 121 and 123 and the second magnet unit 220 becomes closer, increasing an attachment force, and a size of the housing 190 becomes smaller, thereby enabling miniaturization of the neural stimulator 100. FIG. 4A is a perspective view schematically showing a neural stimulator of a cochlear implant according to an embodiment, FIG. 4B is a cross-sectional view schematically showing the neural stimulator shown in FIG. 4A, and FIG. 4C is an exploded perspective view schematically showing the neural stimulator shown in FIG. 4A. Referring to FIGS. 4A to 4C, the neural stimulator 100 includes a first coil unit 110, a first magnet unit 120, and a housing 190 containing these. Most of the descriptions of FIGS. 1A to 3C described above are equally applied to the neural stimulator 100 of FIGS. 4A to 4C. However, in the case of the neural stimulator 100 of FIGS. 4A to 4C, a bottom opening 198 is formed on a lower surface of the housing 190, and the first magnet unit 120 may be separated or inserted through the bottom opening 198 in a direction of an arrow ® while lifting the housing 190 in a direction of an arrow @. FIG. 5A is a perspective view schematically showing a neural stimulator of a cochlear implant according to an embodiment, FIG. 5B is a cross-sectional view schematically showing the neural stimulator shown in FIG. 5A, and FIG. 5C is an exploded perspective view schematically showing the neural stimulator shown in FIG. 5A. Referring to FIGS. 5A to 5C, the neural stimulator 100 includes a first coil unit 110, a first magnet unit 120, and a housing 190 containing these. Most of the descriptions of FIGS. 1A to 3C described above are equally applied to the neural stimulator 100 of FIGS. 5A to 5C. However, in the case of the neural stimulator 100 of FIGS. 5A to 5C, a top opening 197 is formed on an upper surface of the housing 190, and the first magnet unit 120 may be separated or inserted through the top opening 197 while lifting a ring portion 126 formed at one end of the upper case 128 in a direction of an arrow @. FIG. 6A is a view schematically showing a neural stimulator of a cochlear implant according to an embodiment. Referring to FIG. 6A, the neural stimulator 100 includes a first coil unit 110, a first magnet unit 120, a neural stimulation processing unit 130, a neural stimulation electrode unit 140, and a housing containing these. Most of the descriptions of FIGS. 1A and 1B and the descriptions of FIGS. 2 and 3A to 3C described above are equally applied to the neural stimulator 100 of FIG. 6. However, the first magnet unit 120 of the neural stimulator 100 of FIG. 6 is in a position rotated 90 degrees clockwise from the first magnet unit 120 of the neural stimulator 100 of FIG. 2. In addition, the first magnet unit 120 may be at a position rotated by 0 to 360 degrees clockwise, and even in this case, since the first magnets 121 and 123 are located at the center portion of the first coil unit 110, the second magnet unit 220 located at the center portion of the second coil unit 210 is attached to the first magnets 121 and 123 by magnetic force, so that the centers of the first coil unit 110 and the second coil unit 210 may coincide with each other. Accordingly, wireless transmission and reception efficiency of power and data between coils can be maximized. In addition, even if the external apparatus 200 rotates during a process of being attached to the neural stimulator 100, the wireless transmission and reception of power and data between coils may be constantly maintained. In addition, the first magnet unit 120 may include a first S-N pole in a vertical direction located at the center of the first coil unit 110, and one or more N-S poles located at the periphery of the first coil unit. For example, the first magnet unit 120 may further include a third magnet positioned symmetrically at 180 degrees with respect to the second magnets 122 and 124 based on the first magnets 121 and 123, and in this case, the first magnets 121 and 123, the second magnets 122 and 124, and the third magnet have magnetic fields that mutually cancel each other. In addition, the first magnet unit 120 may include a plurality of N-S poles located at the peripheral portion of the first coil unit 110 at intervals of an arbitrary angle, centered on the first S-N pole in the vertical direction. For example, the first magnet unit 120 may include 3 pairs of N-S poles located at the peripheral portion of the first coil unit 110 at intervals of 120 degrees, centered on the first S-N pole in the vertical direction. FIG. 6B is a view schematically showing a neural stimulator of a cochlear implant according to an embodiment, and FIG. 6C is a cross-sectional view schematically showing the neural stimulator shown in FIG. 6B. Referring to FIGS. 6B and 6C, the neural stimulator 100 includes a first coil unit 110, a first magnet unit 120, and a housing containing these. Most of the descriptions of FIGS. 1A and 1B and the descriptions of FIGS. 2 and 3A to 3C described above are equally applied to the neural stimulator 100 of FIGS. 6B and 6C. However, unlike the first coil unit 110 of FIG. 3B configured as a flat plate shape entirely, a part of the first coil unit 110 of the neural stimulator 100 of FIGS. 6B and 6C is configured as a laminated type. Accordingly, by securing more internal space of the housing where the first magnet unit 120 is disposed, the first magnet unit 120 can use a thicker magnet that increases magnetic force. In 18 addition, since the first magnet unit 120 is located closer to the subject's skin, an attachment force with the external apparatus 200 can be increased. FIG. 7A is a view schematically showing a subject wearing a cochlear implant according to an embodiment entering an MRI environment, FIG. 7B is a view schematically showing a subject wearing a cochlear implant according to the prior art entering an MRI environment, and FIG. 8 is a view schematically showing a simulation for the MRI environment shown in FIGS. 7A and 7B. The cochlear implant shown in FIG. 7A is the aforementioned cochlear implant of FIGS. 2 to 3C. The conventional cochlear implant shown in FIG. 7B is a cochlear implant configured with a rotating type magnet in order to prevent the upright phenomenon of the magnet. Referring to FIGS. 7A, 7B, and 8, an MRI having a width of 0.44 m, a length of 0.2 m, and a magnetic flux density of 3T is used, and arrows inside the MRI are magnetic field vectors. FIG. 9A is a graph measuring electromagnetic force according to the position of the subject in the MRI environment by performing a simulation for the MRI environment shown in FIG. 7A, and FIG. 9B is a graph measuring electromagnetic force according to the position of the subject in the MRI environment by performing a simulation for the MRI environment shown in FIG. 7B. In the graphs of FIGS. 9A and 9B, the x-axis represents a distance away from the center with the center inside the MRI as 0 mm, and the y-axis represents electromagnetic force. Referring to FIGS. 9A and 9B, electromagnetic forces received by the cochlear implant in x, y, and z directions of the MRI environment 19 when the subject passes through the MRI are shown. The electromagnetic force received by the cochlear implant according to an embodiment at an entrance and an exit of the MRI is reduced by approximately 50% compared to the electromagnetic force received by the cochlear implant according to the prior art. FIG. 10A is a graph measuring torque according to the position of the subject in the MRI environment by performing a simulation for the MRI environment shown in FIG. 7A, and FIG. 10B is a graph measuring torque according to the position of the subject in the MRI environment by performing a simulation for the MRI environment shown in FIG. 7B. In the graphs of FIGS. 10A and 10B, the x-axis represents a distance away from the center with the center inside the MRI as 0 mm, and the y-axis represents torque. Referring to FIGS. 10A and 10B, torques received by the cochlear implant in x, y, and z directions of the MRI environment when the subject passes through the MRI are shown. A torque received when the cochlear implant according to an embodiment passes through the MRI is almost cancelled. However, since a torque received when the cochlear implant according to the prior art passes through the MRI is not cancelled, the cochlear implant implanted into a body of the subject may be aligned with a direction of a magnetic field inside, thereby causing danger. FIG. 11A is a view measuring an attachment force of the cochlear implant according to the embodiment shown in FIG. 7A, and FIG. 11B is a view measuring an attachment force of the cochlear implant according to the prior art shown in FIG. 7B. In FIG. 11A, the neural stimulator 100 is inclined by about 3.5 degrees, the magnetic flux density of the magnet of the neural stimulator 100 is 226 mT, the magnetic flux density of the magnet of the external apparatus 200 is 469 mT, and the measured attachment force is about 0.089 N. In FIG. 11B, the neural stimulator and the external apparatus according to the prior art are parallel to each other, the magnetic flux density of the magnet of the neural stimulator is 226 mT, the magnetic flux density of the magnet of the external apparatus is 469 mT, and the measured attachment force is about 0.08 N. Accordingly, the attachment force of the cochlear implant according to an embodiment is about 11.7% higher than the cochlear implant according to the prior art. In the cochlear implant according to an embodiment, electromagnetic force is cancelled, and torque is cancelled, making it safe in an MR examination environment, and the attachment force is also increased. Furthermore, in the cochlear implant according to an embodiment, two or more pairs of magnetic poles have one or more magnetic poles disposed around the circumference based on the magnetic pole at the center of the neural stimulator, so that wireless transmission and reception efficiency of power and data between coils can be maximized. Although preferred embodiments of the present invention have been described in detail above, the scope of rights of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of rights of the present invention.
Claims
[CLAIMS]
1. A cochlear implant comprising:a neural stimulator for stimulating an auditory nerve connected to a cochlea,wherein the neural stimulator comprises:a first coil unit for receiving power, data, or both from an external apparatus;a first magnet unit attached to the external apparatus by magnetic force and including two or more pairs of magnetic poles arranged to have mutually cancelling magnetic fields;a neural stimulation processing unit for processing a neural stimulation signal; anda neural stimulation electrode for stimulating the auditory nerve based on the neural stimulation signal.
2. The cochlear implant of claim 1,wherein the first magnet unit extends in one direction from a center portion to a peripheral portion of the first coil unit.
3. The cochlear implant of claim 2,wherein the external apparatus comprises:a second coil unit connected to the first coil unit in an inductive link manner; anda second magnet unit attached to the first magnet unit.
4. The cochlear implant of claim 3,wherein the first coil unit and the second coil unit are at positions overlapping each other.
5. The cochlear implant of claim 3,wherein the second magnet unit is located at a center portion of the second coil unit.
6. The cochlear implant of claim 1,wherein the two or more pairs of magnetic poles comprise a first S-N pole in a vertical direction located at a center of the first coil unit, and one or more NS poles located at a periphery of the first coil unit.
7. The cochlear implant of claim 6,wherein magnetic fields of the first S-N pole and the one or more N-S poles mutually cancel each other.
8. The cochlear implant of claim 7,wherein the one or more N-S poles are located at the periphery of the first coil unit at intervals of an arbitrary angle, centered on the first S-N pole.
9. The cochlear implant of claim 1,wherein the first magnet unit is separated from or inserted into the neural stimulator.
10. A magnet structure for a cochlear implant, located inside a neural stimulator for stimulating an auditory nerve connected to a cochlea,comprising:a first coil unit for receiving power, data, or both from an external apparatus; anda first magnet unit attached to the external apparatus by magnetic force, including two pairs of magnetic poles arranged to have mutually cancelling magnetic fields, and extending in one direction from a center portion to a peripheral portion of the first coil unit.