Monte Carlo evaluation of static and dynamic 6FFF treatments - Evaluation of dose distributions calculated with AAA, Acuros XB, and Collapsed Cone (RayStation and DoseCheck)

Sammanfattning: There are several benefits to removing the standard flattening filter and using so-called flattening filter free (FFF) treatments in external radiation therapy with photons. The main advantage is the possibility of significantly shortening the treatment time, de spite this FFF is not widely used yet. This thesis evaluates static and dynamic 6FFF dose distributions calculated with algorithms AAA, Acuros XB, and two implementations of Collapsed Cone (RayStation, and DoseCheck) with Monte Carlo calculations. A Monte Carlo 6FFF accelerator model was first validated in a water phantom and a previously developed Monte Carlo system was calibrated for 6FFF. Eight clinically planned patient plans, including prostate plans, brain plans, and plans in the thorax region, as well as one lung phantom plan were recalculated with all algorithms. The resulting dose distri butions were then evaluated against Monte Carlo using DVH evaluations. It was found that Acuros XB had the best agreement with Monte Carlo followed by AAA, both algo rithms having a comparable agreement as previously evaluated 6X plans. DoseCheck’s implementation of Collapsed Cone was found to underestimate the dose and RaySta tion’s differed the most from Monte Carlo. In conclusion, this study suggests that dose distributions calculated with AAA and Acuros XB do not lose accuracy when the flat tening filter is removed. Further, the algorithms used in DoseCheck and Raystations should be more investigated.