Room: AAPM ePoster Library
A new-type CT-integrated linear accelerator (uRT-linac 506c) was introduced into clinical application by United Imaging Healthcare (UIH) Co., Ltd (Shanghai, China), which had a diagnostic-quality CT scanner compactly fixed behind the gantry of C-arm linac. Recently, this linac was installed and put into clinical operation in our department. In the present contribution, the commissioning results and preliminary clinical experience were to be reported.
Commissioning results of mechanical testing and imaging system (MV_CBCT and kV_FBCT) testing were presented. Machine performance over a period of three months was summarized. A series of end-to-end cases on different treatment sites were tested preclinically. In the first stage of clinical usage, the pretreatment QA results of about 50 sIMRT patient plans on breast and rectum were reported. Efficiency of the routine IGRT workflow using CBCT/FBCT was evaluated.
The mechanical isocenter diameter was measured as less than 0.6 mm. The CT-based IGRT accuracy was less than 0.5 mm considering couch precision from RT to CT position. Over the past three months, deviation of linac output was 0.5±0.3% from reference, and less than 0.2% for flatness and symmetry. Absolute point dose agreements were within 2% for all QA cases. Gamma passing rates of 3D dose distributions measured by Delta4 were achieved better than 95% per beam (3% DD/2mm DTA). Concerning the IGRT workflow, it took about 100 seconds and 70 seconds from scanning to registration for CBCT and FBCT, respectively.
The commissioning and plan QA results show that the uRT-linac 506c platform has a comparable performance as linacs from other vendors. Its long-term reproducibility and stability are still under inspection. Other techniques like dIMRT and ARC deliveries will be clinically used soon. The CT/linac combination provides seamless workflow from simulation to treatment, and enables personalized adaptive radiotherapy with less effort.