SU-E-T-245: Detection of the Photon Target Damage in Varian Linac Based On Periodical Quality Assurance Measurements

Purpose: To determine the best dosimetric metric measured by our routine QA devices for diagnosing photon target failure on a Varian C‐series linac. Methods: We have retrospectively reviewed and analyzed the dosimetry data from a Varian linac with a target degradation that was undiagnosed for one year. A failure in the daily QA symmetry tests was the first indication of an issue. The beam was steered back to a symmetric shape and water scans...