S. Guatelli, CPS Innovations, Knoxville, 13 th -21 st January 2004 Brachytherapy exercise.
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S. Guatelli,CPS Innovations,
Knoxville, 13th -21st January 2004
http://cern.ch/geant4/geant4.htmlhttp://www.ge.infn.it/geant4
Brachytherapy exerciseBrachytherapy exercise
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
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
OOAD
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- ….
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
Part 1Part 1
Use case: Use case: model a radioactive source in a phantommodel a radioactive source in a phantom
1. Use case: model a 192Ir 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 125I brachytherapy seed
7. Use case: model the radioactive source as a primary generator of monochromatic photons
8. Exercise: model the spectrum of a 125I source
Run Brachy1
1. It will appear: the visualization of the box2. It will appear: |idle> (interactive mode)3. type /run/beamOn number of events4. The simulation is executed5. Type exit
Default visualization driverOGLIX
defined in VisualisationMacro.mac
About VisualizationOGLIX : Immediate visualization No images saved!
DAWN : Interactive panel images saved
At the |idle> prompt, type help,
information about interactive commands
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 commandsEg. rotation of the geometry magnification…
How to work with DAWN:
The interactive panel appears:• devices: choose the format of the image• camera: choose the geometryparameters (rotation, magnification...)
Model a 192Ir brachytherapy seed
Open BrachyDetectorConstruction in the editor
Follow the guided tour by Susanna
How the geometry is build:3 m m ste e l c a b le
5.0 m m
0.6 m m
3.5 m m
1.1 m m
Ac tive Ir-192 C o re
ExpHall: world volume
Phantom: Box
Capsule of the source
Iridium corethe mother volume is the
containing volume!
Before starting
Documentation: http://geant4.web.cern.ch/geant4 click on documentation click on User’s Guide: For Application Developers
very useful !
Exercise: model a soft tissue phantom
Composition of soft tissue material
(from NIST data base)
Guidance– define necessary elementselements– define tissue materialmaterial– associate the tissue material to the phantom
volume
element Fractional mass
H 0.104472
C 0.23219
N 0.02488
O 0.630238
Na 0.00113
Mg 0.00013
P 0.00133
S 0.00199
Cl 0.00134
K 0.00199
Ca 0.00023
Fe 0.00005
Zn 0.00003
Start: brachyExe1
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
Titanium capsule tipsTitanium tube
Iodium core:Inner radius :0Outer radius: 0.30mmHalf length:1.75mm
Air:Outer radius:0.35mm half length:1.84mm
Titanium tube:Outer radius:0.40mmHalf length:1.84mm
Titanium capsule tip:Semisphereradius:0.40mm
Model a I-125 brachytherapic sourcein brachyExe2
Model the source geometry
Air
Iodium core
Golden marker
Golden marker:Inner radius :0Outer radius: 0.085 mmHalf length:1.75mm
Precise geometry and material model of any type of source
Mean gamma energy :28.45keV
Exercise: model a 125I brachytherapy seed
Guidance– define necessary elements, materialselements, materials– define solids, logical volumes, physical volumessolids, 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!
Exercise: model a source spectrum
Description of the spectrum
Guidance– In brachyExe3– Change in the BrachyPrimaryGeneratorAction
Solution brachyExe4
Energy(keV) Probability
27.4 0.783913
31.4 0.170416
35.5 0.045671
Part 2Part 2Use 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
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…
Collect the energy deposit in a phantom
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(); …….
Analysis
How to store information in 1D histograms, in 2D histograms and ntuples
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
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