Implementation in clinical use of a new plan verification software for conformational and modulated treatments

Abstract

Introduction Single point monitor units check is mandatory for all treatment plans in France. However, this check is not reliable for intensity modulated plans because of high dose gradients. A recently released solution called Mobius3D allows performing multiple treatment plan verifications. Purpose To evaluate this new software for 3D-conformational and intensity modulation treatment plans and to study the different metrics available for treatment plan verification. Materials and methods Single point dose calculations of 144 static fields selected by experimental design were compared to the TPS calculation (AAA, Eclipse, Varian). For intensity modulation plans, a DLG correction was determined by measurements in a cylindrical homogeneous phantom. Finally, several metrics were compared for 30 VMAT treatment plans. Results The mean difference between TPS and Mobius3D calculations for static fields is −0.2 ± 0.8% with a maximum of −2.5% in homogeneous medium but differences up to 5.7% were observed in the thoracic phantom. With a DLG correction set to −1.5 mm, the VMAT treatment plans had a mean gamma analysis inside the body of 96.2% but some went down to 66.4% due to regions located outside the fields. Results of the gamma analysis inside the PTV or the mean dose delivered to the PTV were more homogeneous. Conclusion A large tolerance level was applied in presence of heterogeneities for 3D-conformational. For intensity modulation treatment plans, the gamma analysis inside the PTV was considered reliable knowing that Mobius3D also provides gamma analysis for organs at risk. Disclosure No disclosure.