Volume cutting for virtual petrous bone surgery

Abstract

A profound knowledge of anatomy and surgical landmarks of the temporal bone is a basic necessity for any otologic surgeon. Because this knowledge, so far, has been mostly taught by limited temporal bone drilling courses, our objective was to create a system for virtual petrous bone surgery that allows the realistic simulation of specific laterobasal surgical approaches. A major requirement was the development of an interactive drill-like tool, together with a new technique for realistic visualization of simulated cut surfaces. The system is based on a volumetric, high-resolution model of the temporal bone, derived from CT. Interactive volume cutting methods using a new multivolume scheme have been developed. In this scheme, cut regions are modeled independently in additional data volumes using voxelization techniques. The voxelization is adapted to successive cutting operations as needed for the simulation of a drill-like tool. A new visualization technique was developed for artifact-free rendering of sharp edges, as formed by the intersection of a cut and an object surface. The new multivolume visualization technique allows high-quality visualization of interactively generated cut surfaces. This is a necessity for a realistic simulation of petrous bone surgery. Our system therefore facilitates comprehension of the complex morphology, and enables the recognition of surgical landmarks, which is most important if injury to delicate organs (e.g., the facial nerve or auditory ossicles) is to be avoided. The system for virtual petrous bone surgery allows the simulation of specific surgical approaches with high-quality visualization. The user can learn about the complex three-dimensional anatomy of the temporal bone from the viewpoint of a real otosurgical procedure.

Integration of high-resolution data for temporal bone surgical simulations

“…As noted earlier, most of the current temporal bone simulation platforms make use of clinical resolution CT data [8, 9, 12, 13]. The use of clinical scanners provides a ubiquitous source for acquiring image data.…”

“…We are exploring automated processes to accelerate this as mentioned above. Similar timing has been described using clinical resolution data and thresholding as the segmentation process for the VOXEL-man system [8, 9, 27]. …”

“…Noble et al 2008 were able to resolve and segment this structure in clinical resolution scans – 0.3 x 0.3 x 0.4mm voxel size [35] for the purposes of pre-surgical planning for cochlear implant surgery. The Voxel-Man system uses 0.33 x 0.33mm in plane resolution and 0.4 to 1mm slice thickness [8, 27]. In our experience, however, a resolution of 0.1 x 0.1 x 0.1mm voxel size was necessary to provide sufficient detail to reliably identify and process the associated voxels for proper representation in our simulator (Fig 5).…”

The Visible Ear Simulator

“…Moreover, these imaging sources offer the possible rendering of custom reconstructions for drilling rehearsals in preparation for planned surgery (2,3,7). However, the maximum resolution of clinical imaging techniques limits the detail of the 3D reconstruction (to a crude 8Y25 voxels/mm 3 ) and the accuracy of the segmentation whether manual or automatic.…”

Otologic Skills Training

“…Most VR temporal bone simulators use a volumetric model that supports haptic interaction for drilling with force feedback and uses different technologies to accomplish 3D stereo graphics. VR simulators are based on either CT-derived data (Voxel-Man 26 , the Ohio State University 27 , the Stanford BioRobotics lab 28 , and the University of Melbourne 29 ), or on cryo sections of a fresh frozen human temporal bone (Visible Ear Simulator 30, 31 ).…”