Image guided computer based surgical navigation systems comprised of computer hardware and computer software for use in medical, surgical and endoscopic navigation; computer hardware and software for three-dimensional volume visualisation and interpretation of physical data in connection with medical, surgical, and endoscopic navigation systems; computer hardware and software for image production and image management of medical, surgical, radiological and endoscopic procedures; computer software for interpretation and diagnosis of medical, surgical, radiological or endoscopic physical data; computer hardware and software to facilitate the development of medical imaging in surgical applications; computerised three-dimensional workstation comprised of computer hardware and software for assisting surgeons with image data; computer graphics workstations comprising special purpose computer graphics display hardware, operating software and special purpose application software dedicated to the generation, examination and analysis of medical imaging data which has been acquired from other medical imaging devices