Effects of 10 MV and Flattening-Filter-Free Beams on Peripheral Dose in a Cohort of Pediatric Patients

Purpose To assess the effect of flattening-filter-free (FFF) and 10 MV radiation therapy beams on the peripheral dose received by a population of pediatric patients undergoing volumetric modulated arc therapy (VMAT). Methods and Materials Twenty-six previously delivered 6 MV flattened VMAT pediatric radiation therapy treatments plans were replanned with 6 MV flattened, 6 MV FFF, and 10 MV FFF VMAT. Monte Carlo simulation code EGSnrc was used in conjunction with a measurement-based model to obtain 3-dimensional dose distributions. Peripheral dose delivered by FFF beams was compared with that delivered by 6 MV flattened beams. A statistical analysis was performed to determine whether certain clinical factors (eg, target volume, location) were associated with a change in integral relative radiation dose. Neutron dose measurements assessed the neutron contribution from the 6 MV flattened and 10 MV FFF x-ray beams. Results Both the 6 MV FFF and 10 MV FFF beams delivered significantly lower peripheral radiation doses than 6 MV flattened ( P Conclusions Both FFF beams significantly ( P