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Simulation of heavy ion therapy system using Geant4. Satoru Kameoka※1,※2

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simulation of heavy ion therapy system using geant4

Simulation of heavy ion therapy system using Geant4

Satoru Kameoka※1,※2

Takashi SASAKI※1,※2, Koichi MURAKAMI※1,※2, Tsukasa ASO※2※3, Akinori KIMURA※2※4, Masataka KOMORI※5, Tatsuaki KANAI※5, Nobuyuki KANEMATSU※5, Yuka KOBAYASHI※5, Syunsuke YONAI※5, Yousuke KUSANO※6,Takeo NAKAJIMA※6, Osamu TAKAHASHI※6, Mutsumi TASHIRO※7, Yoshihisa IHARA※8, Hajime KOIKEGAMI※8

High Energy Accelerator Research Organization (KEK)※1,

CREST JST※2, Toyama National College of Maritime Technology※3, Ashikaga Institute of Technology※4, National Institute of Radiological Sciences※5, Accelerator Engineering Corporation※6, Gunma University※7

Ishikawa-harima Heavy Industries※8

motivation
Motivation
  • Background
    • Effectiveness of Heavy ion beam for cancer treatment
    • Medical application of heavy ion beam
      • Complex physics processes
      • Various specialized instruments
    • Need for a reliable simulator for treatment planning
    • Geant4 – toolkit for the simulation of the passage of particle through matter
  • Objective of this work
    • Implementation of the geometry of a heavy ion beam line of NIRS-HIMAC
    • Validation through comparison with experimental data
physical dis advantage of heavy ion beam
Dose-localizing capability (Bragg peak)

High biological effect (cell-killing capability)

Beam fragmentation

Physical (dis)advantage of heavy ion beam

Bragg peak

X-ray

neutron

g-ray

Relative dose (%)

proton

tail

Heavy ion

Site of

cancer

Depth of penetration

© NIRS

heavy ion therapy at nirs himac
Heavy ion therapy (at NIRS-HIMAC)
  • NIRS – National Institute of Radiological Science (Japan)
  • HIMAC – Heavy Ion Medical Accelerator in Chiba
  • First facility for heavy ion therapy in the world
  • Over 2,000 cases have been treated on trial basis
  • Broad beam method using wobbler-scatterer system
broad beam method
Broad beam method

Patient body

Collimator

Wobbler magnets

Ridge

Filter

Range

Shifter

Target volume

(tumor)

X

Y

Scatterer

Beam

Compensator

(Bolus)

By = Ay sin(wt)

Bx = Ax sin(wt+p/2)

Ridge

Filter

Bragg peak

dose

Spread-out

Bragg peak

Depth

general introduction of geant4
General introduction of Geant4
  • Toolkit for the simulation of the passage of particle through matter
  • Designed with object-oriented software technology
  • Abundant physics models based on experimental data
  • Powerful capability to describe complex geometry
experimental setup geometry implementation in geant4 simulation
Experimental setup / Geometry implementation in Geant4 simulation

Multi-leaf

Collimator

(open)

Acrylic

vessel

Vacuum window

Range shifter

(unused)

Dose

Monitor

(ionization

Chamber)

Water

target

Collimator

Wobber magnets

Collimator

Scatterer

(lead)

X

Y

Beam

12C

Beam profile

Monitor

(ionization

Chamber)

Ridge filter

(aluminum)

Treatment position

(isocenter)

Secondary emission

monitor

New beam line of NIRS-HIMAC for R & D

(overhead view)

target sensitive detector
Target / sensitive detector

Water

target

2 mm

Sensitive

region

1 mm

2 mm

400 mm

Beam (12C)

300 mm

enabled physics processes in geant4
Enabled physics processes in Geant4
  • Ions
    • Electromagnetic interactions
      • Ionization
      • Multiple scattering
    • Inelastic hadronic reaction
      • Inclusive reaction cross section based on empirical formulae
      • Intranuclear cascade
    • Radioactive Decay
  • Other particles (secondaries)
    • Electromagnetic interactions
    • Hadronic interactions
results 12 c 290 mev n
Results (12C 290 MeV/n)

Spread-out Bragg peak

Single Bragg peak

w/ Ridge filter

wo/ Ridge filter

Relative dose

Relative dose

Depth in water (mm)

Depth in water (mm)

Offset = - 0.8 mm

Offset = -1.0 mm

results 12 c 400 mev n
Results (12C 400 MeV/n)

Spread-out Bragg peak

Single Bragg peak

w/ Ridge Filter

wo/ Ridge Filter

Relative dose

Relative dose

Depth in water (mm)

Depth in water (mm)

Offset = -1.2 mm

Offset = -2.8 mm

summary
Summary
  • Geometry of the new beamline of NIRS-HIMAC was implemented in Geant4.
  • (Single) Bragg peak is well reproduced by Geant4 simulation.
  • Geant4 tends to underestimate the tail dose coming from the beam fragmentation.
  • To conduct thorough validation of ion physics models of Geant4, comparison with more detailed experiment including the identification of secondary particles is required.
radiation therapy of cancer
Radiation therapy (of cancer)
  • Important ‘local treatment’ (as well as surgery)
  • Photon beam (X-ray or gamma ray)
    • Flux attenuates exponentially in matter with increasing depth
  • Unavoidable exposure of surrounding normal tissue limits tolerable dose
horizontal dose profile
Horizontal dose profile

Relative dose

Position (mm)

objective
Objective
  • To establish reliable simulation framework for heavy ion therapy based on Geant4 in order to extract the parameters of specialized instruments to optimize clinical effect (treatment planning)
  • To implement the geometry of a heavy ion beamline of NIRS-HIMAC in Geant4 and assess the usability of the simulator through comparison with experimental data
instruments for heavy ion therapy
Instruments for heavy ion therapy
  • Devices to spread beam laterally
    • Broad beam method (describe in the next slide …)
      • Wobbler magnet
      • Scatterer
    • Dynamic beam delivery
  • Devices to shape lateral beam profile
    • Collimator
  • Devices to modulate beam range
    • Range shifter
    • Ridge filter
    • Compensator (Bolus)
    • Dynamic modulation (by accelerator)
  • Detector
    • Dosimeter
    • Beam profile monitor

Spot scanning method

wobbler scatterer system
Wobbler-scatterer system
  • Wobbler magnets + scatterer + ridge filter
resutls

Central

region

Peripheral

region

Resutls
  • この絵と一緒に(isocenterでの) beam profileを見せる

Beam profile

at surface of water target

400 mm

300 mm

implementation of the beamline geometry in the simulation
Implementation of the beamline geometry in the simulation
  • Show the output of viewer

Acrylic

vessel

water

Treatment position

(isocenter)

Vacuum window

Wobbler magnet

NIRS-HIMAC