Spatial orientation in translumenal surgery.

"Natural Orifice Translumenal Endoscopic Surgery" (NOTES) is assumed to offer significant benefits to patients, such as reduced trauma as well as reduced collateral damage. But the potential advantages of this new technology can only be achieved through safe and standardized operation methods. Several barriers, which have been identified during clinical practice in flexible intra-abdominal endoscopy, can only be solved with computer-assisted surgical (CAS) systems. In order to assist the surgeon during the intervention and enhance his visual possibilities, some of these CAS systems require 3-D information of the intervention site, for others 3-D information is even mandatory. Therefore it is evident that the definition and design of new technologies for CAS systems must be strongly considered. A 3-D endoscope, called "Multisensor-Time-of-Flight" (MUSTOF) endoscope, is actually being developed. Within these developments, an optical 3-D time-of-flight (TOF) sensor is attached to the proximal end of a common endoscope. The 3-D depth information obtained by this enhanced endoscope can furthermore be registered with preoperatively acquired 3-D volumetric datasets such as CT or MRI. These enhanced or augmented 3-D data volumes could then be used to find the transgastric or transcolonic entry point to the abdomen. Furthermore, such acquired endoscopic depth data can be used to provide better orientation within the abdomen. Moreover it can also prevent intra-operative collisions and provide an optimized field of view with the possibility for off-axis viewing. Furthermore, providing a stable horizon on video-endoscopic images, especially within non-rigid endoscopic surgery scenarios (particularly within NOTES), remains an open issue. Hence, our recently presented "endorientation" approach for automated image orientation rectification could turn out as an important contribution. It works with a tiny micro-electro-mechanical systems (MEMS) tri-axial inertial sensor that is placed on the distal tip of an endoscope. By measuring the impact of gravity on each of the three orthogonal axes the rotation angle can be estimated with some calculations out of these three acceleration values, which can be used to automatically rectify the endoscopic images using image processing methods. Using such enhanced, progressive endoscopic system extensions proposed in this article, translumenal surgery could in the future be performed in a safer and more feasible manner.