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

OverviewOverview  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 Radiotherapy & PEM Radiotherapy & SPECT Radiotherapy 2003 EGS4GEANT4GEANT3

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

Homogeneous Phantom 10x10 cm 2 15x15 cm 2 10x10 cm 2 Differences 15x15 cm 2 Differences  Simulation with EGS4 of photon beams produced by a Siemens Mevatron KD2 clinical linear accelerator  Phase-space distributions interface with GEANT4  Validation against experimental data: ddepth dose and profile curves

 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 Water Styrophoam gcm -3 Heterogeneous Phantom Photons (LowE) + electrons (Standard) 10x10 cm 2 Field 5x5 cm 2 Field

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

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

 Alderson-Rando anthropomorphic phantom  15 x 15 cm 2 lateral single field  Voxel size: 0.4 x 0.4 x 10 cm 3  21 LiF TLDs (TLD-100) (experimental uncertainty: 3-4%)  Comparison with PLATO (2.2.15) and HELAX-TMS (5.0A) Photon beam PDD 9.8 cm25 cm Thorax Irradiation

 Agreement better than 2% between GEANT4 and TLD dosimeters  Differences up to 11% for PLATO near lung-tissue interface Calculated Dose / Measured Dose Thorax Irradiation

 Voxel: 2 x 2 x 5 mm 3  37 CT slices ~ 600k volumes  Two lateral opposed fields: 5 x 5 cm 2, 10 x 10 cm 2  Comparison with PLATO (2.3.3)  11 LiF TLDs for 5 x 5 cm 2  27 LiF TLDs for 10 x 10 cm 2 Photon beam Head Irradiation

exp. uncertainty: 4% 5 x 5 cm 2 Opposed Fields 10 x 10 cm 2 Opposed Fields

5 x 5 cm 2 – Mean deviations10 x 10 cm 2 – Mean deviations L1 Differences G4(%)-PLATO(%) Head Irradiation 10x10 cm 2

 PLATO: ~25%-45% overestimate dose in and near air cavities  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% CT numbers along L1 Profile L1 Head Irradiation 10x10 cm 2

Positron Emission Mammography (PEM)

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

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

Preliminary Results  PhantomFactory: 18 F decay at Radioactive Decay Module and photon acolinearity annihilation angle Lu X-ray Escape peak  PEMsim: Deposited energy in 2 x 2 x 20 mm 3 LuAP crystal keV = 9% 9 mrad ENSDF Data

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

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