A patient‐to‐computed‐tomography image registration method based on digitally reconstructed radiographs

An automatic method for the accurate registration of computed tomography (CT) data with two camera‐calibrated radiographs is presented. The registration is based on the skull as visualized both in the plain radiographs and in radiographs digitally reconstructed from CT. A reference coordinate system is established based on the radiographic projection parameters obtained using an angiographic stereotactic localizer. The CT‐derived reconstructed radiographs are aligned iteratively at multiple resolutions until a best match is found by adjusting the position and orientation of the CT data set relative to the reference coordinate system. The results of experiments with a skull phantom performed under stereotactic control which show that reliable registration is possible with an accuracy better than 1 mm are presented. Possible applications include intraoperative patient‐to‐CT frameless registration and registration of radiographic data with frameless CT for depth electroencephalogram electrode position confirmation.