1. S. Guatelli, CPS Innovations, Knoxville, 13 th -21 st January 2004 http://cern.ch/geant4/geant4.html http://www.ge.infn.it/geant4 Brachytherapy exercise

2. Plan of this exercise Learn the basics of how to build a simple user application –Mandatory user classes –Optional user actions Learn the basics of how to use interactive facilities –User Interface –Visualisation –Histogramming How we’ll proceed –Illustrate design and implementation basic features –Propose a simple exercise on the same topic –Show the solution

3. User requirements (main ones listed only) The user shall be able to define a radioactive source in a phantom The user shall be able to define initial position, direction and energy spectra of primary particles The user shall be able to change the absorber material of the phantom The user shall be able to define electrons, positrons, photons The user shall be able to define the electromagnetic processes involved The user shall be able to calculate the total absorbed energy in the phantom –3D distribution in the volume –2D distribution in the plane containing the source The dose should be collected in 1. mm wide voxels The user shall be able to visualise the geometry involved and the trajectories of the particles The application provides the simulation of dose distribution of brachytherapic sources in a phantom

4. OOAD

5. Implementation Exercise Brachy –header files in include/*.hh, source code in src/ *.cc –main in Brachy.cc –macro: VisualisationMacro.mac Classes –BrachyDetectorConstruction –BrachyPrimaryGeneratorAction –BrachyPhysicsList –BrachyRunAction –BrachyEventAction -BrachyVisManager -….

6. How to run Define necessary environment variables –source setup.csh Define analysis –setenv G4ANALYSIS_USE 1 How to compile and link –gmake How to run –$G4WORKDIR/bin/Linux/Brachy Default macro :VisualisationMacro.mac

7. Part 1 Use case: model a radioactive source in a phantom 1.Use case: model a 192 Ir brachytherapy seed 2.Use case: model a water phantom 3.Use case: visualise the geometry 4.Exercise: model a soft tissue phantom 5.Exercise: select phantom material from the UI 6.Exercise: model a 125 I brachytherapy seed 7.Use case: model the radioactive source as a primary generator of monochromatic photons 8.Exercise: model the spectrum of a 125 I source

9. Run Brachy1 1.It will appear: the visualization of the box 2.It will appear: |idle> (interactive mode) 3.type /run/beamOn number of events 4.The simulation is executed 5.Type exit Default visualization driver OGLIX defined in VisualisationMacro.mac About Visualization OGLIX : Immediate visualization No images saved! DAWN : Interactive panel images saved At the |idle> prompt, type help, information about interactive commands

10. More about visualisation How to change driver: in VisualisationMacro.mac /vis/open OGLIX #/vis/open DAWNFILE #/vis/open OGLIX /vis/open DAWNFILE How to work with OGLIX: At the |idle> prompt Type help Type the number corresponding to /vis/ Information about visualization commands Eg. rotation of the geometry magnification… How to work with DAWN: The interactive panel appears: devices: choose the format of the image camera: choose the geometry parameters (rotation, magnification...)

11. Model a 192 Ir brachytherapy seed Open BrachyDetectorConstruction in the editor Follow the guided tour by Susanna How the geometry is build: ExpHall: world volume Phantom: Box Capsule of the source Iridium core the mother volume is the containing volume !

13. Before starting Documentation: http://geant4.web.cern.ch/geant4http://geant4.web.cern.ch/geant4 click on documentation click on User’s Guide: For Application Developers very useful !

14. Exercise: model a soft tissue phantom Composition of soft tissue material (from NIST data base) Guidance elements –define necessary elements material –define tissue material –associate the tissue material to the phantom volume elementFractional mass H0.104472 C0.23219 N0.02488 O0.630238 Na0.00113 Mg0.00013 P0.00133 S0.00199 Cl0.00134 K0.00199 Ca0.00023 Fe0.00005 Zn0.00003 Start: brachyExe1

15. Exercise: select phantom material from UI Select a water/tissue phantom –The user shall be able to change interactively the material of the phantom Guidance –create a BrachyDetectorMessenger –Create a BrachyDetectorMessenger pointer in BrachyDetectorConstruction –Create the member function SetMaterial in BrachyDetectorConstruction –Help! Novice example N02 Solution : brachyExe2

16. Titanium capsule tips Titanium tube Iodium core: Inner radius :0 Outer radius: 0.30mm Half length:1.75mm Air: Outer radius:0.35mm half length:1.84mm Titanium tube: Outer radius:0.40mm Half length:1.84mm Titanium capsule tip: Semisphere radius:0.40mm Model a I-125 brachytherapic source in brachyExe2 Model the source geometry Air Iodium core Golden marker Golden marker: Inner radius :0 Outer radius: 0.085 mm Half length:1.75mm Precise geometry and material model of any type of source Mean gamma energy :28.45keV

17. Exercise: model a 125 I brachytherapy seed Guidance elements, materials –define necessary elements, materials solids, logical volumes, physical volumes –define solids, logical volumes, physical volumes –suggestion: proceed incrementally (i.e. implement one/few features at a time, compile, verify that it is OK, add a new feature etc…) Solution brachyExe3 Pay attention to overlapping volumes!

18. Exercise: model a source spectrum Description of the spectrum Guidance –In brachyExe3 –Change in the BrachyPrimaryGeneratorAction Solution brachyExe4 Energy(keV)Probability 27.40.783913 31.40.170416 35.50.045671

19. Part 2 Use case: calculate the energy deposit in a phantom due to a radioactive source 9.Use case: generate physics interactions in the phantom 10.Exercise: select alternative physics processes 11.Exercise: modify the production thresholds 12.Use case: collect the energy deposit in the phantom 13.Exercise: model the hits as consisting of the energy deposited in each voxel and the coordinates of the voxel centre 14.Use case: produce a 1-D histogram with the energy deposited in the phantom 15.Exercise: produce a 2-D histogram with the dose distribution in the phantom

20. Exercise: select alternative e.m. processes Replace LowEnergy processes with standard ones –For gamma and e- Change the production thresholds to 0.2 mm for all the particles involved Guidance –Novice Example N02 –User Guide: for Application Developers –Physics ReferenceManual Solution brachyExe5 In brachyExe4…

21. Collect the energy deposit in a phantom

23. Exercise: hits consisting of Edep, x,y,z Add Edep –Associate Edep to the voxel coordinates Guidance –In brachyExe5 –In BrachyEventAction –Take inspiration from Solution brachyExe6 i=((*CHC)[h])->GetZID(); k=((*CHC)[h])->GetXID(); …….

24. Analysis How to store information in 1D histograms, in 2D histograms and ntuples

27. Exercise: add a 2-D histogram Produce a 2-D histogram with the dose distribution in the phantom Guidance –In brachyExe6 –Complete the method FillHistogramWithEnergy(…) in BrachyAnalysisManager –Similar implementation as in 1-D histogram –Store the information (x, z, Edep) in the 2D histogram in BrachyEventAction –Edep is the weight Solution brachyExe7