Quality Assurance Procedures Implementation for Varian TrueBeam

Department of radiation oncology of Oncology Nevada updated its linear accelerator (LINAC) from Varian Clinac iX to a newer model known as Varian TrueBeam. The Varian TrueBeam LINAC includes 6x, 6xFFF (i.e., 6x without flattening filter known as flattening filter free), 10x, 10xFFF, 15x photon beams and 6e, 9e, 12e MeV electron beams. This system is also equipped with a 6 degree of freedom (DOF) couch, RapidArc, kV on board imager, MV portal imager and Cone Beam CT (CBCT) imaging. This system allows the clinical delivery of modern image guided radiation therapy (IGRT) modalities such as IMRT/VMAT, and SRS/SRT/SBRT. The periodic quality assurance (QA) tests of these systems include verification of the beam output and energy constancy, as well as beam profile constancy. These parameters are critical to ensure that patients receive quality care. The AAPM (American Association of Physicists in Medicine (AAPM) Task Group (TG) 142 recommends daily, monthly, and annual QA of the linear accelerators with predesignated tolerances for non-IMRT, IMRT, and SRS/SBRT treatment techniques. In the Oncology Nevada clinic, various devices are used for the periodic QA on the linear accelerators. These devices include, Machine Performance Check (MPC) IsoCal calibration phantom, Sun Nuclear Daily QA 3, Sun Nuclear IC Profiler, solid water phantom, and 1D water phantom. Daily QA tests are performed utilizing the Varian TrueBeam Machine Performance Check and Sun Nuclear Daily QA 3. This report will focus on the essential QA procedures performed on the Varian TrueBeam LINAC including daily QA in which the output constancy is compared to the baseline. Various safety and mechanical tests, as recommended by TG-142, will also be performed. The Sun Nuclear IC Profiler will be used for monthly QA to verify photon and electron beam profile constancy. Solid-water-based beam output and energy constancy checks will also be performed. Implementation of these QA procedures are part of the medical physicist’s tasks. By setting up those devices and implementing the measurement procedures, physicists perform the daily and monthly QA following the recommendations of the AAPM TG-142. Additional tests in the TG-142 protocol include the geometry isocenter, jaw position, Multileaf Collimator (MLC) position, couch lateral, longitudinal, vertical, rotation positions, daily output energy constancy check, beam profile constancy check, and beam output and energy constancy check. The goal of the project is to setup available equipment and implement measurement procedures in order to determine baseline values for both daily, monthly, and annual QA, which are required to fulfill TG-142 recommendations for LINAC QA and ensure patient care quality