Abstract: An interstitial implant system for implanting surgical instruments in body tissue comprises a planning bridge and an implant needle applicator. The planning bridge includes a pair of parallel plates positioned one on each side of the body tissue having corresponding matrices of apertures engageable by marking instruments for marking entry and exit points in the tissue thereby determining a series of linear paths. A thumb-slide actuated needle applicator has a tubular needle injector and semicircular arm providing an entry point and a target point which rest, respectively, upon the previously marked body tissue. By holding the applicator at both points, a needle inserted therein will follow the path previously determined by the entry and exit points.