The authors would like to thank Dr. Nikola Ivanovic for reviewing the protocol and Rahma Sweedy for doing the statistical analysis.

This study received approval from the principal Institutional Review Board (E-21-5737) and was conducted following the ethical principles outlined in the Declaration of Helsinki. Data were retrospectively collected from medical records at our tertiary CI center. Due to the anonymized nature of data analysis, informed consent was not required. The study included 20 ears from patients across various age groups.
Inclusion criteria were as follows: patients with normal inner ear anatomy who received CI between 2020 and 2023, underwent both pre-&#160;and post-operative CT scans, and were implanted with CI devices from the same manufacturer, compatible with the surgical planning software used. Temporal bone CT scans are routinely performed as part of the pre-operative assessment for cochlear implant patients at our center, while post-operative CT scans are only done when medically necessary to minimize radiation exposure. Exclusion criteria included CI patients who had undergone revision surgeries or had cochlear ossification, cochlear otosclerosis, or temporal bone fractures involving the otic capsule. Details of the equipment and software are provided in the Table of Materials.
1. Uploading and measuring cochlear parameters
NOTE: The measurement protocol employed in this study comprised a series of sequential steps designed to assess the effectiveness of the pre-and post-operative CT image fusion technique in evaluating electrode location in CI recipients (Figure 1).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/67062/67062fig01.jpg" /> 
Figure 1: Measurement protocol comparison. This figure illustrates the protocol for measuring cochlear parameters using the Automatic Fusion method compared to the Manual method. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/67062/67062fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<ol>
	<li>Press the Import button in the software&#39;s Data Management module to upload the post-operative and pre-operative CT images, and select the DICOM files.</li>
	<li>Manually define the center of&#160;modiolus, round window, and cochlear metrics, including the A-value (cochlear diameter), B-value (cochlear width), and H-value (cochlear height) in the 3D Ear-Cochlea module4 (Figure 2).</li>
	<li>Calculate the Cochlear Duct Length (CDL) using the A and B values, applying the Alexiades method to the Elliptic-Circular Approximation (ECA)2,4. 
	NOTE: The detailed steps of the post-operative analysis are described by Canfarotta et al.21. These measurements provide anatomical landmarks for CDL estimation.</li>
</ol>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/67062/67062fig02.jpg" /> 
Figure 2: Manual measurement of post-operative A, B, and H values. Post-operative images are imported into the software, and the A-value (marked in green), B-value (marked in blue), and H-value (marked in red) are manually measured. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/67062/67062fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
2. Electrode contact identification and AID/CF calculation
<ol>
	<li>Open the Implant Assessment module. The software will automatically identify the twelve electrode contact points on the post-operative CT images.</li>
	<li>Manually adjust the detected contact points, if necessary, before confirming their positions.</li>
	<li>Allow the software to use these points, along with the pre-defined cochlear metrics, to automatically calculate the Angular Insertion Depth (based on Escude et al.22) and the Characteristic Frequency (based on Greenwood et al.23) for each contact (see Figure 3). 
	NOTE: This manual approach is considered the standard method for measuring AID and CF, and it is referred to as &#34;Manual&#34; in this study.</li>
</ol>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/67062/67062fig03.jpg" /> 
Figure 3: Identification of electrode contacts. This figure shows the identification of the twelve electrode contacts from the post-operative CT images. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/67062/67062fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
3. Image fusion
<ol>
	<li>Press the Add icon in the user interface to import the pre-operative CT images into the Image Fusion panel.</li>
	<li>Allow the software to automatically begin registering the pre-operative CT images with the pre-uploaded post-operative CT images using the automatic fusion feature, which applies a mutual information algorithm.</li>
	<li>Access the Manual Alignment feature in the pre-operative image menu if manual adjustments to the fusion are needed. This fusion process enhances visualization and allows a more comprehensive assessment of cochlear anatomy and electrode placement with fewer artifacts. The fusion aims to improve visualization for better evaluation (see Figure 4).</li>
</ol>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/67062/67062fig04.jpg" /> 
Figure 4: Fusion of pre-&#160;and post-operative CT images. Pre-operative CT images are imported into the software and fused with post-operative CT images. The overlay is displayed in olive color, with the electrodes highlighted in bright blue. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/67062/67062fig04large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
4. Automatic cochlear parameter measurement on pre-operative image
<ol>
	<li>Re-measure the cochlear parameters on the newly imported pre-operative image within the 3D - Cochlea module.</li>
	<li>Select the Automatic option in the module menu to execute automatic cochlear parameter measurements. This feature is available only for pre-operative images without implant electrodes, as no metal artifacts exist.</li>
	<li>Use the automatic algorithm to reconstruct the inner ear anatomy in 3D. The 3D model will serve as the base for the automatic cochlear parameter measurements as described by Abari et al.24. 
	NOTE: The 3D reconstruction aids in precise measurement of cochlear parameters (see Figure 5).</li>
</ol>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/67062/67062fig05.jpg" /> 
Figure 5: Automated measurement of cochlear parameters. From the fused images, the software automatically measures the main cochlear parameters (indicated by green, blue, and red points), performs 3D reconstruction (cochlea in orange, internal auditory canal in green, and semicircular canals in brown), and updates the information regarding the electrode contacts. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/67062/67062fig05large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
5. Updating electrode contact points with new cochlear parameters
<ol>
	<li>Confirm the new Cochlear Duct Length (CDL) measurements obtained from the pre-operative images.</li>
	<li>Allow the previously identified electrode contact points from the post-operative images to automatically update with the new cochlear parameter information, defining the &#34;Automatic Fusion&#34; approach.</li>
	<li>Perform calculations based on the fused images (pre-operative and post-operative) for Angular Insertion Depth (AID) and Characteristic Frequency (CF), which are important for confirming electrode array placement, cochlear coverage, and building the Anatomy-Based Fitting (ABF) map (see Figure 5). 
	NOTE: AID and CF are critical for confirming electrode positioning and cochlear coverage in cochlear implant (CI) practice (see Figure 6).</li>
</ol>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/67062/67062fig06.jpg" /> 
Figure 6: Automatic definition of AID and CF. This figure depicts the automatic definition of the AID (Acoustic Impedance Distribution) and CF (Center Frequency) for each individual electrode contact based on the fused images. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/67062/67062fig06large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
6. Calculating the mean angular error and frequency error
<ol>
	<li>Calculate the mean angular error between the Manual and Automatic Fusion methods for each electrode contact.</li>
	<li>Calculate the frequency error in semitones between both methods (Manual and Automatic Fusion) for each electrode contact.</li>
	<li>Use these calculations to provide quantitative indicators of the difference and accuracy between the two methods. Note that semitones are the smallest musical intervals commonly used in Western music25.</li>
</ol>
7. Statistical analysis
<ol>
	<li>Feed the manually calculated cochlear parameters, Angular Insertion Depth (AID), and Characteristic Frequency (CF) from post-operative CT imaging, along with the automatically fused calculated data from the pre-and post-operative CT image fusion technique for each electrode contact, into statistical analysis software (R software).</li>
	<li>Use means and standard deviations for descriptive statistics of quantitative variables, while applying counts and percentages for categorical variables.</li>
	<li>Conduct a comparative analysis between the manually measured AID and frequencies and the automatically fused measurements using a pairwise Bonferroni-adjusted paired t-test or Wilcoxon signed rank test, depending on the normality assumption tested using the Shapiro-Wilk test. 
	NOTE: Assume that all comparisons have clinically relevant standardized effect sizes (Cohen&#39;s d)26. Consider a statistically significant P value to be less than 0.05.</li>
</ol>

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Yassin Abdelsamad and Tahir Sharif work for MED-EL with scientific roles only. The authors have no financial interests in the products described in this manuscript and have nothing else to disclose.

The findings of the present study revealed comparable measurements between Manual and Automatic Fusion methods for most cochlear parameters and frequencies. While Manual measurements exhibited marginally higher values for certain parameters, such as the B value and CDL, no clinically significant differences were observed overall. This discrepancy could be attributed to artifacts in the post-operative CT, which may affect measurement accuracy. Furthermore, this study builds upon prior research by specifically evaluating AID27, providing valuable insights into the consistency of fusion-based assessments.
A prior study by Paouris et al.28 demonstrated that the Automated method provides reliable measurements with reduced execution time, proving advantageous for efficient pre-operative planning in otological surgeries. The study by Paouris et al.28 focused on pre-operative CT scans, which ensure faster and more consistent CDL measurements, exhibiting high agreement with manual measurements. Another study by Al-Dhamari et al. concluded that the Automated method may yield more accurate cochlear measurements than those produced manually29. Thus, it offers a feasible option with the potential for routine clinical application in cochlear implantation procedures. Cochlear measurements represent the first critical step in the current measurement protocol, as they directly influence the angle and frequency assignment. Recent research indicates that manual cochlear measurements conducted by various experienced users using the otological software may exhibit minor discrepancies while remaining reliable21,27. Another investigation comparing manual and automatic measurements revealed significant differences between the automatic CDL measurements and the CDLs calculated based on manual A-value measurements30. In a previous study, the otological software version 3.0 was compared to preclinical 3D reconstruction software and the established A-value method.
The findings indicated superior accuracy in measurements obtained from the software, with cochlear width (B-value) exerting a stronger influence on CDL determination compared to diameter31. The definition of AID is another critical point in the workflow. While discrepancies were noted in AID measurements at select electrode contacts, the clinical significance of these differences remains to be fully elucidated. Although most AID and frequency measurements showed no significant differences between Manual and Automatic Fusion methods, slight discrepancies were observed in specific electrode contacts.
Finally, the image fusion step is the last critical&#160;in the chain, as the angle of the electrode contact point is calculated based on the cochlear coordinates defined in the first step. Overall, these results contribute to the ongoing refinement of imaging techniques and measurement methodologies in cochlear implantation, with implications for optimizing patient outcomes and enhancing surgical planning processes. Integrating pre-&#160;and post-operative scan information may help assess critical parameters such as AID and CF due to their clear and artifact-free images. Furthermore, the adoption of Anatomy-based Fitting (ABF) in cochlear implant programming can capitalize on these measurements to optimize device fitting and enhance patient performance.
Presently, relying on post-operative scans with artifacts or low resolution often necessitates prolonged measurement times, requires experienced personnel, and may result in inaccurate readings, which impact frequency allocation and contribute to frequency-to-place mismatch. Therefore, pre-and post-operative CT image fusion might streamline the measurement process. This approach confirms the proper placement of the electrode array post-operatively and instills confidence in building the Anatomy-based Fitting (ABF), ultimately optimizing patient outcomes.
It takes 5-10 minutes&#160;to measure cochlear parameters manually, which is the initial step in the Manual process28. Combined with the image fusion stage in the proposed Automatic Fusion technique, this phase would run automatically and take about 2 minutes. The electrode contacts detection phase, the last step in both the Manual and Automatic Fusion techniques, is automated in both processes. Therefore, there is no time savings in this phase. Thus, the proposed Automatic Fusion method could reduce the total time from nearly 11 minutes using the Manual method to approximately 3 minutes.
Nonetheless, it is essential to acknowledge the current study&#39;s limitations, including its retrospective nature and relatively small sample size. Since post-operative CT scans are performed only when medically necessary to avoid unnecessary radiation exposure, a limited number of participants were included. Although the small sample size may increase the probability of type II error (false negative results), additional statistical considerations were made, including effect size estimation (Cohen&#39;s d), which represents the standardized differences between the two approaches instead of relying solely on p-value interpretation. The very small estimated effect sizes confirmed the results and helped mitigate the impact of this limitation on the study findings. Future research should be conducted to validate the current findings in larger cohorts. Overall, the present study contributes to the growing body of evidence supporting the use of image fusion technology in cochlear implant field, offering another tool for further advancements in the Anatomy-based Fitting (ABF) area.
In summary, the proposed Automatic Fusion method could be utilized to measure cochlear parameters, angular insertion depth, and center frequency. Manual measurements yielded slightly different values for certain parameters, such as the B value and CDL, compared to Automatic Fusion measurements. The Automatic Fusion method outperforms the Manual method as it is artifact-free, much easier, does not require experienced personnel, and takes less time. These findings indicate that Automatic image fusion techniques did not show a statistical difference compared to Manual methods in AID and frequency measurements. This article is the first to utilize OTOPLAN pre- and post-operative CT image fusion features as a potential tool for building ABF maps for cochlear implant recipients.

Cochlear implant (CI) surgery is a transformative treatment for individuals with severe-to-profound sensorineural hearing loss, offering substantial improvements in auditory function and quality of life1. A critical factor for the success of CI surgery is the accurate placement of the electrode array within the correct cochlear compartment, specifically the scala tympani, as optimal electrode positioning, is consistently linked to superior hearing outcomes2. Thus, careful pre-operative planning and assessment of cochlear anatomy are essential to ensure the electrode array is positioned appropriately. Ensuring that the electrode array is fully inserted within the scala tympani is crucial for maximizing patient benefits and achieving optimal clinical outcomes3.
Pre-operative estimation of the insertion depth angle of CI electrode arrays is considered important for effective surgical planning. This estimation relies significantly on obtaining accurate measurements of key cochlear parameters, such as cochlear duct length (CDL), from pre-operative computed tomography (CT) scans4. These measurements enable essential predictions regarding cochlear coverage and angular insertion depth during CI surgery when the electrode length is known. A major predictor of CDL is the A-value, defined as the distance between the round window and the farthest point on the basal turn. Prior studies have highlighted the crucial role of pre-operative imaging and planning in guiding surgical decisions and optimizing outcomes for CI recipients5.
Pre-operative CT imaging is standard practice in many CI clinics for evaluating inner ear anatomy and cochlear parameters before surgery. Pre-operative CT provides clear, artifact-free images that support effective planning and optimize surgical procedures6. However, pre-operative CT analysis alone has limitations in accurately predicting the actual angular insertion depth (AID) and center frequency (CF) of electrode contacts along the CI electrode array. Consequently, post-operative imaging remains necessary to confirm electrode array positioning, assess any displacement or translocation, and determine the true AID of each contact7.
Post-operative imaging confirms the accuracy of electrode placement and aids in creating individualized fitting maps tailored to each patient&#39;s unique cochlear anatomy. These fitting maps are essential for optimizing auditory performance by ensuring precise stimulation of the auditory nerve fibers. Recent studies have shown that individualized fitting maps, or anatomy-based fitting (ABF), improve speech comprehension in both quiet and noisy environments compared to standard or clinical fitting maps8,9,10,11,12,13. Additionally, recipients tend to prefer ABF maps when their electrode array achieves adequate stimulation of the cochlea&#39;s apical region8. The frequency-to-place mismatch is the discrepancy between the CF of electrode contacts based on their physical location within the cochlea and the default settings4. Mertens et al. reported that the impact of frequency-to-place mismatch decreases with prolonged device use14. Other studies have demonstrated that reducing frequency-to-place mismatch with ABF in CI recipients enhances speech perception in noisy environments without affecting understanding in quiet settings11,13.
Various imaging modalities, including X-ray15,16, cone-beam CT17, and magnetic resonance imaging (MRI)18,19, have been used to evaluate CI recipients. However, CT imaging remains the preferred method due to its high spatial resolution and ability to capture detailed cochlear anatomy. CT imaging allows for precise assessment of inner ear structures, such as the scala tympani and scala vestibuli, facilitating accurate electrode placement.
Despite the many benefits of CT imaging, certain challenges persist, particularly with low-resolution post-operative scans. Metallic electrode contacts can produce image artifacts that obscure adjacent structures, complicating the accurate measurement of critical parameters like AID and CF. Recent studies have shown that fusing pre-&#160;and post-operative CT scans enhances image clarity over standard scans, enabling more accurate assessments and improving electrode location by providing complementary information from both pre-&#160;and post-operative images20.
Currently, post-operative CT image analysis often involves manual measurements using software tools, which require substantial training, are time-intensive, and may be prone to variability and error, limiting their efficiency and broader applicability. There is limited literature on the potential of automated measurements from fused images to address these limitations and provide reliable measurements of AID for electrode contacts. This research aims to evaluate whether the fusion of pre-&#160;and post-operative CT images can effectively assess cochlear characteristics and electrode placement in CI recipients. It further investigates how image fusion could advance anatomy-based fitting (ABF) and enhance measurement accuracy for both angular insertion depth (AID) and center frequency (CF).

<table><tbody><tr><td>CI devices&amp;nbsp;</td><td>MED-EL, Innsbruck, Austria</td><td></td><td></td></tr><tr><td>OTOPLAN software&amp;nbsp;</td><td>CASCINATION, MED-EL, Innsbruck, Austria</td><td>version 4 (3.0.0)&amp;nbsp;</td><td>Otology Planning Software</td></tr><tr><td>R software</td><td>R Foundation for Statistical Computing, Vienna, Austria</td><td>version 4.2.2</td><td>Language and Environment for Statistical Computing</td></tr></tbody></table>

enhancing electrode location assessment in cochlear implantation via computed tomography image fusion

This study aimed to determine whether fusing pre-&#160;and post-operative computed tomography (CT) images could help in assessing electrode placement and center frequency (CF) in cochlear implant (CI) recipients. A secondary objective was to compare automatic fusion with manual methods for measuring cochlear parameters. The study included twenty ears with CIs that underwent both pre-&#160;and post-operative CT scans. Manual measurements of cochlear parameters were initially taken from the post-operative CT images, followed by automatic detection using fused pre-&#160;and post-operative CT images with otological software (OTOPLAN). Angular insertion depth (AID) and CF of each electrode contact were calculated using both methods, and error differences were assessed. The analysis showed significant differences between the two methods for cochlear width (B-value) and cochlear duct length (CDL); however, these differences were not clinically significant. Furthermore, there was no statistically significant difference in cochlear diameter (A-value). The mean differences were 0.04 mm for the A-value, 0.21 mm for the B-value, and 0.73 mm for the CDL. The comparison of AID and CF revealed non-significant differences between manual and automatic fusion methods across all electrode contacts, except for electrode number five. According to this study, fusing pre-&#160;and post-operative CT images can be used to determine electrode positions in CI recipients. Automatic fused images can potentially measure cochlear parameters, AID, and CF with reduced human interference. Therefore, this method may serve as another basis for creating anatomy-based fitting.

This study included 20 ears from CI recipients, with 11 implants on the left side and nine on the right side. The average age of the participants was 13.3 years, comprising 55% female and 45% male. Table 1 presents a comparative analysis of manual versus automatic fusion methods for measuring cochlear parameters, revealing statistically significant differences in certain measurements. Specifically, manual measurements showed a significantly higher B value and cochlear duct length (CDL) compared to automatic fusion measurements (6.9 mm &#177; 0.4 mm and 36.3 mm &#177; 1.8 mm vs. 6.7 mm &#177; 0.4 mm and 35.6 &#177; 1.9 mm, respectively). However, no significant difference was observed in the A value between manual and automatic fusion measurements (9.2 mm &#177; 0.5 mm vs. 9.2 mm &#177; 0.4 mm, respectively; p-value = 0.541), as depicted in Figure 7.
<img alt="Figure 7" class="xfigimg" src="/files/ftp_upload/67062/67062fig07.jpg" /> 
Figure 7: Violin plot of cochlear parameter measurements. A violin plot (including a box plot) compares measured cochlear parameters using the Automatic Fusion and Manual methods. Panel (A) represents the A-value, (B) the B-value, and (C) the Cochlear Duct Length. Significance is indicated as follows: ns (non-significant), *(0.05 &#8805;p&#8805; 0.01), and **(0.01 &#62; p &#8805; 0.001) for pairwise Bonferroni-adjusted paired t-tests. The bars crossing the box plots represent 95% confidence intervals (n = 20). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/67062/67062fig07large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Regarding AID, Table 1 illustrates that the average manual AID values ranged from 544.6 &#177; 88.3 to 36.0 &#177; 25.5 degrees across all electrode contacts. In contrast, automatic fusion measured AID values ranged from 552.9 &#177; 78.1 to 35.7 &#177; 29.6 degrees. The comparative analysis revealed non-significant differences at all electrode contacts, except for the fifth electrode, which showed slight evidence of a significant increase in manually measured AID compared to the corresponding automatic fusion measurement (303.0 &#177; 47.9 vs. 296.5 &#177; 44.8 degrees, respectively; p-value = 0.04). These findings are illustrated in Figure 8 and Figure 9, which show the mean differences between the two methods at all electrode contacts, along with their 95% confidence intervals. Furthermore, the estimated standardized Cohen&#39;s d effect sizes26 for all the investigated mean AID differences indicated a lower than medium effect size for the fifth electrode (d = 0.45), while the remaining electrode contacts showed very small effect sizes ranging from 0.0 to 0.4. The clinical magnitudes of the effect sizes were assessed and interpreted according to Statistical Power Analysis for the Behavioral Sciences by Cohen Jacob26.
<img alt="Figure 8" class="xfigimg" src="/files/ftp_upload/67062/67062fig08.jpg" /> 
Figure 8: Comparison of AID measurements. This figure compares the AID measurements obtained through Automatic Fusion versus Manual methods at all electrode contacts. Significance is indicated as ns (non-significant) and *(0.05 &#8805;p&#8805; 0.01) for pairwise Bonferroni-adjusted paired t-tests or Wilcoxon signed-rank tests (n = 20). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/67062/67062fig08large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 9" class="xfigimg" src="/files/ftp_upload/67062/67062fig09.jpg" /> 
Figure 9: Average differences in AID measurements. The average differences between Automatic Fusion and Manual AID measurements at all electrode contacts are presented. Error bars represent 95% confidence intervals for the mean difference (n = 20). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/67062/67062fig09large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Analysis of frequencies revealed that average manually measured frequencies ranged from 365.6 &#177; 163.6 to 10,444.0 &#177; 2,399.1 Hz across all electrode contacts (Table 2). In contrast, frequencies measured using automatic fusion ranged from 342.2 &#177; 142.7 to 10,512.0 &#177; 2,634.5 Hz. The comparative analysis showed non-significant differences at all contacts, as illustrated in Figure 10 and Figure 11. These figures depict the mean frequency-to-place mismatch (in semitones) between manual and automatic fusion methods across all contacts. The data are presented in bar charts with error bars representing standard deviations, with a maximum average semitonal difference of 0.8. Furthermore, the estimated standardized effect sizes for all investigated mean frequency differences ranged from 0.1 to 0.4, indicating small to lower than medium values, as interpreted according to Statistical Power Analysis for the Behavioral Sciences by Cohen Jacob26.
<img alt="Figure 10" class="xfigimg" src="/files/ftp_upload/67062/67062fig10.jpg" /> 
Figure 10: Frequency measurement comparison. This figure compares the frequencies measured through Automatic Fusion and Manual methods at all electrode contacts. Significance is indicated as ns (non-significant) for pairwise Bonferroni-adjusted paired t-tests (n = 20). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/67062/67062fig10large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 11" class="xfigimg" src="/files/ftp_upload/67062/67062fig11.jpg" /> 
Figure 11: Average frequency shifts. Average frequency shifts (in semitones) between Manual and Automatic Fusion measured frequencies at all electrode contacts are shown. Error bars represent standard deviations (n = 20). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/67062/67062fig11large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Overall, the results demonstrate the efficacy of the pre-operative and post-operative CT image fusion technique in assessing and measuring electrode locations in CI recipients. While some measurements exhibited slight differences between manual and automatic fusion methods, the findings suggest an overall lack of statistically significant differences, providing valuable insights into individualized CI programming.
Table 1: Comparison of cochlear parameters. Analysis of cochlear parameters and AID measurements obtained through Manual versus Automatic Fusion methods. Statistical significance is indicated as follows: *(0.05 &#8805;p&#8805; 0.01) and **(0.01 &#62; p&#8805; 0.001). Data are presented as mean (standard deviation). 1: t-value for pairwise Bonferroni-adjusted paired t-test; 2: v-value for pairwise Bonferroni-adjusted Wilcoxon signed-rank test. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/67062/67062_Table 1.xlsx" target="_blank">Please click here to download this Table.</a>
Table 2: Center frequency measurements. Comparative analysis of center frequencies measured through Manual and Automatic Fusion methods. Statistical significance is indicated as follows: *(0.05 &#8805;p&#8805; 0.01) and **(0.01 &#62; p&#8805; 0.001). Data are presented as mean (standard deviation). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/67062/67062_Table 2.xlsx" target="_blank">Please click here to download this Table.</a>

This protocol demonstrates a method for fusing pre-operative and post-operative computed tomography images for cochlear implant recipients. The approach may enhance the measurement accuracy of insertion depth and the center frequency of electrode array contacts. Additionally, this method has potential applications in anatomy-based fitting, an emerging area within the cochlear implant field.

Enhancing Electrode Location Assessment in Cochlear Implantation via Computed Tomography Image Fusion

This study aimed to determine whether fusing pre-&#160;and post-operative computed tomography (CT) images could help in assessing electrode placement and ...

enhancing-electrode-location-assessment-cochlear-implantation-via

Nanyang Technological University

Research

JoVE Journal

Neuroscience

394 Views.  King Saud University. This protocol demonstrates a method for fusing pre-operative and post-operative computed tomography images for cochlear implant recipients. The approach may enhance the measurement accuracy of insertion depth and the center frequency of electrode array contacts. Additionally, this method has potential applications in anatomy-based fitting, an emerging area within the cochlear implant field.

Video: Enhancing Electrode Location Assessment in Cochlear Implantation via Computed Tomography Image Fusion

Bioelectric Analyses of an Osseointegrated Intelligent Implant Design System for Amputees

The projected number of American amputees is expected to rise to 3.6 million by 2050.  Many of these individuals depend on artificial limbs to perform routine activities, but prosthetic suspensions using traditional socket technology can prove to be cumbersome and uncomfortable for a person with limb loss.  Moreover, for those with high proximal amputations, limited residual limb length may prevent exoprosthesis attachment all together. Osseointegrated implant technology is a novel operative procedure which allows firm skeletal attachment between the host bone and an implant. Preliminary results in European amputees with osseointegrated implants have shown improved clinical outcomes by allowing direct transfer of loads to the bone-implant interface.  Despite the apparent advantages of osseointegration over socket technology, the current rehabilitation procedures require long periods of restrictive load bearing prior which may be reduced with expedited skeletal attachment via electrical stimulation.  The goal of the osseointegrated intelligent implant design (OIID) system is to make the implant part of an electrical system to accelerate skeletal attachment and help prevent periprosthetic infection. To determine optimal electrode size and placement, we initiated proof of concept with computational modeling of the electric fields and current densities that arise during electrical stimulation of amputee residual limbs.  In order to provide insure patient safety, subjects with retrospective computed tomography scans were selected and three dimensional reconstructions were created using customized software programs to ensure anatomical accuracy (Seg3D and SCIRun) in an IRB and HIPAA approved study.  These software packages supported the development of patient specific models and allowed for interactive manipulation of electrode position and size. Preliminary results indicate that electric fields and current densities can be generated at the implant interface to achieve the homogenous electric field distributions   required to induce osteoblast migration, enhance skeletal fixation and may help prevent periprosthetic infections.  Based on the electrode configurations experimented with in the model, an external two band configuration will be advocated in the future.

There is a need to develop alternative prosthesis attachment due to limb loss attributed to vascular occlusive diseases and trauma. The goal of the work is to introduce an osseointegrated intelligent implant design system to increase skeletal fixation and reduce periprosthetic infection rates for patients needing osseointegrated technology.

The projected number of American amputees is expected to rise to 3.6 million by 2050.  Many of these individuals depend on artificial limbs to perform ...

Biology

Computed Tomography and Optical Imaging of Osteogenesis-angiogenesis Coupling to Assess Integration of Cranial Bone Autografts and Allografts

A major parameter determining the success of a bone-grafting procedure is vascularization of the area surrounding the graft. We hypothesized that implantation of a bone autograft would induce greater bone regeneration by abundant blood vessel formation. To investigate the effect of the graft on neovascularization at the defect site, we developed a micro&#8211;computed tomography (&#181;CT) approach to characterize newly forming blood vessels, which involves systemic perfusion of the animal with a polymerizing contrast agent. This method enables detailed vascular analysis of an organ in its entirety. Additionally, blood perfusion was assessed using fluorescence imaging (FLI) of a blood-borne fluorescent agent. Bone formation was quantified by FLI using a hydroxyapatite-targeted probe and &#181;CT analysis. Stem cell recruitment was monitored by bioluminescence imaging (BLI) of transgenic mice that express luciferase under the control of the osteocalcin promoter. Here we describe and demonstrate preparation of the allograft, calvarial defect surgery, &#181;CT scanning protocols for the neovascularization study and bone formation analysis (including the in vivo perfusion of contrast agent), and the protocol for data analysis.
The 3D high-resolution analysis of vasculature demonstrated significantly greater angiogenesis in animals with implanted autografts, especially with respect to arteriole formation. Accordingly, blood perfusion was significantly higher in the autograft group by the 7th day after surgery. We observed superior bone mineralization and measured greater bone formation in animals that received autografts. Autograft implantation induced resident stem cell recruitment to the graft-host bone suture, where the cells differentiated into bone-forming cells between the 7th and 10th postoperative day. This finding means that enhanced bone formation may be attributed to the augmented vascular feeding that characterizes autograft implantation. The methods depicted may serve as an optimal tool to study bone regeneration in terms of tightly bounded bone formation and neovascularization.

Implantation of autologous and allogeneic bone grafts constitute accepted approaches to treat major craniofacial bone loss. Yet the effect of graft composition on the interplay among neovascularization, cell differentiation and bone formation is unclear. We present a multimodal imaging protocol aimed to elucidate the angiogenesis-osteogenesis interdependence at the graft proximity.

A major parameter determining the success of a bone-grafting procedure is vascularization of the area surrounding the graft. We hypothesized that ...

Bioengineering

Subdural Soft Electrocorticography (ECoG) Array Implantation and Long-Term Cortical Recording in Minipigs

Neurological impairments and diseases can be diagnosed or treated using electrocorticography (ECoG) arrays. In drug-resistant epilepsy, these help delineate the epileptic region to resect. In long-term applications such as brain-computer interfaces, these epicortical electrodes are used to record the movement intention of the brain, to control the robotic limbs of paralyzed patients. However, current stiff electrode grids do not answer the need for high-resolution brain recordings and long-term biointegration. Recently, conformable electrode arrays have been proposed to achieve long-term implant stability with high performance. However, preclinical studies for these new implant technologies are needed to validate their long-term functionality and safety profile for their translation to human patients. In this context, porcine models are routinely employed in developing medical devices due to their large organ sizes and easy animal handling. However, only a few brain applications are described in the literature, mostly due to surgery limitations and integration of the implant system on a living animal.
Here, we report the method for long-term implantation (6 months) and evaluation of soft ECoG arrays in the minipig model. The study first presents the implant system, consisting of a soft microfabricated electrode array integrated with a magnetic resonance imaging (MRI)-compatible polymeric transdermal port that houses instrumentation connectors for electrophysiology recordings. Then, the study describes the surgical procedure, from subdural implantation to animal recovery. We focus on the auditory cortex as an example target area where evoked potentials are induced by acoustic stimulation. We finally describe a data acquisition sequence that includes MRI of the whole brain, implant electrochemical characterization, intraoperative and freely moving electrophysiology, and immunohistochemistry staining of the extracted brains.
This model can be used to investigate the safety and function of novel design of cortical prostheses; mandatory preclinical study to envision translation to human patients.

Subdural Soft Electrocorticography ECoG Array Implantation and Long-Term Cortical Recording in Minipigs

Here, we present a method for the long-term performance and safety assessment of soft subdural electrode arrays in a minipig model, describing surgical method and tools, postoperative magnetic resonance imaging, electrophysiology of the auditory cortex, electrochemical properties of the implant, and postmortem immunochemistry.

Neurological impairments and diseases can be diagnosed or treated using electrocorticography (ECoG) arrays. In drug-resistant epilepsy, these help ...

Performing Intracochlear Electrocochleography During Cochlear Implantation

Electrocochleography (ECochG) measures inner ear potentials generated in response to acoustic stimulation of the ear. These potentials reflect the residual function of the cochlea. In cochlear implant candidates with residual hearing, the implant electrode can directly measure ECochG responses during the implantation process. Various authors have described the ability to monitor the inner ear function by continuous ECochG measurements during the surgery. The measurement of ECochG signals during surgery is not trivial. There are no interpretable signals in up to 20% of cases. For a successful recording, a standardized procedure is recommended to achieve the highest measurement reliability and avoid possible pitfalls. Therefore, seamless collaboration between the CI surgeon and CI technician is key. This video consists of an overview of the system setup and a stepwise procedure of performing intracochlear ECochG measurements during CI surgery. It shows the surgeon's and the CI technician's roles in the process, and how a smooth collaboration between the two is made possible.

Electrocochleography (ECochG) measures inner ear potentials generated in response to acoustic stimulation. In cochlear implant (CI) candidates, such inner ear potentials can be measured directly with the implant electrodes. In this video, we systematically explain how to perform ECochG recordings during CI surgery.

Electrocochleography (ECochG) measures inner ear potentials generated in response to acoustic stimulation of the ear. These potentials reflect the ...

Medicine

Robotic Cochlear Implantation for Direct Cochlear Access

Robot-assisted systems offer great potential for gentler and more precise cochlear implantation. In this article, we provide a comprehensive overview of the clinical workflow for robotic cochlear implantation using a robotic system specifically developed for a minimally invasive, direct cochlear access. The clinical workflow involves experts from various disciplines and requires training to ensure a smooth and safe procedure. The protocol briefly summarizes the history of robotic cochlear implantation. The clinical sequence is explained in detail, beginning with the assessment of patient eligibility and covering surgical preparation, preoperative planning with the special planning software, drilling of the middle ear access, intraoperative imaging to confirm the trajectory, milling of the inner ear access, insertion of the electrode array, and implant management. The steps that require special attention are discussed. As an example, the postoperative outcome of robotic cochlear implantation in a patient with advanced otosclerosis is presented. Finally, the procedure is discussed in the context of the authors' experience.

Robotic cochlear implantation is a procedure for minimally invasive inner ear access. Compared to conventional surgery, robotic cochlear implantation involves additional steps that need to be carried out in the operating room. In this article we give a description of the procedure and highlight the important aspects of robotic cochlear implantation.

Robot-assisted systems offer great potential for gentler and more precise cochlear implantation. In this article, we provide a comprehensive overview of ...

The Miniature Pig: A Large Animal Model for Cochlear Implant Research

Cochlear implants (CI) are the most effective method to treat people with severe-to-profound sensorineural hearing loss. Although CIs are used worldwide, no standard model exists for investigating the electrophysiology and histopathology in patients or animal models with a CI or for evaluating new models of electrode arrays. A large animal model with cochlea characteristics similar to those of humans may provide a research and evaluation platform for advanced and modified arrays before their use in humans. 
To this end, we established standard CI methods with Bama mini-pigs, whose inner ear anatomy is highly similar to that of humans. Arrays designed for human use were implanted into the mini pig cochlea through a round window membrane, and a surgical approach followed that was similar to that used for human CI recipients. Array insertion was followed by evoked compound action potential (ECAP) measurements to evaluate the function of the auditory nerve. This study describes the preparation of the animal, surgical steps, array insertion, and intraoperative electrophysiological measurements. 
The results indicated that the same CI used for humans could be easily implanted in mini-pigs via a standardized surgical approach and yielded similar electrophysiological outcomes as measured in human CI recipients. Mini-pigs could be a valuable animal model to provide initial evidence of the safety and potential performance of novel electrode arrays and surgical approaches before applying them to human beings.

Miniature pigs (mini-pigs) are an ideal large animal model for research into cochlear implants. Cochlear implantation surgery in mini-pigs can be utilized to provide initial evidence of the safety and potential performance of novel electrode arrays and surgical approaches in a living system similar to human beings.

Cochlear implants (CI) are the most effective method to treat people with severe-to-profound sensorineural hearing loss. Although CIs are used worldwide, ...

A State-of-the-Art Method for Preserving Residual Hearing During Cochlear Implant Surgery

The developments in surgical techniques and cochlear implant (CI) electrode design have expanded the indications for CI treatment. Currently, patients with high-frequency hearing loss may benefit from CIs when low-frequency residual hearing can be preserved, as this enables combined electric-acoustic stimulation (EAS). The possible benefits of EAS include, for example, improved sound quality, music perception, and speech intelligibility in noise.
The risks of inner ear trauma and a deterioration or even complete loss of residual hearing vary according to the surgical technique and the type of electrode array used. Short, lateral-wall electrodes with shallower angular insertion depths have demonstrated higher rates of hearing preservation than longer electrodes. The very slow insertion of the electrode array through the round window of the cochlea contributes to insertion atraumaticity and, thus, may lead to favorable hearing preservation results. However, residual hearing can be lost even after an atraumatic insertion. 
Electrocochleography (ECochG) can be used to monitor inner ear hair cell function during the insertion of the electrode. Several investigators have demonstrated that the ECochG responses during surgery may predict postoperative hearing preservation results. 
In a recent study, we correlated the patients' subjective hearing perception with simultaneously recorded intracochlear ECochG responses during the insertion. This is the first report evaluating the association between intraoperative ECochG responses and hearing perception in a subject undergoing cochlear implantation under local anesthesia without sedation. The combination of intraoperative ECochG responses with the patient's real-time feedback to sound stimuli has excellent sensitivity for the intraoperative monitoring of cochlear function. This paper presents a state-of-the-art method for the preservation of residual hearing during CI surgery. We describe this treatment procedure with the special consideration of performing the surgery under local anesthesia, which makes it feasible for monitoring the patient's hearing during the insertion of the electrode array.

The preservation of cochlear structures and possible residual hearing is one important factor to consider during cochlear implant surgery. Here, we present a state-of-the-art method for preserving residual hearing during cochlear implant surgery under local anesthesia.

The developments in surgical techniques and cochlear implant (CI) electrode design have expanded the indications for CI treatment. Currently, patients ...

Real-Time Telemetric Impedance Measurements During Cochlear Implantation

Performing Repeated Intraoperative Impedance Telemetry Measurements during Cochlear Implantation

Impedance measurements are routinely performed during cochlear implantation (CI) after finalized electrode insertion. They may allow conclusions on the electrode's and implant's function. In the postoperative setting, the analysis of impedance changes enables the identification of scarring or inflammation processes around the electrode. Recent studies report associations between impedance telemetry and the site of stimulation. Consequently, repeated impedance measurements during cochlear implant electrode insertion may enable objective feedback on whether the electrode is positioned inside the perilymph or outside the inner ear. With the presented novel method, impedances can be measured in real-time during cochlear implantation. This protocol systematically explains how to perform repeated impedance recordings during CI surgery. These repeated measurements are challenging since they depend on multiple intraoperative methodological factors starting with the draping of the patient. Thus, for successful recordings, a standardized procedure is mandatory. In this article, we comprehensively illustrate the system setup and procedure of performing intraoperative measurements during CI surgery.

Author Spotlight: Advancements in Impedance Monitoring for Cochlear Implant Surgery

Here we present a protocol to conduct repeated impedance telemetry measurements during cochlear implantation (CI). They may allow conclusions on the electrode's and implant's function. Repeated impedance measurements enable objective feedback on whether the electrode is positioned inside the perilymph or outside the inner ear.

Impedance measurements are routinely performed during cochlear implantation (CI) after finalized electrode insertion. They may allow conclusions on the ...

Extracting the Cochlea from a Human Temporal Bone: A Cadaveric Protocol

The extraction of the cochlea from a cadaver human temporal bone may be required for different studies of the inner ear. For histological evaluations, the inner ear must be extracted from the temporal bone to facilitate histologic processing; likewise, some micro-computed tomography devices are too small to accommodate the complete temporal bones; additionally, the image quality can be enhanced when the cochlea is isolated.
The inner ear is located within the petrous part of the temporal bone. The inner ear can be divided into the osseous labyrinth or otic capsule and the membranous labyrinth inside the otic capsule. Furthermore, the inner ear can be divided into the vestibular system (the semicircular canals and the vestibule) and the cochlea. The appreciation of the location and orientation of the cochlea within the temporal bone is difficult, as it is embedded within bony structures and thus cannot be directly visualized. Nevertheless, there are distinct anatomical structures that can help guide the process to allow a reliable drill-out of the cochlea. The landmarks in the posterior parts of the cochlea are the facial nerve, semicircular canals, and the vestibule. In the middle, the inferior borders of the cochlea are identified by the round window and the basal turn of the cochlea. In the anterior border, one encounters the carotid artery; the landmark for the superior border is the genicular ganglion (GG) of the facial nerve. The medial structures are determined by the locations of the internal auditory canal, the superior semicircular canal, and the canal of the internal carotid artery.
In this article, we present a method for extracting the cochlea reliably out of the temporal bone by drill-out while following several anatomical landmarks.

This article presents a reliable method for extracting the human cochlea from the cadaver temporal bone by drill-out while following distinct anatomical landmarks.

The extraction of the cochlea from a cadaver human temporal bone may be required for different studies of the inner ear. For histological evaluations, the ...

Hearing Preservation with Long Electrodes in Electric-Acoustic Stimulation

Enhanced Cochlear Coverage and Hearing Preservation in High-Frequency Hearing Loss via Electric Acoustic Stimulation with Longer Electrode

Electric-acoustic stimulation (EAS) is a promising treatment to improve hearing ability in patients with high-frequency hearing loss (HL). In EAS surgeries, shorter electrodes have been preferred to avoid the presence of an electrode covering the residual hearing region. However, our earlier studies showed that EAS with longer electrodes (28 mm) could preserve acoustic hearing. Additionally, we reported that the hearing preservation (HP) scores were independent of the length of the inserted electrodes, consistent with the systematic review. As most EAS patients gradually lose residual hearing over time due to the natural course of HL, in these cases, providing broader cochlear coverage using longer electrodes was beneficial toward better place-pitch matching. In addition to preparing for the deterioration in&#160;hearing in&#160;the future, EAS with longer electrodes could offer various types of map strategies. Herein, we show the pre-, intra-, and post-procedures for EAS surgery. Appropriate preoperative evaluation, less invasive surgery, flexible lateral-wall electrodes, and steroid administration resulted in good HP following EAS with longer electrodes.

Author Spotlight: Optimizing EAS with Long Electrodes for Enhanced Cochlear Coverage and Hearing Preservation

Electric acoustic stimulation (EAS) with longer electrodes can offer broader cochlear coverage and various types of maps in cases of high-frequency hearing loss. Combining less invasive surgery, flexible lateral-wall electrodes, and steroid administration permits deeper insertion with little or no surgical trauma, resulting in good preservation of hearing.