Development of an adjustable beam flattening system for modification of passive beam delivery technique in proton therapy

The purpose of this work is to introduce a simple method for the maximization of beam intensity on the target volume in proton therapy based on passive beam delivery system. In this method, the treatment area of the lateral beam profile is adjusted with the lateral size of the target to maximize the contribution of protons in target bombarding in order to achieve a more effective treatment. For this aim, an adjustable beam flattening system was designed to modify dose delivery by creating any arbitrary lateral homogeneous dose profile, using multi-foil scattering and beam wobbling systems. The multi-foil scattering system includes several uniform scatterer foils with different thicknesses. By this system the proper scatterer foil is automatically inserted in front of the incident proton beam for each treatment. The adjustable beam flattening system is controlled by a computer program developed with several options. This program allows the user to create the desired flat beam profile by providing the best scatterer thickness and an appropriate beam deflection angle, where both are fundamental parameters in the flat dose profile generation.