Experience on Commissioning the first Halcyon Linear Accelerator in China

Abstract Objective: This study is aimed to establish a proper clinical commissioning procedure for the Halcyon 1.0 linear accelerator (linac) with pre-configured reference beam data (RBD) set and to ensure the commissioning results meet the clinical treatment requirements. Methods: Four parts were carried out during the commissioning work on the first Halcyon linac in China, which were according to the characteristics of this linac, the experience of the acceptance tests and commissioning procedure of our existing linacs and treatment planning systems (TPS), reports of AAPM & IAEA and relevant publications with the choice of appropriate quality assurance (QA) tools and procedures. These four aspects were as follows: 1. Commissioning of the Halcyon linac; 2. commissioning of the Eclipse TPS; 3. QA and quality control (QA & QC) of the Halcyon linac; 4. QA & QC of the Eclipse TPS and developing the corresponding procedures. Results: The 3D radius of the isocenter of gantry and collimator rotation from Winston-Lutz test was 0.64mm, the coincidence of the virtual isocenter and the treatment isocenter was quite well, and the maximum travel position deviation was 0.7mm. Percentage Depth Doses (PDDs) was 63.3% at 10cm at the reference setup and the tolerance was within 1%. The Machine Performance Check (MPC) results were within the relevant tolerance, and the gantry isocenter size measured from MPC test was 0.67mm. The pre-configured beam model data was in agreement with the measured data. In the process of rotation, the speed of gantry rotation and multi-leaf collimator (MLC) movement and the control of dose rate were all accurate with all deviations were controlled below 2%. The CT values of Surface and Interior of the carbon fiber treatment couch were -750HU and -950HU, respectively. All MPPG 5.a recommended regular field gamma compare tests met the requirements. The task group 119 test was also performed on Halcyon, the point dose difference for intensity-modulated radiation therapy (IMRT) and RapidArc techniques were -0.003 ± 0.011 and - 0.012 ± 0.006, respectively, with confidence limits of 0.025 and 0.024. Conclusion: The measured data of the Halcyon linac are in good consistency with the pre-configured beam model data in Eclipse TPS. The commissioning results of the IMRT technique and the RapicArc technique are all within the tolerance ranges recommended by AAPM and relevant publications, which could meet the needs of clinical requirements. The pre-configured data can facilitate the commissioning work and the validation and replace fully collecting beam data, which will be the trend of the commissioning of linac in the future.