Wedged field using the half-field method with a flattening filter-free photon beam

In this study, we propose a novel wedged field using a half-field flattening filter-free beam without a metallic filter or a moving jaw, and investigate the characteristics of the proposed technique. Dose distributions of the proposed method were first determined in virtual-water or anthropomorphic phantom using a radiotherapy planning system. We evaluated the wedge angle as a function of the field size, collimator rotation, and depth. The wedge angle at 10 MV was observed to be greater than that at 6 MV. The minimum angles at 6 and 10 MV were 17.7 degrees and 40.4 degrees, respectively, while the maximum angles were 33.9 degrees and 48.4 degrees, respectively. We determined that the wedge angle depended on the nominal beam energy and field size, and we verified that the proposed method is capable of delivering a gradient dose distribution and reducing treatment time.