Monte Carlo simulation of conical collimators for stereotactic radiosurgery with a 6 MV flattening‐filter‐free photon beam

Purpose Conical collimators, or cones, are tertiary collimators that attach to a radiotherapy linac and suited for the stereotactic radiosurgery treatment of small brain lesions. The diameter most used cones makes difficult acquisition dosimetry data needed commissioning planning systems. Although many publications report dosimetric conical radiosurgery, works use different setups, which complicates comparisons. In other cases, cone output factors reported do not take into account effect on detector response. Finally, few exist with flattening-filter-free (FFF) beams from modern models. This work aims at obtaining characterization manufactured by Brainlab AG (Munich, Germany) in 6 MV FFF beam TrueBeam STx (Varian Medical Systems). Methods Percentage depth dose curves, lateral profiles were obtained using Monte Carlo simulations diameters 4, 5, 6, 7.5, 8, 10, 12.5, 15, 17.5, 20, 25, 30 mm. simulation head was carried out PRIMO software, water phantom run general-purpose code PENELOPE. model validated comparing results measurements performed 7.5 mm field diode, microDiamond EBT3 radiochromic film. addition, those done comparison purposes, reproducing experimental setups available publications. Results acquired developed model. accurately reproduced depths maximum ratio 20- 10-cm (PDD20/10 ). A good agreement between simulated profiles: differences full-width half-maximum smaller than 0.2 mm, penumbra 80%-20% 0.25 difference average 0.0%, 3.0%, respectively, well within statistical uncertainty (4.4% coverage factor k = 2). It also found agreed 2% literature variety setup conditions, detectors, qualities, manufacturers. Conclusion has been validated. dataset this work, consisting percentage doses, factors, is useful benchmark cone-based