US-12616838-B2 - Patient specific frequency mapping procedure for hearing implant electrode arrays

US12616838B2US 12616838 B2US12616838 B2US 12616838B2US-12616838-B2

Abstract

A patient-specific frequency mapping procedure, a fitting system for carrying out said procedure and computer program product for a cochlear implant or an electric-acoustic stimulation device having an electrode array that has been implanted into the cochlea of said patient is disclosed.

Inventors

Richard Penninger
Mathias Kals
Reinhold Schatzer
Dirk Meister
Peter Nopp
Daniel Hofer

Assignees

Med-El Elektromedizinische Geräte Ges.m.b.H.

Dates

Publication Date: 20260505
Application Date: 20211001
Priority Date: 20201001

Claims (15)

1 . A patient-specific frequency mapping procedure for a cochlear implant or an electricacoustic stimulation device, the cochlear implant or the electroacoustic stimulation device having an electrode array that has been implanted into the cochlea of said patient, wherein said implanted electrode array comprises a number of stimulation electrodes at corresponding electrode locations within the cochlea, wherein said procedure comprises: providing or receiving tonotopic frequency information, said tonotopic frequency information comprising, for each of said stimulation electrodes, a place frequency associated with the patient-specific location of said stimulation electrode in the cochlea where said stimulation electrode is placed, determining, using said tonotopic frequency information and a tonotopic subset selection criterion, a tonotopic subset of adjacent stimulation electrode(s), assigning a tonotopic frequency band to each stimulation electrode within said tonotopic subset using a first band boundary determination rule, wherein said first band boundary determination rule determines an upper and a lower boundary of the tonotopic frequency band for each given stimulation electrode within said tonotopic subset, such as to ensure that the lower boundary is at a frequency that is lower than the place frequency of the given stimulation electrode but higher than the place frequency of the adjacent electrode in apical direction, and the upper boundary is at a frequency that is higher than the place frequency of the given stimulation electrode but lower than the place frequency of the adjacent electrode in basal direction, wherein said tonotopic frequency band(s) associated with said tonotopic subset of stimulation electrode(s) define a tonotopic frequency range, assigning a lower boundary to a frequency band associated with the most apical stimulation electrode within the electrode array, said lower boundary being lower than 200 Hz irrespectively of the place frequency of the most apical stimulation electrode, assigning an upper boundary to a frequency band associated with the most basal stimulation electrode, said upper boundary being lower than 20 kHz, irrespectively of the place frequency of the most basal stimulation electrode, determining an apical frequency band for each stimulation electrode in an apical subset of stimulation electrode(s) using a second band boundary determination rule, said apical frequency band(s) covering an apical frequency range extending between the tonotopic frequency range and said lower boundary of said frequency band associated with the most apical stimulation electrode, wherein said apical subset comprises all stimulation electrode(s) to the apical side of said tonotopic subset of stimulation electrode(s), wherein said second band boundary determination rule is either independent of the place frequencies of the stimulation electrode(s) in said apical subset or, when the second band boundary determination rule does account for some or all of said place frequencie(s) associated with said apical subset, a distribution of boundaries is provided that is closer to a logarithmically evenly spaced distribution within said apical frequency range than if the first band boundary determination rule was applied to the apical subset of stimulation electrode(s), and determining a basal frequency band for each stimulation electrode in a basal subset of stimulation electrode(s) using a third band boundary determination rule, said basal frequency band(s) covering a basal frequency range extending between the tonotopic frequency range and said upper boundary of said frequency band associated with the most basal stimulation electrode, wherein said basal subset comprises all stimulation electrode(s) to the basal side of said tonotopic subset of stimulation electrode(s), wherein said third band boundary determination rule is either independent of the place frequencies of the stimulation electrodes in said basal subset or, when the second band boundary determination rule does account for some or all of said place frequencie(s) associated with said basal subset, a distribution of boundaries is provided that is closer to a logarithmically evenly spaced distribution within said basal frequency range than if the first band boundary determination rule was applied to the basal subset of stimulation electrode(s) and; delivering electrical stimulation from the electrode array using the determined tonotopic subset, apical frequency band, and basal frequency band, and the assigned boundaries.
2 . The procedure of claim 1 , wherein each of said stimulation electrodes corresponds to an active electrode contact of said electrode array, or wherein said procedure includes forming a virtual electrode contact by cooperative operation of two or more electrode contacts.
3 . The procedure of claim 1 , wherein at least one of said lower boundary assigned to said frequency band associated with the most apical stimulation electrode and said upper boundary of said frequency band associated with the most basal stimulation electrode is independent of the place frequency of the corresponding most apical and most basal stimulation electrode, respectively, and is a predetermined, patient-independent value.
4 . The procedure of claim 1 , wherein said tonotopic subset selection criterion comprises a lower and an upper frequency threshold, wherein said selection criterion is fulfilled for a stimulation electrode having a place frequency within a range between said lower and upper frequency thresholds.
5 . The procedure of claim 4 , wherein said lower threshold is between 900 Hz and 1000 Hz.
6 . The procedure of claim 4 , wherein said upper threshold is between 2700 Hz and 3300 Hz.
7 . The procedure of claim 4 , wherein said tonotopic subset selection criterion further comprises information regarding residual hearing of the patient for low frequencies, wherein in case of sufficient residual hearing, the procedure extends said tonotopic subset all the way to the most apical stimulation electrode.
8 . The procedure of claim 1 , wherein said procedure ensures that said tonotopic subset comprises at least two stimulation electrodes.
9 . The procedure of claim 1 , wherein said procedure ensures that one or both of said apical and basal subsets comprises at least two stimulation electrodes.
10 . The procedure of claim 1 , wherein for some or all of said stimulation electrodes, the upper boundary of the respective frequency band coincides with the lower boundary of the adjacent frequency band in basal direction.
11 . The procedure of claim 1 , wherein said first band boundary determination rule determines the upper and lower boundaries of said tonotopic frequency band of a given stimulation electrode using one of an arithmetic mean, a geometrical mean or a logarithmic mean of the place frequency of the given stimulation electrode and the place frequency of a respective adjacent stimulation electrode, or using a computation rule that leads to a value between said arithmetic and logarithmic mean.
12 . The procedure of claim 1 , wherein said second band boundary determination rule determines the band boundaries within said apical frequency range such that the logarithms of the boundaries are evenly spaced between the logarithm of the lower boundary of the tonotopic frequency band of the most apical stimulation electrode among the tonotopic subset and the logarithm of the lower boundary of the frequency band associated with the most apical stimulation electrode within the electrode array, or such that the logarithms of all of the boundaries deviate from the evenly spaced logarithmic values by no more than 10%.
13 . The procedure of claim 1 , wherein said third band boundary determination rule determines the band boundaries within said basal frequency range such that the logarithms of the boundaries are evenly spaced between the logarithm of the upper boundary of the tonotopic frequency band of the most basal stimulation electrode among the tonotopic subset and the logarithm of the upper boundary of the frequency band associated with the most basal stimulation electrode within the electrode array, or such that the logarithms of all of the boundaries deviate from the evenly spaced logarithmic values by no more than 15%.
14 . A non-transitory computer readable medium having instructions that when executed by a computer, perform the method of claim 1 .
15 . A fitting system for carrying out a patient-specific frequency mapping procedure for a cochlear implant or an electric-acoustic stimulation device, the cochlear implant or the electric-acoustic stimulation device having an electrode array that has been implanted into the cochlea of said patient, wherein said implanted electrode array comprises a number of stimulation electrodes at corresponding electrode locations within the cochlea, said system comprising: means for generating or an interface for receiving tonotopic frequency information, said tonotopic frequency information comprising, for each of said stimulation electrodes, a place frequency associated with the patient-specific location of said stimulation electrode in the cochlea where said stimulation electrode is placed, a signal processor configured to: determine, using said tonotopic frequency information and a tonotopic subset selection criterion, a tonotopic subset of adjacent stimulation electrode(s), for assigning a tonotopic frequency band to each stimulation electrode within said tonotopic subset using a first band boundary determination rule, wherein said first band boundary determination rule determines an upper and a lower boundary of the tonotopic frequency band for each given stimulation electrode within said tonotopic subset such as to ensure that the lower boundary is at a frequency that is lower than the place frequency of the given stimulation electrode but higher than the place frequency of the adjacent electrode in apical direction, and the upper boundary is at a frequency that is higher than the place frequency of the given stimulation electrode but lower than the place frequency of the adjacent electrode in basal direction, wherein said tonotopic frequency band(s) associated with said tonotopic subset of stimulation electrode(s) define a tonotopic frequency range, for assigning a lower boundary to a frequency band associated with the most apical stimulation electrode within the electrode array, said lower boundary being lower than 200 Hz, irrespectively of the place frequency of the most apical stimulation electrode, the signal processor further configured to: assigning an upper boundary to a frequency band associated with the most basal stimulation electrode, said upper boundary being lower than 20 kHz, irrespectively of the place frequency of the most basal stimulation electrode, and determining an apical frequency band for each stimulation electrode in an apical subset of stimulation electrode(s) using a second band boundary determination rule, said apical frequency band(s) covering an apical frequency range extending between the tonotopic frequency range and said lower boundary of said frequency band associated with the most apical stimulation electrode, wherein said apical subset comprises all stimulation electrodes to the apical side of said tonotopic subset of stimulation electrode(s), wherein said second band boundary determination rule is either independent of the place frequencie(s) of the stimulation electrode(s) in said apical subset or, when the second band boundary determination rule does account for some or all of said place frequencie(s) associated with said apical subset, a distribution of boundaries is provided that is closer to a logarithmically evenly spaced distribution within said apical frequency range than if the first band boundary determination rule was applied to the apical subset of stimulation electrode(s), and the signal processor further configured to: determine a basal frequency band for each stimulation electrode in a basal subset of stimulation electrode(s) using a third band boundary determination rule, said basal frequency band(s) covering a basal frequency range extending between the tonotopic frequency range and said upper boundary of said frequency band associated with the most basal stimulation electrode, wherein said basal subset comprises all stimulation electrode(s) to the basal side of said tonotopic subset of stimulation electrode(s), wherein said third band boundary determination rule is either independent of the place frequencie(s) of the stimulation electrode(s) in said basal subset or, when the second band boundary determination rule does account for some or all of said place frequencie(s) associated with said basal subset, a distribution of boundaries is provided that is closer to a logarithmically evenly spaced distribution within said basal frequency range than if the first band boundary determination rule was applied to the basal subset of stimulation electrode(s) and; a pulse generator configured to deliver electrical stimulation from the electrode array using the determined tonotopic subset, apical frequency band, and basal frequency band, and the assigned boundaries.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a 371 national phase entry of Patent Cooperation Treaty Application PCT/EP2021/025380, filed Oct. 1, 2021, which in turn claims priority from EP 201997228, filed Oct. 1, 2020. Each of the above-described applications is hereby incorporated herein by reference in it entirety. FIELD OF THE INVENTION The present invention relates to hearing implant systems, and more specifically, to techniques for patient-specific frequency mapping in a cochlear implant or an electro-acoustic stimulation device having an electrode array. BACKGROUND ART A normal ear transmits sounds as shown in FIG. 1 through the outer ear 101 to the tympanic membrane 102, which moves the bones of the middle ear 103 (malleus, incus, and stapes) that vibrate the oval window and round window openings of the cochlea 104. The cochlea 104 is a long narrow duct wound spirally about its axis for approximately two and a half turns. It includes an upper channel known as the scala vestibuli and a lower channel known as the scala tympani, which are connected by the cochlear duct. The cochlea 104 forms an upright spiraling cone with a center called the modiolar where the spiral ganglion cells of the acoustic nerve 113 reside. In response to received sounds transmitted by the middle ear 103, the fluid-filled cochlea 104 functions as a transducer to generate electric pulses which are transmitted to the cochlear 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. To improve impaired hearing, hearing prostheses have been developed. For example, when the impairment is related to operation of the middle ear 103, a conventional hearing aid may be used to provide mechanical stimulation to the auditory system in the form of amplified sound. Or when the impairment is associated with the cochlea 104, a cochlear implant with an implanted stimulation electrode array 110 can electrically stimulate auditory nerve tissue with small currents delivered by multiple electrode contacts 112 distributed along the electrode array 110. FIG. 1 also shows some components of a typical cochlear implant system, including an external microphone that provides an audio signal input to an external signal processor 111 where various signal processing schemes can be implemented. The processed signal is then converted into a digital data format, such as a sequence of data frames, for transmission into the implant 108. Besides receiving the processed audio information, the implant 108 also performs 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 an electrode lead 109 to the implanted electrode array 110. Typically, the electrode array 110 includes multiple electrode contacts 112 on its surface that provide selective stimulation of the cochlea 104. Depending on context, the electrode contacts 112 are also referred to as electrode channels. In cochlear implants today, a relatively small number of electrode channels are each associated with relatively broad frequency bands, with each electrode contact 112 addressing a group of neurons with an electric stimulation pulse having a charge that is derived from the instantaneous amplitude of the signal envelope within that frequency band. In some coding strategies, stimulation pulses are applied at a constant rate across all electrode channels, whereas in other coding strategies, stimulation pulses are applied at a channel-specific rate. Various specific signal processing schemes can be implemented to produce the electrical stimulation signals. Signal processing approaches that are well-known in the field of cochlear implants include continuous interleaved sampling (CIS), channel specific sampling sequences (CSSS) (as described in U.S. Pat. No. 6,348,070, incorporated herein by reference), spectral peak (SPEAK), and compressed analog (CA) processing. FIG. 2 shows various functional blocks in a signal processing arrangement for producing electrode stimulation signals to electrode contacts in an implanted cochlear implant array according to a typical hearing implant system. A pseudo code example of such an arrangement can be set forth as: Input Signal Preprocessing: BandPassFilter (input_sound, band_pass_signals) Envelope Extraction: BandPassEnvelope (band_pass_signals, band_pass_envelopes) Stimulation Timing Generation: TimingGenerate (band_pass_signals, stim_timing) Pulse Generation: PulseGenerate (band_pass_envelopes, stim_timing, out_pulses) In the arrangement shown in FIG. 2, the initial input sound signal is produced by one or more sensing microphones, which may be omnidirectional and/or directional. Preprocessor Filter Bank 201 pre-processes this input sound signal with a bank of multiple parallel band pass