GAMOS tutorial RadioTherapy Exercises

1. GAMOS tutorialRadioTherapyExercises Pedro Arce Dubois CIEMAT http://fismed.ciemat.es/GAMOS Introducción a GEANT4

2. Ex. 1: Basic example Ex. 2: Write and read back a phase space file Ex. 3: Score dose in phantom Ex. 4: Optimise simulation Ex. 5: Brachytherapy source simulation The exercises are sequential Use the commands of the previous exercise (only change what indicated) RT simulation Exercises GAMOS radiotherapy tutorial

3. Geometry: Tube of radius 100cm, length 200cm, made of Water, with axis along X Placed inside box 30cm X 30cm X 40cm, made of Aluminium Standard low energy electromagnetic physics Primary particle: gamma 10 MeV at (0,0,0) in random direction Exercise 1a: simple geometry GAMOS radiotherapy tutorial

4. Visualize geometry and tracks Use OGLIX Use VRML2FILE Exercise 1b: visualisation GAMOS radiotherapy tutorial

5. Use standard electromagnetic physics Use Penelope physics Make statistics on processes/particles Exercise 1c: use different e.m. physics GAMOS radiotherapy tutorial

6. 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 2.10-3 g/cm3 Placed starting at Z = 13.5 cm JAWS XY: Cubes of 20x20x20 cm made of tungsten, forming a field 10x10 cm in Z=100 cm, with focus at z=0cm Jaws X placed starting at Z = 200 Jaws Y placed starting at Z = 320 RT Exercise 2a: define linac geometry GAMOS radiotherapy tutorial

7. 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 events RT Exercise 2b: Write phase space files GAMOS radiotherapy tutorial

8. Use the phase space file generated after the jaws as primary generator Use 100 events Run 100 events, and observe how the particles are reused 1) Do not reuse particles 2) Do not reuse particles but recycle full phase space file 3 times 3) Reuse each particle 5 times and use mirroring in X RT Exercise 2c: Read phase space files GAMOS radiotherapy tutorial

9. Create a simple phantom of 1X1X1 m Divide it in 10X10X100 voxels First ten Z planes of Water, density 1 g/cm3 Second ten Z planes of G4_LUNG_ICRP, density 0.3 g/cm3 Rest of planes of G4_BONE_COMPACT_ICRU, density 1.85 g/cm3 Place it starting at Z = 900 mm Use phase space file of previous exercise and run 100 events, reusing 5 times RT Exercise 3a: Create simple phantom GAMOS radiotherapy tutorial

10. Use a phase space after the jaws, generated with 1,000,000 initial particles (see exercise 2b) Use 10000 events Read this phase space file and run 100 events, reusing 50 times 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, profiles) Write dose in a file, with dose squared, to allow summation of files RT Exercise 3b: score dose in phantom GAMOS radiotherapy tutorial

11. Repeat exercise 3b using a real phantom: Phantom in EGS format: exercise3_64x64x39.egsphant RT Exercise 3c: use a real phantom GAMOS radiotherapy tutorial

12. Simulate the same setup as exercise 2b, but after writing the phase space, let the particles reach the simple phantom of exercise 3b Reuse particles 10 times when they are close to the phantom Score the dose using 100,000 particles and compare it to the dose calculated with 1,000,000 in exercise 2b RT Exercise 3d: accelerator + dose GAMOS radiotherapy tutorial

13. Define regions for each of the linac parts (target, collimator, flattening filter, monitor and jaws) Get which is the highest cuts we can use in each region for electrons and gammas without killing any particle 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 RT Exercise 4a: optimise production cuts for linac GAMOS radiotherapy tutorial

14. 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 Use equal-weight particle 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) Compare the efficiency in the total simulation: accelerator + dose calculation RT Exercise 4b: use bremsstrahlung splitting GAMOS radiotherapy tutorial

15. 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 dose killed by these two user limits with the total dose when no user limit is applied Get the time saved when these two user limits are used RT Exercise 4c: optimise minimum range user limits for dose calculation in phantom GAMOS radiotherapy tutorial

16. Use the geometry of exercise3 Use as primary particle iodine (Z=53, A=125), of energy 0 RT Exercise 5a: use an isotope as source GAMOS radiotherapy tutorial

17. Define the following brachytherapy source: Tube of radius 0.5 mm and length 3.7 mm, plus two end caps that are half spheres of radius 0.5 mm, made of titanium Place inside it a tube of radius 0.25 and length 1.5 mm, made of iodine Place four source at (1,1,0), (1,-1,0), (-1,1,0), (-1,-1,0) Use voxelised phantom of exercise3 Calculate the dose deposited in the phantom voxels Realize that the phantom is overlapping with the brachytherapy source, and use the GAMOS utilities to solve this problem RT Exercise 5b: place a brachytherapy source inside a voxelised phantom GAMOS radiotherapy tutorial