iBNCTProject

H. Kumada, K. Takada, T. Aihara, A. Matsumura

H. Sakurai, T. Sakae

Proton Medical Research Centre, University of Tsukuba

Verification of dose estimation for Monte-

Carlo based treatment planning system

for boron neutron capture therapy

iBNCTProjectProgress of boron neutron capture therapy (BNCT)

Boron neutron capture therapy (BNCT) is based on the nuclearreaction that occurs when boron-10 is irradiated with neutrons of theappropriate energy to produce high-energy alpha particles and recoilinglithium-7 nuclei. Therefore BNCT is categorized to external beamtherapy using neutron beam. Clinical trials for BNCT is being performedusing research rectors so far. However in recent years, manyaccelerator-based neutron sources for BNCT are being developed.In Japan in particular, some devices have been generated enoughneutrons, and two facilities are already being carrying out clinicaltrials using cyclotron-based neutron source for BNCT.

University of Tsukuba is also developing a linac-base BNCT device.

Kyoto University

Research Reactor

Institute (Osaka)

National Cancer Center

Hospital (Tokyo)

Southern Tohoku BNCT Research

Center (Fukushima)University of Tsukuba (Ibaraki)

BNCT facilities in Japan

iBNCTProjectDevelopment of Peripheral Equipment for BNCT

【RFQ+DTL Type Linac for BNCT】

【Treatment Management System】

《B

ea

m T

ran

sp

ort

Syste

m》

《Patient Positioning System》《PG-SPECT》

《Neutron Monitor》

Proton BeamNeutronBeam

《Neutron Generator》

《Beryllium

Target》

スペクトル可変機構

中性子ターゲット

中性子

即発γ線検出器

10Bと中性子反応で生じる即発γ線

即発γ線SPECTベース・リアルタイム３D線量モニター

中性子遮蔽壁

陽子線

【Treatment Planning System】

Not only neutron generator with accelerator but also peripheral devices

which are needed to perform BNCT, are being developed.

Monte-Carlo based treatment planning system

Patient positioning system by using motion capture technology

Real-time neutron monitor, PG-SPECT etc.

Treatment room

Linac

iBNCTProjectDose estimation process with Tsukuba-Plan

Monte-Carlo Calculation

Set Material Set Region of Interest Set Irradiation

Condition

Dosimetry Mode

iBNCTProjectFeatures of Tsukuba-Plan

Tsukuba-Plan has employed “PHITS” as the dose calculation engine.PHITS is multi-purpose MC transport code, and it can determinedoses for neutrons, photons as well as protons, heavy ions.Therefore Tsukuba-Plan with PHITS enables to perform doseestimation for not only BNCT but also for external beam therapiesas particle therapy and X-ray therapy. And it is also adaptable tobrachytherapy.

➡ Dose estimation/treatment planning for each radiotherapy➡ Treatment planning for combined radiotherapy➡ Dose estimation for total dose given to a patient

And Tsukuba-Plan allows to estimate incidental dose caused bysecondary neutrons in particle therapy.

Furthermore, PHITS has “MKM” which can perform micro-dosimetry.Thus Tsukuba-Plan can determine equivalent dose based onmicro-dosimetry in addition to conventional way as “RBE xPhysical dose”

iBNCTProjectApplication of Tsukuba Plan to Proton therapy and X-ray therapy

1st

scatterer

MLC

Middle

collimator

BolusRidge filter

2nd

scatterer

Head phantom

Dose estimation for proton therapyProton therapy in University

of Tsukuba Hospital

X-ray Therapy 6 MVIrradiation field: 5 cm×5 cm

0.0%

20.0%

40.0%

60.0%

80.0%

100.0%

120.0%

0.0 100.0 200.0R

ela

tiv

e d

os

e

Depth in water (mm)

Measured data

PHITS calculation

0.0%

20.0%

40.0%

60.0%

80.0%

100.0%

120.0%

-80.0-60.0-40.0-20.0 0.0 20.0 40.0 60.0 80.0

Re

lati

ve

do

se

Distance from the beam axis(mm)

Measured data

PHITS calculation

Comparison results of PDD and OCR for 6-MV beam

Target

Region

X-ra y Bea mD i r e c t i o n

Two-field fractionated X-ray irradiation

Proton

Therapy

0%

20%

40%

60%

80%

100%

120%

-50 -40 -30 -20 -10 0 10 20 30 40 50

Re

lati

ve

do

se

(%

)

Distance from the beam axis (mm)

Snout 120, MD 90 (Center of SOBP)

Measurement

PHITS calculation

Measure Depth:90 mm SOBP:40 mm

0.0%

20.0%

40.0%

60.0%

80.0%

100.0%

120.0%

0.0 50.0 100.0 150.0

Re

la t

ive

do

se

Depth in water (mm)

Measurement data

PHITS calculation

2D dose distribution

Target

Region

Poster No. 124: H. Kumada, et al., “Application expansion of the Monte-Carlo based treatment planning system for BNCT to particle radiotherapy and X-ray therapy.”

Secondary neutron dose estimation in Proton therapy

Proton dose distributions Secondary neutron dose distributions

Poster No. 125: K. Takada, et al., “Fundamental study for practical application of radiotherapy treatment planning system capable of evaluation neutron dose generated by various radiotherapy beams.”

iBNCTProject

Verification for the dose estimation

performance of Tsukuba Plan for

boron neutron capture therapy (BNCT)

iBNCTProject

Tsukuba Plan

Southern Tohoku Hospital, BNCT Center

National Cancer Center Hospital

Irradiation roomAccelerator

Kyoto University KUR, BNCT facility

University of Tsukuba, iBNCT Facility

Verification in all BNCT facilities in Japan

iBNCTProject

JRR-4 in JAEA

Create three neutron source for BNCT

iBNCT accelerator-based neutron source for BNCT in University of Tsukuba

Water phantomBeam Port

Water Phantom

KUR in Kyoto University Research Reactor

Water Phantom

Thermal neutron flux distributions in a cylindrical water phantom

0.0E+00

5.0E+08

1.0E+09

1.5E+09

2.0E+09

2.5E+09

3.0E+09

3.5E+09

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0T

he

rma

l N

eu

tro

n F

lux (

n/c

m2s

)

Depth from phantom surface (cm)

グラフタイトル

Experimental Values

Tsukuba Plan Calculations

iBNCTProjectVerification (2) in iBNCT accelerator-based neutron source

Experiments in iBNCT facility

in Univ. Tsukuba

Water phantom experiments

0.0E+00

2.0E+07

4.0E+07

6.0E+07

8.0E+07

1.0E+08

1.2E+08

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0

熱中性子束

（n

/cm

2 ・ｓ）

Phantom 表面からの深さ （cm）

陽子電流：平均0.09mＡ 水ファントム実験結果

金箔実験値

LiCAF実験値

モンテカルロ計算値

Experimental values for

thermal neutron flux

To confirm characteristics of neutron

beam emitted from beam aperture,

several experiments with a water

phantom had been carried out.

For measurement of thermal neutron

flux distribution, some gold wires and

gold foils were set inside the phantom,

and the distributions were measured.

Some scintillators detectable thermal

neutrons were also located in the

phantom.

For gamma-ray dose distribution,

many TLDs were set in the phantom,

and measured the gamma-ray dose

distribution.

Dose estimations by using Tsukuba Plan

3D-Model of water phantom

Thermal neutron flux distributions

Calculation Model

Compare

iBNCTProjectComparison with Tsukuba-Plan Calculations and Experiments

Calculation time

Intel Xeon E5

32 Core Workstation X 3

= 90 Core parallel computing

Calculation time : about 18 min.

(statistical errors around target

region < 5% )

Co

mb

ina

tion

Thermal neutron flux distributions

0.0E+00

1.0E+08

2.0E+08

3.0E+08

4.0E+08

5.0E+08

6.0E+08

7.0E+08

8.0E+08

9.0E+08

0.0 2.0 4.0 6.0 8.0 10.0

Th

erm

al N

eu

tro

n F

lux

(n/c

m2s)

Depth from surface (cm)

Calculations

Measurements

0.0E+00

5.0E+07

1.0E+08

1.5E+08

2.0E+08

2.5E+08

3.0E+08

3.5E+08

4.0E+08

4.5E+08

5.0E+08

0.0 2.0 4.0 6.0 8.0 10.0

Therm

al N

eutr

on F

lux

(n/c

m2s)

Distance from center (cm)

Calculations Surface

Measurements Surface

Calculations Depth 0.5cm

Meaurements Depth 0.3cm

Beam central axis

Lateral distributions

surface

Depth from surface: 0.5cm

0.0E+00

5.0E+07

1.0E+08

1.5E+08

2.0E+08

2.5E+08

3.0E+08

3.5E+08

4.0E+08

4.5E+08

5.0E+08

0.0 2.0 4.0 6.0 8.0 10.0

Therm

al N

eutr

on F

lux

(n/c

m2s)

Distance from center (cm)

Calculations Surface

Measurements Surface

Calculations Depth 0.5cm

Meaurements Depth 0.3cm

surface

Depth from surface: 0.5cm

Normalization point:

Depth: 5cm

0.5

Gamma-ray dose rate distributions

0.0E+00

5.0E-01

1.0E+00

1.5E+00

2.0E+00

2.5E+00

3.0E+00

3.5E+00

4.0E+00

0.0 2.0 4.0 6.0 8.0 10.0

Ga

mm

a-r

ay

do

se r

ate

(G

y/h)

Depth from surface (cm)

Calculation

Measurements

0.0E+00

5.0E-01

1.0E+00

1.5E+00

2.0E+00

2.5E+00

3.0E+00

3.5E+00

4.0E+00

0.0 2.0 4.0 6.0 8.0 10.0

Gam

ma-r

ay d

ose rate

(G

y/h

)Distance from center (cm)

Calculation Surface

Measurements Surface

Calculation Depth 2cm

Measurements Depth 2cm

Calculation Depth 2cm

Measurements 10cm

Beam central axis

Lateral distributions

surface

Depth: 2cm

Depth: 10cm

10

iBNCTProject

Calculation models Calculation Results

Set irradiation conditionsSet ROI and target point

Dose estimation for realistic human model

iBNCTProject

0

10

20

30

40

50

60

70

80

90

100

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0

グラフ タイト ル

iBNCT Left Brain

KUR Left Brain

JRR-4 Left Brain

JRR412cmBeam Left Brain

iBNCT Tumor

KUR Tumor

JRR-4 Tumor

JRR412cmBeam Tumor

Vo

lum

e（％）

Dose（Gy-Eq）

iBNCT Source・Tumor

KUR Source・Tumor

JRR4, 10cm port・Tumor

JRR4, 12cm port・Tumor

Influence for difference for beam sources, D.V.H.

iBNCTProjectFutures: Estimation for whole body exposure

Dose estimation

for whole body

exposure using

Tsukuba-Plan

Near future

Measurement for whole

body exposure in

BNCT using a whole

body phantomDose estimation for whole body exposure

in BNCT irradiation using PHITS

(a)人体ファントム照射シミュレーションモデル

(b)熱中性子束2次元分布計算結果

人体ファントム

ビーム孔

At the moment

iBNCTProject

University of Tsukuba is being developed the Monte Carlo based

treatment planning system “Tsukuba-Plan” for BNCT.

Tsukuba-Plan has employed PHITS as a MC dose calculation engine.

Tsukuba-Plan enables to perform dose estimation/ treatment planning

for not only BNCT but also particle therapy, X-ray therapy. And the

system is also applicable to the dose estimation for brachytherapy.

Incidental doses caused by secondary neutrons in radiation

therapy are also able to be estimated.

Conclusions

At present, several verification in BNCT dosimetry for Tsukuba-

Plan are being carrying out.

In comparison between measurements from water phantom

experiments and calculations, distributions for thermal neutron flux

and gamma-ray dose in the phantoms were in good agreement.

Further verifications are planned in order to put into practical use of

BNCT treatment and to get license for pharmaceutical approval.