Maria Grazia Pia, INFN Genova and CERN 1

A selection of Geant4 medical physics applications

Maria Grazia PiaINFN Genova and CERN

Maria Grazia Pia, INFN Genova and CERN 2

The Magic Cube (INFN Torino)

Sandwich of 12 parallel plate (25x25) cm2 ionization chambers

Each chamber: passive material (N2,G10,Mylar) anode (0.035 mm Cu) active material (3 mm N2) passive material air gap (2 cm, tissue equivalent of

adjustable thickness) Thickness of a chamber as water

equivalent ~1.1 mm

Between 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)

Verification of the beam system to compare the prescribed and delivered 3D dose distribution

Maria Grazia Pia, INFN Genova and CERN 3

A chamber of the Magic Cube

Air 6 mm Mylar 0.05 mm N2 3 mm G10 0.1 mm Cu (cathode) 0.035 m N2 3 mm (active) Cu (anode) 0.035 mm G10 0.1 mm N2 6 mm Mylar 0.05 mm Air 6 mm Air 20 mm

Maria Grazia Pia, INFN Genova and CERN 4

Tests with theMagic Cube Test at GSI (Carbon beam)

linearity: better than 1% uniformity: better than 3% position and width: precision of

about 1 mm

Test at PSI (proton beam) Protons beam of 137 MeV Cube rotated by 180o

No absorbers inside the Cube Range shifter of water in front

of the Cube

Test at CPO Orsay (p beam)

Maria Grazia Pia, INFN Genova and CERN 5

Bragg peak, Magic cube data and Geant4

Experimental data: Bragg peak of a 270 MeV/u carbon ion beam Geant4 and experimental data,

PSI test with proton beam

distance(cm)

Maria Grazia Pia, INFN Genova and CERN 6

Brachytherapy (National Inst. Cancer Research, Genova)

Application of Geant4 to the verification of a brachytherapy calibration procedure

Calibration of the radionuclide source strength is an essential part of any brachytherapy QA programme

MicroSelectron High Dose Rate (HDR) system at Nat. Inst. Cancer Research The 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 treatments Geant4 Low Energy electromagnetic physics processes Geant4 Radioactive Decay Module

Maria Grazia Pia, INFN Genova and CERN 7

Brachyterapy at Nat. Inst. Cancer Research, Genova

The source holder is a standard endobronchial treatment catheter, the chamber is a 0.6 cc Capintec chamber connected to a Capintec 192 electrometer

The 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.

S. Agostinelli, R. Corvo, F. Foppiano, S. Garelli, G. Sanguineti

Maria Grazia Pia, INFN Genova and CERN 8

Treatment planning with Geant

Reconstruction of the lung contour (black pixels)

Reconstruction of the optical nerves (black pixels)

CT slice of a head with the dose deposition of a proton beam obtained with the GEANT code

Geant interfaced to a file obtained with a Computer Tomography (CT) scan

Maria Grazia Pia, INFN Genova and CERN 9

CT 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 for inverse planning technique of active dose delivery

Software interface for Geant4 that reads input data in DICOM3 format developed at Medical Dept., University of Piemonte Orientale and INFN Torino

Maria Grazia Pia, INFN Genova and CERN 10

Geant4 for scatter compensation in Megavoltage 3D CT

Use GEANT4 to obtain digitally reconstructed radiographs (DRRs), including full scatter simulation

This represents a great improvement over approaches based on ray-casting.

Maria Grazia Pia, INFN Genova and CERN 11

Use 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 radiographs

This will help to produce a more accurate megavoltage 3D CT reconstruction and therefore a more reliable tool for patient positioning and treatment verification

Activity in progress at the Italian National Institute for Cancer Research, Genova

Other possible areas of application of Geant4: LINAC head simulation Scatter analysis in total body irradiation

Maria Grazia Pia, INFN Genova and CERN 12

In vivo dosimetry for mammography

TLD characterization for mammography screening simulation of dose deposition and glow curve

Mammography simulation Goal: minimize dose on patient Comparison between experimental data TLD in vivo dosimetry

and Geant4 simulation

Activity at Medical Physics Dept., Umberto I Hospital of Ordine Mauriziano, Torino

in progress

Maria Grazia Pia, INFN Genova and CERN 13

Acknowledgments

Many 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)