Methods using fiducial markers

When extreme precision is required, such as in the case of image-based surgery, the registration can be based on external fiducial markers, visible in both imaging modalities, implanted on the patient. Mandava [100] and Maurer [102,103] present such methods where the exact location of the markers is precisely extracted from both scans, and the best transformation is the one that minimizes the misfit between the pairs of corresponding markers. The precision achievable by this approach is evaluated by Fitzpatrick [52].
Unfortunately, the use of markers is both time-consuming in the image acquisition phase and sometimes painful for the patient, which restricts its use to some specific applications, such as stereotactic surgery.