Optimizing dosimetric accuracy for cancer treatment with flattened and flattening filter-free photon 6 megavoltage beams: Using GAMOS and GATE Monte Carlo codes

his research investigates the optimization of cancer treatment by analyzing the dosimetric characteristics of 6 megavoltage flattened and flattening filter-free photon beams through detailed Monte Carlo simulations utilizing the GAMOS and GATE codes. Photon beams generated by a Varian medical linear accelerator were assessed based on critical factors such as dose rate, percentage depth doses(PDDs), out-of-field doses(OFDs), beam profiles scatter factor, energy spectrum, surface dose, and head and total scatter correction factor. The results demonstrate that FFF beams, as modeled with GAMOS and GATE, provide a notably higher dose rate-approximately 2.3 times greater than that of FF beams-potentially leading to reduced treatment durations. Specifically, the dose rate for FFF beams was 3.8 Gy/min compared to 1.6 Gy/min for FF beams. Additionally, the FFF beams produced a 25.0% decrease in out-of-field dose(OFD) 3.5 cm away from the field edge, attributed to reduced head scatter. However, simulations also indicated increased surface and buildup doses for FFF beams, with surface doses being around 15% higher than FF beams. By substituting the air below the secondary collimator jaws of the linear accelerator with helium(He), the ratio of surface dose was reduced from 1.24 to 1.14, while the buildup dose and dmax values were brought back in line with those of FF beams. This in-depth Monte Carlo analysis underscores the potential benefits of FFF beams in delivering more efficient radiation doses and lowering out-of-field exposure. Nonetheless, managing surface and build-up doses remains essential. With appropriate modifications, FFF technology could significantly enhance cancer treatment outcomes while reducing radiation exposure to surrounding healthy tissue, making it a promising tool for clinical use.