SU‐E‐T‐54: A New Method for Optimizing Radiation Isocenter for Linac‐Based SRS

TL;DRAbstract

Purpose: To develop a new method to minimize deviation of linac x‐ray beams from the centroid of the volumetric radiation isocenter for all combinations of gantry and table angle. Methods: A set of ball‐bearing (Winston‐Lutz) images was used to determine the gantry radiation isocenter as the midrange of deviation values. Deviations in the cross‐plane direction were minimized by calibration of MLC leaf position offset, and by adjusting beam position steering for each energy. Special attention was also paid to matching the absolute position of isocenter across all energies by adjusting position steering in the gun‐target axis. Displacement of table axis from the gantry isocenter, and recommended table axis adjustment for contemporary Elekta linacs, was also determined. Eight images were used to characterize the volumetric isocenter for the full range of gantry and table rotations available. Tabulation of deviation for each beam was used to test compliance with isocenter tolerance. Result

Chat with Paper

AI Agents for this Paper