Research Article Semiautomatic Cochleostomy Target and Insertion Trajectory Planning for Minimally Invasive Cochlear Implantation Wilhelm Wimmer, 1,2 Frederic Venail, 3,4 Tom Williamson, 1 Mohamed Akkari, 3 Nicolas Gerber, 1 Stefan Weber, 1 Marco Caversaccio, 1,2 Alain Uziel, 3,4 and Brett Bell 1 1 ARTORG Center for Biomedical Engineering Research, University of Bern, 3010 Bern, Switzerland 2 Department of ENT, Head and Neck Surgery, Inselspital, University of Bern, 3010 Bern, Switzerland 3 Otology and Neurotology Department, University Hospital of Montpellier, 34961 Montpellier, France 4 Institute for Neurosciences of Montpellier, INSERM U1051, 34091 Montpellier, France Correspondence should be addressed to Brett Bell; brett.bell@artorg.unibe.ch Received 14 March 2014; Accepted 17 June 2014; Published 2 July 2014 Academic Editor: Claus-Peter Richter Copyright © 2014 Wilhelm Wimmer et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A major component of minimally invasive cochlear implantation is atraumatic scala tympani (ST) placement of the electrode array. Tis work reports on a semiautomatic planning paradigm that uses anatomical landmarks and cochlear surface models for cochleostomy target and insertion trajectory computation. Te method was validated in a human whole head cadaver model ( = 10 ears). Cochleostomy targets were generated from an automated script and used for consecutive planning of a direct cochlear access (DCA) drill trajectory from the mastoid surface to the inner ear. An image-guided robotic system was used to perform both, DCA and cochleostomy drilling. Nine of 10 implanted specimens showed complete ST placement. One case of scala vestibuli insertion occurred due to a registration/drilling error of 0.79 mm. Te presented approach indicates that a safe cochleostomy target and insertion trajectory can be planned using conventional clinical imaging modalities, which lack sufcient resolution to identify the basilar membrane. 1. Introduction Te aims of minimally invasive cochlear implant (CI) surgery are manifold. On the one hand, minimally invasive access to the cochlea is gained through a direct cochlear access (DCA), which is a small tunnel drilled from the mastoid surface to the cochlea passing through the facial recess [1, 2]. In addition to a minimally invasive access, the preservation of intracochlear structures during and afer electrode array insertion is an important research topic. Once access to the tympanic cavity is established, the cochlea must be opened to enable CI electrode array inser- tion. Two criteria are primarily considered in the current defnition of atraumatic electrode insertion. First, the scala tympani (ST) is the favored intracochlear lumen for implant placement, especially in terms of retaining residual hearing [3–7]. Second, the ideal insertion trajectory should align with the center line of the ST to prevent damage to the basilar membrane, the modiolus, or the spiral ligament during insertion. Te ST can be accessed either through a strict round window (RW) approach, a RW related cochleostomy, or a promontory cochleostomy separated from the RW. Drilling the cochleostomy in the correct location is one of the major challenges the surgeon faces during the surgery. Te position is chosen intraoperatively according to the anatomical situation of the promontory (i.e., inferior or anteroinferior to the RW membrane) to avoid damage to basal intracochlear structures [8–14]. In this context, image-guided cochleostomy approaches have been investigated to aid the surgeon in determining the proper drill site, but, to our knowledge, no clinical data has been published [15, 16]. Correct planning of the cochleostomy site and insertion trajectory rely on an accurate representation of the anatomy during planning. However, clinically applicable imaging modalities do not provide suf- fcient imaging resolution for direct detection of the ST. Hindawi Publishing Corporation BioMed Research International Volume 2014, Article ID 596498, 8 pages http://dx.doi.org/10.1155/2014/596498