Stereotactic systems and procedures for depth electrode placement: technical aspects.

The authors describe the conversion of the Leksell spherical system to that of the orthogonal approach for depth electrode placement, by the addition of relatively simple devices to the main frame. These modifications have created the need for new instrumentation such as teleradiology with laser beam centering and the use of an all-purpose stereotactic chair. The main device used for the orthogonal approach is an instrument and electrode carrier moving on sliding side bars. This system can also take advantage of the newer imaging techniques, such as CT scanning, digital angiography and NMR, by the addition of computer markers which are interchangeable with the frame side bars.