Effect of fiducial marker localization on stereotactic target coordinate calculation in CT slices and radiographs

Novel methods are presented which allow the estimation of the effect of stereotactic fiducial marker localization on target localization in a stereotactic surgery planning program based on the integration of image data from various modalities. The results of simulations are presented. A method for the evaluation of the effect of fiducial marker localization error on stereotactic localization, both for computed tomography (CT) and digitized radiography. Is proposed based on perturbation studies. For tomographic data, the comparison of the stability of two types of fiducial localizers: a standard commercial device based on nine (six vertical and three oblique) rods and an imaginary system with an extra set of rods, called '4-N', is discussed. Results of the perturbation studies clearly indicate the necessity of sub-pixel registration of the fiducial markers in CT. On the other hand, results demonstrate that stereotactic localization based on projection images is less sensitive to fiducial localization error than CT. Finally, the authors present an algorithm for the localization of fiducial markers to sub-pixel accuracy in radiographs acquired with a commercial angio localizer.