Frameless laser-guided stereotaxis: A system for CT-monitored neurosurgical interventions.

OBJECTIVE: Since a simple, rapid and accurate stereotactic system allowing CT monitoring would offer the neurosurgeon several advantages, the feasibility and application accuracy of frameless laser-guided freehand point stereotaxis for neurosurgical interventions was studied. METHODS: A Cartesian coordinate grid mounted upon the far wall of a CT scan room defined a plane. The scanner isocenter defined the origin of a three-dimensional coordinate system. Phantom entry point and target point coordinates were determined by the positional CT cursor. These coordinates were entered into a computer which determined the coordinates of the grid intersection point with a line passing through the entry and target points. A tripod-mounted laser assembly comprising two encased lasers oriented retrograde and antegrade along opposite vectors, was positioned near the grid. The retrograde laser was positioned to illuminate the marked grid intersection point while the antegrade laser simultaneously illuminated the entry point; the beams were thereby aligned along the line of trajectory. The tip of a probe was placed on the entry point; the hub was then moved into the path of the antegrade laser, thereby aligning the probe with the line of trajectory. The probe was then inserted to the target at a trigonometrically calculated distance. RESULTS: Ten consecutive phantom tests averaged 17.5 min. Phantom test application accuracy averaged +/-2 mm at an average insertion distance of 7.1 cm. CONCLUSION: Phantom tests indicate that simple, rapid and accurate CT-monitored frameless laser-guided freehand point stereotaxis is feasible. Clinical investigation is warranted.

Optical breast lesion localization fiber: preclinical testing of a new device.

Preclinical testing was performed of an optical breast lesion localization fiber to guide surgical excision. The prototype device comprised dual 0.010- inch (0.254-mm)-diameter hooks attached to the tip of a 1,000-microns (0.03937-inch)-diameter optical fiber, which allowed retention in soft tissue after passage through a 17-gauge extra-thin-wall needle. The proximal end of the optical fiber was attached to a 15-mW, 635-nm diode laser, with a thumbscrew connector. The tip of the optical fiber was visible through several centimeters of breast tissue in two human mastectomy specimens, which facilitated determination of the location of the hooks. The optical localization fiber may allow lesions to be approached at surgery by many different paths. Clinical tests are indicated to further evaluate this device.

MR mammographic localization. Work in progress.

The authors present phantom test results for a stereotaxic device that may permit simple, rapid, and accurate needle biopsy and localization of breast lesions detected at contrast material-enhanced magnetic resonance (MR) mammography. The mechanical accuracy of this prototype MR breast localizer is approximately plus or minus 3.5 mm at 5 cm.