Peripheral doses in radiotherapy: A comparison between IMRT, VMAT and Tomotherapy

The goal of this intercomparison is to determine the peripheral doses during treatment of prostate and head and neck cancers. In the case of prostate cancer, two different treatment techniques are compared: intensity-modulated radiation therapy , on a Varian Clinac 2100 C/D and Tomotherapy. VMAT (also on a Varian Clinac 2100 C/D) was compared to Tomotherapy, for H&N cancer. The treatment devices are located at the university hospitals of Leuven and Brussels. A common treatment protocol was agreed and the same protocol was used by each partner. For the higher energy modalities we also assessed the neutron contribution to the total dose, by using bubble detectors. The performance of the different treatment techniques, when faced with the same dose distribution constraints, was evaluated. The doses were evaluated with an anthropomorphic phantom loaded with TLD detectors. We can conclude that low energy radiation techniques, namely VMAT and Tomotherapy, have more interesting performances when compared to IMRT at energies of 10 MV and 18 MV, with respect to peripheral dose. On the one hand the former are associated with lower photon doses and, on the other hand, there is no contribution from neutrons to the total dose.