X-ray based imaging for computer-assisted surgery.

X-ray based imaging is routinely used for preoperative diagnosis and planning, for intraoperative guidance and control, and for the postoperative evaluation of computer-assisted surgery (CAS) in the majority of its applications. Standard radiography, fluoroscopy and computed tomography (CT) are the modalities of outstanding importance. In this report we will review the state of the art in fluoroscopy and in CT with respect to technology and physics, but -- except for detector technology -- we will neglect standard radiography. Recent technical developments which aim at providing CT capabilities for standard fluoroscopy equipment are of particular topical importance; they can significantly improve workflow in the operating room (OR). Considerations regarding x-ray doses are of high concern. Our analysis indicates that most types of applications, including CT, do not bear considerable risks. However, fluoroscopic interventions with long exposure times have to be carefully monitored.