Design and test of a miniaturized lightweight superconducting heavy-ion gantry

BackgroundParticle therapy, particularly carbon ion therapy, has emerged as a promising modality for tumor treatment, offering advantages in physical dose distribution and biological damage to the target. However, gantries with room-temperature magnet designs utilized in such therapies exhibit high magnetic stiffness, which significantly constrains the efficiency and scalability of large rotating systems.PurposeThis study aims to present the design and engineering validation of a novel miniaturized lightweight heavy ion gantry incorporating superconducting magnets.MethodsFirstly, the gantry was designed based on arc-shaped composite superconducting magnets with a bending radius of 2 m and a bending angle of 45°, and the symmetric beam spot method was employed to optimize the beam optics, ensuring consistent beam spot size during rotation. Then, finite element analysis was performed to optimize the main structure, reducing the rotating part weight from 150.6 t to 135 t through zero-order optimization methods while maintaining structural integrity. Finally, a full-scale engineering prototype was fabricated and tested, including stress measurements at 20 monitoring points during 360° rotation and precision testing of the isocenter using laser tracking systems.ResultsThe stress test results show that the deviations between calculated and measured stress at 20 monitoring points are less than 10% for most locations, with a maximum stress of 49 MPa at 0° position. The measured isocenter displacement envelope radius is 0.27 mm, which is less than the design requirement of 0.5 mm. The gantry achieves a maximum rotation speed of 6°·s-1 with an acceleration time of 10.7 s, and the emergency braking overshoot angle is 4°, meeting all technical specifications. Furthermore, beam simulation results incorporating the position errors of superconducting magnets demonstrate that the beam spot at the isocenter satisfies clinical treatment requirements.ConclusionsThe successful development of a miniaturized lightweight heavy ion gantry in this study with a rotation radius of 5.9 m and a total weight of 165 t, represents a significant reduction of approximately 73% in weight compared to conventional room-temperature magnet gantries (>600 t). The achieved isocenter positioning accuracy of 0.27 mm and stress deviation of less than 10% validate the reliability of the superconducting magnet-based design. This study provides a practical and cost-effective solution for heavy ion therapy facilities, laying a solid foundation for future clinical applications and full-beam testing.