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P. Rodrigues , A. Trindade, L.Peralta, J. Varela

GEANT4 Workshop, 2002 30 September – 4 October. GEANT4 Medical Applications at LIP. P. Rodrigues , A. Trindade, L.Peralta, J. Varela. LIP – Lisbon. Radiotherapy. Radiotherapy & SPECT. Radiotherapy & PEM. 1999. 2000. 2001. 2002. 2003. EGS4. GEANT3. GEANT4. Overview.

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P. Rodrigues , A. Trindade, L.Peralta, J. Varela

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  1. GEANT4 Workshop, 2002 30 September – 4 October GEANT4 Medical Applications at LIP P. Rodrigues, A. Trindade, L.Peralta, J. Varela LIP – Lisbon

  2. Radiotherapy Radiotherapy & SPECT Radiotherapy & PEM 1999 2000 2001 2002 2003 EGS4 GEANT3 GEANT4 Overview • Use of GEANT4 for medical applications has started at end of 2000 (version 2.0) • Work in Radiotherapy has offered a fine opportunite to compare GEANT4 with EGS4 and GEANT3 • Recently GEANT4 was adopted by the Portuguese PEM Collaboration

  3. GEANT4 Dose Calculation Engine for Radiotherapy In collaboration with: CROC-IPOFG A. Chaves, C. Alves M.C. Lopes C. Oliveira

  4. 15x15 cm2 Differences Differences 10x10 cm2 10x10 cm2 15x15 cm2 Homogeneous Phantom • Simulation with EGS4 of photon beams produced by a Siemens Mevatron KD2 clinical linear accelerator • Phase-space distributions interface with GEANT4 • Validation againstexperimental data: ddepth dose and profile curves

  5. 10x10 cm2Field 5x5 cm2Field Water Styrophoam 0.0275 gcm-3 Heterogeneous Phantom • Water-styrophoam/bone-water • Stringest test on dose calculation algorithms • Accuracy of results are highly dependent on electron transport schemes (for Monte Carlo) and approximations (for TPS) • GEANT4/GEANT3 comparison with HELAX-TMS and PLATO Photons (LowE) + electrons (Standard)

  6. Styrophoam Electron Transport at Low Energies MCNP4b GEANT4 Low • Differences between G4-Standard and G4-Low Energy EM GEANT3 GEANT4 Std GEANT4 (Low+Std) • Evaluation of electron range for different GEANT4 releases Lead

  7. TPS Volume Contour User Interface Particle Transport Dose Deposition Phase Space Data ROOT Dose AnalysisService CT Images TPS 3D Dose Matrix Material Parameterization GEANT4 Dose Calculation Engine

  8. Thorax Irradiation • Alderson-Rando anthropomorphic phantom • 15 x 15 cm2lateral single field • Voxel size: 0.4 x 0.4 x 10 cm3 • 21 LiF TLDs (TLD-100) (experimentaluncertainty: 3-4%) • Comparison with PLATO (2.2.15) and HELAX-TMS (5.0A) 9.8 cm 25 cm PDD Photon beam

  9. Thorax Irradiation • Agreement better than 2% between GEANT4 and TLD dosimeters • Differences up to 11% for PLATO nearlung-tissue interface Calculated Dose / Measured Dose

  10. Photon beam Photon beam Head Irradiation • Voxel: 2 x 2 x 5 mm3 • 37 CT slices ~ 600k volumes • Two lateral opposed fields: 5 x 5 cm2, 10 x 10 cm2 • Comparison with PLATO (2.3.3) • 11 LiF TLDs for 5 x 5 cm2 • 27 LiF TLDs for 10 x 10 cm2

  11. exp. uncertainty: 4% exp. uncertainty: 4% Head Irradiation 5 x 5 cm2 Opposed Fields 10 x 10 cm2 Opposed Fields exp. uncertainty: 4% exp. uncertainty: 4%

  12. Differences G4(%)-PLATO(%) Head Irradiation 10x10 cm2 5 x 5 cm2 – Mean deviations 10 x 10 cm2 – Mean deviations L1

  13. Head Irradiation 10x10 cm2 CT numbersalong L1 Profile L1 • PLATO:~25%-45%overestimate dose in and near aircavities • Effect of bone structures on dose are present in GEANT4 • In some tumours sites (ex: larynx T2/T3-stage) a 5% under dosage will decrease local tumour control probability from ~75% to ~50%

  14. Positron Emission Mammography (PEM)

  15. APD matrix 32 Crystals LuAP 8 mm 16 mm FrontEnd Electronics 256 crystals 64 mm General PEM Detector Configuration • Basic module: 8x4 crystals and APD matrix • LuAP(20mm) • Module assembly of 8 modules: 256 crystals • PEM detector 24 modules 3072 crystals • Basic requirements: • Large solid angle coverage • High-density, high-Z and fast crystals • Fast data acquisition system 96 mm 128 mm

  16. PEM Simulation System • Benefits from GEANT4 dose calculation engine code re-use. Under development PhantomFactory MIRD type phantoms CT based phantoms CAD based phantoms Heterogeneous phantoms Homogeneous phantoms PEMsim Detector Design and Optimization DIGITsim Digitization with APD readout simulation Radioactive Decay Generic Source ROOT I/O Reconstruction LMF

  17. 9 mrad Lu X-ray Escape peak Preliminary Results • PhantomFactory: 18F decay at Radioactive Decay Module and photon acolinearity annihilation angle ENSDF Data • PEMsim: Deposited energy in 2 x 2 x 20 mm3 LuAP crystal Resolution@511 keV = 9%

  18. Distance to center of FOV Head separation distance LuAP thickness Espected value: 20 mm Preliminary Results – PEM System Sensitivity

  19. Summary and Next Steps at LIP… • GEANT4 in Radiotherapy: • Fine agreement with experimental data, compliant with strict limits • Radiotherapy is interesting environment for tuning and testing of GEANT4 Low Energy Models • Comparison with other benchmarked MC codes in medical applications • Current work: • Ongoing development of current PEM simulation code based on GEANT4 (plus test of optical photon transport - R. Moura - LIP/IST) • Development and implementation in GEANT4 of a more accurate Bremsstrahlung angular generator for low energies

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