short communications J. Synchrotron Rad. (2021). 28, 327–332 https://doi.org/10.1107/S1600577520014952 327 Received 17 July 2020 Accepted 10 November 2020 Edited by R. W. Strange, University of Essex, United Kingdom Keywords: perimodiolar electrodes; cochlear implants; synchrotron X-ray microtomography; phase-contrast imaging. Supporting information: this article has supporting information at journals.iucr.org/s Synchrotron radiation X-ray microtomography for the visualization of intra-cochlear anatomy in human temporal bones implanted with a perimodiolar cochlear implant electrode array Fergio Sismono, a * Lucia Mancini, b Marc Leblans, a Jana Goyens, c Glynnis De Greve, a Sara Schneiders, a Karen Beckers, a Joris Dirckx, d Bert De Foer e and Andrzej Zarowski a a European Institute for ORL-HNS, GZA Hospitals Antwerp, Oosterveldlaan 24, Wilrijk, Antwerp 2610, Belgium, b Elettra Sincrotrone Trieste S.C.p.A., S.S. 14 Area Science Park, 34149 Basovizza, Trieste Italy, c Department Biology, Lab Functional Morphology, University of Antwerp, Universiteitsplein 1, Wilrijk, Antwerp 2610, Belgium, d Laboratory of Biomedical Physics, University of Antwerp, Groenenborgerlaan 171, Antwerp 2020, Belgium, and e Department of Radiology, GZA Hospitals Antwerp, Oosterveldlaan 24, Wilrijk, Antwerp 2610, Belgium. *Correspondence e-mail: fergio.sismono@gza.be Recently, synchrotron radiation computed microtomography (SRmCT) has emerged as a promising tool for non-destructive, in situ visualization of cochlear implant electrode arrays inserted into a human cochlea. Histological techniques have been the ‘gold standard’ technique for accurate localization of cochlear implant electrodes but are suboptimal for precise three-dimensional measure- ments. Here, an SRmCT experimental setup is proposed that offers the benefit of a high spatial and contrast resolution (isotropic voxel size = 4.95 mm and propagation-based phase-contrast imaging), while visualizing the soft-tissue structures and electrode array of the cochlear implant simultaneously. In this work, perimodiolar electrode arrays have been tested, which incorporate thick and closely spaced platinum–iridium contacts and wiring. These data can assist cochlear implant and hearing research, can be used to verify electrode segmentation techniques for clinical computed tomography or could be utilized to evaluate cochlear implant electrode array designs. 1. Introduction Cochlear implants (CIs) are medical devices that restore hearing and speech understanding in moderate to profoundly deaf patients who are unable to receive adequate benefit from conventional hearing aids. CIs directly stimulate the auditory nerve through an electrode array inserted in the cochlea. Using a microphone and an external speech processor, sounds are captured from the environment and transformed into electrical signals that are distributed over the electrode contacts of the implanted electrode array. Each contact carries the information corresponding to a specific acoustic frequency band and electrically stimulates the target auditory neurons within the cochlea. In this way, the whole speech-related frequency spectrum of captured sound can be conveyed to the auditory system. The position of the CI electrodes with respect to the anatomical structures in the cochlea varies as a result of the surgical procedure and is of importance for the final hearing outcome of the CI recipient. For instance, the final perfor- mance on speech recognition tests is significantly better when the electrodes are implanted into the scala tympani, the inferior partition of the cochlear duct, rather than the scala vestibuli, the superior partition (Holden et al., 2013; Shaul et ISSN 1600-5775 # 2021 International Union of Crystallography