How proton therapy works
A machine called a synchrotron or cyclotron speeds up the protons. The protons’ speed determines the energy level. High-energy protons travel deeper in the body than low-energy ones.
The protons go to the targeted place in the body. There, they deposit the specific radiation dose in the tumor.
With proton therapy, radiation does not go beyond the tumor. In contrast, with photon-based external-beam radiation therapy, x-rays continue depositing radiation as they exit the body. This means that the radiation leaving the body may damage nearby healthy tissue. That damage can cause side effects.
Treatment planning
Like other external-beam radiation therapy technologies, proton treatment requires planning. Before treatment, you have a specialized computed tomography (CT) or magnetic resonance imaging (MRI) scan. During this scan, you are on a table in the same position as during treatment. This may require an immobilization device.
Ref :
https://home.cern/about/accelerators/super-proton-synchrotron