Virtual-reality endoscopic navigation system in mediastinal natural orifice transluminal endoscopic surgery (with video).

The approaches to mediastinal surgery are open thoracic, thoracoscopic, and mediastinoscopy. However, using natural orifice transluminal endoscopic surgery (NOTES) would be minimally invasive if the mediastinum is reached via the esophagus. One disadvantage of NOTES was no information outside the wall. We focused on the electromagnetic tracking solution. The sensor position in the space created by the magnetic field generator can be determined. We performed a computed tomography (CT) of a pig before constructing the target mediastinal organs in 3D. The pig was placed in the magnetic field space, and the endoscope with the sensor was subsequently inserted orally and synchronized with the 3D image. By simultaneously viewing the actual and the virtual endoscopic image in 3D, the mediastinum can be visualized through the esophagus. We determined six points in advance in the 3D images, and the esophageal lumen closest to the esophagus from the points was marked with a clip under the endoscope. The CT scans showed that the mean error between the clip position and the closest point from the target point to the esophagus was 4.7 mm across three trials. We named this system the virtual-reality endoscopic navigation system (VENaS). VENaS can help determine the shortest distance to the point away from the esophagus and the 3D relation with the surrounding organs during esophageal endoscopy, and also displays gravity direction and an overhead view, thereby making it easy to approach areas with tumors or malformations in the mediastinum and increasing the realism of mediastinal NOTES.