P. Tingtian; Peking Union Medical College Hospital, Beijing, China
Purpose/Objective(s): To evaluate the modeling data and commission accuracy of the frameless robotic radiosurgery system in Precision3.3 planning system based on AAPM MPPG.5a Guide. Materials/
Methods: The different depth profiles, PDD curves and absolute output of MLC fields with different sizes and different SSDs were measured by a three-dimensional water tank, and the ? pass rate and point dose pass rate were analyzed under the same conditions as in the planning system. The point dose and plane dose end-to-end tests were performed on head and neck, chest, abdomen and pelvis phantoms, etc., and ionization chambers and film were used for the phantom tests. The point dose deviation and ? pass rate of plane dose got by fiil were analyzed. Ten CT images of patients with different sizes and sites were selected. The MLC collimator was used for planning design. The end-to-end test. Results: for point dose deviation were -0.53%±4.76%, the ? pass rate of 1mm, 1% of plane dose was 81.8%±11.9%, and the ?-pass rate of 2mm, 2% was 98.5%±1.3%. The point dose deviation of clinical patient hybrid verification plan was 1.93%±2.76%, the ?-pass rate of 1mm, 1% of SRS mapcheck was 91.3%±4.8%, and the ?-pass rate of 2mm, 2% was 98.8%±2.0%. The point dose deviation of the basic field of FSPB algorithm was -0.5%±1.7%, the ?-pass rate of 1mm, 1% of different depth profiles was 97.6%±0.3%, and the ?-pass rate of 2mm, 2% was 100%. The ? pass rate of 1mm, 1% of PDD was 95.4%±3.3%;The end-to-end test results were point dose deviation of-2.6%±6.5%, the ? pass rate of 1mm, 1% of film was 67.4%±13.7%, and the ?-pass rate of 2mm, 2% was 90.4%±10.1%. The point dose deviation of clinical patient hybrid verification plan was 3.6%±4.1%, the ?-pass rate of 1mm, 1% of SRS mapcheck was 85.7%±10.2%, and the ? pass rate of 2mm, 2% was 97.9%±4.1%. Conclusion: For the frameless robotic radiosurgery system with multileaf collimator, the calculation results of the Precision planning system by the Monte Carlo algorithm are closer to the measured results, and the calculation results of the FSPB algorithm in the heterogeneous tissue area are greater than the measured results. In the point dose measurement, the size of the ionization chamber has a great impact on the measurement results, and the smaller the size of the ionization chamber, the more realistic the measurement results are.It is recommended that the Monte Carlo algorithm be used as the final dose calculation method in the clinical work.
