Design and validation of novel scattering foils for modulated electron radiation therapy

Modulated Electron Radiation Therapy (MERT) continues to be an area of interest to various groups, however, the scattering foils used in beam flattening have not been optimized for this modality. In this work, the feasibility of novel scattering foils specifically designed for MERT is investigated using Monte Carlo methods. Different designs based on foil material, shape and thickness were analyzed. It was shown that low atomic number materials such as aluminum were optimal, while shaped foils such as those employed in current dual foil designs were not necessary. Aluminum foil thickness between 0.36 mm and 1.50 mm were capable of sufficiently broadening beams with energies between 12 MeV and 20 MeV respectively, with beams of lower energies receiving sufficient scatter from the treatment head components and air scatter. Finally, custom foils were manufactured based upon previously simulated designs and were placed into the beamline of a 2100 EX accelerator, and showed excellent agreement between the simulated and measured PDDs and profiles. Custom foils achieved higher dose rates on the central axis compared to the clinical foils by factors of 5.4, 4.9 and 4.5 for 12 MeV, 16 MeV and 20 MeV, respectively.