Geant4 Highlights for Medical Physics Applications

1. Geant4 highlightsof relevance for medical physics applications Maria Grazia Pia INFN Genova and CERN

2. Geant4 features relevant for medical applications • The transparency of physics • Extensibility in any domain to satisfy new user requirements • thanks to OO technology(Open-Closed Principle) • open design: new physics, new features can be easily added, without any perturbation to the existing code • Adopts standards wherever available (de jure or de facto) • Use of evaluated data libraries • Quality Assurance based on sound software engineering • Subject to independent validation by a large user community worldwide • User support organization by a large international Collaboration of experts

3. A look at the past • Physics simulation was handled through “packages” • monolithic: either take all of a package or nothing • difficult to understand the physics approach • hard to disentangle the data, their use and the physics modeling

4. Transparency of Geant4 physics • No “hard coded” numbers • Explicit use of units throughout the code • Separation between the calculation of cross sections and the generation of the final state • Calculation of cross-sections independent from the way they are accessed (data files, analytical formulae etc.) • Distinction between processes and models • Cuts in range(rather than in energy, as usual) • consistent treatment of interactions near boundaries between materials • Modular design, at a fine granularity, to expose the physics • physics independent from tracking • Public distribution of the code, from one reference repository worldwide

5. Physics processes relevant for medical applications • Low Energy extensions of electromagnetic interactions • 250 eV electrons, photons • ~ 1 keV positive hadrons, ions • ICRU-compliant and ICRU-consistent • Barkas effect taken into account for antiprotons, negative ions • further extensions and refinements in progress • Radioactive Decay Module • simulation of radioactive sources, including all the secondary emissions • Multiple scattering • new improved model, taking into account also lateral displacement • Hadronic interactions • ample variety of complementary and alternative models • Neutrons • exploiting all the evaluated n data libraries worldwide

6. Other features relevant for medical applications • Powerful tools relevant for complex geometries (CT) • “smart voxels” • fast algorithms for volume navigation performance • volumes can be parameterised by material • Fast and full simulation in the same environment • detailed handling of physics processes or possibility of parameterisations for faster processing • Visualisation tools • wide variety functionalities available for all the most common drivers • UI and GUI • user-friendly environement • can be easily tailored according to the user’s needs • GGE and GPE for automatic code generation • Ample documentation available from the web

7. The Geant4 Collaboration • An international Collaboration of ~100 scientists from >40 institutes • wide expertise in a variety of physics and software domains • Manages Geant4 distribution, development and User Support • CERN, KEK, SLAC, TRIUMF, JNL (Common) • ESA, INFN +TERA, Lebedev,IN2P3, Frankfurt Univ. • Atlas, BaBar, CMS, LHCB • COMMON (Serpukov, Novosibirsk, US universities etc.) • possible new memberships under discussion • Based on a Memorandum of Understanding among the parties

8. User support • Wide international user community, in a variety of fields of application • HEP and nuclear physics, astrophysics, space sciences, shielding and radioprotection, medical physics, theoretical physics, fine arts etc. • Effective model of user support • granular organisation • provided by a wide network of experts, each one in its domain of expertise • automatic tools for bug notifications • consultancy, requests of enhancements and new developments etc. • priority given to member parties