Design and implementation of a robust and cost-effective double-scattering system at a horizontal proton beamline

Purpose:
With an increasing number of proton therapy facilities coming into operation, also the interest for research at proton beams increases. Though many centers provide beam at an experimental room, some of these rooms do not feature a device for radiation field shaping, a so called nozzle.
Therefore, a robust, mobile, and cost-effective double-scattering system for horizontal proton beamlines has been designed and implemented.

Materials and methods:
The nozzle is based on the double scattering technique. Two lead scatterers, an aluminum ridge-filter and two brass collimators were optimized in a simulation study to form a laterally homogeneous 10 cm x 10 cm field with a spread-out Bragg-peak (SOBP).
The parts were mainly manufactured using 3D printing techniques and the system was set up at the experimental beamline of the University Proton Therapy Dresden (UPTD).
Measurements of the radiation field were carried out using a water phantom.

Results:
High levels of dose homogeneity were found in lateral (dose variation ΔD < ±2%) as well as in beam direction (ΔD < ±3% in the SOBP). The system has already been used for radiobiology and physical experiments.

Conclusion:
The presented setup allows for creating clinically realistic extended radiation fields at fixed horizontal proton beamlines and is ready to use for internal and external users.
The excellent performance combined with the simplistic design let it appear as a valuable option for proton therapy centers intending to foster their experimental portfolio.