Objective: Virtual endoscopy (vE) allows simulated three-dimensional (3-D) visualization of anatomical structures by computerized reconstruction of radiological images. The aim of this study was to evaluate the feasibility of vE and its potential benefits for endoscopic transsphenoidal pituitary surgery. Patients and methods: vE was realized using a commercially available ray-casting software plugin of a picture archiving and communications system (PACS). For this study, the vE system was

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... ed with volume segmentation, transparency and cutting tools. The data for vE were derived from high resolution computed tomography (CT) scans of 22 patients with pituitary pathology (20 pituitary adenomas, 2 Rathke's cleft cysts) preoperatively. Anatomical structures were identified on vE images and compared with the intraoperative endoscopic view. Results: The simulated 3-D vE images were found comparable to the intraoperative endoscopic anatomy in terms of distortion and angle of view. vE was found particularly useful for the preoperative depiction of 1) the nasal anatomy and its variations for choosing the side of the approach, 2) the sphenoid sinus septae and chambers for improved intraoperative orientation, 3) the transparent 3-D simulated visualization of the pituitary gland, tumor and adjacent anatomic structures in relation to the sphenoid sinus landmarks for planning the opening of the sellar floor. We conclude that vE harbours the potential to become a valuable tool in endoscopic pituitary surgery for training purposes and preoperative planning. Furthermore, vE may add to the safety of interventions in case of anatomical variations.