A soft-modulating and double-scattering beam delivery system for proton therapy

The proton therapy is a new developing method in the radiation oncology. Th e superior dose localization capabilities of proton beams suggest the possi bility of depositing a higher dose into the cancer while reducing the unwan ted radiation damage in surrounding normal tissues. The merit can be realiz ed with the aid of the beam delivery system, whose functions are energy adj ustment, energy modulation, beam spreading and collimation. In this paper a new soft-modulating and double-scattering beam delivery system is proposed . It uses a program-controlled modulator to change proton energy and thereb y the proton range in the body so that the Bragg peak is spread out. Moreov er, a larger treatment field can be obtained with two scatterers. The deliv ery system has high reliability and flexibility, and is especially good for conformal therapy.