A simple trajectory guidance device that assists freehand and interactive image guided biopsy of small deep intracranial targets.

Frameless image guided stereotactic systems are rapidly becoming incorporated into routine neurosurgical practice. In our unit, the Elekta Viewing Wand has been applied to a comprehensive range of neurosurgical procedures, including pituitary, posterior fossa, skull base, atlantoaxial, and epilepsy surgery. The system allows a minimally invasive surgical exposure and provides instant and continual navigational information during surgery. Subjective studies have shown this intraoperative information to facilitate the surgeon's perception of anatomic relations and identification of structures, thus improving surgical safety. Furthermore, in comparison to traditional stereotactic frames, the frameless system has been reported to reduce operative time. The technology involves the use of a localizing mechanical arm to which a pointer or biopsy probe is attached. This localizing arm is hand-held and is therefore only as steady as the surgeon's hand. This precludes the use of the Viewing Wand for functional procedures and for the safe biopsy of small, deep-seated intracranial lesions. Both types of procedures are very dependent on a steady linear approach to the target for a successful outcome. We have designed a simple guidance device that eliminates the risk of unwanted drift or angular movements of the probe as it is advanced toward the target. When used with the Viewing Wand, this device guides the wand biopsy probe along a predetermined, fixed linear trajectory to the intracranial target. We report the successful use of the fixed trajectory guidance device (FTGD) with the Elekta Viewing Wand in a series of 12 patients.