Static superconducting gantry-based proton CT combined with X-ray CT as prior image for FLASH proton therapy

Proton FLASH therapy with an ultra-high dose rate is in urgent need of more accurate treatment plan system (TPS) to promote the development of proton computed tomography (CT) without intrinsic error compared with the transformation from X-ray CT. This paper presents an imaging mode of proton CT based on static superconducting gantry different from the conventional rotational gantry. The beam energy for proton CT is fixed at 350 MeV, which is boosted by a compact proton linac from 230 MeV, and then delivered by the gantry to scan the patient’s body for proton imaging. This study demonstrates that the static superconducting gantry-based proton CT is effective in clinical applications. In particular, the imaging mode, which combines the relative stopping power (RSP) map from X-ray CT as prior knowledge, can produce much a higher accuracy RSP map for TPSs and positioning and achieve ultra-fast image for real-time image-guided radiotherapy. This paper presents the conceptual design of a boosting linac, static superconducting gantry and proton CT imaging equipment. The feasibility of energy enhancement is verified by simulation, and results from Geant4 simulations and reconstruction algorithms are presented, including the simulation verification of the advantage of the imaging mode.