Author: Liang-Hsin Chen, Hsiang-Kuang Tony Linag 👨🔬
Affiliation: National Taiwan University Cancer Center, Department of Biomedical Engineering, National Taiwan University 🌍
Purpose: The characteristics of scanning proton beam is one of crucial factors to affect dose delivering accuracy in proton theray. Therefore, this study aims to evaluate and monitor the stability of scanning proton beam with energy ranging from 70-240 MeV (in 10 MeV increasements) at 12 gantry angles (0°-330° in of 30° increasements).
Methods: We utilized XRV-124 device to evaluate radiation isocenters of a scanning proton beam across energies ranging from 70-240 MeV (in 10 MeV increments) at 12 gantry angles. Besides, spot size (at various gantry angles compared to 0° gantry angle) and beam delivering angles were measured at radiation isocenter for proton beam with total 18 energies (70-240 MeV at increasements of 10 MeV) at 12 gantry angles. After acquiring data, we analyze and evaluate the stability of beam characteristics over a machine hard-test period of approximately 10 months.
Results: The radiation isocenters was within 1.4 mm for 18 different energies at 12 gantry angles. Additionally, all spot sizes of the proton beam for each energy at 12 angles were compared to those at 0° gantry angle. The measured spot size at radiation isocenter varied from -12.1% to 10%, with a maximum deviation -12.1% in the x-direction and 10.0% in the y-directions. The delivery gantry angle accuracy was within 0.2 degree across 18 energie levels at 12 angles.
Conclusion: According to our study results, we verified that the radiation isocenter of scanning proton beam with energy ranging from 70-240 MeV at 12 gantry angles, exhibited excellent stability, with an average distance deviation of less than 1.4 mm. Furthermore, the spot sizes of proton beam for 18 energy levels at 12 gantry angles were consistent. The beam delivery angle exhibited high precision and accuracy.