1、The GEANT4 simulation toolkit, and how it could be used for SPECT and PET simulations,Giovanni Santin INFN, Trieste & CERN, Geneva giovanni.santints.infn.it on behalf of the Geant4 Collaboration MonteCarlo Simulations in Nuclear Medicine 16 - 17 july 2001 - Paris,MC in Nuclear Medicine - Paris 16 Ju
2、ly 2001 Geant4 for PET & SPECT G.Santin,2,Summary,Introduction to GEANT4Medical applications: DNA, brachytherapy, .PET & SPECT: some ideas and conclusions,MC in Nuclear Medicine - Paris 16 July 2001 Geant4 for PET & SPECT G.Santin,3,The Geant4 Collaboration,An international Collaboration of 100 scie
3、ntists 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 universitie
4、s etc.) possible new memberships under discussion Based on a Memorandum of Understanding among the parties,Budker Inst. of Physics IHEP Protvino MEPHI Moscow Pittsburg University,MC in Nuclear Medicine - Paris 16 July 2001 Geant4 for PET & SPECT G.Santin,4,The role of Geant,Geant is a simulation too
5、l, that provides a general infrastructure for the description of geometry and materials particle transport and interaction with matter the description of detector response visualisation of geometries, tracks and hits The user develops the specific code for the primary event generator the geometrical
6、 description of the set-up the digitisation of the detector response,MC in Nuclear Medicine - Paris 16 July 2001 Geant4 for PET & SPECT G.Santin,5,The transparency of physics,Advanced functionalities in geometry, physics, visualisation etc.,Extensibility to satisfy new user requirements thanks to th
7、e OO technology,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 ex
8、perts,Features relevant for medical applications,MC in Nuclear Medicine - Paris 16 July 2001 Geant4 for PET & SPECT G.Santin,6,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
9、 disentangle the data, their use and the physics modeling,MC in Nuclear Medicine - Paris 16 July 2001 Geant4 for PET & SPECT G.Santin,7,Transparency of Geant4 physics,No “hard coded” numbers Explicit use of units throughout the code Separation between the calculation of cross sections and the genera
10、tion 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 Modu
11、lar design, at a fine granularity, to expose the physics physics independent from tracking Public distribution of the code, from one reference repository worldwide The transparency of the physics implementation contributes to the validation of experimental physics results,MC in Nuclear Medicine - Pa
12、ris 16 July 2001 Geant4 for PET & SPECT G.Santin,8,Physics processes relevant for medical applications,Hadronic interactions ample variety of complementary and alternative models,Multiple scattering new improved model, taking into account also lateral displacement,Low Energy extensions of electromag
13、netic 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 se
14、condary emissions,Neutrons exploiting all the evaluated n data libraries worldwide,MC in Nuclear Medicine - Paris 16 July 2001 Geant4 for PET & SPECT G.Santin,9,Low Energy Electromagnetic Physics,Geant4 Low Energy Electromagnetic package extends the coverage of physics interactionsNeeded for space a
15、nd medical applications, n physics, antimatter searches,down to 250 eV for electrons and gbased on the LLNL data librariesshell effectsdown to 100 eV in the near futurebased on Penelope Electron Photon Transport,down to 1 keV for hadrons and ionsBethe-Bloch above 2 MeVZiegler and ICRU parameterisati
16、ons (with material dependence)free electron gas modelquantal harmonic oscillator modelcharge dependence (Barkas effect),http:/www.ge.infn.it/geant4/lowE/,MC in Nuclear Medicine - Paris 16 July 2001 Geant4 for PET & SPECT G.Santin,10,Low Energy Electromagnetic Physics,Photon attenuation coefficient i
17、n water,Ion ionisation,Shell effects,Barkas effect,Protons, Ziegler,MC in Nuclear Medicine - Paris 16 July 2001 Geant4 for PET & SPECT G.Santin,11,Other features relevant for medical applications,Powerful tools relevant for complex geometries (CT)CAD tool front-end fast algorithms for volume navigat
18、ion performance volumes can be parameterised by materialFast and full simulation in the same environment detailed handling of physics processes or possibility of parameterisations for faster processingVisualisation tools wide variety functionalities available for all the most common driversUI and GU
19、I user-friendly environement can be easily tailored according to the users needs GGE and GPE for automatic code generationAmple documentation available from the web,MC in Nuclear Medicine - Paris 16 July 2001 Geant4 for PET & SPECT G.Santin,12,Code, Examples and Documentation,Code 1M lines of code,
20、2000 classes (continuously growing) publicly available from the web Documentation 6 manuals Getting started & installation guide User guide for application & toolkit developer Software & physics reference manuals Examples distributed with the code navigation between documentation and examples code s
21、imple detectors different experiment types demonstrate essential capabilities,MC in Nuclear Medicine - Paris 16 July 2001 Geant4 for PET & SPECT G.Santin,13,Quality Assurance,Extensive use of Quality Assurance systems fundamental for a toolkit of wide public use Commercial tools Insure+, Logiscope e
22、tc. C+ coding guidelines scripts to verify their applications automatically Code inspections within working groups and across groups,Testing Unit testing in most cases down to class level granularity Integration testing sets of logically connected classes Test-bench for each category eg.: test-suite
23、 of 375 tests for hadronic physics parameterised models System testing exercising all Geant4 functionalities in realistic set-ups Physics testing comparisons with experimental data Performance Benchmarks,MC in Nuclear Medicine - Paris 16 July 2001 Geant4 for PET & SPECT G.Santin,14,Geometry,Multiple
24、 representations CGS (Constructed Solid Geometries) simple solids STEP extensions polyhedra, spheres, cylinders, cones, toroids, etc. BREPS (Boundary REPresented Solids) volumes defined by boundary surfaces include solids defined by NURBS (Non-Uniform Rational B-Splines) External tool for g3tog4 geo
25、metry conversion,CAD exchange interface through ISO STEP (Standard for the Exchange of Product Model Data) Fields of variable non-uniformity and differentiability use of various integrators, beyond Runge-Kutta time of flight correction along particle transport,Role: detailed detector description and
26、 efficient navigation,MC in Nuclear Medicine - Paris 16 July 2001 Geant4 for PET & SPECT G.Santin,15,Things one can do with Geant4 geometry,One can do operations with solids,These figures were visualised with Geant4 Ray Tracing tool,.and one can describe complex geometries, like Atlas silicon detect
27、ors,MC in Nuclear Medicine - Paris 16 July 2001 Geant4 for PET & SPECT G.Santin,16,Geant4 geometry examples,Borexino at Gran Sasso Lab.,Chandra (NASA),CMS (LHC, CERN),GLAST (NASA),ATLAS at LHC, CERN,MC in Nuclear Medicine - Paris 16 July 2001 Geant4 for PET & SPECT G.Santin,17,Visualization and UI,V
28、isualisation Various drivers OpenGL, OpenInventor, X11, Postscript, DAWN, OPACS, VRML User Interfaces Command-line, Tcl/Tk, Tcl/Java, batch+macros, OPACS, GAG, MOMO Also choice of User Interfaces: Terminal (text) or GUI: Momo (G4), OPACS, Xmotif,MC in Nuclear Medicine - Paris 16 July 2001 Geant4 for
29、 PET & SPECT G.Santin,18,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 organisati
30、on 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,MC in Nuclear Medicine - Paris 16 July 2001 Geant4 for PET & SPECT G.Santin,19,- DNA,Mu
31、lti-disciplinary Collaboration of astrophysicists and space scientists particle physicists medical physicists biologists physicians,Study of radiation damage at the cellular and DNA level in the space radiation environment (and other applications, not only in the space domain: radiotherapy, radiobio
32、logy, .),http:/www.ge.infn.it/geant4/dna/,capability to model DNA as a “geometry”capability to handle biochemical processes,Geant4,a, C, Fe, .,MC in Nuclear Medicine - Paris 16 July 2001 Geant4 for PET & SPECT G.Santin,20,Geant4 allows a complete flexible description of the real geometry,Brachythera
33、py,Radioactive sources are used to deposit therapeutic doses near tumors while preserving surrounding healthy tissues,Courtesy of National Inst. For Cancer Research, Genova, Italy,Montecarlo topics:Dose calculationComputation of dose deposition kernels for treatment planning dose calculation algorit
34、hms based on convolution/superposition methodsSeparation of primary, first scatter and multiple scatter components for complex dose deposition modelsComputation of other model-dependent parameters, e.g. anisotropy functionAccurate computation of dose deposition in high gradient regions (i. e. near s
35、ources)Verification of experimental calibrations,Naso-pharynx endocavitary treatment,MC in Nuclear Medicine - Paris 16 July 2001 Geant4 for PET & SPECT G.Santin,21,source geometryauto-absorptionencapsulationshielding effects,Anisotropy,Geant4 Radioactive Decay Module is capable of handling the gener
36、ation of the whole radioactive chain of the 192Ir source,Isodose curves,The simulated source is placed in a 30 cm water box,10.000.000 photons, 1 mm3 voxels 12 h CPU time on Intel Pentium 300 MHz,Courtesy of National Inst. For Cancer Research, Genova, Italy,Courtesy of National Inst. For Cancer Rese
37、arch,MC in Nuclear Medicine - Paris 16 July 2001 Geant4 for PET & SPECT G.Santin,22,Pixel Ionisation Chamber Relative dose with 6 MV photons beam,Dosimetric Studies,G4 vs experimental data,Deposited energy vs Depth in water,MC in Nuclear Medicine - Paris 16 July 2001 Geant4 for PET & SPECT G.Santin,
38、23,Bragg Peak of Protons in Water,Magic Cube Relative dose with 270 MeV protons beam in water,Deposited energy vs Depth in water,Courtesy of INFN & ASP, Torino, Italy,and experimental data,Sandwich of 12 parallel plate (25x25) cm2 ionization chambersEach chamber: passive material (N2,G10,Mylar) anod
39、e (0.035 mm Cu) active material (3 mm N2)passive material air gap (2 cm, tissue equivalent of adjustable thickness)Thickness of a chamber as water equivalent 1.1 mm,MC in Nuclear Medicine - Paris 16 July 2001 Geant4 for PET & SPECT G.Santin,24,Geant4 for scatter compensation in Megavoltage 3D CT,Use
40、 GEANT4 to obtain digitally reconstructed radiographs (DRRs), including full scatter simulation This represents a great improvement over approaches based on ray-casting.The study of DRRs synthesized by Geant4 allows users to produce a model for scatter compensation of megavoltage radiographs This wi
41、ll help to produce a more accurate megavoltage 3D CT reconstruction and therefore a more reliable tool for patient positioning and treatment verification Activity in progress at the Italian National Institute for Cancer Research, Genova Other possible areas of application of Geant4: LINAC head simul
42、ation Scatter analysis in total body irradiation,MC in Nuclear Medicine - Paris 16 July 2001 Geant4 for PET & SPECT G.Santin,25,Work in progress,In vivo TLD dosimetrySimulation of the energy deposition of low energy photons in TLD LiF100 nanodosimeters Used to calculate dose to patient in radiodiagn
43、ostic examinations:mammographyvirtual colonscopy,CT image interfaceInterface between Geant4 and DICOM3 CT scan images format in order to perform in tissue simulation,Courtesy of IST, Genova and IRCC Institute for Cancer Research and Treatment, Italy,CT slice of a head with the dose deposition of a p
44、roton beam obtained with the GEANT code,Medical Dept., University of Piemonte Orientale and INFN Torino,MC in Nuclear Medicine - Paris 16 July 2001 Geant4 for PET & SPECT G.Santin,26,PET & SPECT simulations with Geant4. Why not?,Detailed description of both human tissues and properties detector geom
45、etry and response (non-linear resolution function of the PET scanner, etc.) Energy range of Physics processes involved covered by the G4 standard or LowEnergy extension of EM processes Past experience in the medical physics community shows reliability and innovation in G4 simulations Injected radioa
46、ctive tracer described by the Radioactive Decay Module Simulation of patient motion with geometry modification inside the same run,MC in Nuclear Medicine - Paris 16 July 2001 Geant4 for PET & SPECT G.Santin,27,Geant4 is a simulation Toolkit, providing advanced tools for all the domains of detector s
47、imulation Geant4 is characterized by a rigorous approach to software engineering Its areas of application span diverse fields: HEP and nuclear physics, astrophysics and space sciences, medical physics, radiation studies etc. Geant4 is open to extension and evolution Geant4 physics keeps evolving wit
48、h attention to User Requirements facilitated by the OO approach An abundant set of physics processes is available, often with a variety of complementary and alternative physics models. Continuos physics validation test. Geometry description: powerful, accurate and rich Wide and growing medical user communityUser Support granted by the Geant4 Collaboration G4 URL: http:/wwwinfo.cern.ch/asd/geant/geant4.html,Summary,
