Planning and analyzing of surgical interventions are often based on computer models derived from computed tomography images of the patient. In the field of cochlear implant insertion the modeling of several structures of the inner ear is needed. One structure is the overall helical shape of the cochlea itself. In this paper we analyze the cochlea by applying statistical shape models with medial representation. The cochlea is considered as tubular structure. A model representing the skeleton of training data and an atomic composition of the structure is built. We reduce the representation to a linear chain of atoms. As result a compact discrete model is possible. It is demonstrated how to place the atoms and build up their correspondence through a population of training data. The outcome of the applied representation is discussed in terms of impact on automated segmentation algorithms and known advantages of medial models are revisited.
Due to rapid developments in the research areas of medical imaging, medical image processing and robotics,
computer assistance is no longer restricted to diagnostics and surgical planning but has been expanded to surgical
and radiological interventions. From a software engineering point of view, the systems for image-guided therapy
(IGT) are highly complex. To address this issue, we presented an open source extension to the well-known
Medical Imaging Interaction Toolkit (MITK) for developing IGT systems, called MITK-IGT. The contribution
of this paper is two-fold: Firstly, we extended MITK-IGT such that it (1) facilitates the handling of navigation
tools, (2) provides reusable graphical user interface (UI) components, and (3) features standardized exception
handling. Secondly, we developed a software prototype for computer-assisted needle insertions, using the new
features, and tested it with a new Tabletop field generator (FG) for the electromagnetic tracking system NDI
Aurora ®. To our knowledge, we are the first to have integrated this new FG into a complete navigation system
and have conducted tests under clinical conditions. In conclusion, we enabled simplified development of imageguided
therapy software and demonstrated the utilizability of applications developed with MITK-IGT in the
Electromagnetic tracking (EMT) systems are gaining increased attention in various fields of image-guided surgery. One of the main problems related to EMT systems is their vulnerability to distortion due to metallic objects. Several methods have been introduced to evaluate electromagnetic trackers, yet, the data acquisition has to be manually performed in a time consuming procedure, which often leads to a sparse volume coverage. The aim of this work is to present a fully automatic calibration system. It consists of a novel, parallel robotic arm and has the potential to collect a very large number of tracking data while scanning the entire tracking volume of a field generator. To prove the feasibility of our system, we evaluate two electromagnetic field generators (NDI Planar and Tabletop) in an ideal metal-free environment and in a clinical setup. Our proposed calibration robot successfully performed throughout the experiments and examined 1,000 positions in the tracking volume of each field generator (FG). According to the results both FGs are highly accurate in an ideal environment. However, in the examined clinical setup, the Planar FG is strongly distorted by metallic objects. Whereas the Tabletop FG provided very robust and accurate tracking, even if metallic objects where lying directly underneath the FG.