Sinus Endoscopy - Application of Advanced GPU Volume Rendering for Virtual Endoscopy

Abstract

For difficult cases in endoscopic sinus surgery, a careful planning of the intervention is necessary. Due to the reduced field of view during the intervention, the surgeons have less information about the surrounding structures in the working area compared to open surgery. Virtual endoscopy enables the visualization of the operating field and additional information, such as risk structures (e.g., optical nerve and skull base) and target structures to be removed (e.g., mucosal swelling). The Sinus Endoscopy system provides the functional range of a virtual endoscopic system with special focus on a realistic representation. Furthermore, by using direct volume rendering, we avoid time-consuming segmentation steps for the use of individual patient datasets. However, the image quality of the endoscopic view can be adjusted in a way that a standard computer with a modern standard graphics card achieves interactive frame rates with low CPU utilization. Thereby, characteristics of the endoscopic view are systematically used for the optimization of the volume rendering speed. The system design was based on a careful analysis of the endoscopic sinus surgery and the resulting needs for computer support. As a small standalone application it can be instantly used for surgical planning and patient education. First results of a clinical evaluation with ENT surgeons were employed to fine-tune the user interface, in particular to reduce the number of controls by using appropriate default values wherever possible. The system was used for preoperative planning in 102 cases, provides useful information for intervention planning (e.g., anatomic variations of the Rec. Frontalis), and closely resembles the intraoperative situation.

Context-aware volume navigation

“…Volumetric navigation. Most navigation techniques for volumetric data are specialized for navigation in tubular structures to support various virtual endoscopy applications: Virtual angioscopy [9], virtual colonoscopy [11], virtual sinus endoscopy [16] and virtual bronchoscopy [2]. Most of these techniques attach the virtual endoscope (i.e., the camera) to a precomputed or manually determined centerline [21].…”

“…The benefit of this property becomes clear, when considering other visualization systems. For instance, the virtual endoscopy system proposed by Krüger et al [16] is a good example. To incorporate collision detection within their GPU-based rendering technique, an extra copy of the data set and knowledge about the renderer and its parameters are required on the CPU.…”

“…The example of the visualization system presented by Krüger et al [16], highlights also another requirement for navigation algorithms: The need for collision detection and avoidance. This is in line with the work by Wojciechowski, who also emphasizes the importance of collision detection when dealing with navigation metaphors [32].…”

Comparison of manual steering and steering via joystick of a flexible rhino endoscope

“…To simulate the reduced field of view during an examination with a flexible endoscope in the nasal cavity and the resulting poor possibilities for orientation and overview compared to open surgery [9], a setup was chosen in which the test person can't get an overview of the region of interest. Therefore a graph paper with five points numbered from zero to four was placed at the bottom of a cup.…”

Intra-operative virtual endoscopy for image guided endonasal transsphenoidal pituitary surgery

“…The visualization of more recent systems is based on highly optimized software [11] or GPU based [7] raycasting algorithms that allow to add more realism, like realistic lightening or wetness, without loosing interactivity. Dominating render mode today is direct iso-surface rendering, a techniques that directly generates a virtual endoscopic image based on individual patient data without pre-processing of the images and generation of intermediate geometry.…”