Registration accuracy and practicability of laser-directed surface matching.

The aim of our study was to evaluate the registration accuracy and practicability of a new laser registration technique in comparison to marker registration. From January to August 2001, 36 patients (23 male, 13 female) with brain lesions were operated with navigational guidance. Thirty-five patients were registered by paired-point registration. In 16 patients, a second registration was carried out using a special laser pointer for surface matching (z-touch trade mark, BrainLab, Heimstetten, Germany). Accuracy was evaluated by touching seven anatomic landmarks and a target fiducial with the nonsterile pointer. The distance from the virtual pointer tip to these points was determined on the monitor display (600% zoom). Laser registration is fully retrospective and allows registrations when no markers are applied. z-touch trade mark registration is more sophisticated and time-consuming than marker-based registration (registration time for z-touch trade mark = 7.4 +/- 3.7 min; for markers = 4.1 +/- 1.7 min; p < 0.005). Marker registration proved to be more accurate than z-touch trade mark registration with regard to localization of anatomical landmarks and target fiducials (precision with z-touch trade mark = 2.77 +/- 1.64 mm; with markers = 1.31 +/- 0.87 mm; p < 0.01). Although the registration error was increased and preparation time prolonged with the z-touch trade mark technique, it proved to be a valuable option, especially in children.