The Effect of Denser Material than Air in front of Clinical Radiotherapy X-Ray Beam

摘要

scatter photon produced during radiationtherapy with high energy photons is the main source of unwanted out-of-field and superficial received doses of patients. Surface buildup dose is dependent on electron contamination primarily from the unblocked view of the flattening filter and secondarily from air and collimation systems. We performed a comprehensive set of surface and buildup dose measurements with a thin window parallel-plate (PPC-40) chamber to examine effects of attenuating media in front of 6 MV X ray. To evaluate the impact of beam segmentation on buildup dose, measurements were performed with 10 × 10 cm2 fields, Measurements were performed in Solid Water using parallel plate chambers and diode for a 6 MV X-ray beam.