An accurate adjustable applicator for magnetic resonance imaging-based stereotactic procedure using the Leksell G frame

OBJECTIVE: An applicator system for the Leksell G frame was constructed to enable accurate placement of the frame for stereotactic magnetic resonance imaging (MRI) and successful stereotactic surgery. The applicator prevents inaccurate placement of the fiducial box on the patient's head and prevents contact of the frame holder with the patient's shoulder while in the MRI u nit. It also helps to ensure optimal positioning of desired targets within the three-dimensional stereotactic space defined by the frame. METHODS: The applicator is made of transparent acrylic plates, which simula te the fiducial box that is attached to the frame for the preoperative ster eotactic MRI study. An air cuff at the top supports the frame at any desire d height and makes minute adjustments possible. Side cuffs help to keep the frame at the desired position from right to left. Indicators attached to t he frame for the anterior fiducial plate prevent potential contact of the p late with the anterior posts and help avoid a poor fit caused by bending of the frame from excessive torque on the cranium fixation screws. Indicators for the MRI frame holder on the foot screws predict potential collision of the holder with the patient's shoulder before actually applying the holder on the frame. The applicator shows the range and limits of the Leksell ste reotactic are. RESULTS: This applicator system has been used effectively in more than 89 M RI-based functional stereotactic procedures. These include pallidotomy, tha lamotomy, implantation of deep brain stimulators, and implantation of depth electrodes. It has functioned well and has facilitated excellent operative results in these cases. CONCLUSION: This simple frame applicator eliminates the need for reapplicat ion of the stereotactic frame and additional imaging studies, thus providin g successful and appropriate frame placement for stereotactic surgery.