for boron neutron capture therapy H. Kumada , K. Takada, T. Aihara, - - PowerPoint PPT Presentation

iBNCT Project ct

• 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

iBNCT Project ct

Progress of boron neutron capture therapy (BNCT)

Boron neutron capture therapy (BNCT) is based on the nuclear reaction that occurs when boron-10 is irradiated with neutrons of the appropriate energy to produce high-energy alpha particles and recoiling lithium-7 nuclei. Therefore BNCT is categorized to external beam therapy using neutron beam. Clinical trials for BNCT is being performed using research rectors so far. However in recent years, many accelerator-based neutron sources for BNCT are being developed. In Japan in particular, some devices have been generated enough neutrons, and two facilities are already being carrying out clinical trials 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

iBNCT Project ct

De Develop lopment ent of Pe Peripher heral al Eq Equipment ent for BN BNCT

【RFQ+DTL Type Linac for BNCT】 【Treatment Management System】

《Beam Transport System》

《Patient Positioning System》

《PG-SPECT》 《Neutron Monitor》

Proton Beam

Neutron Beam

《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 と中性子反応で生じる即発γ線

即発γ線 ベース・リアルタイム３ 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

iBNCT Project ct

Dose estimation process with Tsukuba-Plan

Monte-Carlo Calculation

Set Material Set Region of Interest Set Irradiation Condition Dosimetry Mode

iBNCT Project ct

Fe Feature ures of Ts Tsuku kuba-Pla Plan

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

➡ 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 by secondary neutrons in particle therapy. Furthermore, PHITS has “MKM” which can perform micro-dosimetry. Thus Tsukuba-Plan can determine equivalent dose based on micro-dosimetry in addition to conventional way as “RBE x Physical dose”

iBNCT Project ct

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

1st scatterer MLC Middle collimator Bolus Ridge filter 2nd scatterer Head phantom

Dose estimation for proton therapy

Proton therapy in University

• f Tsukuba Hospital

X-ray Therapy

6 MV

Irradiation field: 5 cm×5 cm

0.0% 20.0% 40.0% 60.0% 80.0% 100.0% 120.0% 0.0 100.0 200.0 Relative dose 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

Relative dose Distance from the beam axis(mm) Measured data PHITS calculation

Comparison results of PDD and OCR for 6-MV beam

T arget Region

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

Two-field fractionated X-ray irradiation

Proton Therapy

• 50
• 40
• 30
• 20
• 10

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 Rela tive dose 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.”

iBNCT Project ct

Verification for the dose estimation performance of Tsukuba Plan for boron neutron capture therapy (BNCT)

iBNCT Project ct

Tsukuba Plan

Southern Tohoku Hospital, BNCT Center National Cancer Center Hospital

Irradiation room Accelerator

Kyoto University KUR, BNCT facility University of Tsukuba, iBNCT Facility

Verification in all BNCT facilities in Japan

iBNCT Project ct

JRR-4 in JAEA

Create three neutron source for BNCT

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

Water phantom

Beam 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 10.0

Thermal Neutron Flux (n/cm2s) Depth from phantom surface (cm) グラフ タイトル

Experimental Values Tsukuba Plan Calculations

iBNCT Project ct

Verification (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/cm2・ｓ）

Phantom 表面からの深さ （cm） 陽子電流：平均 Ａ 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

• f 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

iBNCT Project ct

Comparison 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% ) 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

Thermal Neutron Flux (n/cm2s)

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

Thermal Neutron Flux (n/cm2s) 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

Thermal Neutron Flux (n/cm2s) 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

Gamma-ray dose rate (Gy/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

Gamma-ray dose rate (Gy/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

iBNCT Project ct

Calculation models Calculation Results Set irradiation conditions Set ROI and target point

Dose estimation for realistic human model

iBNCT Project ct

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

Volume（％） 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.

iBNCT Project ct

Future res: : Estim imat atio ion for whole e body expos

• sur

ure

Dose estimation for whole body exposure using Tsukuba-Plan

Near future

Measurement for whole body exposure in BNCT using a whole body phantom Dose estimation for whole body exposure in BNCT irradiation using PHITS

人体フ ァ ント ム照射シミ ュ レーショ ンモデル 熱中性子束 次元分布計算結果

人体フ ァ ント ム ビーム孔

At the moment

iBNCT Project ct

 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.

Con

• nclusions

lusions

• 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.