Pedro Arce Introducción a GEANT4 1 GAMOS tutorial RadioTherapy Exercises Pedro Arce Dubois CIEMAT

Pedro Arce Introducción a GEANT4 2 RT simulation Exercises Ex. 0: Installation Ex. 1: Basic example Ex. 2: Write and read back a phase space file Ex. 3: Score dose in phantom Ex. 4: optimize simulation The exercises are sequential Use the commands of the previous exercise (only change what indicated

Pedro Arce Introducción a GEANT4 3 Exercise 0: installation Download installation scripts from S.2.0.0/scripts.tgz S.2.0.0/scripts.tgz Uncompress it tar xvzf scripts.tgz Install it (under csh) cd scripts csh source installGamos.csh $HOME/gamos

Pedro Arce Introducción a GEANT4 4 Exercise 1: simple geometry Geometry: Tube radius 100cm length 200cm of Water, axis along X inside Box 30cm X 30cm X 40cm of Aluminun Standard electromagnetic physics Primary particle: gamma 10 MeV at (0,0,0) in random direction

Pedro Arce Introducción a GEANT4 5 Exercise 1b: visualisation Visualize geometry and tracks Use OGLIX Use VRML2FILE

Pedro Arce Introducción a GEANT4 6 Exercise 1c: use different e.m. physics Use low energy electromagnetic Use Penelope (Make statistics on processes/particles)

Pedro Arce Introducción a GEANT4 7 RT Exercise 2a: define linac geometry TARGET: Box of 4X4X0.5 cm made of copper Placed starting at Z = 0 PRIMARY COLLIMATOR: Tube of radius 10 cm, length 6 cm made of tungsten, with a conical hole of radius 4 to 20 mm Placed starting at Z = 1.6 cm FLATTENING FILTER: Polycone: (Z, R)= (0, 1.25) (10., 9.) (17., 13.8) (17., 27.8) (18., 27.8) made of a mixture of silicon, iron and manganese in equal proportions Placed starting at Z = 8. cm MONITOR: Tube of radius 10 cm, length 3. cm made of a mixture Argon 40% and CO2 60%, density g/cm 3 Placed starting at Z = 13.5 cm JAWS XY: Trapezoids of 10 cm in Z so that they configure a field 40X40 cm made of tungsten Jaws X placed starting at Z = 200 Jaws Y placed starting at Z = 320

Pedro Arce Introducción a GEANT4 8 RT Exercise 2b: Write phase space files Write a phase space file after each of the components of the linac Make plots to see what is stored in the phase space files (particle types, energy, position, direction) Use 10,000 initial histories

Pedro Arce Introducción a GEANT4 9 RT Exercise 2c: Read phase space files Use the phase space file generated after the jaws with 10,000 as primary generator Run 100 events, and observe how the particles are reused Force that particles are not reused Recycle full phase space file 10 times Reuse each particle 5 times and use mirroring in X and Y to obtain four different configurations

Pedro Arce Introducción a GEANT4 10 RT Exercise 3a: Create simple phantom Create a simple phantom of 1X1X1 m Divide in 10X10X100 voxels First ten Z planes of Water, density 1 g/cm 3 Second ten Z planes of G4_LUNG_ICRP, density 0.3 g/cm 3 Rest of planes of G4_BONE_COMPACT_ICRU, density 1.85 g/cm 3 Place it starting at Z = 900 mm

Pedro Arce Introducción a GEANT4 11 RT Exercise 3b: score dose in phantom Use a phase space after the jaws, generated with 1,000,000 initial particles Use events Score dose in each of the phantom voxels Print a report of the dose in each voxel, with errors Make histograms of dose in voxels (PDD, Profile) Write dose in a file, with errors

Pedro Arce Introducción a GEANT4 12 RT Exercise 3c: use a real phantom Repeat exercise 3b using a real phantom: Phantom in EGS format: exercise3_8x8x39.egsphant

Pedro Arce Introducción a GEANT4 13 RT Exercise 4a: optimise production cuts for linac Define regions for each of the linac parts (target, collimator, flattening filter, monitor and jaws) Get which is the highest cut we can use in each region for electrons and gammas so that we still produce all the particles that would reach the simple phantom Set the cuts and compare time and number of particles in phase space For all these exercises count the time spent per region and per particle/energy interval

Pedro Arce Introducción a GEANT4 14 RT Exercise 4b: use bremsstrahlung splitting Use uniform bremsstrahlung splitting Try splitting 100 times and see bias in phase space Use zplane bremsstrahlung splitting, using as plane the upper plane of the phantom Compare the time and number of particles in phase space Compare the distribution of particles (phase space histos)

Pedro Arce Introducción a GEANT4 15 RT Exercise 4c: optimise minimum range user limits for phantom Define a minimum range user limit equal to one tenth of the minimum of the three voxel dimensions Define a minimum range user limit equal to the minimum of the three voxel dimensions Compare the time and dose histograms Count how many particles are killed