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

What is the hadron-therapy?

Use of ions for the radiotherapeutictreatment of tumours

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8 MV X-rays200 MeV protons20 MeV electronscobalt 60

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 TOTHE TUMOUR SPARING THE SOURRONDING TISSUES

In Catania we developed a facility

CATANAfor the treatment ofocular tumours with proton beams of 62

AMeV

LNSSuperconducting Cyclotron is the

unique machine in inItaly and South Europe used for protontherapy

Treatment of thechoroidal melanoma

In Italy about 300 new cases for year

Laboratori Nazionali del Sud –INFN Catania, Italy

CyclotronLocation

Proton BeamTreatment

Room Location

•0 ° respect the switching magnet

•80 meter after extraction

•3 m proton beam line

LAYOUT OF LNSPRESENT TREATMENT ROOM

Scattering system

Modulator &Range shifter

Monitorchambers

Ligth field

Laser

A brief description of the treatment

•The surgical phase

•The Treatment planning phase

•The verification phase

•The treatment phase

Surgical Phase (Tantalum clips insertions)

CLIPS: characterizeposition and size oftumor volume

two X-Rays tubes for the visualization of the clips

Treatment Planning System

EYEPLANEYEPLAN

In origin developed by Michael Goiten eTom Miller ( Massachussetts General

Hospital) e ora mainteined by Martin Sheen(Clatterbridge Center for Oncology) e Charle

Perrett (PSI)

Treatment Planning System Output

Isodoses curves for different planes

θ

Fixation Light

φ

θ Polar Angleφ Azimutal Angle

Isocenter

Fixation Point

Patiens look at the fixation lightduring the treatment

PROTON BEAM

Patient Distribution by Origin Region

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N.B Total number of patients : 52

Hadron-Therapy Center of Sicilian Region

Project approved on March, 7 2003

DETECTORS USED FOR DOSE DISTRIBUTION MEASUREMENTS

DEPTH DOSE DISTRIBUTION LATERAL DOSE DISTRIBUTION

•Markus Ionization chamber •GAF Chromic Film

2 mm

Sensible Volume = 0.05 cm3

Markus Chamber layout Irradiated GAF Chromic

Resolution 100 µm for DDP and 200 µm for LDP

Experimental ‘PURE’ Bragg curve

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Depth in water (mm)

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Markus Ionization Chamber

31.150.503.194.6830.14MARKUS

Practical Range(d10%, ICRU 59)

Distal -dose

falloffd80%-20%

F.W.H.M.PEAK –PLATEAU

RATIO

PEAK DEAPTH

DETECTOR

Experimental ‘modulated’ Bragg curve

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Modulated region

Experimental Lateral Dose Distribution

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Radiochromic Film

R 90%-50% Ps [mm]

Pd [mm]

Simmetry [%]

Homogeneity at 95% level

[mm] LNS 0.92 0.8 1 2.4 21 CCO 0.93 0.75 0.75 2.6 23

Why to start a Simulation Work ?

Therapy with hadrons still represents apioneering thecnique

Today the development of ahadron-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 moregeneral approach in the medical-physics field

Why to start a Simulation Work ?

This work concerns mainly:

Design and optimization of thetansport beam line elements:

Test of the elements

Test of the detectorsReconstruction of the dosedistributions:

To measure dose distribution also in difficult experimental region

To verify the radiotherapytreatment planning systems

Why to start a Simulation Work ?

So we start our simulation work using GEANT4:

•To simulate our complete beam linewith 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

Why GEANT4 for a Medical Application?

User support from experts

Free and “Transparent”code

Transparency of physics Use of evaluated data libraries

Independent validationby a large user community worldwide Specific facilities

controlled by a friendly UI

Our GEANT4 Application:

hadronTherapy.cc

Complete simulation of CATANAhadron-therapy beam line with two dosemeters

• Depth Dose Distribution in Water ( Bragg curve ):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

Design of hadronTherapy Application

hadronTherapy design

Water box + detectorfor Bragg curve as simulated

Bragg Curve Reconstruction

Water box with ionisation chamber

Bragg Curve Reconstruction

Detector is simulated with20 K air cylindrical slices, 200 µm thick to reproduce experimental Markus chamber responce

Energy deposited ineach slice is collected

We calculated range values for the detectorsimulation validation from Bragg curve

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

Beam Line elements simulation

• Scattering system

• Collimators system

• Monitor chambers

• Final and Patient’s collimator

Scattering system

DOUBLE SCATTERER FOIL WITH CENTRAL STOPPER15 µm + 25 µm + 7 mm thick copper beam stopper

Permits to obtain an homogeneus lateraldose distribution at isocenter

Collimators system

Monitor chambers system

GEANT4 simulation

Real hadron-therapy beam line

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

Physics models

StandardProcesses

Standard +hadronic

Low Energy Low Energy+ hadronic

“beam’s picture” at isocenter

Differenze al di sotto del 3% anche sul picco

Beam Line Validation

Package basse energie+

fisica adronica

WATER

Beam Line Validation

ALLUMINUMRanges comparison with experimental datafor water and copper

Lateral Dose Validation

Difference in penumbra = 0.5 %

Difference in FWHM = 0.5 %

Difference Max in the homogeneity region = 2 %

Isodoses Comparison (qualitative comparison)

Dose level at 80% and 60 % of the maximum

Red: radiochromic film

Blue: GEANT4

Isodoses Comparison (a more quantitative approach)

Difference of the areas for differtent isodose levels between GEANT4 and Experimental Data

Collimator Diameter = 20 mm

Collimator Diameter = 25 mm

Difference below 5 %

Difference below 8 %

Future developments

Simulation of the Modulator Wheel to Obtain the Therapeutical Spread OutBragg Peak

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(Work in progress)

Future developments

Insertion of DICOM images (i.e. Like those from a Computed Tomography Examination)

More realistic doses distribuition

Development of new statistical toolsfor 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

Future developments

The application will be inserted soon(we hope in the first release of 2004) in the publicdistribution 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

Thank you

Maria Grazia Pia

and

Susanna Guatelli

INFN Section of Genova (Italy)

For their scientific help and practical support they give me during the period I spent at CERN

in the study of GEANT4 code