results from the recent carbon test beam at himac

Koichi Murakami Geant4 Physics Verification and Validation (17-19/Jul./2006)

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Results from the recent Results from the recent carbon carbon

test beam at HIMACtest beam at HIMAC

Koichi MurakamiStatoru Kameoka

KEK CRC

supported by


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IntroductionIntroduction A joint project among Geant4 developers, astro-phy

sicists and medical physicists in JapanDevelopment of software framework for simulation in radi

otherapy≫funded by the Core Research for Evolutional Science and Techno

logy (CREST) program organized by Japan Science and Technology Agency (JST) from 2003 to 2008

The project goalprovides a set of software components for simulation in r

adiotherapy (especially hadrontherapy),≫well designed general purpose software framework≫DICOM/DICOM-RT interface ≫application of GRID computing technology≫visualization tools

In addition, physics validation is one of key issues.


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Physics Validation in RadiotherapyPhysics Validation in Radiotherapy

Geant4 has to reproduce precise dose distributions in human body. which requires correct simulation for the interactions between vario

us types of beams (X-ray, proton, heavy ions) and materials along beam line

reliable descriptions of ≫electromagnetic processes≫hadronic/nuclear processes≫nuclear decay processesin the relevant energy regions and particle types.

These are non-trivial issues! Physics validation is one of the most critical aspects in the

project.


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Hadrontherapy Facilities in JapanHadrontherapy Facilities in Japan

The Energy Research Center Wakasa Bay (Tsuruga: 200 MeV)

Hyogo Ion Beam Medical Center

(Nishi-Harima: 320 MeV/u)

Shizuoka Cancer Center(Mishima: 230 MeV)

NIRS(Chiba: 90 MeV,

400MeV/u)

NCC East Hospital (Kashiwa: 235 MeV)

U. of Tsukuba PMRC (Tsukuba: 250 MeV)

Ion beamProton beam

Jpn 　 (world)# Proton beam facilities: 5 (23) # Ion beam facilities: 2 (4)


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HIMAC at NIRSHIMAC at NIRSOperation since 1994Treatment beam: 12COver 2,000 patients have

been treated

Experiment Areas

RFQ Linac800 KeV/u

Alvarez Linac6 MeV/u

Synchrotron800 MeV/u

Treatment Rooms

Ion Source

~65 m


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Hadron (proton/carbon) BeamHadron (proton/carbon) Beam

Hadron beams allow conformation of dose distribution better than photons and electrons;

Ref. http://www.nirs.go.jp/tiryo/himac/himac2.htm

proton

carbon

Ｘ -ray

-rayneutron

Rel

ativ

e D

ose

(%

)

50

100

5.0 10.0 15.00.0Depth - Human Body (cm)

A sharp peak of energy deposition at the end of the range (Bragg peak)

The sharp fall-off of the Bragg peak for carbon beam

A small range straggling Carbon produces a longer

tail after the Bragg peak.


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Conformation of Irradiation FieldConformation of Irradiation FieldPatient body

Wobbler magnets

YX

Ridge Filter

Scatterer

RangeShifter

Collimator

Compensator(Bolus)

Target volume(tumor)

Bragg peak

Spread-outBragg peak

(SOBP)Depth

dose

Beam

RidgeFilter

By = Ay sin(t)

Bx = Ax sin(t+/2)

Spiral beam divergenceto create a uniform irradiation field


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Experimental SetupExperimental Setup

Treatment position(isocenter)

Vacuum window

Watertarget

Acrylicvessel

Test beam line of HIMAC(NIRS)

Secondary emissionmonitor

Wobber magnets

X Y Scatterer(lead)

DoseMonitor

(ionization Chamber)

Collimator

Ridge filter(aluminum)

Range shifter(unused)

Multi-leafCollimator

(open)

Collimator

Beam profileMonitor

(ionizationChamber)

Beam12C

Beam Energy290, 400 MeV/u


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Water target / Scored regionWater target / Scored region

• Dose distribution in a water target was measured using the horizontal arrayed dosimeters• voxel size of each element is 2 x 2 x 1 mm.• scanning along the depth direction

400 mm

2 mm

1 mm

2 mmWatertarget

Beam (12C)

Scored region


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Physics ListPhysics List

Generic Ions elastic scattering Binary light ion cascade or JQMD

≫cross section : Tripathi / Shen radioactive decay ionization / multiple scattering

Hadron elastic scattering L(H)EP+Binary cascade ionization / multiple scattering

electron/gamma standard EM


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Bragg Peak SimulationBragg Peak Simulation(Binary Cascade)(Binary Cascade)

290MeV/u

40oMeV/u

• Overall profile of Bragg peak seems to be well reproduced, but…•We found a small bump just before the peak… What is this!?


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Bragg Peak – more in detailBragg Peak – more in detail

BC JQMD

•Secondaries of 11C produce the bump of BC.

• JQMD shows no bump.

•Production rates of 11C (one neutron stripped off) and 11B (one proton stripped off) are different between Binary Cascade and JQMD.

•Production rate of 11C in BC is over created.


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Comparison between Experiment and SimulationComparison between Experiment and Simulation(290 MeV/u)(290 MeV/u)

Bragg Peak

SOBP (Spread-Out Bragg Peak)w/ Ridge Filter

offset=-0.8mm offset=-1mm

tends to underestimate the tail effectcoming from beam fragments


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Comparison between Experiment and SimulationComparison between Experiment and Simulation(400 MeV/u)(400 MeV/u)

offset=-1.2mm

offset=-2.8mm

Bragg Peak

SOBP w/ Ridge Filter

tends to underestimate the tail effectcoming from beam fragments

slight inconsistency in offset values?


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Tail Effect – more in detail Tail Effect – more in detail

Bragg Peak

290MeV/u 40oMeV/u

SOBP

Tail effect is underestimated by 10-20%.

Binary Cascade


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SummarySummary A joint project among Geant4 developers and medical physicists

in Japan is on-going. Physics validation in medical application (particle therapy) is a

critical issue. A new test beam line in HIMAC was constructed, and

experimental data was obtained. It is a good chance to validate Geant4 ion physics. Geometry of the test beam line was implemented in Geant4, and

comparisons with simulation were carried out. We tried the Binary Cascade model and the JQMD model for

describing ion interactions. Overall profile of the Bragg peaks are well reproduced by Geant4

simulation. … but, we found a problem with the Binary Cascade model in our

problem domain. We hope that it will be improved. The tail effect coming from ion fragments is not fully reproduced.

Geant4 tends to underestimate the effect. There are some space to be improved.


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AcknowledgementsAcknowledgements

T.Sasaki, K.Amako, G.Iwai (KEK) T.Aso (TNCMT) A.Kimura (Ashikaga Univ.) T. Koi (SLAC) M.Komori, T.Kanai, N.Kanematsu, Y.Kobayashi, S.Yona

i (NIRS), Y.Kusano, T.Nakajima, O.Takahashi (AEC) M.Tashiro (Gunma Univ.) Y.Ihara, H.Koikegami (IHI) supported by

results from the recent carbon test beam at himac

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