Gabriele Cosmo
193 lines
11 KiB
Plaintext
193 lines
11 KiB
Plaintext
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=========================================================
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Geant4 - Brachytherapy example
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=========================================================
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README
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---------------------
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The brachytherapy example is currently maintained and upgraded by Susanna Guatelli (1), Albert Le (1) and Dean Cutajar (1), with the support of
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Luciano Pandola (2)
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1. Centre For Medical Radiation Physics (CMRP), University of Wollongong, NSW, Australia.
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2. LNS, INFN, Catania, Italy.
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------------------------------------------------------------------------
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Contact: susanna@uow.edu.au
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deanc@uow.edu.au
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geant4-advanced-examples@cern.ch
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------------------------------------------------------------------------
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List of past co-authors:
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S. George, S. Agostinelli, F. Foppiano, S. Garelli, M. G. Pia, M. Tropeano
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-----------------------------------------------------------------
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----> Introduction.
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Brachytherapy example simulates the energy deposit in a water phantom, produced by:
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1) Iridium sources (Flexisource and TG186).
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2) Iodine sources (Bebig Isoseed and Oncura 6711 I-125).
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3) Leipzig Applicator with an iridium source (model from the Istituto Tumori, Genova, Italy).
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The Flexisource, an Ir-192 source manufactured by Nucletron, an Elekta company, is a source commonly used for high dose rate brachytherapy treatments.
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The geometry of the Flexisource was adapted from D. Granero, J. Pérez-Calatayud, E. Casal, et al,
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"A dosimetric study on the Ir-192 high dose rate Flexisource", Med. Phys. 33 (12), 2006, 4578-82.
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The TG186 source is a generic Ir-192 source created to provide developers of model based dose engines with a method of validating new dose calculation techniques.
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Details of the TG186 source may be obtained from Facundo Ballester, Åsa Carlsson Tedgren, Domingo Granero, et al,
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"A generic high-dose rate 192Ir brachytherapy source for evaluation of model-based dose calculations beyond the TG-43 formalism", Med. Phys. 42, 2015, 3048-62
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In particular in this example it is shown how to:
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- model a radioactive source in terms of radiation field and geometry
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- model the radiation field with the General Particle Source with two alternative methods:
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1) Define the energy spectrum of photons exiting the radioactive core
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2) Modelling the Radioactive decay
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- calculate the energy deposition in a phantom by means of the G4 scoring mesh
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- define the physics by means of a Geant4 Modular Physics List
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- save results in an analysis ROOT file
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- calculate the dose rate distribution along the main axis of the source
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- compare the calculated dose rate distribution to reference data.
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In the case of the example, the dose rate distribution of a Flexisource is compared to D. Granero,
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J. Pérez-Calatayud, E. Casal, et al,"A dosimetric study on the Ir-192 high dose rate Flexisource", Med. Phys. 33 (12), 2006, 4578-82.
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The dose rate distribution of the Oncura 6711 I-125 source is compared to J. Dolan, Z. Lia, J. F. Williamson, "Monte Carlo and experimental
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dosimetry of an I-125 brachytherapy seed", Med. Phys. 33(12), 2006.
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The example can be executed in multithreading mode.
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------------------------------------------------------------------------
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----> 1.Experimental set-up.
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The default source is a Ir-192 Flexisource set in the center of a water phantom with size 30 cm.
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The phantom is set in the World volume filled with air.
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The primary radiation field is defined by means of the GeneralParticleSource
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-------------------------------------------------------------------------
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----> 2.SET-UP
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A standard Geant4 example CMakeLists.txt is provided.
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------------------------------------------------------------------------
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----> 3.How to run the example.
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- Batch mode:
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$G4WORKDIR/bin/Linux-g++/Brachy FlexiSourceMacro.mac
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$G4WORKDIR/bin/Linux-g++/Brachy LeipzigSourceMacro.mac
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$G4WORKDIR/bin/Linux-g++/Brachy IridiumSourceMacro.mac
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$G4WORKDIR/bin/Linux-g++/Brachy IodiumSourceMacro.mac (model of the Bebig Isoseed I-125)
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$G4WORKDIR/bin/Linux-g++/Brachy OncuraIodineSourceMacro.mac (model of the Oncura 6711 I-125)
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$G4WORKDIR/bin/Linux-g++/Brachy LeipzigSourceMacro.mac
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- Interative mode:
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3) $G4WORKDIR/bin/Linux-g++/Brachy
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VisualisationMacro.mac is loaded automatically.
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* How to change the absorber material of the phantom:
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idle>/phantom/selectMaterial materialName
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---------------------------------------------------------------------------------
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----> 4. Primary radiation Field
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The radiation field is defined with the General Particle Source.
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Two alternative options are offered:
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1) Define gamma as primary radiation field. The gamma are originated from the radioactive core.
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This radiation field is defined in:
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iodine_source_primary.mac and iridium_source_primary.mac
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2) Model the radioactive Decay. The primary particle is the radionuclide.
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This option is modelled in iodine_decay.mac and TG186_iridium_decay.mac
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The GPS macros are executed in VisualisationMacro.mac by default, FlexiSourceMacro.mac, IodineSourceMacro.mac, LeipzigSourceMacro.mac
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- The Flexisource is the default source of the example.
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- In VisualisationMacro.mac the source is the default one. iridium_source_primary.mac is executed to define the radiation field emerging from the iridium core.
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- In FlexiSourceMacro.mac the Flexi Ir source geometry is selected via interactive command. The radiation field is defined in the iridium_source_primary.mac.
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- In IodineSourceMacro.mac, the Bebig Isoseed I-125 brachytherapy source is modelled. The radiation field is modelled in terms of emitted photons in iodine_source_primary.mac.
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Alternatively the radioactive decay of I can be modelled using teh macro iodine_decay.mac.
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- In LeipzigSourceMacro.mac, A Leipzig applicator (design provided by Istituto Tumori, Genova) is modelled. The iridium_source_leipzig_primary.mac defines the radiation field of the Ir core.
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- The TG186SourceMacro.mac models the reference bIr brachytherapy source. The radiation field can be either defined with the iridium_source_primary.mac (spectrum of the emitted photons) or with TG186_iridium_decay.mac (model of the Ir decay).
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- OncuraIodineSourceMacro.mac models both the geometry and the radioactive decay of the Oncura 6711 I-125 source.
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--------------------------------------------------------------------------------
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----> 5. Physics List
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The electromagnetic Livermore Low Energy physics is active as well as the radioactive decay.
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The cut is 0.05 mm.
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Fluorescence and Auger electron emission are included.
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------------------------------------------------------------------------
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----> 6. Scoring mesh
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The scoring mesh is used to calculate the energy deposition in the plane containing the source (z=0 plane)
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integrated over the whole run. The scoring mesh is defined in the input macro files.
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The default output format of the scoring is changed in the class BrachyUserScoreWriter.
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The scoring mesh is fixed with a size of 20.025 cm along x and y. The bin size is 0.25 mm along x, y and z.
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When running in interactive mode there is no scoring mesh.The user has to add it with appropriate UI
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------------------------------------------------------------------------
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----> 6. Analysis
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G4Analysis is used to create and fill histograms in ROOT output files.
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The installation of ROOT is required to plot the results of the simulation contained
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in primary.root and brachytherapy.root(http://root.cern.ch/drupal/).
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------------------------------------------------------------------------
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----> 7. Simulation output
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The output is:
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- ASCII file EnergyDeposition.out, with xx (mm), yy(mm), zz(mm), and energy deposition (keV), in the phantom.
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To limit the use of memory, the energy deposition is scored only in the plane containing the source, however this can be changed by the user.
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By default:
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EnergyDeposition_Flexi.out contains the Edep when the Flexi source is selected.
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EnergyDeposition_iodine.out contains the Edep when Iodine Bebig Isoseed source is selected.
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EnergyDeposition_TG186.out contains the Edep when the TG186 source is selected.
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EnergyDeposition_Leipzig.out contains the Edep when the Iridium source with Leipzig applicator is selected.
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EnergyDeposition_Oncura.out contains the Edep when the Iodine Oncura 6711 source is selected.
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- brachytherapy.root, containing a 2D histogram with the energy deposition in the phantom. The macro macro.C is provided as example
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to open brachytherapy.root in ROOT interactive session and to plot the results of the simulation.
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- primary.root, with 1D histogram of the energy spectrum of photons emitted by the radionuclide (see section 4).
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plot_primary.C is provided as example to open primary.root and to plot the energy spectra
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-------------------------------------------------------------------------------
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----> 8.Visualisation
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A macro is provided ad example of visualisation: VisualisationMacro.mac.
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-------------------------------------------------------------------------------
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-----> 9. Comparison to reference data
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The ROOT macros macro.C and plot_primary.C are provided to plot the results of the simulation, contained
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in the brachytherapy.root file.
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The ROOT macro TG43_relative_dose.C has brachytherapy.root as input file. It calculates the dose rate distribution along the main axis of
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the brachytherapy source. The dose rate is normalised to 1 at 1 cm distance from the centre.
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The output file is geant4_dose.txt with two columns:
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distance from the centre (cm) dose rate distribution
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The user can then compare the dose rate distribution calculated with the example to reference data.
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Directory "comparison":
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As an example, the dose rate distribution calculated with the Flexisource is compared to reference data from D. Granero, J. Pérez-Calatayud, E. Casal, et al, "A dosimetric study on the Ir-192 high dose rate Flexisource", Med. Phys. 33 (12), 2006, 4578-82.
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The compare.C is a ROOT macro which reads the dose rate distribution calculated with the Flexisource (geant4.txt generated with the advanced example and 280 M histories ) against the reference.
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The directory "comparison" contains:
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- the reference data, granero.txt
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- the data obtained in Geant4.10.3: geant4.txt, 280 M events. geant4.txt is obtained when executing the macro TG43_relative_dose.C
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- comparison.C - macro to read geant4.txt and granero.txt and compare them in the same plot
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-----> 10. Regression testing of Geant4
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- the macros to run are in test_macro
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- the results should be processed with analysis.C
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