U.S. patent application number 15/662391 was filed with the patent office on 2017-11-23 for inductive signal and energy transfer through the external auditory canal.
The applicant listed for this patent is MED-EL Elektromedizinische Geraete GmbH. Invention is credited to Dominik Hammerer, Christoph Von Ilberg, Martin Zimmerling.
Application Number | 20170333713 15/662391 |
Document ID | / |
Family ID | 43598185 |
Filed Date | 2017-11-23 |
United States Patent
Application |
20170333713 |
Kind Code |
A1 |
Von Ilberg; Christoph ; et
al. |
November 23, 2017 |
Inductive Signal and Energy Transfer through the External Auditory
Canal
Abstract
An inductive coil arrangement is described for an ear canal of a
recipient patient. An external transmitter coil is configured for
implantation in the pinna cartilage of the outer ear of a recipient
patient and has transmission wire loops wound about a first radial
center. An implantable receiver coil is configured for implantation
behind the pinna of the outer ear under the skin atop and parallel
to the underlying skull bone of the recipient patient opposite to
the transmitter coil with the pinna cartilage between. The receiver
coil has receiver wire loops wound about a second radial center,
the loops and the second radial center all lying substantially in a
common plane, and the receiver coil is adapted for receiving the
communication signal from the transmitter coil.
Inventors: |
Von Ilberg; Christoph;
(Kronberg/Ts, DE) ; Hammerer; Dominik; (Innsbruck,
AT) ; Zimmerling; Martin; (Patsch, AT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MED-EL Elektromedizinische Geraete GmbH |
Innsbruck |
|
AT |
|
|
Family ID: |
43598185 |
Appl. No.: |
15/662391 |
Filed: |
July 28, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12957550 |
Dec 1, 2010 |
|
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15662391 |
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61265399 |
Dec 1, 2009 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61N 1/37229 20130101;
H04R 25/606 20130101; A61N 1/36038 20170801 |
International
Class: |
A61N 1/36 20060101
A61N001/36; A61N 1/372 20060101 A61N001/372 |
Claims
1. An inductive coil arrangement for an outer ear of a recipient
patient, the inductive coil arrangement comprising: an external
transmitter coil for implantation in the pinna cartilage of the
outer ear of a recipient patient and having a plurality of
transmission wire loops wound about a first radial center, the
loops and the first radial center all lying substantially in a
common plane, and wherein the transmitting coil is adapted for
transmitting an ear implant communication signal; and an
implantable receiver coil for implantation behind the pinna of the
outer ear under the skin atop and parallel to the underlying skull
bone of the recipient patient opposite to the transmitter coil with
the pinna cartilage between, wherein the receiver coil has a
plurality of receiver wire loops wound about a second radial
center, the loops and the second radial center all lying
substantially in a common plane, and wherein the receiver coil is
adapted for receiving the communication signal from the transmitter
coil.
2. An inductive coil arrangement according to claim 1, wherein the
coils are air coils without magnetic cores.
3. An inductive coil arrangement according to claim 1, further
comprising: an encapsulation layer of biocompatible material
covering at least one of the coils.
4. An inductive coil arrangement according to claim 3, wherein the
transmitter coil includes an encapsulation layer having a plurality
of ventilation openings.
5. An inductive coil arrangement according to claim 4, wherein the
ventilation openings have a uniform size and shape.
6. An inductive coil arrangement according to claim 4, wherein the
ventilation openings have different sizes.
7. An inductive coil arrangement according to claim 1, wherein the
transmission wire loops are concentrated at one or more radii from
a central axis of the transmitter coil.
8. An implantable medical system including an inductive coil
arrangement according to any of the claims 1-7.
Description
[0001] This application is a divisional of co-pending U.S.
application Ser. No. 12/957,550, filed Dec. 1, 2010, which in turn
claims priority from U.S. Provisional Patent Application
61/265,399, filed Dec. 1, 2009, both of which are incorporated
herein by reference in their entireties.
FIELD OF THE INVENTION
[0002] The present invention relates to implantable medical
devices, and more specifically to an inductive coil arrangement for
such devices.
BACKGROUND ART
[0003] A normal ear transmits sounds as shown in FIG. 1 through the
outer ear 101 to the tympanic membrane (eardrum) 102, which moves
the bones of the middle ear 103, which in turn vibrate the oval
window and round window openings of the cochlea 104. In response to
received sounds transmitted by the middle ear 103, the fluid filled
cochlea 104 functions as a transducer to generate electric pulses
that are transmitted to the acoustic nerve 113, and ultimately to
the brain. Hearing is impaired when there are problems in the
ability to transduce external sounds into meaningful action
potentials along the neural substrate of the cochlea 104.
[0004] In some cases, hearing impairment can be addressed by a
cochlear implant that stimulates auditory nerve tissue with
electrical stimulation signals delivered by multiple electrode
contacts distributed along an implant electrode. FIG. 1 shows some
components of a typical cochlear implant system where an external
microphone provides an audio signal input to an external signal
processing stage 111 that implements one of various known signal
processing schemes. The processed signal is converted by the
external signal processing stage 111 into a digital data format
communication signal for transmission by a transmitter coil 107
into an implanted receiver stimulator 108. Besides extracting the
audio information, the receiver stimulator 108 may perform
additional signal processing such as error correction, pulse
formation, etc., and produces a stimulation pattern (based on the
extracted audio information) that is sent through electrode wires
109 to an implant electrode 110. Typically, the implant electrode
110 includes multiple electrodes on its surface that provide
selective stimulation of the cochlea 104.
[0005] Hearing systems such as those described above are known to
have various difficulties associated with the transmitter coil 107.
For example, in the arrangement described above, the transmitter
coil 107 and the receiver stimulator 108 include permanent magnets
used to hold the transmitter coil 107 in correct position over the
receiver stimulator 108. These magnets create problems with
magnetic resonance imaging (MRI) or at the skin which covers the
receiver stimulator 108. In addition, the location of the
transmitter coil 107 on the head behind the outer ear 101 leaves it
exposed to impact (e.g., during sports) or being accidentally wiped
or brushed off (e.g., while brushing the hair).
[0006] U.S. Pat. No. 4,696,287 by Hortmann et al. disclosed a coil
system for an implanted hearing aid where the external transmitter
coil was located in the ear canal with its windings wrapped
perpendicular to the axis of the ear canal, and where the implanted
receiver coil was a ring surrounding the ear canal. U.S. Pat. No.
7,120,501 by Boylston et al. disclosed a hearing implant system
which included a transmitter coil in the ear canal and a receiver
coil positioned in the middle ear on the other side of the ear drum
from the transmitter coil. Both of the above systems required that
the implanted receiver coil have wire windings concentrated at
certain specific radii and no uniform winding from the center to an
outer radius was possible. WO 9809588 by Seligman et al. disclosed
a coil arrangement with one coil in the outer ear canal and another
implanted beside the ear canal, where each coil included two
orthogonally wound sub-coils around a ferrite core.
SUMMARY OF THE INVENTION
[0007] Embodiments of the present invention are directed to an
inductive coil arrangement for the ear canal of a recipient
patient. An inner transmitter coil is inserted into the ear canal
for transmitting a communication signal through the skin of the
outer wall of the ear canal. The transmitter coil includes
transmission wire loops that lie in a common plane which curves
around the central axis of the ear canal conformal to the outer
wall of the ear canal. An outer receiver coil is implanted under
the skin of the outer wall of the ear canal for receiving the
communication signal from the transmitter coil. The receiver coil
includes receiver wire loops that lie substantially in a common
plane which curves around the central axis of the ear canal
substantially parallel to the transmitter coil.
[0008] The coils may curve partially around the circumference of
the ear canal in a C-shape, or completely around the circumference
of the ear canal. An innermost end of the transmitter coil nearest
the tympanic membrane may include a sealing edge that folds back
when the transmitter coil is inserted into the ear canal. The
transmitter coil may include a helical ridge for promoting a
screwing insertion movement when the transmitter coil is inserted
into the ear canal. The coils may be air coils without magnetic
cores.
[0009] There also may be an encapsulation layer of biocompatible
material covering at least one of the coils. The encapsulation
layer may include a substance that inhibits production of cerumen
(ear wax). The encapsulation layer also may have ventilation
openings for ventilation of the underlying skin. The ventilation
openings may have a uniform size and shape, or they may be
different sizes.
[0010] In some embodiments, the transmission wire loops may be
concentrated at one or more radii from a central axis of the
transmitter coil. And some embodiments may also include an ear
canal microphone attached to the inner transmitter coil for sensing
sound present in the ear canal. Some embodiments may also further
include a secondary external transmitter coil for positioning over
the skin behind the ear of the patient to transmit a communication
signal through the skin, and a secondary receiver coil for
implantation under the skin behind the ear of the patient to
receive the communication signal from the secondary external
transmitter coil.
[0011] Embodiments of the present invention also include an
inductive coil arrangement for a recipient patient. An external
transmitter coil fits into the outer ear of the patient and
transmits a communication signal through the skin of the outer ear.
An implantable receiver coil is implantable under the skin of the
outer ear between the pinna cartilage and the underlying skull bone
for receiving the communication signal from the transmitter
coil.
[0012] In further specific embodiments, the receiver coil lies in a
plane under the pinna cartilage and atop and parallel to the
underlying skull bone. there may also be an implantable connecting
lead for connecting the receiver coil to an implanted stimulator to
couple the communication signal to the implanted stimulator. An
external processor may be connected to the transmitter coil for
generating the communication signal.
[0013] Embodiments of the present invention also include an
implantable medical device or system including an inductive coil
arrangement according to any of the above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 shows elements of a human ear having a typical
cochlear implant system.
[0015] FIG. 2 shows an example of a coil arrangement according to
one specific embodiment of the present invention.
[0016] FIG. 3 illustrates placement of an embodiment with respect
to the ear canal of a patient recipient.
[0017] FIG. 4 A-B shows examples of an embodiment where the coils
are embedded in a carrier having ventilation openings.
[0018] FIG. 5 shows an embodiment where the receiver coil is
implanted on the backside of the pinna cartilage structure between
bone and pinna.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
[0019] Partially implantable systems such as hearing implants (HI)
include both external and implantable components. Hearing implants
include, e.g., cochlear implants (CI's), middle ear implants
(MEI's), bone conduction implants, etc. In such systems, transfer
of electrical energy and data signals is based on an external
primary coil (referred to as the transmitter coil) and an internal
secondary coil (referred to as the receiver coil). Many partially
and totally implantable medical systems also require regular
charging cycles for their implantable batteries. Instead of the
traditional transcutaneous inductive link located on the side of
the head near the mastoid bone above and behind the pinna (outer
ear) as with existing HI systems, embodiments of the present
invention transfer energy and data signals inductively through the
skin at the outer wall of the ear canal.
[0020] FIG. 2 shows an inductive coil arrangement for an ear canal
of a recipient patient according to one embodiment of the present
invention. An inner transmitter coil 205 inserts into the ear canal
207. External processor 201 generates a communication signal
providing energy and data components which coupling lead 203
provides to the transmitter coil 205. The coupling lead 203 may be
stiff enough to help maintain the transmitter coil 205 in correct
position in the ear canal 207. The transmitter coil 205 includes
transmission wire loops that lie substantially in a common plane
which curves around the central axis of the ear canal 207 conformal
to the outer wall. The communication signal is transmitted by the
transmitter coil 205 through the skin of the outer wall of the ear
canal 207.
[0021] An outer receiver coil 206 is implantable under the skin of
the outer wall of the ear canal 207 for receiving the communication
signal from the transmitter coil 205. The receiver coil 206
includes receiver wire loops that lie substantially in a common
plane which curves around the central axis of the ear canal 207
substantially parallel to the transmitter coil 205. Receiver lead
204 (e.g., around 30 mm long) couples the received communication
signal from the receiver coil 206 to an implanted receiver
stimulator 202 which then extracts the power and data components
from the communication signal and generates an implant stimulation
signal. For example, as shown in FIG. 2, the implanted receiver
stimulator 202 provides the implant stimulation signal via
electrode wires 109 to implant electrode 110 which includes
stimulation electrodes 112 that stimulate neural tissue of the
cochlea 104. The receiver coil 206 is relatively thin (e.g. based
on a laminate arrangement), but relatively stiff such that it can
easily fit between the skin covering the ear canal 207 and the
underlying bone. Since (at least the outer part of) the ear canal
207 is flexible, the receiver coil 207 and its connected receiver
lead 204 should be mechanically robust against small movements.
[0022] Typically, the transmitter coil 205 and the receiver coil
206 are air coils without magnetic cores. The transmitter coil 205
and receiver coil 206 may curve as shown in FIG. 3 partially around
the circumference of the ear canal 207 in a C-shape. In other
embodiments, the coils may curve more or less completely around the
circumference of the ear canal 207. In addition or alternatively,
the transmitter coil 205 may include a helical ridge for promoting
a screwing insertion movement when the transmitter coil 205 is
inserted into the ear canal 207. Embodiments of an ear canal
inductive coil system should be tolerant with regard to the
relative position and orientation between the transmitter coil 205
and receiver coil 206, but the transmitter coil 206 still might
benefit from a stable position to promote reliable and constant
signal and energy transfer of the communication signal.
[0023] FIG. 4 A-B shows embodiments of an inductive coil 401 as
described above which includes an encapsulation layer 404 of soft
biocompatible material covering the wire loops 402. In FIG. 4 A-B,
the encapsulation layer 404 also includes ventilation openings 403
for ventilation of the underlying skin. The ventilation openings
403 may be as shown in FIG. 4A where they are a uniform size and
shape. Or in other embodiments, the ventilation openings 403 may be
as shown in FIG. 4B where they are different sizes. The
encapsulation layer 404 may include a substance that inhibits
production of cerumen (ear wax) in the ear canal 207. In some
embodiments, the wire loops may 402 be concentrated as shown in the
embodiment in FIG. 4B at one or more radii 405 from a central axis
of the inductive coil 401.
[0024] One of skill in the art will appreciate that there are
various technical, medical and surgical considerations associated
with such arrangements. For example, skin thickness around the
mastoid region (where transcutaneous transmission occurs in the
prior art) is relatively thick and rather variable over the patient
population--typically 4 to 7 mm, but with extreme cases of only 1
mm in very young children, to more than 8 or even 10 mm in some
adults. By contrast, skin thickness in the ear canal 207 is
relatively small (1 to 2 mm) and its variance over the patient
population also is relatively small. Thus, the power transfer
coefficient of an ear canal inductive coil system is higher than in
a conventional mastoid region transcutaneous link system as a
result of the reduced distance between the transmitter coil 205 and
the receiver coil 206. Moreover, embodiments of the present
invention do not use holding magnets which disadvantageously absorb
and dissipate energy from the communication signal.
[0025] The associated surgical procedure will be easier and faster
compared with existing methods and no bone drilling may be needed.
The placement of the receiver coil 206 between the bony wall and
the skin of the ear canal 207 can be performed from any surgical
access from behind the outer ear 101 which is in use for the
placement of hearing implants. The receiver coil 206 may be placed
in a small pouch where the skin covering the ear canal 207 is
surgically lifted off from the ear canal bone, with a posterior
approach. The receiver coil 206 should be placed in a lateral or
medial position such that the transmitter coil 205 can fit
comfortably in the outer portion of the ear canal 207 without being
located too close to the tympanic membrane 102. For example, the
coils may be placed on the back side (posterior side) of the ear
canal 207. Alternatively, coil placement on the superior (upper) or
on the inferior (lower) wall of the ear canal 207 also may be
workable. Coil placement on the anterior side (front side) of the
ear canal 207 may be less desirable since the anterior ear canal
wall is not adequately convex, and also in such a location the
coils might interfere with vascular stripes and nerve supply of the
ear canal 207. If the receiver coil 206 is placed more laterally in
the ear canal 207, small parts of the pinna cartilage can be
resected.
[0026] Though there is growth in the ear canal 207 of young
children, it seems likely that a single size of the receiver coil
206 can fit all patients from very young children to adults. For
the transmitter coil 205, different sizes may be needed to cover
young children as well as adults. The risk of secondary atrophy of
the skin between the receiver coil 206 and the transmitter coil 205
should be significantly minimized because the without holding
magnets, less pressure on the skin between the coils is needed.
There should not be risk of infection for the skin pouch in the ear
canal 207 since the skin can be left intact through the surgical
procedure. Postoperative soft packing of the ear canal 207 may be
recommended to avoid hematoma of the skin pouch. Moreover, because
the total volume of the implanted receiver coil 206 is smaller,
less implanted material is in contact with the surrounding tissues
(advantageous in case of allergic reactions).
[0027] Ear canal inductive coils would also be compatible with
combined electric-acoustic stimulation (EAS) hearing systems. The
transmitter coil 205 does not fill a significant amount of space in
the ear canal 207 since it lies flat in conformity with the outer
wall of the ear canal 207. There would be still enough space within
the outer ear canal 207 to additionally place a loudspeaker or tube
from an in-the-ear component of an EAS system to deliver sound to
the tympanic membrane 102.
[0028] The transmitter coil 205 should be removable at night
(during sleep) so that the ear canal 207 can recover from the
mechanical stress of carrying the coil. The transmitter coil 205
should also be easily cleanable and should be designed to take into
account the presence of cerumen (earwax) in the ear canal 207. That
is, the transmitter coil 205 should be designed so it can be
inserted into the external ear canal 207 without pushing earwax
towards the tympanic membrane 102. For example, an innermost end of
the transmitter coil 205 nearest the tympanic membrane 102 may
include a sealing edge that folds back when the transmitter coil
205 is inserted into the ear canal 207. The sealing edge then may
lift off slightly when taking the transmitter coil 205 out of the
ear canal 207. The transmitter coil 205 may also be coated by a
material which reduces the production of earwax.
[0029] Embodiments of the present invention provide a better
aesthetic appearance than current systems which rely on a bulky
behind-the-ear (BTE) coil arrangement. With transfer of the data
and energy components of the communication signal through the ear
canal 207, the transmitter coil 205 is much smaller and no longer
visible, and instead, only a less obtrusive BTE sound processor 201
is visible.
[0030] Other advantages of an ear canal coil arrangement include
that there no attachment magnets are needed for fixation of the
transmitter coil 205 either in the implanted receiver coil 206 or
in the external transmitter coil 205 placed inside the ear canal
207. This is highly beneficial in case the patient needs to undergo
Magnetic Resonance Imaging (MRI). Moreover, the probability that an
ear canal coil might be wiped off unintentionally (e.g. when
combing the hair or when dressing or undressing) is much reduced
over conventional coils placed on the side of the head. And
particularly for children, the ear canal coil arrangement is better
protected and less sensitive for destructive forces such as
accidental impact.
[0031] In addition, the receiver stimulator 202 can be surgically
placed closer to the outer ear 101 than in hearing implant systems
with conventional inductive links located on the side of the head.
In conventional hearing implant systems, the position of the
receiver coil and the receiver stimulator directly attached to it
is somewhat limited by the possible usable locations for the
external transmitter coil. For example, the external transmitter
coil cannot be located too close to the outer ear 101 since then it
would collide with the BTE sound processor 111.
[0032] On the other hand, in some embodiments, in addition to the
ear canal arrangement of the transmitter coil 205 and implanted
receiver coil 206, it may be useful to also include a secondary
receiver coil, for example, as conventionally in the receiver
stimulator 202, which is arranged to cooperate with a corresponding
secondary external transmitter coil, for example, as conventionally
in the BTE sound processor 111. This alternative conventional BTE
coil arrangement may provide a secondary insurance channel in the
event of problems or failure with the in the ear canal coils, or at
any time that the patient user finds that the BTE coils are more
suitable for use.
[0033] Some embodiments may also include an ear canal microphone
attached to the transmitter coil 205 for sensing sound present in
the ear canal 207. Since there is already the coupling lead 203
between the BTE processor 201 and the transmitter coil 205, this
may be also exploited to add an ear canal microphone, either by
attaching the microphone and the connecting cables to the
connection wires for the transmitter coil 205, or by using the same
cables and modulating the signals.
[0034] An ear canal transmitter coil 205 and implanted receiver
coil 206 can be significantly smaller than the coils in
conventional inductive link systems. While conventional inductive
link coils have a diameter of about 25 to 30 mm, the coils for an
ear canal inductive signal and energy transfer link may be much
smaller, e.g., 10 to 15 mm. This is possible because of the reduced
distance between the primary transmitter coil 205 and the secondary
receiver coil 206, and because there is no attachment magnet that
absorbs energy from the alternating magnetic fields associated with
transmission of the communication signal. With reduced coil size,
the voltages induced from external alternating magnetic fields (as
during MRI) generally are also reduced.
[0035] If the implanted receiver coil 206 bends around more than
about half of the circumference of the external ear canal 207, it
will be very sensitive to the non-homogeneous magnetic field from
the transmitter coil 205, but less sensitive to homogeneous
alternating magnetic fields coming from more distant coils such as
MRI scanners. Furthermore, due to the curved plane arrangement of
the transmitter coil 205 and receiver coil 206, good inductive
coupling can be achieved with relatively low loss of magnetic flux.
This is even the case with the air coils that used and described
above, and there is no need to use magnetic cores or ferrites to
realize acceptable inductive coupling.
[0036] The RF pulses in MRI scanners in bore systems (with
horizontal orientation) are present in x- and y-direction (i.e.
within an axial plane). And coils of conventional BTE inductive
links are oriented about a generally sagittal plane, but coils
placed in the ear canal are oriented in a mainly axial or coronal
plane. As a result, the RF pulses from an MRI scanner induce lower
voltages in the secondary receiver coil of an ear canal inductive
link system than in the secondary receiver coil of a conventional
inductive link system.
[0037] FIG. 5 shows an embodiment where the receiver coil 501 is
implanted on the backside of the cartilage structure of the outer
ear 101 (the pinna) to lie in a plane under the pinna and atop and
parallel to the underlying skull bone. For example, in one typical
such embodiment, the implanted receiver coil 501 has a diameter of
.about.10 mm. A corresponding external transmitter coil can be
integrated into an individually fitted ear piece which is placed in
outer ear 101. The receiver coil 501 may be coupled by a connecting
lead 502 to an implanted stimulator 503. The connecting lead 502
should be highly flexible to avoid open circuits, e.g. by using
stranded gold wires incorporating carbon filaments. The receiver
coil 501 can be fixed to the cartilage structure of the outer ear
101, for example with a few sutures at the outer circumference of
the receiver coil 501. Such an embodiment leaves the ear canal
unobstructed, an advantage which especially helpful for potential
candidates for hybrid electric-acoustic systems (EAS).
[0038] Embodiments of the invention also include implantable
devices and systems having an inductive coil arrangement as
discussed above. Although various exemplary embodiments of the
invention have been disclosed, it should be apparent to those
skilled in the art that various changes and modifications can be
made which will achieve some of the advantages of the invention
without departing from the true scope of the invention.
* * * * *