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International audience; The robust delineation of the cochlea and its inner structures combined with the detection of the electrode of a cochlear implant within these structures is essential for envisaging a safer, more individualized, routine image-guided cochlear implant therapy. We present Nautilus—a web-based research platform for automated pre- and post-implantation cochlear analysis. Nautilus delineates cochlear structures from pre-operative clinical CT images by combining deep learning and Bayesian inference approaches. It enables the extraction of electrode locations from a post-operative CT image using convolutional neural networks and geometrical inference. By fusing pre- and post-operative images, Nautilus is able to provide a set of personalized pre- and post-operative metrics that can serve the exploration of clinically relevant questions in cochlear implantation therapy. In addition, Nautilus embeds a self-assessment module providing a confidence rating on the outputs of its pipeline. We present a detailed accuracy and robustness analyses of the tool on a carefully designed dataset. The results of these analyses provide legitimate grounds for envisaging the implementation of image-guided cochlear implant practices into routine clinical workflows.

The use of image processing techniques to estimate the position of intra-cochlear electrodes has enabled the creation of personalized maps to meet the individual stimulation needs of cochlear implant (CI) recipients. The aim of this study was to evaluate a novel technique of electrode deactivation based on postoperative cone beam computed tomography (CBCT) images in post-lingually deafened adult CI recipients. Based on postoperative CBCT images, the positioning of the electrodes was estimated in relation to the modiolus in 14 ears of 13 post-lingually deafened adult CI recipients. The electrodes sub-optimally positioned or involved in kinking and tip fold-over were deactivated. Speech perception scores in silence and in noise were obtained from subjects using the standard map and were followed up 4 weeks after image-based electrode deactivation reprogramming technique (IBEDRT). The participants selected their preferred map after 4 weeks of IBEDRT use. There were statistically significant improvements in the speech recognition tests in silence and noise when comparing IBEDRT performance to the standard map. All participants elected the IBEDRT as their new preferred map. IBEDRT is a promising technique for fitting CI recipients and minimizing channel interaction increased by the positioning of the electrodes sub-optimally placed, thereby improving their auditory performance. We propose a novel electrode deactivation technique based on postoperative CBCT imaging, with a limited number of deactivated electrodes and a low-dosing scanning which could be applied for clinical routine.

Objective: This study investigated the audiological and tinnitus outcomes of cochlear implantation (CI) in adults with single-sided deafness (SSD) and tinnitus. Study Design: Multicentered prospective, non-randomized intervention study. Setting: Six French CI centers. Patients: Twenty-six patients with SSD and incapacitating tinnitus (Tinnitus Handicap Inventory [THI] >58) underwent cochlear implantation. Interventions: First, CIs delivered only masking white noise stimulation for 1 month and then standard CI stimulation. Main Outcome Measures: Before and after CI surgery, patients completed the THI, Tinnitus Reaction Questionnaire (TRQ), Subjective Tinnitus Severity Scale (STSS), and two visual analogue scales quantifying tinnitus loudness and annoyance. Speech perception in spatialized noise was tested at 13 months. Results: The first month of white noise stimulation triggered a significant improvement in THI scores (72 ± 9 to 55 ± 20, p

Introduction Electrically evoked auditory brainstem responses provide reliable clinical information to assist professionals in the auditory rehabilitation of cochlear implant users. Objective This study aimed to investigate intraoperative evoked auditory brainstem response recordings in Evo®-cochlear implant electrode array recipients and its correlation with their behavioral levels and auditory performance. Methods This is a retrospectivey study. Intraoperative evoked auditory brainstem responses were recorded in adult Evo®-cochlear implant electrode array recipients. Wave V latencies, amplitudes and interpeak III-V intervals were recorded in three different electrode locations and compared to the sentence recognition scores obtained from subjects after six months of device use. Evoked auditory brainstem responses thresholds were also recorded and compared to the behaviorally determined levels of the subjects in the sound processor activation. Results Evoked auditory brainstem responses thresholds were significantly correlated with both, behavioral T- and C-levels and they were recorded at audible electrical stimulation levels in all subjects. There was a significant correlation between interpeak III-V interval recorded in the apical electrode and sentence recognition scores of the subjects. Conclusions Intraoperative evoked auditory brainstem responses can be used to establish audible levels for fitting the sound processor in Evo®-cochlear implant recipients and it could help professionals to plan further actions aiming to improve their auditory performance. Resumo Introdução Os potenciais auditivos de tronco encefálico evocados eletricamente fornecem informações clínicas confiáveis que auxiliam no processo de reabilitação auditiva de usuários de implante coclear. Objetivo Investigar o registro intraoperatório dos potenciais auditivos de tronco encefálico evocados eletricamente em usuários do feixe de eletrodos Evo® e sua correlação com os níveis comportamentais e desempenho auditivo dos indivíduos. Método Estudo retrospectivo. Os potenciais auditivos de tronco encefálico intraoperatórios foram registrados em usuários adultos de implante coclear com feixe de eletrodos Evo®. As latências e amplitudes da onda V e os intervalos interpico III-V foram registrados em três diferentes eletrodos e comparados às pontuações de reconhecimento de sentenças após 6 meses de uso do implante coclear. Os limiares dos eABRs foram comparados aos níveis comportamentais dos indivíduos na ativação do processador de som. Resultados Os limiares do eABR foram significativamente correlacionados aos níveis comportamentais T e C e registrados em níveis de estimulação elétrica audíveis em todos os indivíduos. Houve uma correlação significativa entre o intervalo interpico III-V no eletrodo apical e a pontuação de reconhecimento de sentenças dos indivíduos. Conclusões O eABR intraoperatório pode ser usado para estabelecer níveis audíveis de estimulação elétrica na ativação do processador sonoro em usuários de implante coclear‐Evo® e pode auxiliar os profissionais no planejamento de ações visando melhorar o desempenho auditivo nesses pacientes.

Background: A prospective longitudinal multicentre study was conducted to assess the one-year postsurgical hearing preservation profile of the EVOTM electrode array. Methods: Fifteen adults presenting indications of electro-acoustic stimulation (pure-tone audiometry (PTA) thresholds ≤70 dB below 750 Hz) were implanted with the EVO™ electrode array. Hearing thresholds were collected at five time-points from CI activation to twelve months (12M) after activation. Hearing thresholds and hearing preservation profiles (HEARRING group classification) were assessed. Results: All subjects had measurable hearing thresholds at follow-up. No case of complete loss of hearing or minimal hearing preservation was reported at any time point. At activation (Nact = 15), five participants had complete hearing preservation, and ten participants had partial hearing preservation. At the 12M time point (N12m = 6), three participants had complete hearing preservation, and three participants had partial hearing preservation. Mean hearing loss at activation was 11 dB for full range PTA and 25 dB for PTAs low-frequency (125–500 Hz). Conclusions: This study provides the first longitudinal follow-up on associated hearing profiles to the EVO™ electrode array, which are comparable to the literature. However, other studies on larger populations should be performed.

International audience; Metal Artifacts creates often difficulties for a high-quality visual assessment of post-operative imaging in computed tomography (CT). A vast body of methods have been proposed to tackle this issue, but these methods were designed for regular CT scans and their performance is usually insufficient when imaging tiny implants. In the context of post-operative high-resolution CT imaging, we propose a 3D metal artifact reduction algorithm based on a generative adversarial neural network. It is based on the simulation of physically realistic CT metal artifacts created by cochlea implant electrodes on preoperative images. The generated images serve to train 3D generative adversarial networks for artifacts reduction. The proposed approach was assessed qualitatively and quantitatively on clinical conventional and cone-beam CT of cochlear implant postoperative images. These experiments show that the proposed method outperforms other general metal artifact reduction approaches.

Objective This prospective longitudinal cohort study at six tertiary referral centers in Canada and Denmark describes the clinical efficiency and surgical safety of cochlear implantation with the Oticon Medical Neuro cochlear implant system, including the Neuro Zti implant, the EVO electrode array, and the Neuro One sound processor. Methods Patients were adult cochlear implant candidates with bilateral sensorineural hearing loss. Results The mean HINT scores in quiet pre-operatively and at 3, 6, and 12 months post-activation were 13%, 58%, 67%, and 72%, respectively, and in noise (+10 dB SNR) 13%, 46%, 53%, and 59%, respectively. The mean improvement from baseline to 6 months post-activation was 54% in quiet and 40% in noise. The surgical major complication incidence rate was 0% and the post-surgical major complication incidence rate (until 12 months post-activation) was 4%. There was no adverse event that was fatal, that required explantation, or that resulted in sound processor nonuse, and no implant failure. Conclusion Cochlear implantation with the Oticon Medical Neuro system enables speech identification both in quiet and in noise and audiologic outcomes continue to improve in the year following activation. No substantial adverse events occurred during the surgical implantation procedure and during the 12 months post-activation. Funding Agencies|Oticon Medical

International audience; To assess the quality of insertion of Cochlear Implants (CI) after surgery, it is important to analyze the positions of the electrodes with respect to the cochlea based on post-operative CT imaging. Yet, these images suffer from metal artifacts which often entail a difficulty to make any analysis. In this work, we propose a 3D metal artifact reduction method using convolutional neural networks for post-operative cochlear implant imaging. Our approach is based on a 3D generative ad-versarial network (MARGANs) to create an image with a reduction of metal artifacts. The generative model is trained on a large number of pre-operative "artifact-free" images on which simulated metal artifacts are created. This simulation involves the segmentation of the scala tym-pani, the virtual insertion of electrode arrays and the simulation of beam hardening based on the Beer-Lambert law. Quantitative and qualitative evaluations compared with two classical metallic artifact reduction algorithms show the effectiveness of our method.

Objective: To propose a method for quantitative assessment of the migration of lateral-wall, straight electrode arrays after surgery based on postoperative Cone Beam Computed Tomography (CBCT) images and automated medical image analysis techniques. Methods: A preliminary study is conducted on 19 implanted ears. For each implantation, two CBCT images are objectively analyzed. Electrode arrays are consistently projected into the same coordinate system in order to estimate precisely the migration of each electrode. Spatial configuration changes are characterized with the overall curvature of the electrode array. Results: From the samples analyzed no significant electrode migration, extrusion or electrode curvature changes were found. Mean infinitesimal local migration reveals a tendency where apical electrodes tend to move away from the modiolus and basal electrodes away from the round window. Conclusion: CBCT images demonstrate adequate resolution with limited artifacts to assess the electrode array position in vivo. Automated medical image analysis techniques and consistent coordinate system allow to quantitatively estimate migration and extrusion effect for lateral-wall, straight electrode array.

A new type of advanced drug delivery systems is proposed: Miniaturized implants, which can be placed into tiny holes drilled into (or close to) the oval window. They consist of two parts: 1) A cylinder, which is inserted into the hole crossing the oval window. The cylinder (being longer than the depth of the hole) is partly located within the inner ear and surrounded by perilymph. This provides direct access to the target site, and at the same time assures implant fixation. 2) A cuboid, which is located in the middle ear, serving as a drug reservoir. One side of the cuboid is in direct contact with the oval window. Drug release into the cochlea occurs by diffusion through the cylindrical part of the Ear Cubes and by diffusion from the cuboid into and through the oval window. High precision molds were used to prepare two differently sized Ear Cubes by injection molding. The miniaturized implants were based on silicone and loaded with different amounts of dexamethasone (10 to 30 % w/w). The systems were thoroughly characterized before and upon exposure to artificial perilymph at 37°C. Importantly, drug release can effectively be controlled and sustained during long time periods (up to several years). Furthermore, the implants did not swell or erode to a noteworthy extent during the observation period. Drug diffusion through the polymeric matrix, together with limited dexamethasone solubility effects, seem to control the resulting drug release kinetics, which can roughly be estimated using mathematical equations derived from Fick's second law. Importantly, the proposed Ear Cubes are likely to provide much more reliable local long term drug delivery to the inner ear compared to liquid or semi-solid dosage forms administered into the middle ear, due to a more secured fixation. Furthermore, they require less invasive surgeries and can accommodate higher drug amounts compared to intracochlear implants. Thus, they offer the potential to open up new horizons for innovative therapeutic strategies to treat inner ear diseases and disorders.

The aim of this study was to evaluate the potential improvements of speech perception and sound quality provided by a multiband single channel noise-reduction algorithm based on the modified Wiener-filter adapted to cochlear implant sound processing.This study was a longitudinal trial with a repeated-measures design. Outcome measures were performed on the first day when the noise reduction feature was provided and after a one month habituation period. Objective measures included pure-tone thresholds and vocal audiometry assessments. Speech perception was measured in quiet and in the presence of two types of noise: a stationary speech shaped noise and a two-talker cocktail noise. Subjective sound quality was assessed using a ten item questionnaire.Thirteen post-lingual deaf adults, experienced users of a cochlear implant system, took part in this study.The noise-reduction algorithm provided a benefit for the perception of speech presented in a stationary speech shaped noise and an overall improvement in subjective sound quality ratings.It was shown that a single channel noise reduction system based on a modified Wiener-filter approach can improve speech in noise perception performance and subjective sound quality in cochlear implant patients.

Conventional loudness coding with CIs by pulse current amplitude has a disadvantage: Increasing the stimulation current increases the spread of excitation in the auditory nerve, resulting in stronger channel interactions at high stimulation levels. These limit the number of effective information channels that a CI user can perceive. Stimulus intensity information (loudness) can alternatively be transmitted via pulse phase duration. We hypothesized that loudness coding by phase duration avoids the increase in the spread of the electric field and thus leads to less channel interactions at high stimulation levels. To avoid polarity effects, we combined this coding with pseudomonophasic stimuli. To test whether this affects the spread of excitation, 16 acutely deafened guinea pigs were implanted with CIs and neural activity from the inferior colliculus was recorded while stimulating with either biphasic, amplitude-coded pulses, or pseudomonophasic, duration- or amplitude-coded pulses. Pseudomonophasic stimuli combined with phase duration loudness coding reduced the lowest response thresholds and the spread of excitation. We investigated the channel interactions at suprathreshold levels by computing the phase-locking to a pulse train in the presence of an interacting pulse train on a different electrode on the CI. Pseudomonophasic pulses coupled with phase duration loudness coding reduced the interference by 4-5% compared to biphasic pulses, depending on the place of stimulation. This effect of pseudomonophasic stimuli was achieved with amplitude coding only in the basal cochlea, indicating a distance- or volume dependent effect. Our results show that pseudomonophasic, phase-duration-coded stimuli slightly reduce channel interactions, suggesting a potential benefit for speech understanding in humans.

International audience; Despite remarkable advances made to ameliorate how cochlear implants process the acoustic environment, many improvements can still be made. One of most fundamental questions concerns a strategy to simulate an increase in sound intensity. Psychoacoustic studies indicated that acting on either the current, or the duration of the stimulating pulses leads to perception of changes in how loud the sound is. The present study compared the growth function of electrically evoked Compound Action Potentials (eCAP) of the 8th nerve using these two strategies to increase electrical charges (and potentially to increase the sound intensity). Both with chronically (experiment 1) or acutely (experiment 2) implanted guinea pigs, only a few differences were observed between the mean eCAP amplitude growth functions obtained with the two strategies. However, both in chronic and acute experiments, many animals showed larger increases of eCAP amplitude with current increase, whereas some animals showed larger of eCAP amplitude with duration increase, and other animals show no difference between either approaches. This indicates that the parameters allowing the largest increase in eCAP amplitude considerably differ between subjects. In addition, there was a significant correlation between the strength of neuronal firing rate in auditory cortex and the effect of these two strategies on the eCAP amplitude. This suggests that pre-selecting only one strategy for recruiting auditory nerve fibers in a given subject might not be appropriate for all human subjects.

Introduction The preservation of residual hearing is currently an important challenge for cochlear implant surgeries. Indeed, if patients exhibit functional hearing after cochlear implantation, they can benefit from the combination of acoustical stimulation, usually in the low-frequencies and electrical stimulation in the high-frequencies. This combined mode of stimulation has proven to be beneficial both in terms of speech perception and of sound quality. Finding the right procedures for conducting soft-surgeries and designing electrode arrays dedicated to hearing preservation is an open issue. Objective The objective of this study is to evaluate the combination of a soft-surgery procedure implicating round-window insertion and the use of dexamethasone and hyaluronic acid during surgery, with the use of a specifically designed straight soft electrode array, on hearing preservation in patients with functional hearing in the low frequencies. Methods This pre-clinical trial was conducted on seven patients with residual hearing in the low frequencies. The surgical method used employed a round window insertion and the use of topical dexamethasone. Results The soft-surgery protocol could be successfully followed in five patients. In this group, the average hearing threshold shift compared with pre-operative values was of 18.7 +/− 16.1 dB HL up to 500 Hz and 15.7 +/− 15.1 up to 1 kHz, demonstrating satisfying levels of hearing preservation. Conclusion We were able to demonstrate the possibility of preserving residual hearing in most of the patients using the EVO electrode. Significant residual hearing preservation levels were was obtained when a soft surgical approach involving round window insertion, dexamethasone and hyaluronic use during the surgery.

French phonemes perception in noisy conditions, in the case of a Binaural Cochlear Implant (BCI) coding, is seen in the present study. In the current work, the action of binaural noise reduction algorithms is investigated, through the use of a vocoder simulation with normal hearing listeners. Three binaural noise reduction algorithms, used in classical hearing aids, have been considered: beamformer, Doerbecker algo- rithm combined with Ephraim and Malah noise estimator and Doerbecker algorithm combined with Scalart noise estimator. Then a cochlear implant (CI) coding (bins grouped into frequency bands) transformed the signal at the end of the processing chain. Also, a percentage of the input signal was "re-injected" (added) before CI coding. Twenty-six normal hearing subjects participated in the experiment and they listened to sessions including 3 signal-to-noise ratios, 3 re-injection coefficients; they evaluated the coded signal (phoneme recognition). Then, a noise was added to jam the signal. The noise came from five different noise angles and the speech was issued from the front (zero deg azimuth). Altogether, experimental sessions tested 150 conditions. Best results were obtained using the beamformer algorithm. Doerbecker with Ephraim and Malah estimator led to good results; this strategy was more efficient than the Doerbecker with Scalart estimator. Results were more sensitive to the speech processing strategy than to the noise angle. Re-injection of the input signal improved the recognition. In this BCI coding environment, noise reduction algorithms led to an improvement of 20% in phoneme recognition.

The purpose of the present study was to test the behavior of two different generations of cochlear implant systems subjected to a clinical radiotherapy scheme and to determine the maximal acceptable cumulative radiation levels at which the devices show out-of-specification behaviors. Using stereotactic irradiation (Cyberknife, 6 MV photon beam), three Digisonic SP and three Neuro devices were submitted to 5 Gy doses that cumulated to 60 Gy (12 sessions) and 80 Gy (16 sessions), respectively. A follow-up series of irradiation was then applied, in which Digisonic SP devices received two additional fractions of 50 Gy each, cumulating to 160 Gy, and Neuro devices three additional fractions of 20, 40, and 150 Gy, cumulating to 290 Gy. Output current values were monitored during the treatment. At clinical doses, with 60 or 80 Gy cumulative radiation exposure, no single measurement showed more than 10% divergence from the reference measure. The cochlear implants tested in this study showed high resistance to clinically relevant cumulative radiation doses and showed no out-of-bounds behavior up to cumulative doses of 140 or 160 Gy. These observations suggest that cochlear implant users can undergo radiotherapy up to cumulative doses well above those currently used in clinical situations without risk of failure.

A new type of miniaturized implants for local controlled drug delivery to the inner ear is proposed: Hybrid Ear Cubes. They are composed of two main parts: (i) a cylinder, which is placed into a tiny hole (0.4 mm) drilled into (or close to) the oval (or round) window, and (ii) a cuboid, which is placed into the middle ear. The drug is released at a pre-programmed rate into the perilymph: (i) via the cylindrical part of the implant, which is in direct contact with this liquid, and (ii) via diffusion from the cuboid through the oval/round window. Importantly, the cylindrical part assures a reliable fixation of the drug delivery system at the site of administration. Furthermore, the cuboid provides a relatively "large" drug reservoir, without expulsing perilymph from the cochlea. The required surgery is minimized compared to the placement of an intracochlear implant. In contrast to previously proposed Ear Cubes, which are mono-block systems, Hybrid Ear Cubes consist of two halves, which can: (i) be loaded with different drugs, (ii) be loaded with the same drug at different concentrations, and/or (iii) be based on two different matrix formers. This offers a substantially increased formulation flexibility. Different types of silicone-based Hybrid Ear Cubes were prepared, loaded with 10% dexamethasone in one half and 0-60% dexamethasone in the other half. Importantly, tiny drug crystals were homogeneously distributed throughout the respective implant halves. The observed drug release rates were very low (e.g.,0.5% after 2 months), which can be attributed to the type of drug and silicone as well as to the very small surface area exposed to the release medium. Importantly, no noteworthy implant swelling was observed.

International audience; 1 The importance of spectro-temporal modulation cues in conveying tonal information for 2 lexical tones was assessed in native-Mandarin and native-French adult listeners using a 3 lexical-tone discrimination task. The fundamental frequency (F0) of Thai tones was either 4 degraded using an 8-band vocoder that reduced fine spectral details and frequency-modulation 5 cues, or extracted and used to modulate the F0 of click trains. Mandarin listeners scored lower 6 than French listeners in the discrimination of vocoded lexical tones. For click trains, Mandarin 7 listeners outperformed French listeners. These preliminary results suggest that the perceptual 8 weight of the fine spectro-temporal modulation cues conveying F0 information is enhanced 9 for adults speaking a tonal language.

The aim of this study was to assess dose attenuation by a Digisonic SP cochlear implant (CI) and evaluate its impact on treatment planning. The Digisonic CI was irradiated with 6 MV photons. Overall dose attenuation was assessed with MOSFET dosimeters and Gafchromic films. In addition, we evaluated the attenuation of separate CI components. Dose attenuation was also calculated using different radiation treatment planning systems (TPS) softwares and dose calculation algorithms. The CI was placed on a head phantom. Single-beam and multiple-beam plans were evaluated for dose attenuation using two radiation techniques (Conformal and Stereotactic radiotherapy) and four different algorithms (Clarkson, Point Kernel-Superposition, Ray Tracing and Monte Carlo). MOSFET and Gafchromics film showed maximal 6-7.5% radiation dose attenuation, at the center of the CI. Computerized TPS-based dose attenuation by the implant was 4-8.1%, using a single ipsilateral field. No clinically meaningful dose attenuation was found in multiple field plans owing to the contribution of various beam paths with only a couple going through the implant using either conventional conformal or stereotactic treatment plans. Dose attenuation induced by a Digisonic SP CI is about 6%, for single 6 MV photon field. This dose reduction is unlikely to be clinically significant, as single-field radiotherapy plans to this anatomic region are uncommon.

Cochlear implant (CI) provides good auditory performances in quiet, but recognition in noisy environments is still a challenge for CI users. Bilateral hearing can improve speech perception; it has been shown with normal hearing aids, but how source localization is affected is still an open question. In this study source localization is studied in the case of a binaural cochlear implant coding. Signal was received on the two ears and then processed using the classical noise reduction algorithm, suggested by Doerbecker and based on the spectral properties of the signal. Two correction strategies, Ephreim & Malah and Scalart, have been inserted in the processing chain. Tests were conducted, “in simulation” with 20 normal hearing listeners who received a cochlear implant coded signal. An analytic interpretation of the results offers a frame to quantify the different contributions. Results show that the Doerbecker’s algorithm affects the source localization. This effect was lowered when a percentage of the input signal was re-injected into the system. Both correction strategies were equivalent.

This study aimed to assess whether the capacity of cochlear implant (CI) users to identify speech is determined by their capacity to perceive slow (20 Hz) temporal modulations.This was achieved by studying the correlation between (1) phoneme identification in quiet and in a steady-state or fluctuating (8 Hz) noises, and (2) amplitude-modulation detection thresholds (MDTs) at 8 Hz (i.e. slow temporal modulations).Twenty-one CI users, unilaterally implanted with the same device, were tested in free field with their everyday clinical processor.Extensive variability across subjects was observed for both phoneme identification and MDTs. Vowel and consonant identification scores in quiet were significantly correlated with MDTs at 8 Hz (r = - 0.47 for consonants, r = - 0.44 for vowels; p0.05). When the masker was a steady-state noise, only consonant identification scores tended to correlate with MDTs at 8 Hz (r = - 0.4; p = 0.07). When the masker was a fluctuating noise, consonant and vowel identification scores were not significantly correlated with MDTs at 8 Hz.Sensitivity to slow amplitude modulations is correlated with vowel and consonant perception in CI users. However, reduced sensitivity to slow modulations does not entirely explain the limited capacity of CI recipients to understand speech in noise.

International audience; The aim of this study is to define an automated and reproducible framework for cochlear anatomical analysis from high-resolution segmented images and to provide a comprehensive and objective shape variability study suitable for cochlear implant design and surgery planning. For the scala tympani (ST), the scala vestibuli (SV) and the whole cochlea, the variability of the arc lengths and the radial and longitudinal components of the lateral, central and modiolar paths are studied. The robustness of the automated cochlear coordinate system estimation is validated with synthetic and real data. Cochlear cross-sections are statistically analyzed using area, height and width measurements. The cross-section tilt angle is objectively measured and this data documents a significant feature for occurrence of surgical trauma.

International audience; Cochlear implants (CI) are used to treat severe hearing loss by surgically inserting an electrode array into the cochlea. Since current electrodes are designed with various insertion depth, ENT surgeons must choose the implant that will maximise the insertion depth without causing any trauma based on preoperative CT images. In this paper, we propose a novel framework for estimating the insertion depth and its uncertainty from segmented CT images based on a new parametric shape model. Our method relies on the posterior probability estimation of the model parameters using stochastic sampling and a careful evaluation of the model complexity compared to CT and µCT images. The results indicate that preoperative CT images can be used by ENT surgeons to safely select patient-specific cochlear implants.

Recent studies suggest that normal-hearing listeners maintain robust speech intelligibility despite severe degradations of amplitude-modulation (AM) cues, by using temporal-envelope information recovered from broadband frequency-modulation (FM) speech cues at the output of cochlear filters. This study aimed to assess whether cochlear damage affects this capacity to reconstruct temporal-envelope information from FM. This was achieved by measuring the ability of 40 normal-hearing listeners and 41 listeners with mild-to-moderate hearing loss to identify syllables processed to degrade AM cues while leaving FM cues intact within three broad frequency bands spanning the range 65–3,645 Hz. Stimuli were presented at 65 dB SPL for both normal-hearing listeners and hearing-impaired listeners. They were presented as such or amplified using a modified half-gain rule for hearing-impaired listeners. Hearing-impaired listeners showed significantly poorer identification scores than normal-hearing listeners at both presentation levels. However, the deficit shown by hearing-impaired listeners for amplified stimuli was relatively modest. Overall, hearing-impaired data and the results of a simulation study were consistent with a poorer-than-normal ability to reconstruct temporal-envelope information resulting from a broadening of cochlear filters by a factor ranging from 2 to 4. These results suggest that mild-to-moderate cochlear hearing loss has only a modest detrimental effect on peripheral, temporal-envelope reconstruction mechanisms.

Léger et al. [J. Acoust. Soc. Am. 131, 1502-1514 (2012)] reported deficits in the identification of consonants in noise by hearing-impaired listeners using stimuli filtered into low- or mid-frequency regions in which audiometric thresholds were normal or near-normal. The deficits could not be fully explained in terms of reduced audibility or temporal-envelope processing. However, previous studies indicate that the listeners may have had reduced frequency selectivity, with auditory filters broadened by a factor of about 1.3, despite having normal or near-normal audiometric thresholds in the tested regions. The present study aimed to determine whether the speech-perception deficits could be explained by such a small reduction of frequency selectivity. Consonant identification was measured for normal-hearing listeners in quiet and in unmodulated and modulated noises using the same method as Léger et al. The signal-to-noise ratio was set to -3 dB for the masked conditions. Various amounts of reduced frequency selectivity were simulated using a spectral-smearing algorithm. Performance was reduced only for spectral-smearing factors greater than 1.7. For all conditions, identification scores for hearing-impaired listeners could not be explained by a mild reduction of frequency selectivity.

A simplified mathematical theory is presented allowing for in silico simulation of the effects of key parameters of miniaturized implants (size and composition) on the resulting drug release kinetics. Such devices offer a great potential, especially for local drug treatments, e.g. of the inner ear. However, the preparation and characterization of these systems is highly challenging, due to the small system dimensions. The presented mathematical theory is based on Fick's second law of diffusion. Importantly, theoretical predictions do not require the knowledge of many system-specific parameters: Only the "apparent" diffusion coefficient of the drug within the implant matrix is needed. This parameter can be easily determined via drug release measurements from thin, macroscopic films. The validity of the theoretical model predictions was evaluated by comparison with experimental results obtained with a cochlear implant. The latter consisted of miniaturized electrodes, which were embedded in a silicone matrix loaded with various amounts of dexamethasone. Importantly, independent experimental results confirmed the theoretical predictions. Thus, the presented simplified theory can help to significantly speed up the optimization of this type of controlled drug delivery systems, especially if long release periods are targeted (e.g., several months or years). Straightforward experiments with thin, macroscopic films and computer simulations can allow for rapid identification of optimal system design.

Consonant identification was measured for normal-hearing listeners using nonsense Vowel-Consonant-Vowel (VCV) stimuli embedded in a steady-state or fluctuating noise masker and presented at a fixed, global signal-to-noise ratio (SNR) yielding 50% correct identification for steady noise. Fluctuations in the masker were obtained by applying sinusoidal amplitude modulation to the noise. VCVs and noise were either left intact (unprocessed) or degraded by removing temporal fine structure (TFS) cues within 32 frequency bands with bandwidths chosen to match psychophysical estimates of auditory filter bandwidth. For unprocessed stimuli, masking release (MR) - that is better identification in fluctuating than in steady noise - was observed at both masker frequencies tested (8 and 32 Hz). MR increased monotonically and similarly with the modulation depth m of the noise masker (from m=12.5% to 100%) at both masker modulation frequencies. The effect of masker modulation depth on release was different for reception of place of articulation and reception of voicing and manner. The effect of masker modulation depth on release was also significantly affected when TFS cues were removed. These data provide evidence that listeners "glimpse" into noise valleys where maximum SNR may be as low as -5 dB (m=12.5%), and suggest a specific contribution of TFS cues to the glimpsing process.

International audience; The volume of the cochlea is a key parameter for electrode-array design. Indeed, it constrains the diameter of the electrode-array for low-traumatic positioning in the scala timpani. The present report shows a model of scala timpani volume extraction from temporal bones images in order to estimate a maximum diameter of an electrode-array. Nine temporal bones were used, and passed to high-resolution computed tomography scan. Using image-processing techniques, scala timpani were extracted from images, and cross-section areas were estimated along cochlear turns. Cochlear implant electrode-array was fitted in these cross-sections. Results show that the electrode-array diameter is small enough to fit in the scala timpani, however the diameter is restricted at the apical part.

Technological advances in the domain of digital signal processing adapted to cochlear implants (CI) are partially responsible for the ever-improving outcomes observed with this neural prosthesis. The goal of the present study was to evaluate audiometric outcomes with a new signal processing strategy implemented in Oticon Medical-Neurelec cochlear implant systems, the xDP strategy. The core of this approach is a preset-based back-end output compression system, modulating a multi-channel transfer function depending on the intensity and information content of input sounds. Twenty adult CI patients, matched for age and CI experience, were included in this study. Pure-tone thresholds and vocal audiometry scores were measured with their former signal processing strategy and with xDP. Speech perception was assessed using dissyllabic words presented in quiet, at different intensity levels: 40, 55, 70, and 85 dB SPL, and in a cocktail party noise at a signal-to-noise ratio of +10 dB. Results with the xDP strategy showed, as awaited, no major modification of pure-tone thresholds. A global increase of speech perception scores was observed after a 1-month habituation period, with significant improvements for speech perception in quiet for moderate (55 dB SPL), loud speech sounds (85 dB SPL), and speech-in-noise comprehension. Subjective signal quality assessment showed a preference for Crystalis(xDP) over the former strategy. These results allow the quantification of improvements provided by the xDP signal processing strategy.

Communication and warning are two basic tasks devoted to the auditory system and it is worth to see them together when assistive techniques are considered for hearing rehabilitation. French phonemes recognition in noisy conditions and acoustic source localization, in the case of a cochlear implant (CI) coding simulation, are compared in this chapter. Three binaural noise reduction systems have been considered: the Beamformer algorithm, the Doerbecker's processing combined with the Ephraim & Malah's noise estimator or with the Scalart's noise reduction strategy. This study has been conducted with twenty normally hearing subjects. Results show that the Beamformer algorithm and the Doerbecker's processing improved the phoneme recognition scores. The best results in recognition were obtained using the Beamformer algorithm. On the contrary, the beamformer algorithm and the Doerbecker's processing lowered the source localization. A small reinjection of the signal (20%) was profitable to the Beamformer algorithm; this improvement was not seen with the Doerbecker's processing.