Commissioning experience with the world’s first CT-integrated linear accelerator uRT-linac 506c
PO-1789
Abstract
Commissioning experience with the world’s first CT-integrated linear accelerator uRT-linac 506c
Authors: YU|, Lei(1)*[yuleibuaa@buaa.edu.cn];Wang|, Jiazhou(1);Hu|, Weigang(1);
(1)Fudan University Shanghai Cancer Center, Radiation Oncology, Shanghai, China;
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Purpose or Objective
A newly-designed linear accelerator which integrated with helical CT (uRT-linac 506c) was introduced into clinical application by United Imaging Healthcare Co., Ltd (UIH, Shanghai, China). It combines a C-arm medical linear accelerator with a diagnostic-quality 16-slice CT imager, providing seamless workflow from simulation to treatment, and enabling personalized adaptive radiotherapy. Recently, this linac was installed and prepared for clinical operation in our department. In this study, the characteristics of uRT-linac 506c and beam commissioning data were to be reported.
Material and Methods
The processes of mechanical and imaging system tests, commissioning data collection and Treatment Planning System (TPS) modelling were summarized. The accuracy of Image-Guided Radiotherapy (IGRT) was investigated through CBCT/FBCT image registration and couch correction. Finally, a series of end-to-end 2D/3D plans, including static/dynamic Intensity Modulated Radiation Therapy (s/dIMRT) and UIH ARC therapy (uARC) plans on different treatment sites, were tested to estimate the overall accuracy for a treatment scheme before clinical usage.
Results
The mechanical RT isocenter diameter was measured as less than 0.6 mm. TPS model parameters were adjusted to reproduce the beam commissioning data within 1% deviation. The overall accuracy of CT-based IGRT was less than 1 mm considering the accuracy of couch motion from CT to RT position, as shown in Figure 1. Absolute point dose agreements for commissioning plans between ion chamber measurements and TPS calculations were within 2% for all cases, as listed in Table 1. The average gamma passing rates of 2D dose distributions measured by EBT3 film were 95.4±3.0% for Collapse Cone (CC) convolution dose calculation algorithm and 95.6±2.9% for Monte Carlo (MC) algorithm (3% DD, 3 mm DTA and 10% threshold), respectively.
Conclusion
The commission results show that the uRT-linac 506c platform has a comparable beam performance as the linacs from other vendors. As the first clinical model type, its long-term reproducibility and stability are still under inspection. The integrated CT system, as a highlight, allows a diagnostic-quality visualization of internal patient anatomical structures for more accurate image guidance, and paves the way towards advanced and adaptive radiotherapy.