A General Purpose Brachytherapy Software Simulation + Analysis (isodose calculation) 2/10/2002 Geant4 Workshop CERN Susanna Guatelli Univ. and INFN Genova CERN Technical Student AIDA

Brachytherapy application Br a medical therapy used for cancer treatment Brachytherapy is a medical therapy used for cancer treatment. Radioactive sources are used to deposit therapeutic doses near tumors, while preserving surrounding healthy tissue. brachytherapy is an advanced example of Geant4. Its aim is to calculate the dose delivered to tissue surrounding the sources.

Endocavitary brachytherapy Uterus,vagina, lung Superficial brachytherapy Skin Interstistial brachytherapy Prostate Ir-192 Leipzig Applicator Ir-192 I-125 The brachytherapy example calculates dose in the phantom for all these techniques

Validation of the software Simulation of the dose distribution of the interstitial source Isoseed I-125 Comparison with experimental data measurements of the distribution of dose with films (performed at the Institute of Medical Physics of San Paolo Hospital, Savona, Italy) Comparison with the actual protocol about interstitial seeds (TG43)

User Requirements Model of a simple geometry Physical processes for e-,e+, gamma Primary particles Track of the particles Visualization of the experimental setup Calculation of the energy deposit in the plane containing the source Analysis and store of the results (histograms)

Design of the validation test

Implementation The spectrum of primary particles is implemented The phantom is a box filled with water The geometry of the source is implemented Low Energy processes are implemented for gamma Standard processes for e+ Low Energy or Standard for e- Cut in range 0.1 mm Detector is the phantom: divided in voxels (dimension 1mm) Visualization of the geometry involved 1D histogram filled with the initial energy of the gamma (check!) 2D histogram filled with the energy deposit in the plane containing the source in relation to the position (voxel) in the plane itself

Results Spectrum of the gammas delivered by the source Energy delivered in the plane containing the source Distribution of dose dose distribution Standard and Low Energy Packages for e - give the same results No agreement with the protocol Agreement with experimental measurements More Studies are required !

Dose distribution: TG 43 protocol, experimental data (S. Paolo Hospital, Savona), G4-LowE G4 Standard and LowE agree  Protocol  Data (SV)  G4-LowE

User requirements of brachytherapy example distribution of doseThe aim of the software is to calculate the distribution of dose of brachytherapeutic sources in 3D in the phantom and the isodose curves isodose curves in planes. The user shall be able to define the type of the brachytherapic source The user shall be able to define the materials of the phantom The software can be interfaced with CT images (it’s possible to define the materials of the real geometry involved) Visualisation of the experimental environment Store of the data Software for all the kinds of brachytherapy

Design

Main features of the implementation of the brachytheapy example

Definition of the brachytherapic source Abstract Factory

Geometry: 1) the user can choose the absorber material of the phantom 2)thanks to the parameterisation of the phantom it is possible to define different materials for each elementary volume (voxels) 3) thanks to the parameterisation and the introduction of a map associating geometry and materials it’s possible to interface the software to CT Physical Processes: Low Energy for gamma Standard for e+ Low Energy/Standard for e-

Primary particles: 1)spectrum of the gamma delivered by the radioactive core 2)the direction of emission is random Detector: phantom: divided in voxels ( box, dimension 1mm) Particles: 1)all the particles ( primary and secondary) are tracked 2)cut in range 0.1 mm Visualization of the experimental environment Ntuple : store of the energy deposit in all the phantom 1D histogram : spectrum of gamma delivered by the radioactive core Calculation of the isodose lines

Results Bebig Isoseed I-125 microSelectron-HDR Leipzig applicator Endocavitary brachytherapy Interstitial brachytherapy Superficial brachytherapy

Leipzig applicator Dose in a phantom of soft tissue Work in Progress! 50 MeV100 % 50 % 10 % Isodose voxels

nt4 INFN Genova M.G. Pia CERN A. Pfeiffer San Paolo Hospital, Savona G. Ghiso National Institute for Cancer Research – IST, Genova A. Agostinelli, F. Foppiano, S. Garelli, M. Tropeano, R.aaanMarti Collaborations And Geant4 collaboration, AIDA/Anaphe group