The use of pre- and intra-operative images for surgical guidance

Summary Surgical navigation has become possible thanks to the combination of localizer systems and digital imaging systems. The application to neurosurgery has especially taken off, using pre-operative CT/MR images. Craniotomies as well as stereotaxic surgery benefit from pre-operative virtual imaging, as the surgical plan can be optimized by choosing the best from several simulated routes to circumvent eloquent areas. Virtual imaging has also proved to be useful in neurosurgery for intra-operative localization and navigational guidance. Other clinical applications have also started to use pre-operative imaging, simulation/planning and intra-operative guidance. In orthopedic surgery these techniques are assisting the localization of spinal tumors, placement of pedicle screws and less invasive procedures. In ear-nose-throat (ENJ) surgery the techniques are facilitating endonasal approaches, for example, pituitary tumors or polypectomy. The use of virtual endoscopy can be of additional help here. A limitation of many current systems is the absence of real-time imaging and possibility to update the reference images during therapy. Intra-operative CT imaging can yield valuable intraand post-operative image information to further optimize treatment. Various clinical applications of image guidance are discussed and illustrated with outcome and advantages/disadvantages. In addition, the intra-operative use of CT imaging and its potential consequences are discussed.