Spot scanning for 250 MeV protons

At the Swiss Institute for Nuclear Research a computer optimized treatment planning system has been developed for pion radiotherapy. The principle of this dynamic treatment technique can be adapted for proton therapy. It could prove to be a valid alternative to passive scattering for proton treatment especially of large irregularly shaped volumes. Dose calculations have been performed for specific cases using a 250 MeV pencil beam. The dose distributions and dose volume histograms have been compared with pion therapy. A horizontal experimental beam line, using a degraded 590 MeV proton beam of the PSI ring cyclotron, is set up to verify calculations in phantoms. (orig./MG)