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 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 Site of cancer © NIRS Depth of penetration Relative dose (%) proton Heavy ion X-ray  -ray neutron tail Bragg peak

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 Patient body Wobbler magnets Y X Ridge Filter Scatterer Range Shifter Collimator Compensator (Bolus) Target volume (tumor) Bragg peak Spread-out Bragg peak Depth dose Beam Ridge Filter B y = A y sin(  t) B x = A x sin(  t+  /2)

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 Treatment position (isocenter) Vacuum window Water target Acrylic vessel New beam line of NIRS-HIMAC for R & D (overhead view) Secondary emission monitor Wobber magnets XY Scatterer (lead) Dose Monitor (ionization Chamber) Collimator Ridge filter (aluminum) Range shifter (unused) Multi-leaf Collimator (open) Collimator Beam profile Monitor (ionization Chamber) Beam 12 C

Target / sensitive detector 400 mm 300 mm 2 mm 1 mm 2 mm Water target Beam ( 12 C) Sensitive region

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) w/ Ridge filter wo/ Ridge filter Offset = mmOffset = -1.0 mm Single Bragg peak Spread-out Bragg peak Depth in water (mm) Relative dose

Results ( 12 C 400 MeV/n) Offset = -1.2 mmOffset = -2.8 mm w/ Ridge Filter wo/ Ridge Filter Single Bragg peak Spread-out Bragg peak Depth in water (mm) Relative dose

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.

Spare OHPs

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 Position (mm) Relative dose

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 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 magnets + scatterer + ridge filter

Resutls この絵と一緒に (isocenter での ) beam profile を見せる Central region Peripheral region Beam profile at surface of water target 400 mm 300 mm

Implementation of the beamline geometry in the simulation Show the output of viewer Treatment position (isocenter) Wobbler magnet Vacuum window water Acrylic vessel NIRS-HIMAC