München 2009 – scientific programme

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ST: Fachverband Strahlen- und Medizinphysik

ST 6: Ion Radiation Therapy 1: Radiation fields and effects

ST 6.1: Talk

Wednesday, March 11, 2009, 14:00–14:30, A021

Relevance of light and low energy particles in heavy ion therapy — •Thomas Friedrich, Alexander Schmidt, Thilo Elsässer, and Michael Scholz — GSI Helmholtzzentrum für Schwerionenforschung GmbH, Biophysics, Planckstr. 1, 64291 Darmstadt

When heavy ions penetrate water or biological tissue lighter fragments are produced. We show that under conditions typical for tumor therapy with carbon ions light particles do contribute to the photon equivalent dose in the order of some percent. Hence an uncertainty in the estimate of their contribution does hardly alter the predicted relative biological effectiveness of the radiation field within the target volume. Likewise it is discussed that in particular very low energetic carbon ions (< 500 keV/amu) could be significantly more effective than estimated by the approach currently implemented in treatment planning. In contrast we demonstrate that their contribution to the photon equivalent dose is negligibly small even under extreme model assumptions. Though a more precise mechanistic understanding of low energetic particles is of general interest, it will have only minor impact on treatment planning systems for carbon ion therapy.