overview of the phits code and its application to medical...

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T. Sato1, K. Niita2, N. Matsuda1, S. Hashimoto1, Y. Iwamoto1, H. Iwase3, H. Nakashima1,

T. Fukahori1, S. Chiba4,1, L. Sihver5

1. Japan Atomic Energy Agency, JAEA, Japan2. Research Organization for Information Science and Technology, RIST, Japan

3. High Energy Accelerator Research Organization, KEK, Japan4. Tokyo Institute of Technology, TITech, Japan5. Chalmers University of Technology, Sweden

Workshop on Computational Medical Physics, Nara, Japan, Sep. 2, 2012

Overview of the PHITS Code and its Application to Medical Physics

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Table of Contents1. Overview of PHITS

2. Applications to Medical Physics3. Summary

1.1 General Features1.2 Physical Models1.3 Microdosimetric Function

Particle and Heavy Ion Transport code System

CapabilityTransport and collision of all particles over wide energy range

in 3D phase spacewith magnetic field & gravity

neutron, proton, meson, baryon electron, photon, heavy ions

10-4 eV to 100 GeV/u

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What is PHITS?

All contents of PHITS (source files, binary, data libraries, graphic utility etc.) are fully integrated in one package

All contents of PHITS (source files, binary, data libraries, graphic utility etc.) are fully integrated in one package

All-in-one-Package

OECD/NEA Databank, RSICC (USA, Canada etc.) and RIST (Japan)

Applications

Accelerator Design Radiation Therapy & Protection Space & Geoscience

PHITS Development Team

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GeneralContract

JAEA

KEK

•Programming• Improvement of nuclear reaction model

RIST

Kyushu Univ.

Chalmers (Sweden)

RIKEN

JAXA

•Managing all the projects

•Tutorial•Distribution

• Incorporating EGS5

• Improvement and verification of nuclear reaction model

•Application to space science and biology

•Tutorial in Europe

•Application to space science

•Application to biology using super computer “Kei”

CEA (France)• Implementation and improvement of INCL model

PHITS is a young code (born in 2001), but the project is getting bigger & bigger PHITS is a young code (born in 2001), but the project is getting bigger & bigger

Future plan

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User Interfaces of PHITS

Input fileFree format with user defined variables and formula

You do not have to change the source code of PHITSYou do not have to change the source code of PHITS

Geometry• GG or CG• 2D and 3D viewers

(ANGEL)• SimpleGEO* Tally functionsTrack length, Flux, Heat, Yield, DPA, Production, LET distribution etc.

Output DataText data, histograms, contour maps

* GUI-based software originally for FLUKA, http://theis.web.cern.ch/theis/simplegeo/

2D viewer 3D viewer SimpleGEO

PlatformsWindows, Mac (Application) and Linux (Console, MPI parallel)

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Low-energy NeutronPhoton, Electron

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Physical Processes included in PHITS

Transport betweencollisions

Collision withnucleus

• Magnetic Field• Gravity• Super mirror (reflection)• Mechanical devices, T0 chopper

External Field and Optical devices

Ionization processfor charge particle

• dE/dx : SPAR, ATIMA codeContinuous-slowing-downApproximation (CSDA)

• Microdosimetric function (unique feature)

Nuclear Data (ENDF, JENDL,…)Event Generator Mode

High-energy Particle

Heavy Ion

JAM codeJAMQMD

JQMD code

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Map of Models used in PHITS

Event generator mode:Specify secondary charged particles produced fromlow-energy neutron interaction

IonizationSPAR or ATIMA

Neutron Other hadrons(proton, pion etc.) Nucleus Electron

/Positron

Intra-Nuclear Cascade Model(JAM, Bertini)

+Evaporation & Fission Model

(GEM)

Quantum Molecular Dynamics(JQMD)

+Evaporation

(GEM)Nuclear

Data Library(JENDL-4.0)

Muon

Atomic Data

Library

(JENDL /EPDL)

Atomic Data

Library(JENDL)

Photon

200 GeV 100 GeV/n

20 MeV

10-5 eV

1 MeV

1 keV

10 MeV/n

100 GeV100 GeV

1 keV 1 keV

Photo-Nuclear

20 MeV

Low

←

E

nerg

y →

H

igh

Switching energies can be changed in input file of PHITS

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Microscopic and Macroscopic Simulation

Target size: Cell or DNA （nm ~ μm orders）Ionization and excitation: event-by-eventLowest energy: a few eVPhysical index for expressing radiation quality：Pattern of ionization

Microscopic Simulation (Track structure simulation)

cannot be directly incorporated into marcoscopic simulationcannot be directly incorporated into marcoscopic simulation

Target size: human body or bigger materials (mm ~ m orders)Ionization and excitation：CSDA or Condensed history simulationLowest energy: ~ 1 keVPhysical index for expressing radiation quality: LET

Radiation quality of HZE particles cannot be uniquely determined from LET,because the energy dispersion due to δ-ray productions is not considered

Macroscopic Simulation (PHITS etc)

characterized by ionization density in microscopic sites such as Lineal energy (y) or Specific energy (z)

Time consumptive!!

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Difference of LET and Lineal Energy, y

Schematic drawing of ionization density around trajectory

If one can calculate y distribution in macroscopic matter, it can be used as a better index for expressing the radiation quality in macrodosimetryIf one can calculate y distribution in macroscopic matter, it can be used as a better index for expressing the radiation quality in macrodosimetry

Low-energy radiation(e.g. Proton 3 MeV)

Ionization density： HIGH

δ-rayssite for calculating y

δ-rays

High-energy radiation(e.g. Carbon 350 MeV/n)Ionization density： LOW

LET: Transferred energy within a certain distance SAMEy: Transferred energy within a certain volume DIFFERENT

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Implementation of Microdosimetric Function

Calculate probability density of lineal energy, yf(y), around the trajectory of several kinds of HZE particles,

using a microscopic simulation code TRACEL

Incorporating

Propose a mathematical function* that can instantaneously calculate yf(y) around the trajectory of all HZE particles

Improve PHITS to be capable of estimating yf(y) in macroscopic matters

Based on …

GAP

Calculating the lineal energy distribution, yf(y)

{ } ( )i

s

/ 2(d)2 2 6p7i 1 7

1 p(d) 2(d / d ) (d)1 111

( )/ 1( ) ( ) exp21 2e

y w

k ki iB y C E x

k ikk

y yy w j PAzyf y P yjjφ

μ δπ−

= =

⎧ ⎫− −⎛ ⎞− ⎪ ⎪= + + + ⎨ ⎬⎜ ⎟ Γ− Γ ⎪ ⎪⎝ ⎠ ⎩ ⎭∑ ∑

*T. Sato et al. Radiat. Prot. Dosim. 122, 41 (2006)

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Examples of yf(y) calculated by PHITS

Probability density of y for site diameter 1 μm around the trajectories of high-energy carbon ion and low-energy proton having the same LET

• Data for high-energy carbon ion are shifted to lower y region• Lower RBE of high-energy particle is properly expressed by yf(y)• Data for high-energy carbon ion are shifted to lower y region• Lower RBE of high-energy particle is properly expressed by yf(y)

10−1 100 101 10210−3

10−2

10−1

y (keV/μm)

y f(y

)Proton 3MeVCarbon 350MeV/u

LET = 12 (keV/μm)

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RBE for HSG cell SF in slab phantom irradiated by several kinds of HZE beams

0 10 201

2

3

4

5

Depth from front surface (g/cm2)

RBE

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Cal. (This work)C 290MeV/n Mono

C 290MeV/n SOBPC 400MeV/n SOBP

Ne 230MeV/n MonoFe 200MeV/n Mono

Exp. data: Y. Kase et al, 2006

Application of Microdosimetric Function

Relative Biological Effectiveness (RBE) for Cell-Survival Fraction PHITS + Microdosimetric Kinetic (MK) model*

HZE beam

*R. Hawkins (1996)require yf(y) as the input parameter

Important for using PHITS in treatment planning of charged particle therapyImportant for using PHITS in treatment planning of charged particle therapyT. Sato et al. Radiat. Res. 171, 107 (2009)

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• Boron Neutron Capture Therapy (BNCT) was performed using the research reactor JRR-4 in JAEA before the earthquake

• JCDS can automatically converts the CT and MRI data (DICOM data) of patient to the voxel data written in PHITS input format

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JCDS for Treatment Planning of BNCT

3D view of patient

JAEA Computational Dosimetry System

H. Kumada et al. J. Phys.: Conf. Ser. 74, 021010 (2007)

Dose distribution in patientUsed in the treatment planning of BNCT in JAEA!Used in the treatment planning of BNCT in JAEA!

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CT Dosimetry System: WAZA-ARI

Source models Human models

What is WAZA-ARI?

Experimental study

subroutine, ‘usrsors’

F. Takahashi et al. Prog. Nucl. Sci. Technol. 2011

Web-based system for calculating patient doses from CT examinationOrgan dose data calculated by PHITS coupled with Japanese voxel phantoms for male & female

Calculation of CT Dose

CT examination

Released to public; Used for accumulating CT dose for statistical analysisReleased to public; Used for accumulating CT dose for statistical analysis

• Early and late health risks to normal / healthy tissues from the use of existing and emerging techniques for radiation therapy

• PHITS Part: Chalmers University of Technology & GSI

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ALLEGRO Project

EUROATOM EU FP7 Project, http://allegroproject.org/

Depth-Dose and Lateral-Yield Distributions in waterDepth (cm) Angle (deg)

Yiel

d (1

/sr)

Exp: Haettner et al., RPD 122, 485 (2006)

Carbon400

MeV/n

PHITS Geometry of Electron Linac

Collimator

Filter

Jaws

Courtesy of I. Larsson

Miller

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Biological Dose Estimation

1. Applicable to every radiation (photon, proton, heavy ion, BNCT)2. Considering the effect of secondary particles produced in the beam line

Example of biological dose estimation for SOBP beam in HIMAC

TantalumScatterer

(t = 0.4 mm)

RidgeFilter

PencilBeamCarbon 290 MeV/nucleon

04201100Distance from the center of human body in cm (Not to the scale)

WobblerMagnet

Al Collimator5x5 cm2 hole

voxel phantom

1000 80891

BeamMonitor

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Advantages of the PHITS-based biological dose estimation model

Biological Dose = Physical Dose × RBE for CSF• Estimate the therapeutic effect of charged particle therapy• Microdosimetric function coupled with MK model

T. Sato et al. Radiat. Res. 171, 107 (2009)

0 5 10 150

100

200

Depth from front surface (g/cm2)

Rel

ativ

e do

se

Biological dose (cal)Physical dose (cal.)Physical dose (Measured by Kase)

Dose around tumor regionCourtesy of Dr. Yonai

Calculation of Dose Conversion Coefficients

ICRP/ICRU adult reference computational phantoms

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PHITS Simulation Conditions•Incident particle: neutron, proton, pion, muon, heavy ions (~Ni) •Incident energy: 1 MeV/n* up to 100 GeV/n•Irradiation geometry: ISO, AP, PA, LLAT, RLAT, ROT•Calculated quantity: dose, Q(L), Q(y) & NASA-based dose equivalent

*from 1 meV for neutron

Used for evaluating their reference values

supervision of ICRP C2 Task groups

T. Sato et al. Phys. Med. Biol. 54, 1997, (2009), T. Sato et al. Phys. Med. Biol. 55, 2235, (2010)

Numerical data are openedhttp://phits.jaea.go.jp/ddcc/ICRP Pub.116

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Summary

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Capability of transporting all particles

Simple user interface and graphical output toolsSophisticated nuclear reaction models and libraries

Unique Microdosimetric FunctionJAM, JQMD, JENDL-4 etc.

Over a wide energy range in any materials

Please join in the PHITS tutorial on Wednesday Afternoon @ Conference Room 1

PHITS has been used by more than 700 users in many countries for various applications including medical physics, owing to…

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overview of the phits code and its application to medical...

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