The Beam Stability Study of Varian Linear Accelerator Based on MPC and Morning Check

Abstract

Background: Our hospital has been using Varian VitalBeam linear accelerator since December 2020. Daily quality control of accelerator beam stability in precision radiotherapy is very important. In this paper, we compare and analyze the beam stability of the accelerator with two monitoring methods. Objective: The long-term stability analyze and study of VitalBeam linear accelerator by using machine Machine Performance Check (MPC) and Morning Check. Methods: The energies of 6MV and 10MV x-ray most commonly used by Varian Linear accelerator (VitalBeam) for patient treatment were analyzed and compared，Firstly, the absolute dose of 6MV and 10MV X-ray energies of VitalBeam was calibrated. Collected and analyzed the morning checking data of VitalBeam from November 2021 to May 2022, including the CAX, SYM and FLAT offset data; the MPC daily data was collected and analyzed at the same time, which include beam output change, uniformity change and beam center shift data. The beam output changes were statistically analyzed, and the stability of other data was analyzed. Results: The Morning Check and MPC can accurately detect the change of accelerator beam performance, and the measured values are stable and within the tolerance range，The comparison of 6MV and 10MV beam outputs between the morning detector and MPC was statistically significant (P<0.05). Conclusion: Both MPC and Morning Check can detecte the requirements of accelerator quality assurement, the beam output monitoring morning detector has advantages, but MPC has faster execution efficiency than morning detector instrument, and is more suitable for units with a large number of patients treated daily.