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The brachytherapy advanced example. Susanna Guatelli (CERN/INFN). Geant4 Users Workshop CERN 14 th November 2002. Brachytherapy. Radioactive sources deliver therapeutic doses near tumors, while preserving surrounding healthy tissues.

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    1. Thebrachytherapy advanced example Susanna Guatelli (CERN/INFN) Geant4 Users Workshop CERN 14th November 2002

    2. Brachytherapy Radioactive sources deliver therapeutic doses near tumors, while preserving surrounding healthy tissues Brachytherapy is a medical therapy used for cancer treatment Interstitial brachytherapy prostate I-125 Endocavitary brachytherapy uterus, vagina, lungs Ir-192 source Superficial brachytherapy skin Leipzig Applicator

    3. All the tissues are approximated to water Analytical calculation methods Disadvantages approximate dose calculation density insensitive the source is approximated to a point • precision • reproduction of the real geometry and tissues (CT ) • calculation speed • simple to use ( for hospitals !) Software characteristics for brachytherapy Calculation of dose delivered to tissue Commercial software available es.: Variseed V 7, Prowes • Advantage • high speed dose calculation

    4. Projectsoftware for dose calculation 3D dose distribution calculation Isodose curves Simulation Geant4 Analysis AIDA/Anaphe Monte Carlo method Accurate physical process simulation Test to guarantee the quality of the software Precision Real geometry reproduction Accurate description of the geometry Possibility to interface the sofware to CT Graphical visualization + user interface Dose distribution analysis ( eg. isodose curves ) Simple to use Use in hospitals Parallelisation Access to calculation distributed resources Calculation speed Expansive to new functionalities Public access Other user requirements

    5. functionalities design Software Process Test from a microscopic point of view (on e- ranges) Test the dose distribution of the interstitial source Isoseed I-125 Experimental mesurements Development of the project Sofware planning and development Tests (USDP ) Brachytherapic Application • Dose distribution calculation • Isodose curves in different brachytherapic techniques Results and future Technology Transfer

    6. Design of the brachytherapy example run Primary Particles physics Energy deposit detector analysis visualization geometry and materials event User Interfaces

    7. dose distribution 2 Software tests Test of Geant4 e- electromagnetic processes Microscopic test • e-CSDA range simulations for different absorber • materials • Comparison of different physical models • (Standard/Low Energy) • Comparison with protocol data (Report ICRU 37) CSDA range Test of the dose distribution of Bebig-Isoseed I-125 Comparison with the protocol data

    8. CSDA range test design Primary particles Physics Range Detector

    9. Beryllium • e- delivered from the centre of the box Test: CSDA range • Range = distance between the origin and the point where the kinetic energy of e- is zero • Max step fixed • No secondary particles • No energy loss fluctuations • No multiple scattering • Geant4 packages • Low Energy / Standard

    10. Test results Beryllium Materials Berillium Materials of interest to medical physics elements Beryllium Aluminum Gold Lead Uranium Water Soft tissue Muscle Bone Geant4 packages Low Energy / Standard simulate ranges with good accuracy (~ %)

    11. Dose distribution test design Primary particles Physics Energy deposit Detector

    12. analysis dose Dose distribution test Bebig Isoseed I-125 at the center of the phantom Source composition structure Geometry Random generation point and direction in the radionuclide, Decay gamma energy spectrum Primary particles Cut in range=100mm electromagnetic processes for e+, e-, gamma Physics Track geometry and dose calculation geometry are separated (voxels = 1 mm3) CPU Optimisation 2D histogram: energy deposit in the plane containing the source

    13. The simulation results are NOT in agreement with protocol data simulation TG43 mm Dose distribution results

    14. Experimental measurement of dose distribution with the use of films misura diretta • Measurements performed in water • Better spatial resolution(~ 0.5 mm) • Disadvantage : reduced range of use in comparison with LiF Protocol data • Performed with dosimeters LiF • Lif wide range of use Low spatial resolution • Critical measurements (delicate methodology of use of Lif) • Measurement in plexiglass

    15. Experimental measurements d = 3.1+/- 0.2 mm Optimisation of the experimental set-up film dose measurements of a single source characterised by different exposure time(2, 9 , 12, 30 minutes) Water phantom The measurements disagree with the protocol data and agreewith Geant4 simulation Experimental measurements protocol MC protocol

    16. Experimental measurements results Consequences The results of this work would affect strongly the clinical activity In depth studies will be performed

    17. Generalisation of the software Functionality Abstract Factory • 3D dose distribution • Isodose curves • Choice of the materials of the phantom • Graphical visualisation • Possibility to interface the system to CT • source composition geometry, materials, spectrum Use of abstract classes Radioactive source definition thanks to the design pattern: Abstract Factory Generalisation + Specific aspects of the source Parametrisation of the volumes in the geometry Parametrisation function: volume material Interface to CT Simulation result: energy deposit Analysis: dose distribution and isodose curves Dosimetry

    18. Results: Interstitial brachytherapy Source Bebig Isoseed I-125 0.16 mGy =100% isodose curves The results can be generalised to more sources located in the phantom

    19. Results: Endocavitary brachytherapy Source MicroSelectron-HDR Results: Superficial brachytherapy Leipzig Applicator

    20. Intermediate system between applications and GRID Parallelisation and distributed calculation Speed is a fundamental requirement for software used in clinical practice MC simulations were never used until now in clinical practice due to the long calculation time Parallelisation Access to distributed computing resources First results: factor ~30 increase in speed (conference Siena 2002) Possibility to run the brachytherapy example simulation + analysis via web? Look at A. Mantero Thesis

    21. Technology Transfer Particle physics software aids space and medicine Geant4 is a showcase example of technology transfer from particle physics to other fields such as space and medical science […]. CERN Courier, June 2002 Results of my simulation

    22. 3D dose calculation • Accurate simulation of physics • Realistic experimental configuration • Possibility to interface the system to CT • Applicable to all brachytherapic techniques • Exstensive • GRID compatible New and original Software • Unità Operativa di Fisica Sanitaria, Savona • IT Division, CERN • Geant4 collaboration • Anaphe team • INFN In collaboration with Conclusions Example of collaboration between different environments: Hospital activities and High Energy physics