ORION is a navigation system based on virtual reality that brings about great progress in minimally invasive ear, nose and throat surgery and skull base surgery performed under endoscopic guidance: it allows the surgeon to virtually navigate through the area of interest, while easily seeing on the screen the anatomic structures and the position of the surgical instrument in relation to the target. By matching information from tomographic and endoscopic images, ORION processes and shows in real time the various sections of the patients head including the surgical instrument. Hence the surgeon can readily get oriented in a complex area and execute surgical manoeuvres with safety. The visual feedback from ORION makes it possible to accurately reach even lesions that are small or located in critical points that can not be approached with traditional techniques. It is the case of ports of entry devoid of anatomical points of reference, because of an unconventional anatomy, a target obstructing access or a bone to be removed. The use of this device increases procedure efficacy with respect to cancer removal and intra-operative risk management; besides, being less invasive, ORION enables a shorter post-operative course and, in general, a better quality of life.