Biomodel-guided stereotaxy

OBJECTIVES: To simplify the practice of stereotactic surgery by using an or iginal method, apparatus, and solid anatomic replica for trajectory plannin g and to validate the method and apparatus in a laboratory and clinical tri al. METHODS: The patient is marked with fiducials and scanned by using computed tomography or magnetic resonance imaging. The three-dimensional data are c onverted to a format acceptable to stereolithography. Stereolithography use s a laser to polymerize photosensitive resin into a solid plastic model (bi omodel). Stereolithography can replicate brood vessels, soft tissue, tumor, and bone accurately (<0.8 mm). A stereotactic apparatus is referenced to f iducials replicated in the biomodel. The trajectory for the intervention is determined and saved. The apparatus is attached to the patient fiducials, and the intervention is replicated. RESULTS: Three types of apparatus (template, Brown-Roberts-Wells frame, and D'Urso frame) were tested on phantoms and patients requiring the excision/ biopsy of tumors. The localization errors determined from the phantom studi es were template, 0.82 mm; Brown-Roberts-Wells frame, 1.17 mm; and D'Urso f rame, 0.89 mm. The surgeons reported that clinical use of the template and D'Urso frame was accurate and ergonomic. The Bt own-Roberts-Wells frame was move difficult to use and somewhat inaccurate. CONCLUSION: Biomodel-guided stereotaxy has significant advantages. It is pe rformed quickly; it is based on simple, intuitive methodology; it enhances visualization of anatomy and trajectory planning; it enhances patient under standing; it uses inexpensive equipment; it does not require rigid head fix ation; and it has greater versatility than known techniques. Disadvantages are biomodel cost and a manufacturing time of 12 to 24 hours.