Presentation on theme: "A selection of Geant4 medical physics applications"— Presentation transcript:
1A selection of Geant4 medical physics applications Maria Grazia PiaINFN Genova and CERN
2The Magic Cube (INFN Torino) Verification of the beam system to compare the prescribed and delivered 3D dose distributionSandwich of 12 parallel plate (25x25) cm2 ionization chambersEach chamber:passive material (N2,G10,Mylar)anode (0.035 mm Cu)active material (3 mm N2)passive materialair gap (2 cm, tissue equivalent of adjustable thickness)Thickness of a chamber as water equivalent ~1.1 mmBetween the two chambers and the remaining ten ones there is room to insert a plastic absorber (thickness to choose to match the depth through the proximal edge of the SOBP)
3A chamber of the Magic Cube Air 6 mmMylar 0.05 mmN2 3 mmG mmCu (cathode) mN mm (active)Cu (anode) mmN2 6 mmMylar mmAir 20 mm
4Tests with theMagic Cube Test at GSI (Carbon beam)linearity: better than 1%uniformity: better than 3%position and width: precision of about 1 mmTest at PSI (proton beam)Protons beam of 137 MeVCube rotated by 180oNo absorbers inside the CubeRange shifter of water in front of the CubeTest at CPO Orsay (p beam)
5Bragg peak, Magic cube data and Geant4 Experimental data: Bragg peak of a 270 MeV/u carbon ion beamdistance(cm)Geant4 and experimental data, PSI test with proton beam
6Brachytherapy (National Inst. Cancer Research, Genova) Application of Geant4 to the verification of a brachytherapy calibration procedureCalibration of the radionuclide source strength is an essential part of any brachytherapy QA programmeMicroSelectron High Dose Rate (HDR) system at Nat. Inst. Cancer ResearchThe MicroSelectron Ir-192 sources are supplied by Mallinckrodt Medical B. V. - Holland with a calibration certificate specifying the Air Kerma Rate measure at a distance of 1 m with an uncertainty of 5 %To verify the procedure to calibrate each new MicroSelectron HDR brachytherapy source Geant4 is used to obtain simulated source Air Kerma Rate at distance of 1 m and simulated isodose distribution for the calculation of anisotropy coefficients for unshielded and shielded vaginal treatmentsGeant4 Low Energy electromagnetic physics processesGeant4 Radioactive Decay Module
7Brachyterapy at Nat. Inst. Cancer Research, Genova S. Agostinelli, R. Corvo, F. Foppiano, S. Garelli, G. SanguinetiThe source holder is a standard endobronchial treatment catheter, the chamber is a 0.6 cc Capintec chamber connected to a Capintec 192 electrometerThe IST group follows the direction of Basic Dosimetry on Radiotherapy with Brachytherapy Source of the Italian Association of Biomedical Physics (AIFB)The custom calibration plexiglas jig, used for in air measurements.
8Treatment planning with Geant Geant interfaced to a file obtained with aComputer Tomography (CT) scanReconstruction of the optical nerves (black pixels)Reconstruction of the lung contour(black pixels)CT slice of a head with the dose deposition of a proton beam obtained with the GEANT code
9CT interface and treatment planning Two possible approaches:CT interface + Geant4 “full simulation”CT interface + Geant4 “fast simulation” (physics processes parameterised through an analytical treatment)Geant-based tools forinverse planningtechnique of active dose deliverySoftware interface for Geant4 that reads input data in DICOM3 format developed at Medical Dept., University of Piemonte Orientale and INFN Torino
10Geant4 for scatter compensation in Megavoltage 3D CT Use GEANT4 to obtain digitally reconstructed radiographs (DRRs), including full scatter simulationThis represents a great improvement over approaches based on ray-casting.
11Use of Geant4 for scatter compensation in Megavoltage 3D CT The study of DRRs synthesized by Geant4 allows users to produce a model for scatter compensation of megavoltage radiographsThis will help to produce a more accurate megavoltage 3D CT reconstruction and therefore a more reliable tool for patient positioning and treatment verificationActivity in progress at the Italian National Institute for Cancer Research, GenovaOther possible areas of application of Geant4:LINAC head simulationScatter analysis in total body irradiation
12In vivo dosimetry for mammography TLD characterization for mammography screeningsimulation of dose deposition and glow curveMammography simulationGoal: minimize dose on patientComparison between experimental data TLD in vivo dosimetry and Geant4 simulationActivity at Medical Physics Dept., Umberto I Hospital of Ordine Mauriziano, Torinoin progress
13AcknowledgmentsMany Geant4 collaborators and users have contributed to this talk:S. Agostinelli, F. Foppiano, S. Garelli (Nat. Inst. for Cancer Research)R. Gotta (TERA)F. Bourhaleb, S. Chauvie, G. Nicco (INFN and Univ. Torino)V. Rolando (University of Piemonte Orientale)P. Nieminen (ESA)