SU-F-T-385: Evaluation the Influence of 6 and 15-MV Photon Energies of Intensitymodulated Radiation Therapy for Prostate Cancer

Purpose: This study was aimed to study the effects oflow- and high-energy intensity-modulated (IMRT)photon beams on the planning of target volume and thecritical organs in cases of prostate cancer. Methods: Thirty plans were generated using either 6 MV or 15 MValone, and both 6 and 15 MV beams. For each plangenerated using suitable planning objectives and doseconstraints, which was set to be identical except thebeam energy. The plans were analyzed in terms of targetcoverage, conformity, and homogeneity regardless ofbeam energy. Results: Mean percentage of V 70Gy ofrectal wall in 6 MV, 15 MV and mixed-energy plans was16.9%, 17.8%, and 16.4%, respectively, while the meanpercentage of V 40Gy was 53.6%, 52.3%, and 50.4%.The mean dose to femoral heads in 6 MV, 15 MV, andmixed-energy plans were 30.1 Gy, 25.5 Gy, and 25.4 Gy,respectively. The integral dose of 6 MV plans was 10%(on average) larger than those of 15 MV or mixed-energyplans. Conclusion: The preliminary results suggested thatmixed-energy IMRT plans may take an advantage of thedosimetric characteristics of low- and high-energybeams. Although the reduction of dose to the organs atrisk may not be clinically relevant, in this study, mixingenergy in an IMRT plans showed better OAR sparingand for deep-seated tumors, the overall plan quality wasimproved.