A new artifact-free device for frameless, magnetic resonance imaging-guided stereotactic procedures

OBJECTIVE: A new, artifact-free, nonobstructive device was required for pla nning, guiding, and performing stereotactic procedures in an open magnetic resonance imaging (MRI) system (Signa SP; General Electric, Milwaukee, WI). DESCRIPTION OF INSTRUMENTATION: We devised an MRI-compatible instrument set that was adapted to an optical triangulation system (FlashPoint System; Im age Guided Technologies, Boulder, CO) and consisted of a Pathfinder for pla nning burr holes and trajectories and a Snapper-Stereoguide for guiding min imally invasive instruments such as biopsy cannulae, endoscopes, and laser fibers. The instruments were composed of biocompatible plastic (polyacetal) . During evaluation, special attention was paid to safety, accuracy, operat ion times, and susceptibility artifacts of the system. RESULTS: The first 20 stereotactic procedures performed in the open MRI sca nner included 15 biopsies, 1 cyst and 3 abscess evacuations, and 1 endoscop ic procedure for treatment of multiseptate hydrocephalus. There were no adv erse outcomes, and all biopsies were diagnostic. The frameless stereotactic system in combination with the FlashPoint System proved to be accurate, wi th a mean error of 1.5 mm. The biopsy devices did not cause any susceptibil ity artifacts. Highly vascularized structures were clearly visible and were included in the trajectory planning. With experience, the procedure time w as reduced to less than 1 hour. CONCLUSION: This device was found to be quite helpful for planning and guid ing; stereotactic procedures in the open MRI scanner. Nearly real-time plan ning and monitoring of stereotactic procedures and the positional accuracy of the system make the open MRI system a definite improvement, compared wit h conventional stereotactic systems.