Performance of Delta4 Phantom+ using Flattening-Filter and Flattening Filter-Free beams

The goal of this study was to evaluate the performances of the new pre-treatment system Delta4 Phantom+ in terms of a stable and sensitive tool for achieving a reliable verification. Delta4+ was evaluated for verification with 6FFFMV beams using static beam arrangement. The accelerator output was monitored with the ionization chamber. The device was tested for dose-rate dependence, linearity and stability using its daily output correction. The response of Delta4+ was evaluated for energy 6FFFMV, measuring the gamma index of four Volumetric Modulated Arc Therapy (VMAT) plan. The response of Delta4+ as a function of accelerator dose rate is in agreement with the ionization chamber with a difference smaller than 0,1%. The output is constant for different MU. VMAT plan analysis show values within 98,3%-100% with a threshold of 3%-3mm, while with a threshold of 2%-2mm the values are within 93,5%-97,5%. Delta4+ is an accurate device. For all the measurements made, uncertainties below 1% were obtained.