1. ESTRO, Geneva 2003 The importance of nuclear interactions for dose calculations in proton therapy M.Soukup 1, M.Fippel 2, F. Nuesslin 2 1 Department of Dosimetry and Application of Ionizing Radiation, Czech Technical University in Prague 2 Department for Medical Physics, University of Tuebingen

2. ESTRO, Geneva 2003 Motivation - Non negligible percentage of primary protons in proton therapy undergo nuclear interactions resulting in various secondary particles - Monte Carlo most exact computing method - development of fast Monte Carlo treatment planning system (VMCpro) - radiobiological effect (RBE)

3. ESTRO, Geneva 2003 Monte Carlo codes - Geant4 release 5.2 - Open Source (http://www.cern.ch/geant4)http://www.cern.ch/geant4 - Various models for inelastic hadronic interactions (Binary Cascade, Precompound model etc.) - Various models for electromagnetic interactions (Standard, Low Energy Extension etc.) - Fluka2002.4 - Freely available (http://www.fluka.org) but not Open Sourcehttp://www.fluka.org

4. ESTRO, Geneva 2003 Nuclear interactions with Geant4 versus experiment Phantom and experimental results from H.Paganetti, B.Gottschalk, Medical physics Vol. 30, No.7, 2003 10 -9 pC/incident proton Channel

5. ESTRO, Geneva 2003 Depth dose distributions Fluka2002 Geant4 Geant4 – No nuclear interactions 100 MeV 200 MeV Dose per primary proton [MeV.cm 2 /g] Depth [cm]

6. ESTRO, Geneva 2003 Different materials (ICRU46) and energies e.g. 150MeV primary protons: Absorbed energy due to products of nuclear inelastic interactions Muscle adult 6.0% - Skeleton adult6.4% Soft tissue M5.9% Water5.8% (Binary Cascade, homogenous cylindrical phantom, z=20cm,r=8cm) - Dose distributions – nuclear interactions

7. ESTRO, Geneva 2003 Products of inelastic nuclear processes – Contribution to depth dose distribution 150 MeV water Depth dose per primary proton [MeV.cm 2 /g] Depth [cm]

8. ESTRO, Geneva 2003 Absorbed energy due to inelastic nuclear interactions Precompound Energy of primary protons [MeV] % of absorbed energy

9. ESTRO, Geneva 2003 VMCpro versus Geant4, Fluka2002 (no nuclear interactions) Geant4: 105 min., Fluka2002: 32 min.,VMCpro: 2.5 min. ! Depth [mm] Absorbed dose Depth dose distribution

10. ESTRO, Geneva 2003 Acknowledgements: European Commission – Marie Curie program Deutsche Forschungsgemeinschaft