Superconducting gantry for proton therapy and proton computed tomography

Abstract

This work describes the design of a novel dual-purpose superconducting gantry capable of delivering protons of kinetic energies between 75-330 MeV. It is a single system which can be used for two modalities: proton radiation therapy, and proton computed tomography (pCT) as an imaging method that aims at improving the accuracy of the proton treatment planning. The energy of protons suitable for pCT imaging of an average body patient is approximately 330 MeV and corresponds to the beam rigidity of 2.84 Tm, compared to up to 2.42 Tm rigidity of a treatment beam. Therefore, to fit the novel gantry into a conventional proton treatment room, superconducting magnets are employed. While only a single fixed energy is required for the pCT scan, an energy range must be delivered to the patient to cover the entire tumour depth if the gantry operates in the treatment mode. We hence propose a gantry based on achromatic lattices to allow for an increased energy acceptance (up to +/-5%) as compared to conventional gantries (around +/-1%). This energy acceptance, together with a range shifter mounted downstream of the gantry, eliminates the need of ramping the superconducting magnets during the treatment, allows for a higher particle transmission, and hence opens up possibilities for high dose rate treatments, i.e. FLASH proton therapy. In this thesis the beam-optics model is developed of the achromatic isocentric gantry. Several superconducting magnets are designed using a finite element method for electromagnetic simulations; this includes pure dipoles and a combined-function magnet with both dipole and quadrupole components. The resulting 3D electromagnetic maps of the magnets are used in beam tracking studies for the two operational modes of the gantry (treatment and imaging). Additionally, studies on an energy degrader used in a cyclotron-based proton therapy facility are carried out. Novel materials are examined and an optimum geometry of the degrader out of most common arrangements is found. The integration of the degrader into the gantry is discussed.

Date of Award	1 Aug 2021
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Robert Appleby (Supervisor) & Roger Jones (Supervisor)