SUMMARY

The Leksell Gamma Knife ICON is the most recent production model of the Gamma Knife stereotactic radiotherapy system from Elekta AB. This system has the ability to provide conventional frame-based Gamma Knife treatments and provides an additional Cone-Beam CT integrated functionality. This project will address recent questions about the spatial accuracy of the stereotactic definition of the frame and CT based radiotherapy treatments when the frame is subject to uneven, asymmetrical, and/or varying in magnitude torque on the Gamma Knife frame posts. The project provides a quantitative evaluation of this spatial error as a function of the both torque magnitude and of torque asymmetry from the recommended torque level of 4 inch-lbs up to 14 inch-lbs. Results indicate potentially unacceptable spatial error on the order of 1-2 mm in the case of a 3-pin application, such as in the case of having a previous craniotomy.