Figure 1.

A classification of the registration methods. The upper row represents the intraoperative data (patient’s body) and the lower row the preoperative data (imaging). The dotted lines represent the pairing between the 2 modalities. In the anatomy-based method (A), anatomical landmarks are identified and selected by the operator. In the marker-based method (B), fiducial markers are fixed to the patient’s head. In the surface-based method (C), the red surface on the patient’s face is scanned by a specific instrument. In computer-vision-based method (D), the registration zone is captured by a camera.