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Hypothesis: Image quality of low-dose multi-slice computed tomography (MSCT) after cochlear implantation is comparable to that of cone-beam computed tomography (CBCT)., Background: CBCT has been described as a low-dose alternative with superior image quality to MSCT for postoperative cochlear implant (CI) imaging, but to our knowledge, no dose-matched comparisons of image quality have been published., Materials and Methods: Five human cochleae were implanted with CI electrodes and scanned on two CBCT and two MSCT systems. Four independent observers rated aspects of image quality on a five-point scale. CBCT scans were compared to clinical and dose-matched MSCT scans. Declining-dose MSCT protocols were compared to the clinical protocol. CT phantoms were used to determine effective dose and resolution for each acquisition protocol., Results: Effective dose of the CBCT protocols was 6 to 16% of the clinical MSCT dose. Visibility of cochlear inner and outer walls and overall image quality were positively correlated with radiation dose on MSCT and image quality was better with clinical MSCT than with CBCT protocols. In other comparisons, differences between systems were found, but a distinction between CBCT and MSCT could not be made., Conclusion: CBCT and dose-matched MSCT are both suitable for postoperative CI imaging. Selecting a CT system and radiation dose depends on which cochlear structures need to be visualized.

Objective: It was the aim of this study to investigate the occurrence of electrode migration of a cochlear implant in patients with and without complaints., Methods: We performed a retrospective case review in a tertiary referral center. The electrode position was evaluated in 35 cochlear implantees, 16 with a CII HiFocus1 (non-positioner) and 19 with a HiRes90K HiFocus1J, using multiplanar reconstructions of the postoperative CT scans. Of 5 patients, a second scan was obtained to evaluate complaints of performance drop, vertigo, tinnitus, headache or nonauditory stimulation. Displacements of the electrode contacts were calculated and displacements of >1 mm were considered a migration. The possible correlation with implant type, insertion depth or presence of complaints was analyzed., Results: Migrations were detected in 10 patients (29%). There was a significant effect of the implant type in favour of the HiFocus1, but no relation with the original insertion depth of the device. In the 5 patients scanned because of complaints, two migrations were detected., Conclusions: In our patient population, electrode migration was not uncommon and turned out to occur in patients with and without complaints., (Copyright © 2012 S. Karger AG, Basel.)

Objectives/hypothesis: To study to what extent it is possible to achieve identical insertion depths and to maintain the same performance after cochlear reimplantation., Study Design: Outcome research on a retrospective case series in a tertiary university referral center., Methods: Data were collected for 12 adults and three children who underwent reimplantation during the last 3 years with a new HiRes90K device with HiFocus 1J electrode owing to failure of the feed-through seal. Multislice computed tomography scans were used to compare positions of the original and newly placed electrode arrays. The speech-perception scores on a consonant-vowel-consonant word test before and after reimplantation were compared., Results: All reimplantations were successfully performed by two experienced cochlear implantation surgeons, and no complications were observed. Postoperative imaging showed that the average displacement of the new implant was only 0.59 mm. Reactivation of the implant gave immediate open set speech understanding in all patients, and speech perception rapidly returned to the previous level obtained with the original implant within weeks; it was even significantly better at the 3-month follow-up. No relation was found between changes in performance and the amount of displacement of the electrode array., Conclusions: After cochlear reimplantation with the same device, electrode-array position can be accurately replicated and speech perception can be regained or even improved within weeks., (Copyright © 2011 The American Laryngological, Rhinological, and Otological Society, Inc.)

Setting: Cochlear implant (CI)/tertiary referral center., Subjects: Twenty-five patients implanted with an Advanced Bionics HiRes90K HiFocus1J CI. STUDY DESIGN/MAIN OUTCOME MEASURES: A 3-dimensional cylindrical coordinate system is introduced using the basal turn of the cochlea as the x and y planes and the center of the modiolus as the z axis. The 0-degree angle is defined by the most lateral point of the horizontal semicircular canal. It is applied to both preoperative and postoperative computed tomographies in 25 patients. The angular position of the round window is examined. Interobserver reproducibility is tested by localization of all electrode contacts within the coordinate system. To observe realignment over time, electrode coordinates in postoperative images were projected on preoperative images. Additionally, comparison to existing imaging-related coordinate systems was made., Results: The angular position of the center of the round window is 34.6 +/- 0.4 degrees (standard deviation) with an intraclass coefficient of 1.00. The intraclass coefficient for interobserver reproducibility of the 16 electrode contacts ranged from 0.74 to 1 for the rotational angle (phi) and 0.77 to 1 for the distance to the modiolus (rho). In 21 of 25 patients, a perfect match or minimal displacement of up to 3 electrode contacts was seen. Comparison to existing systems showed good correlation., Conclusion: A 3-dimensional cochlear coordinate system easily applicable in clinical patients is described, which fulfills the requirements set by an international consensus.