The present invention relates to the procedure of surgically inserting a cochlear implant in human patients. In particular, this invention pertains to optical proximity sensing and surface profilometry in cochlear implants.
Cochlea implants are devices that generate hearing sensation through electrical stimulation of the auditory sensory neurons using an array of electrodes in patients with partial or total hearing loss.
Today, technological advancements in cochlear implants have enabled implantation in patients with some degree of residual hearing. Recent studies have shown that preserving residual hearing is crucial for a significantly improved hearing performance through the simultaneous use of an electrical hearing, via a cochlear implant, and an acoustic hearing, via a hearing aid in the same ear. An atraumatic insertion that preserves the residual hearing ability is thus critical to reach the goal of a combined electric-acoustic hearing. Although some intracochlear damage can be avoided by the use of a short implant that does not reach beyond the basal turn of the cochlear canal, most people benefit from a deep insertion of a cochlear implant to allow stimulation of a wide range of frequencies. To achieve this goal, implants incorporating actuators or sensors have been invented, where a compact high-resolution sensor is of overwhelming importance.
One goal of the present invention is to provide an optical mechanism to be incorporated in cochlear implants to help surgeons guide the implant into the cochlea with controlled proximity to the modiolus and to minimize damage to intracochlear structures, including hair cells and neurons. The optical guidance is expected to enhance the efficacy of the implant by preserving any partial hearing capability for a combined electric-acoustic hearing. Furthermore, this optical mechanism can provide valuable information about the status of the hair cells and neurons in the cochlea, which can be used to optimize the controls of the implant and hearing aid.
In a first aspect the invention provides a cochlear implant device comprising an implant body being delimited at least by an implant surface, an electrode array, and at least one proximity sensor. The at least one proximity sensor is configured to provide distance or contact information that is representative of a distance lying between the implant surface and any one of cochlear intra-canal structures.
In a preferred embodiment, the at least one proximity sensor comprises at least one optical waveguide and a photodetector, the at least one optical waveguide being configured to deliver light from a source to a specific location of the implant surface, the at least one optical waveguide being connected to the source, wherein the light is intended to impinge the cochlea intra-canal structures and to be scattered back to the implant surface. The at least one proximity sensor comprises a second optical waveguide being configured to collect the scattered light and deliver it to the photodetector. A signal at an output from the photodetector is configured to provide the distance or contact information.
In a further preferred embodiment, the at least one optical waveguide connected to the source and the second waveguide connected to the detector are a same optical waveguide, namely the at least one optical waveguide.
In a further preferred embodiment, the waveguide is a thin optical fiber.
In a further preferred embodiment, the proximity sensor comprises a plurality of optical waveguides, whereby at least one of the plurality of waveguides is configured to deliver light of at least one wavelength, and further such that the delivered light impinges and is scattered from the cochlear intra-canal structures, wherein scattered light is collected by the plurality of waveguides, the implant device further comprising processing means configured to process an optical power in each waveguide collected and to retrieve the distance information at the position of the sensor.
In a further preferred embodiment, the plurality of sensors is configured to form a canal surface profilometer.
In a further preferred embodiment, the proximity sensor comprises at least one optical waveguide configured to deliver light of multiple wavelengths from a source to a plurality of distinct locations on the implant surface in a one-to-one mapping through fiber Bragg gratings, where the light impinges the cochlear intra-canal structures and is scattered back to the implant surface, the at least one waveguide collecting said scattered light through the fiber Bragg gratings and is configured for an intended delivery of the scattered light to a spectral analyzer, wherein the optical power in each wavelength channel from said spectral analyzer provides distance information between the implant surface to the cochlear intra-canal structures at the position respective to the wavelength.
In a further preferred embodiment, the proximity sensor comprises at least one semiconductor microchip arranged at a specific position on the implant surface with necessary metal wirings for power and communications, the semiconductor microchip comprising at least one light source and one photodetector, the semiconductor microchip being configured such that light from the light source impinges the cochlear intra-canal structures and is scattered back to the implant surface, and the photodetector converts the light intensity into the distance information at the position of the sensor.
In a further preferred embodiment, the light source is a light emitting diode.
In a further preferred embodiment, the light source is a laser diode.
In a further preferred embodiment, the proximity sensor comprises a plurality of semiconductor microchips arranged at specific positions on the implant surface with necessary metal wirings for power and communications, each of the semiconductor microchips comprising at least one light source and one photodetector, light from the light source impinging the cochlear intra-canal structures and being scattered back to the implant surface, the photodetector converting the light intensity into the distance information at the position of that sensor.
In a further preferred embodiment, the light source is a light emitting diode.
In a further preferred embodiment, the light source is a laser diode.
In a further preferred embodiment, the plurality of sensors forms a canal surface profilometer.
In a second aspect, the invention provides a method for fabricating an optical waveguide for use in the implant device described herein above, wherein the optical waveguide is fabricated by an exposure of a waveguide material to a focused laser light such that the waveguide material exposed to the focused laser light obtains a different refractive index than the unexposed material, hence forming a waveguide.
In a further preferred embodiment of the method, the waveguide material comprises silica or polydiphenylsiloxane.
The invention will be understood through the detailed description of preferred embodiments and in reference to the appended drawings, wherein
The present invention concerns an optical proximity sensor based on optical waveguides or optoelectronic semiconductor microchips that are integrated into the cochlea implants. In the waveguide-type sensor, the waveguides can be realized either by changing the optical properties of the implant material or embedding foreign materials of proper optical properties. The distal end of the waveguide leads the incident light to a specific position of the implant surface, such that an increased light is returned to the proximal end when the surface approaches the intra-cochlear canal wall or basilar membrane. In the semiconductor-type sensor, optoelectronic microchips are embedded into the implant body at specific locations, which draws power and communicates with the outside through metal wirings. Each microchip contains a semiconductor light source and a photodetector, such that an increased light is returned to the detector when the surface approaches the intra-cochlear canal wall or basilar membrane. In both types of sensor, the change of returned light signal serves as an indication of imminent contact and provides a feedback or an alarm for the surgeon who performs the insertion procedure.
The present invention provides an integration of a cochlear implant and an optical proximity sensor in order to enable atraumatic cochlear implant surgery. The cochlear implant may be fabricated with a soft polymer, polydimethylsiloxane (PDMS), which encapsulates the electrode array and wirings that stimulate the inner-ear sensory neurons with the electrical signals converted from external acoustic vibrations. As illustrated in
In one embodiment illustrated in
The preferable method to fabricate the waveguides is direct laser-writing through two-photon or ultraviolet laser absorption in the PDMS implant body. When exposed to an intense focused near infrared or ultraviolet laser light, PDMS undergoes a crosslinking process that results in a change of refractive index at the exposed spot. The resulting refractive index contrast ranges from 0.001 to 0.01 depending on the exposure dosage. Direct laser-writing is capable of producing arbitrary three-dimensional waveguides. The relatively low index contrast, however, requires a larger waveguide size and inter-waveguide distance. Consequently the total number of waveguides and sensors that can be packed in one implant is lower compared with other methods.
The waveguides can also be fabricated by embedding thin silica or polydiphenylsiloxane (PDPS) fibers. The refractive indices of silica and PDPS, 1.47 and 1.5 respectively, are much higher than that of PDMS, 1.41, which serves as the cladding in such a scheme. The index contrast of 0.06-0.09 enables the use of very thin fibers of as small as 1 μm diameter. The fibers can also be packed close to each other without inter-fiber coupling of light. In addition, the use of very thin fibers also minimizes any potential change in the mechanical properties of the implant.
In another embodiment, the proximity sensor is constructed with only a single waveguide in the form of a single-mode optical fiber. The single-mode fiber, embedded in the center of the implant, is pre-inscribed with Bragg gratings at distinct sensing locations reflecting a specific spectral content from a broadband source into the perpendicular directions i.e. out of the fiber length. Multiple gratings can be superimposed at the same location to cover several directions in the perpendicular plane. The proximal end of the fiber is illuminated with a broadband light, and light of a specific wavelength is directed toward the canal wall by the Bragg grating. The scattered light from the nearby tissue couples back into the fiber through the same grating, the overall strength of which serves the proximity indicator. At the proximal end, a spectral analyzer separates the channels of different colors and provides the proximity signal at all sensing locations simultaneously.
In yet another embodiment illustrated in
It is to be understood that, by systematic, strategic, and sufficient placement of said sensors, the implant is capable of measuring the surface profile of the cochlea canal given that the shape of the implant is known. This profile information is often highly valuable for optimal treatment of diseases in the inner ear.
In a practical application, the proximity sensors in the implant transmits signals that can be processed and converted into a form of audio or visual feedback to the surgeon that performs the surgical insertion (
Filing Document | Filing Date | Country | Kind |
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PCT/IB2016/055959 | 10/5/2016 | WO | 00 |
Number | Date | Country | |
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62237629 | Oct 2015 | US |