The Dependency of Cochlear Lateral Wall Measurements on Observer and Imaging Type.

HYPOTHESIS: Assessment techniques for the cochlear spatial lateral wall are associated with inter-rater variability, but derived clinical recommendations nonetheless offer value for individualized electrode selection. BACKGROUND: Anatomical variations influence the location of cochlear implant electrodes inside the cochlea. Preoperative planning allows individualization of the electrode based on characterization of the bony lateral wall. METHODS: The study used publicly available digitized temporal bones based on microslicing and computed tomography. Four experienced observers assessed the lateral wall applying manual tracing, linear regression scaling and elliptic-circular approximation methods in all modalities. Radial and height differences were computed in 90-degree steps from the round window center to the apex. Total length, total angular length, and tonotopic frequencies were computed for each reconstruction. RESULTS: Differences were found most pronounced between assessment methods in vertical direction across observers and imaging modalities. One of the five anatomies was consistently found to be of shorter cochlear duct length with estimation techniques yielding more conservative results compared with manual tracings. CONCLUSIONS: Assessment techniques for the bony lateral wall yield method, observer, and image modality related deviations. Automation of the anatomical characterization may offer potential in minimizing inaccuracies. Nonetheless, observers were consistently able to detect a smaller inner ear demonstrating the ability of current methods to contribute to an optimized choice of electrodes based on individual patient anatomy.

Cochlear coverage with lateral wall cochlear implant electrode arrays affects post-operative speech recognition.

OBJECTIVES: The goal was to investigate the relationship between the insertion angle/cochlear coverage of cochlear implant electrode arrays and post-operative speech recognition scores in a large cohort of patients implanted with lateral wall electrode arrays. METHODS: Pre- and post-operative cone beam computed tomography scans of 154 ears implanted with lateral wall electrode arrays were evaluated. Traces of lateral wall and electrode arrays were combined into a virtual reconstruction of the implanted cochlea. This reconstruction was used to measure insertion angles and proportional cochlear coverage. Word recognition scores and sentence recognition scores measured 12 months after implantation using electric-only stimulation were used to examine the relationship between cochlear coverage/insertion angle and implantation outcomes. RESULTS: Post-operative word recognition scores and the difference between post- and pre-operative word recognition scores were positively correlated with both cochlear coverage and insertion angle, however sentence recognition scores were not. A group-wise comparison of word recognition scores revealed that patients with cochlear coverage below 70% performed significantly worse than patients with coverage between 79%-82% (p = 0.003). Performance of patients with coverage above 82% was on average poorer than between 79%-82, although this finding was not statistically significant (p = 0.84). Dividing the cohort into groups based on insertion angle quadrants revealed that word recognition scores were highest above 450° insertion angle, sentence recognition scores were highest between 450° and 630° and the difference between pre- and post-operative word recognition scores was largest between 540° and 630°, however none of these differences reached statistical significance. CONCLUSIONS: The results of this study show that cochlear coverage has an effect on post-operative word recognition abilities and the benefit patients receive from their implant. Generally, higher coverage led to better outcomes, however there were results indicating that insertion past 82% cochlear coverage may not provide an additional benefit for word recognition. These findings can be useful for choosing the optimal electrode array and thereby improving cochlear implantation outcomes on a patient-individual basis.

Image Processing of Conventional Computer Tomography Images for Segmentation of the Human Cochlea.

Against the background of increasing numbers of indications for Cochlea implants (CIs), there is an increasing need for a CI outcome prediction tool to assist the process of deciding on the best possible treatment solution for each individual patient prior to intervention. The hearing outcome depends on several features in cochlear structure, the influence of which is not entirely known as yet. In preparation for surgical planning a preoperative CT scan is recorded. The overall goal is the feature extraction and prediction of the hearing outcome only based on this conventional CT data. Therefore, the aim of our research work for this paper is the preprocessing of the conventional CT data and a following segmentation of the human cochlea. The great challenge is the very small size of the cochlea in combination with a fairly bad resolution. For a better distinction between cochlea and surrounding tissue, the data has to be rotated in a way the typical cochlea shape is observable. Afterwards, a segmentation can be performed which enables a feature detection. We can show the effectiveness of our method compared to results in literature which were based on CT data with a much higher resolution. A further study with a much larger amount of data is planned.

Impedance Values Do Not Correlate With Speech Understanding in Cochlear Implant Recipients.

OBJECTIVE: To evaluate a possible correlation between impedance values and speech perception after cochlear implantation. STUDY DESIGN: Retrospective chart review. SETTING: Tertiary referral center. PATIENTS AND INTERVENTION: All patients implanted with a MedEl Flex28 device in our department with complete audiometric data (Freiburger monosyllabic testing at 65 dB, Hochmaier-Schulz-Moser testing in quiet and in 10 dB noise) and impedance measurements at the 1-year refitting appointment were enrolled in this study. Further inclusion criteria were age > 17 years, native speakers, and no use of electric-acoustic-stimulation. MAIN OUTCOME MEASURES: Mean values for impedances were calculated over all electrode contacts and separately for basal, medial, and apical regions. These data were correlated statistically (Pearson's correlation) with speech testing results. Furthermore, groups of patients with extreme values were built and compared against each other and against the rest of the collective. RESULTS: Impedance values did not correlate significantly with speech performance in any of the audiometric tests neither for all electrode contacts nor for specific clusters of contacts. Patients with the lowest impedances did not perform statistically different than patients with the highest impedances in any condition. CONCLUSION: To our knowledge, this is the first data on a possible correlation between impedances and speech perception. The extent of the impedances as a benchmark for a good performance in speech discrimination tests could not be verified. Further prospective studies, possibly with more precise diagnostic tools, should be carried out to define the value of impedance measurements for cochlear implantation provision.

Patient specific selection of lateral wall cochlear implant electrodes based on anatomical indication ranges.

OBJECTIVES: The aim of this study was to identify anatomical indication ranges for different lateral wall cochlear implant electrodes to support surgeons in the preoperative preparation. METHODS: 272 patients who were implanted with a FLEX20, FLEX24, FLEX28, or a custom-made device (CMD) were included in this study. The cochlear duct length (CDL) and basal cochlear diameter (length A) were measured within preoperative imaging data. The parameter A was then employed to additionally compute CDL estimates using literature approaches. Moreover, the inserted electrode length (IEL) and insertion angle (IA) were measured in postoperative CT data. By combining the preoperative measurements with the IA data, the covered cochlea length (CCL) and relative cochlear coverage (CC) were determined for each cochlea. RESULTS: The measurements of the CDL show comparable results to previous studies. While CDL measurements and estimations cover similar ranges overall, severe deviations occur in individual cases. The electrode specific IEL and CCL are fairly consistent and increase with longer electrodes, but relatively wide ranges of electrode specific CC values were found due to the additional dependence on the respective CDL. Using the correlation of IEL and CCL across electrode arrays, CDL ranges for selected arrays were developed (FLEX24: 31.3-34.4, FLEX28: 36.2-40.1, FLEXSoft: 40.6-44.9). CONCLUSIONS: Our analysis shows that electrode specific CC varies due to the CDL variation. Preoperative measurement of the CDL allows for an individualized implant length selection yielding optimized stimulation and a reduced risk of intraoperative trauma. The CDL, as derived from preoperative CT imaging studies, can help the implant surgeon select the appropriate electrode array to maximize the patient's outcomes.

A crystalline and 3D periodically ordered mesoporous quaternary semiconductor for photocatalytic hydrogen generation.

We have prepared the first crystalline and 3D periodically ordered mesoporous quaternary semiconductor photocatalyst in an evaporation-induced self-assembly assisted soft-templating process. Using lab synthesized triblock-terpolymer poly(isoprene-b-styrene-b-ethylene oxide) (ISO) a highly ordered 3D interconnected alternating gyroid morphology was achieved exhibiting near and long-range order, as evidenced by small angle X-ray scattering (SAXS) and electron microscopy (TEM/SEM). Moreover, we reveal the formation process on the phase-pure construction of the material's pore-walls with its high crystallinity, which proceeds along a highly stable W5+ compound, by both in situ and ex situ analyses, including X-ray powder diffraction (XRPD), Fourier transform infrared spectroscopy (FTIR) and electron paramagnetic resonance (EPR). The resulting photocatalyst CsTaWO6 with its optimum balance between surface area and ordered mesoporosity ultimately shows superior hydrogen evolution rates over its non-ordered reference in photocatalytic hydrogen production. This work will help to advance new self-assembly preparation pathways towards multi-element multifunctional compounds for different applications, including improved battery and sensor electrode materials.

Bilateral Versus Unilateral Cochlear Implantation in Adult Listeners: Speech-On-Speech Masking and Multitalker Localization.

Binaural hearing helps normal-hearing listeners localize sound sources and understand speech in noise. However, it is not fully understood how far this is the case for bilateral cochlear implant (CI) users. To determine the potential benefits of bilateral over unilateral CIs, speech comprehension thresholds (SCTs) were measured in seven Japanese bilateral CI recipients using Helen test sentences (translated into Japanese) in a two-talker speech interferer presented from the front (co-located with the target speech), ipsilateral to the first-implanted ear (at +90° or -90°), and spatially symmetric at ±90°. Spatial release from masking was calculated as the difference between co-located and spatially separated SCTs. Localization was assessed in the horizontal plane by presenting either male or female speech or both simultaneously. All measurements were performed bilaterally and unilaterally (with the first implanted ear) inside a loudspeaker array. Both SCTs and spatial release from masking were improved with bilateral CIs, demonstrating mean bilateral benefits of 7.5 dB in spatially asymmetric and 3 dB in spatially symmetric speech mixture. Localization performance varied strongly between subjects but was clearly improved with bilateral over unilateral CIs with the mean localization error reduced by 27°. Surprisingly, adding a second talker had only a negligible effect on localization.

A Method for Assessing Auditory Spatial Analysis in Reverberant Multitalker Environments.

BACKGROUND: Deficits in spatial hearing can have a negative impact on listeners' ability to orient in their environment and follow conversations in noisy backgrounds and may exacerbate the experience of hearing loss as a handicap. However, there are no good tools available for reliably capturing the spatial hearing abilities of listeners in complex acoustic environments containing multiple sounds of interest. PURPOSE: The purpose of this study was to explore a new method to measure auditory spatial analysis in a reverberant multitalker scenario. RESEARCH DESIGN: This study was a descriptive case control study. STUDY SAMPLE: Ten listeners with normal hearing (NH) aged 20-31 yr and 16 listeners with hearing impairment (HI) aged 52-85 yr participated in the study. The latter group had symmetrical sensorineural hearing losses with a four-frequency average hearing loss of 29.7 dB HL. DATA COLLECTION AND ANALYSIS: A large reverberant room was simulated using a loudspeaker array in an anechoic chamber. In this simulated room, 96 scenes comprising between one and six concurrent talkers at different locations were generated. Listeners were presented with 45-sec samples of each scene, and were required to count, locate, and identify the gender of all talkers, using a graphical user interface on an iPad. Performance was evaluated in terms of correctly counting the sources and accuracy in localizing their direction. RESULTS: Listeners with NH were able to reliably analyze scenes with up to four simultaneous talkers, while most listeners with hearing loss demonstrated errors even with two talkers at a time. Localization performance decreased in both groups with increasing number of talkers and was significantly poorer in listeners with HI. Overall performance was significantly correlated with hearing loss. CONCLUSIONS: This new method appears to be useful for estimating spatial abilities in realistic multitalker scenes. The method is sensitive to the number of sources in the scene, and to effects of sensorineural hearing loss. Further work will be needed to compare this method to more traditional single-source localization tests.

Auditory masking of speech in reverberant multi-talker environments.

Auditory localization research needs to be performed in more realistic testing environments to better capture the real-world abilities of listeners and their hearing devices. However, there are significant challenges involved in controlling the audibility of relevant target signals in realistic environments. To understand the important aspects influencing target detection in more complex environments, a reverberant room with a multi-talker background was simulated and presented to the listener in a loudspeaker-based virtual sound environment. Masked thresholds of a short speech stimulus were measured adaptively for multiple target source locations in this scenario. It was found that both distance and azimuth of the target source have a strong influence on the masked threshold. Subsequently, a functional model was applied to analyze the factors influencing target detectability. The model is comprised of an auditory front-end that generates an internal representation of the stimuli in both ears, followed by a decision device combining d' information across time, frequency and both ears. The model predictions of the masked thresholds were overall in very good agreement with the experimental results. An analysis of the model processes showed that head shadow effects, signal spectrum, and reverberation have a strong impact on target audibility in the given scenario.