Hadron Therapy Medical Applications

Transcription

1 Hadron Therapy Medical Applications G.A. Pablo Cirrone On behalf of the CATANA GEANT4 Collaboration Qualified Medical Physicist and PhD Student University of Catania and Laboratori Nazionali del Sud - INFN, Italy

2 What is the hadron-therapy? Use of ions for the radiotherapeutic treatment of tumours 120 % dose response MV X-rays 200 MeV protons 20 MeV electrons cobalt depth cm of water

3 So we can answare to the question: Why clinical proton beams? penetration depth is well-defined and adjustable most energy at end-of -range protons travel in straight lines dose to normal tissue minimised no dose beyond target PROTONS PERMIT TO DELIVER AN HIGH DOSE TO THE TUMOUR SPARING THE SOURRONDING TISSUES

4 In Catania we developed a facility CATANA for the treatment of ocular tumours with proton beams of 62 AMeV

5 LNS Superconducting Cyclotron is the unique machine in in Italy and South Europe used for protontherapy Treatment of the choroidal melanoma In Italy about 300 new cases for year

6 Laboratori Nazionali del Sud INFN Catania, Italy Cyclotron Location Treatment Room Location Proton Beam

7 PRESENT LAYOUT TREATMENT OF LNS ROOM 0 respect the switching magnet 80 meter after extraction 3 m proton beam line

8 Laser Ligth field Monitor chambers Modulator & Range shifter Scattering system

9 A brief description of the treatment The surgical phase The Treatment planning phase The verification phase The treatment phase

10 Surgical Phase (Tantalum clips insertions) CLIPS: characterize position and size of tumor volume

11 two X-Rays tubes for the visualization of the clips

12 Treatment Planning System EYEPLAN In origin developed by Michael Goiten e Tom Miller ( Massachussetts General Hospital) e ora mainteined by Martin Sheen (Clatterbridge Center for Oncology) e Charle Perrett (PSI)

13 Treatment Planning System Output Isodoses curves for different planes

14 Fixation Point Isocenter Fixation Light θ φ θ Polar Angle φ Azimutal Angle

15 PROTON BEAM Patiens look at the fixation light during the treatment

16 Patient Distribution by Origin Region N.B Total number of patients : 52 20

17 Hadron-Therapy Center of Sicilian Region Project approved on March,

18 DETECTORS USED FOR DOSE DISTRIBUTION MEASUREMENTS DEPTH DOSE DISTRIBUTION LATERAL DOSE DISTRIBUTION Markus Ionization chamber GAF Chromic Film 2 mm Sensible Volume = 0.05 cm 3 Markus Chamber layout Irradiated GAF Chromic Resolution 100 µm for DDP and 200 µm for LDP

19 Experimental PURE Bragg curve Relative Ionizzation (%) Markus Ionization Chamber Depth in water (mm) DETECTOR PEAK DEAPTH PEAK PLATEAU RATIO F.W.H.M. Distal - dose falloff Practical Range (d 10%, ICRU 59) d 80%-20% MARKUS

20 Experimental modulated Bragg curve % Relative Dose (%) Modulated region 80% 20 20% 0 R 90% Depth in water (mm)

21 Experimental Lateral Dose Distribution 100 Radiochromic Film Signal [ % ] Distance from axis [ mm ] R 90%-50% Ps [mm] Pd [mm] Simmetry [%] Homogeneity at 95% level [mm] LNS CCO

22 Why to start a Simulation Work? Therapy with hadrons still represents a pioneering thecnique Today the development of a hadron-therapy facility requires a long experimental work due to the lack of SIMULATION TOOLS Our work is inserted in the more general medical-physics GEANT4 activity and represents just a different application of a more general approach in the medical-physics field

23 Why to start a Simulation Work? This work concerns mainly: Design and optimization of the tansport beam line elements: Test of the elements Reconstruction of the dose distributions: Test of the detectors To measure dose distribution also in difficult experimental region To verify the radiotherapy treatment planning systems

24 Why to start a Simulation Work? So we start our simulation work using GEANT4: To simulate our complete beam line with all its elements and To riproduce all the dose distributions It s impossible to conceive a modern detector w/o simulation Rossi and Greisen 1941, Rev. Mod. Phys. 13:240

25 Why GEANT4 for a Medical Application? Free and Transparent code User support from experts Transparency of physics Independent validation by a large user community worldwide Use of evaluated data libraries Specific facilities controlled by a friendly UI

26 Our GEANT4 Application: hadrontherapy.cc Complete simulation of CATANA hadron-therapy beam line with two dosemeters Depth Dose Distribution in Water (Braggcurve ): Markus type ionization chamber; Lateral Dose Distribution: Radiochromic film; Each element of the line can be modified (in shape, material and position) and other kinds of dosemeters can be easily inserted

27 Design of hadrontherapy Application hadrontherapy design

28 Bragg Curve Reconstruction Water box with ionisation chamber Water box + detector for Bragg curve as simulated

29 Bragg Curve Reconstruction Detector is simulated with 20 K air cylindrical slices, 200 µm thick to reproduce experimental Markus chamber responce Energy deposited in each slice is collected We calculated range values for the detector simulation validation from Bragg curve

30 Validation of detector for the Bragg curve reconstruction Comparison with ICRU/NIST data

31 Beam Line elements simulation Scattering system Collimators system Monitor chambers Final and Patient s collimator

32 Scattering system DOUBLE SCATTERER FOIL WITH CENTRAL STOPPER 15 µm + 25 µm + 7 mm thick copper beam stopper Permits to obtain an homogeneus lateral dose distribution at isocenter

33 Monitor chambers system Collimators system

34 GEANT4 simulation Real hadron-therapy beam line

35 Primary Beam Characteristic On the basis of experimentals Bragg curves we were able to set the characteristics of the primary beam Initial Energy Energy Spread Spatial Distribution Momentum Distribution

36 Physics models Standard Processes Standard + hadronic Low Energy Low Energy + hadronic

37 beam s picture at isocenter

38 Beam Line Validation Package basse energie + fisica adronica Differenze al di sotto del 3% anche sul picco

39 Beam Line Validation WATER Ranges comparison with experimental data for water and copper ALLUMINUM

40 Lateral Dose Validation Difference in penumbra = 0.5 % Difference in FWHM = 0.5 % Difference Max in the homogeneity region = 2 %

41 Isodoses Comparison (qualitative comparison) Red: radiochromic film Blue: GEANT4 Dose level at 80% and 60 % of the maximum

42 Isodoses Comparison (a more quantitative approach) Difference of the areas for differtent isodose levels between GEANT4 and Experimental Data Collimator Diameter = 20 mm Difference below 5 % Collimator Diameter = 25 mm Difference below 8 %

43 Future developments Simulation of the Modulator Wheel to Obtain the Therapeutical Spread Out Bragg Peak Normalized Depth Dose Distribution tumour Depth in water [mm] (Work in progress)

44 Future developments Insertion of DICOM images (i.e. Like those from a Computed Tomography Examination) More realistic doses distribuition Development of new statistical tools for ISODOSES COMPARISON between experimental data and fromtps data Transfer of the application to the GRID Velocity comparable but quality superior respect with the conventional (analytical based) treatment planning systems actually in use

45 Future developments The application will be inserted soon (we hope in the first release of 2004) in the public distribution of the GEANT4 tool as advanced example We imagine our application can be used from other users for the design and development of new hadron-therapy facility and for the test of the treatment planning systems

46 Thank you Maria Grazia Pia and INFN Section of Genova (Italy) Susanna Guatelli For their scientific help and practical support they give me during the period I spent at CERN in the study of GEANT4 code