Phantom assessment of lung dose from proton arc therapy

Purpose: To compare resultant lung dose from proton are therapy of the chest wall to that from electron are therapy, Methods and Materials: A 200 MeV proton beam from the Indiana University Cyclotron was range shifted and modulated to provide a spread out Bragg peak extending from the surface to a depth of 4 cm in water, The chest wall of an Alderson Rando phantom was irradiated by this beam, collimated to a 20 X 4 cm field size, while it rotated on a platform at approximately 1 rpm, For comparison, electron are therapy of the Rando phantom chest wall was similarly performed with 12 MeV electrons and the resultant lung dose measured in each case. Results: Dose-volume histograms for the Rando phantom left lung indicate a reduced volume of irradiated lung for protons at all dose levels and an integral lung dose that is half that for electron are therapy in the case studied, In addition, a more uniform dose coverage of the target volume was achieved with the proton therapy. Conclusion: This study demonstrates a potential role for proton are therapy as an alternative to electron are therapy when lung dose must be minimized, (C) 1997 Elsevier Science Inc.