Accurate stereotactic injection by radially curved injection needles

A method has been developed for planning, constructing, and inserting radially curved injection needles for stereotactic surgery in primates. The stereotactic coordinates of the top of a guide tube and the targeted site, together with sagittal and coronal projections of the slant of the guide tube, are provided for the computer, which calculates the length, curvature, and rotational angle at which a curved injector should be inserted through the guide tube to reach the site. Development of the method included a test surgery in which curved injectors were lowered through one set of guide tubes and straight injectors through another set, targeted on the same points in the brain. Formulas used by the programs are presented, and the source code for the software is available on request.