Project Research
Project 8PR8Translational Research on BNCT for Clinical Application

M. Suzuki
Research Reactor Institute, Kyoto University

Background and Objective
Using Kyoto University Research Reactor (KUR),
patients with malignant tumors greater than 500 havebeen treated with boron neutron capture therapy(BNCT). Malignant brain tumors and head and neckcancers have been main malignancies treated with
BNCT. Our laboratory (Division of Particle Radiation Oncology) has investigated the possibilities for
new applications for BNCT. According to promising
results in pre-clinical study, we have already treatedsome patients with liver cancers with BNCT and carried out clinical study on phase I study on BNCT for
malignant pleural mesothelioma (MPM).
Promising clinical results of BNCT using the research reactor encouraged us to go to further stage of
BCNT using an accelerator-based (AB) BNCT system.
Co-operation of Kyoto University Research Reactor
Institute and Sumitomo Heavy Industry have developed AB BNCT system with compact cyclotron as anaccelerator. In 2012 and 2014, clinical studies on
BNCT for recurrent malignant brain tumors and headand neck tumors to get an approval as a medical device from the Pharmaceuticals and Medical Devices
Agency (PMDA), a Japanese regulatory agency. In atransition period from reactor-based (RB) BNCT into
AB-based BNCT, many research issues should be dissolved from impending and long-term viewpoints.
Main objectives of our project is to dissolve many
impending clinical issues to perform BNCT safely in
AB-BNCT system and to investigate many research
projects for many patients with cancer to be treatedwith AB-BNCT system.

RS1. Clinical studies on BNCT
Although no BNCT using KUR was performed, Fujimoto et al. reported a case report on BNCT for axillary lymph node metastasis of breast cancer which was
carried out in 2013. In this report, BNCT successfully
reduced the size of the lymph node metastases andalleviate the radiating pain in the arm. Case reports
are very meaningful to consider the possibility of new
applications of BNCT.
RS2. Pre-clinical studies on physiological and pharmacological aspects of BNCT
Yanagie et al. reported two pre-clinical studies.
One was a preclinical BNCT study for VX-2 rabbit
liver tumor model using borocaptate sodium (BSH)
entrapped water-in-oil-in-water (WOW) consist withsurfactant HCO40 or PGCR. Another one was a treatment planning study on BNCT for breast cancer

RS3. Medical physics studies on BNCT
Hayashi et al. investigated the influence of various
lithium compounds of the dose response and the stability of polymer gel dosimeters.
Tanaka K et al. reported the imaging plate system tomeasure the beam components such as thermal, epithermal, fast neutrons and gamma rays separately.
Sakurai et al. studied the QA/QC in BNCT using
ionization chamber and Bonner sphere in BNCT irradiation field.

Research Subjects
To advance RB-BNCT into AB-BNCT, a lot of researchers in various research fields such as clinicalradiation oncology, medical physics, pharmacology,
boron chemistry, and accelerator engineering areneeded to be involved in our research projects. In
this viewpoint, this research project consists of threeresearch subjects (RS) as follows,
RS1. Clinical studies on BNCT
RS2. Pre-clinical studies on physiological and pharmacological aspects of BNCT
RS3. Medical physics studies on BNCT.
Main Results
Unfortunately, KUR has been unavailable since May
in 2014. Only 7 reports could be submitted.

27P8- 42 -

PR8-1

Evaluation of Neutron Dosimetryfor Boron Neutron Capture Therapy using Images of Breast Cancer

H. Yanagie1,2,3, T. Nakamura4, H. Horiguchi4, H. Kumada
5, M. Suzuki6, Y. Sakurai6, H. Tanaka6, S. Masunaga6, A.
Maruhashi6, K. Ono6, K. Oyama7, M. Eriguchi7 and H.
Takahashi1,2

7cm field and epithermal neutron beam was irradiatedwith the tangenital direction (33min.) in restricted maximum skin RBE dose as 10Gy-Eq. The maximum tumor
RBE dose was 87.5 Gy-Eq, the mean tumor RBE dose
was 48.3 Gy-Eq, and the minimum tumor RBE dose was
11.5 Gy-Eq. The actual maximum skin RBE dose was
11.1 Gy-Eq (RBE=1.35).

1Department of Innovative Cancer Therapeutics:Alphaparticle & Immuno therapeutics, Meiji Pharmaceutical
University, 2Department of Nuclear Engineering &Management, Graduate School of Engineering, The University of Tokyo, 3Cooperative Unit of Medicine & Engineering, The University of Tokyo Hospital, 4Japan Atomic
Reactor Research Institute, 5Proton Medical ResearchCenter, Tukuba Univercity, 6Research Reactor Institute,
Kyoto University, 7Shin-Yamate Hospital, Anti- Tuberculosis Association.

Simulation 2: Epithermal Neutron mode
Beam colimation : φ8ｃｍ, BPA : 24ppm, T/N=3.5,
Restriction : Skin RBE dose as 10Gy-Eq

INTRODUCTION: The JAERI Computational Dosimetry System (JCDS), which can estimate distributionsof radiation doses in a patient’s head by simulating inorder to support the treatment planning for epithermal
neutron beam BNCT, was developed. Kumada et al had
reported that JCDS is a software that creates a
3-dimensional head model of a patient by using CT scanand MRI images, and that generates a input data file automatically calculation of neutron flux and gamma-ray
dose distributions in the brain with the Monte Carlo code
MCNP, and that displays these dose distributions on thehead model for dosimetry by using the MCNP calculation
results.
We evaluatied the dosimetry of thermal neutron using
JCDS in the condition of Single field irradiation or Bilateral irradiation to tumour constructed with MRI imagingsof a breast cancer patient.
EXPERIMENTS: Neutron dosimetry with JCDS for abreast cancer patient: BNCT was simulated in a patientwith a 7cm tumour in the lower half of the R breast. LiF
collimation was used to selectively irradiate the tumor
while sparing the adjacent normal organs (lung, heart).
The Neutron Beam Facility at JRR4 enables to carry out
boron neutron capture therapy with epithermal neutron
beam.
RESULTS:
Simulation 1: Epithermal Neutron mode
Beam colimation : φ7ｃｍ, BPA : 24ppm, T/N=3.5,
Restriction : Skin RBE dose as 10Gy-Eq
The blood concentration of BPA by drip infusion justbefore NCT was estimated as 24ppm, and T/N ratio wasalso estimated as 3.5 according to 18F-BPA-PET.

Simulation 2: The beam direction was changed to
oblique direction. The maximum tumor RBE dose was
86.6 Gy-Eq, the mean tumor RBE dose was 46.1 Gy-Eq,
and the minimum tumor RBE dose was 19.3 Gy-Eq. The
minimum tumor RBE dose was increased to 19.3 Gy-Eq
from 11.5 Gy-Eq with the epithermal neutron in thisoblique direction( 70% up ).
Simulation 3: Tangenital direction irradiation was performed in Simulation1, and Oblique direction irradiation
was performed in Simulation 2. Combined two directional Irradiation was performed in Simulation 3 (70% of
Simulation １ (Irradiation time 23.9 min ） + 79 ％ of
Simulation 2(Irradiation time：23.9min)) in restrictedmaximum skin RBE dose as 10Gy-Eq.
The maximum tumor RBE dose was 107.3 Gy-Eq, themean tumor RBE dose was 70.3 Gy-Eq, and the minimum tumor RBE dose was 28.0 Gy-Eq. This date shownthat BNCT with two directional epithermal neutron irradiation can increase the RBE tumor dose to 2.4 times ofSimulation 1 and 1.5 times of Simulation 2.
We hope to start BNCT clinical studies for recurrenced &advanced breast cancer patients. The irradiational directions will be decided using the JCDS or SERA simulation
with the restriction of normal tissue tolerant RBE Dose.
We applied the JCDS to dosimetry of epithermal neutron,
direction of neutron beam, and patient’s positioning on
BNCT. High resolution whole body dosimetry system,
as JCDS and SERA will be very useful to evaluate thethermal/epithermal neutron dosimetry and the applicationof BNCT to recurring or advanced breast cancer.
Multi directional irradiations are hope to be available toincrease the tumour RBE dose in the based on the tolerant dose of normal skin in BNCT field.
REFERENCES:[1] H. Yanagie et al., Appl Radiat Isot. 67(2009),
S63-66.

Simulation 1: Beam collimation was performed in

27P8-7- 43 -

PR8-2Anti-tumor Effect of Boron Neutron Capture Therapy (BNCT)
on Axillary Lymph NodeMetastasis of Breast Cancer

T. Fujimoto1, Y. Maekawa2, S. Takao3, S. Hori4,
T. Andoh5, Y. Sakurai6, H. Tanaka6, Y. Kinashi6,
S. Masunaga6, H. Ichikawa5, K. Ono6 and M. Suzuki6
Hyogo Cancer Center, Departments of Orthopaedic
Surgery1and Breast Surgical Oncology32National Hospital Organization Kobe Medical Center,
Breast Surgical Oncology
4Gate Tower Institute for Image Guided Therapy
5
Faculty of Pharmaceutical Sciences and Cooperative
Research Center of Life Sciences,
Kobe Gakuin University
6
Research Reactor Institute, Kyoto University
INTRODUCTION: Breast cancer is the most morbid
malignancy in women, and in Japan about 60,000 new
cases are encountered every year. Although hormone
therapy, chemotherapy and molecularly targeted therapy
have improved its prognosis, 30% of such patients diefrom distant metastases. When systematic pharmacotherapy is not effective in metastatic cases, the disease is difficult to control. In this study, BNCT was assessed for
lymph node metastasis of breast cancer (luminal type A).
Additionally, the uptake of BPA was analyzed with theuse of hormone-sensitive breast cancer cell lines.
PATIENT AND METHODS: (1) Patient: A 65-year-old
woman diagnosed with left breast cancer (luminal A) andaxillary lymph node metastasis underwent axillary lymph
node dissection, mastectomy and radiation therapy for thearea of the left axillary lymph nodes. Althoughsubsequent lymph node and lung metastasis recurred, alltumors disappeared after both chemotherapy andhormone therapy. Nonetheless, local recurrence of tumors
in the left lymph nodes was detected, for which
chemotherapy was ineffective; therefore, intra-arterial
chemo-embolization was carried out at a nearby clinic.
The tumor was, however, not controlled; furthermore,
palsy of the left axillary nerve was detected, and thepatient complained of severe pain all over the upper left
limb. Examination by Gd-enhanced MRI confirmed
regrowth of the tumor; therefore, BNCT was
administered.
(2) Boron concentration in tumor cell lines: Hormone-sensitive breast cancer cell lines (T47D, MCF-7),
clear cell sarcoma (CCS) cell line (MP-CCS-SY) andmelanoma cell line (G-361) were cultured and exposed to
BPA (10, 20, 30 10B µg/ml) in the medium. Subsequently,
the cells were washed, detached and collected; the concentration of 10B in the cells was then determined by
ICP-AES.
RESULTS: An 18F-BPA-PET study conducted before
BNCT showed accumulation of BPA in the tumor, with atumor to blood (T/B) ratio of 2.2. Since the tumor was
located deep in the body, BNCT was administered by
two-gate irradiation to the area of the left axilla, with thepatient in a sitting position: ventrally, 5MW for 47min
and dorsally, 5MW for 27min. The mean value of boron
concentration in blood during BNCT was 29 ppm ventrally and 28.5 ppm dorsally, and neutron fluence on thesurface of the body was 3.34×108 cm-2s-1 ventrally and4.89×108 cm-2s-1 dorsally. The calculated average dose to
the target and the left axillary nerve was 25 Gy-Eq and
4.3 Gy-Eq, respectively. Gd-enhanced MRI revealed thatthe recurrent tumor mass in the left axilla shrank twomonths after BNCT [Fig.1]. Moreover, the patient was
free from the severe pain in the left arm, and the progressof paralysis ceased. Also, the two breast cancer cell lines
demonstrated higher uptake of boron than did the CCS
and melanoma cell lines that have already shown goodoutcome of BNCT [Fig. 2].
CONCLUSION: BNCT was effective in the treatment ofmetastatic breast cancer that had been resistant to all other methods of treatment. Additionally, in vitro studies
demonstrated high uptake of BNCT by hormone-sensitive breast cancer cell lines. These data suggest the applicability of this new method of treatment tometastatic breast cancer.
FIGURES:[Fig.1] Axial Gd-enhanced T1 MRI shows a reduction in
the tumor mass in the area of the left axillary lymph
nodes post-BNCT (B) compared with pre-BNCT (A).

[Fig.2] Two hormone-sensitive breast cancer cell lines(T47D, MCF-7), CCS cell line (MP-CCS-SY) and melanoma cell line (G-361) were tested for their uptake ofboron. Each cell line took up the boron in a concentration-dependent manner. The uptake of 10B by breast cancer cells was higher than that by the CCS and melanoma
cells.

27P8-15- 44 -

PR8-3

Evaluation of Boron Concentrations in Liver by Intra-arterial Delivery of
WOW Emulsion to VX-2 Hepatic Tumor Model for Neutron Capture Therapy
to Hepatocellular Carcinoma
and normal liver tissues were determinated by ICP- Mass
Spectroscopy of Jyuntendo University.

H. Yanagie1,2,3, M. Fujihara4, R. Mizumachi5, Y. Murata5,
Y. Sakurai1,3, K. Mouri1,3, A. Shinohara6,7, T. Matsukawa7,
Y. Oomori7, Y. Morishita8, N. Dewi2, M. Yanagawa9, S.
Yui1,3, K. Yokoyama7, Y. Nonaka1, H. Sugiyama1, Y.
Furuya1, Y. Sakurai10, H. Tanaka10, M. Suzuki10, S.
Masunaga10, K. Ono10, M. Ono3,11, J. Nakajima3,12, M.
Sato13, M. Eriguchi14 and H. Takahashi2,31Department of Innovative Cancer Therapeutics:Alphaparticle & Immunotherapeutics, Meiji Pharmaceutical
University, 2Department of Nuclear Engineering &Management, Graduate School of Engineering, The
University of Tokyo, 3Cooperative Unit of Medicine &Engineering, The University of Tokyo Hospital, 4SPG
Techno Ltd. Co., 5LSI Medience Ltd Co, 6The Graduate
School of Seisen University, 7Jyuntendo University,
8

Department of Human & Molecular Pathology,
Graduate School of Medicine, The University of Tokyo,

9

Veterinary Medical Center, Obihiro University ofAgriculture & Veterinary Medicine, 10Research Reactor
Institute, Kyoto University, 11Department of Cardiac
Surgery, The University of Tokyo Hospital, 12Departmentof Thoracic Surgery, The University of Tokyo Hospital,
13
Department of Radiological Sciences, Faculty of Health
Sciences, Komazawa University, 14Department ofSurgery, Shin-Yamanote Hospital

INTRODUCTION: Water-in-oil-in-water(WOW) emulsion has been used as the carrier of anti-cancer agents bymodifying of IPSO on intra-arterial injections in clinical.
Higashi et al prepared a long term inseparable WOW for
use in arterial injection therapy to treat patients with
hepatocellular carcinoma(HCC) by the double emulcificating technique[1]. We performed preclinical BNCT
study for VX-2 rabbit tumour model using 10BSH entrapped WOW [2, 3]. We also proceeded clinical BNCT
study for HCC using this system[4].
In this study, we prepared 10BSH entrapped WOW in
verifying the component of surfactant, and evaluated theboron delivery activity to measure the 10B concentrationsof organs in VX-2 hepatic tumour model on time course
after intra-arterial injection using ICP-Mas.
EXPERIMENTS: 10BSH entrapped WOW were administrated with intra-arterial injections via proper hepatic artery (10BSH : 20 mg/kg rabbit) on VX-2 rabbit
hepatic tumour models. One and three days after arterial
injections, the boron concentrations of the tumor nodules

RESULTS: VX-2-bearing rabbits (n = 3) were given
intra-arterial injection with 2 ml of 10BSH WOW emulsion consist with surfactant HCO40, or PGCR. The mean
10
B concentration prepared in 10BSH-WOW was 10000
ppm in this experiment. The size of WOW was controlled
to 70 μm.
The 10B concentration in VX-2 tumour was 170.8 ppm,
58.3 ppm by WOW with HCO40 after day1, day3 inta-arterial injection, respectively. The 10B concentrationof tumour was 186.0ppm, 40.4ppm by WOW with PGCR
after day1, day3 same injection, respectively. 10B
concentration in normal liver tissue / blood were 8.0 /0.3 ppm in HCO40 group, and 15.1 / 0.1 ppm in PGCR
group at day 3, respectively in the same procedures ofWOW.
We can deliver 10BSH to tumor site by intra-arterial
injection with WOW emulsion. The effective 10B
concentration (higher than 30ppm) was achieved in day1and day3. It has be able to change the deliverable 10B
atoms according to the sizes of WOW, and the type of
surfactants. We hope to perform toxicity examinations ofWOW emulsion to develop the more suitable WOW
emulsion for intra-arterial born delivery system.
Table1. 10B concentration (ppm) of VX-2 hepatic tumor bearing rabbit model after intrarterial injectionof 10B-WOW emulsion.
WOWTumourNormal liver
Blood
Near Tumour
Another Lobe--------------------------------------------------------------------------------------HCO40
Day1
170.8±27.3
31.9±4.3
33.9±30.9
0.73±0.4Day358.3±23.1
24.7± 17.1
8.02±1.7
0.33± 0.1
Day7
12.9 ±7.5
2.9 ±0.6
1.7±0.4
0.12±0.0
PGCR
Day1
Day3
Day7

186.0±115.2
40.47
40.66

72.79±2.5
56.7
37.3

69.1±42.1
15.1
13.8

1.27±0.5
0.14
0.14--------------------------------------------------------------------The 10B conc. were determined by ICP-Mas. at Jyuntendo
University.

REFERENCES:[1] S Higashi S et al., Cancer, 75(1995):1245–1254.
[2] S Mikado et al., Nucl. Instr. and Meth. A, 605 (2009):
171-174.
[3] H Yanagie et al., Appl Radiat Isot., 69(2011):
1854-1857.
[4] H Yanagie et al., Appl Radiat Isot., 88(2014):32-37.

27P8-18- 45 -

PR8-4

Establishment of QA/QC Using Ionization Chamber andBonner Sphere in BNCT Field (II)Y. Sakurai, H. Ueda, R. Uchida, T. Takata, T. Kawamura,
K. Okazaki, H. Tanaka and M. Suzuki
Research Reactor Institute, Kyoto University
INTRODUCTION: After the restart of the operation of
Kyoto University Reactor (KUR) in May 2010, 235 clinical studies of boron neutron capture therapy (BNCT)
have already been carried out as of May 2016 [1]. Also,
the BNCT clinical trial using Cyclotron-based BNCT
Epi-thermal Neutron Source (C-BENS) started in November 2012 [2]. In the while, the research and development into several types of accelerator-based irradiation
systems are underway by several research groups in theworld at present time. With this situation in mind, it isimportant that the physical and biological estimations fordose quantity and quality are performed consistently
among several irradiation fields, and that the equivalencyof BNCT is guaranteed, even across BNCT systems. The
aim of this research is the establishment of quality assurance and quality control (QA/QC) in BNCT irradiation
field. As part of the QA/QC system, we are developing estimation method for neutron energy
spectrum using Bonner sphere.
METHODS: For our spectrometer using Bonner sphere,liquid such as pure water and/or boric acid solution isused as the moderator [3]. As shown in Fig. 1, a multi-layer concentric-sphere case with several sphere shells
is prepared. The moderator and its diameter are changeable without entering the irradiation room, by the remotesupply and drainage of liquid moderator in the several
layers. For the detector, activation foils are remotelychanged, or online measurement is performed using SOF(scintillator with optical fiber) detector containing boron,
etc.. On the assumption of the application in a typical
BNCT irradiation field, the combination of the moderators for boron-10 (B-10) concentration and diameter was
optimized by our originally-developed method, “High
Independence Selection (HIS)” [4]. For the B-10 concentration, the selection was performed among ten values
such as 0, 0.01, 0.016, 0.028, 0.048, 0.082, 0.14, 0.24,
0.41 and 0.7 weight percent (wt%). For the diameter, theselection was performed among ten values from 11 to 20
cm in 1 cm increment. Manganin foil was assumed to be
used as the detector, which has high response mainly tothermal neutrons. The optimized combination was decided among one hundred and one combinations; thecombinations of ten B-10 concentrations and ten diameters, additionally the case of manganin foil only without
the moderator.

0.028-wt% boron acid solution of 20 cm in diameter.
Then, the optimized structure of the spectrometer was
decided as follows: three sphere shells such as 13, 18 and20 cm in diameter, and three liquid moderators such as
pure water, 0.028-wt% boron acid solution and 0.7-wt%
boron acid solution. It is not thought that this structure isnecessary to be changed when the detector is changed
from manganin foil to boron-containing SOF detector.
CONCLUSION: We have a plan to make the Bonner-sphere spectrometer, based on the optimization result.
Additionally, we have a plan to perform the spectrometry
experiments at Kyoto University Reactor (KUR), etc., inorder to confirm the efficacy of this spectrometer.

Fig. 1. Concept design of the Bonner-sphere spectrometer for QA/QC in BNCT.
REFERENCES:[1] Y. Sakurai et al., Nucl. Instr. Meth. A 453 (2000)
569-596.
[2] H. Tanaka et al., Nucl. Instr. Meth. B 267 (2009)
1970-1977.
[3] H. Ueda et al., Appl. Radiat. Isot. 104 (2015) 25-28.
[4] H. Ueda, Doctoral Thesis (2016).

RESULTS: The optimized combination was selected by
HIS as follows: manganin foil only, 0.7-wt% boron acidsolution of 13 cm in diameter, 0.7-wt% boron acid solution of 18 cm in diameter, 0-wt% boron acid solution(namely pure water) of 18 cm in diameter, and

27P8-23- 46 -

PR8-5

A Consideration of the Influence by the Radiation Type on the Measurementof the Spatial Distributions of the Beam Components in BNCT
Using the Imaging Plate

K. Tanaka, Y. Sakurai1, T. Kajimoto, H. Tanaka1, T.
Takata1, M. Suzuki1 and S. Endo
Graduate School of Engineering, Hiroshima University
1

Research Reactor Institute, Kyoto University

INTRODUCTION: For boron neutron capture therapy(BNCT), measurement of the spatial distributions of neutrons and gamma rays is one of the potential options forthe quality assurance and quality control. It is desirable tomeasure the beam components such as thermal, epithermal, fast neutrons and gamma rays, separately. This study
investigates the usage of the imaging plate (IP) for thispurpose. The influence by the radiation type which deposits the energy in the IP on the resultant beam component distribution is discussed here.
METHODS: Two IPs set in a converter were irradiated[1]at the collimator aperture of the standard epithermal neutron irradiation mode at the Kyoto University Reactor
Heavy Water Neutron Irradiation Facility (KUR-HWNIF).
The converters were the epoxy resin doped with boron
which is attempted to enhance epithermal neutrons via
secondary particles from the 10B(n,α)7Li reaction, andcarbon which is not expected to enhance neutrons due to
its low neutron interaction. The fluence φ was deterj
mined using the following model;
 PSL1   a11
PSL  
 PSL2   a21

a12   1 
    A 
a22   2 

(1),  A1  PSL(2),
where PSLi denotes the signal intensity of the ith IP, aij
the sensitivity of the ith IP for the component j. For j, 1
denotes gamma rays, and 2 epithermal neutrons. In thisanalysis, the energy deposition calculated by the PHITS
code was used as aij. The problem is that the dependenceof the radiation type on the efficiency that the energy
deposition is converted to the IP signal is not included. In
the present report, the dependence of the IP signal on theradiation type is investigated from the previous studies.
Then, its influence on the experimental result of thecomponent distributions is discussed.
RESULTS and DISCUSSION: The dependence of the
IP signal intensity on the radiation type that deposits theenergy in the sensitive region of the IP, or its LET, hasbeen investigated during past years. However, themechanism or its quantitative influence has not beenconcluded consistently among the publications. However,there are several proposals on it.
One of the earliest and most comprehensive studies was
conducted by Thoms in 1996[2]. They categorized theprocesses potential to be influenced into two, i.e., readoutof the IP signal, and fading of the signal.

As to the readout, the influential process is considered
to be the attenuation of the readout light emitted from thesensitive region, the efficiency of converting the energy
deposition into the IP signal will be higher for the alphaparticles than that for the gamma rays. Bennet [3] reported that the readout light is attenuated to 1/e (37%) by
the IP sensitive region with the thickness of 113-211 m
the IP by Fujifilm Co. Ltd used in the experiment[1]. The
sensitive region has the thickness of 50 m and it is supposed to attenuate the readout light by 21-36 %. In addition, the readout light spreads and results in decrease of
the IP signal intensity. The decrease was reported to be by
13 % for the thickness of 50 m by Thoms[2]. Alpha particles and 7Li nuclei deposits its energy within a few micro meters from the IP surface, while the recoil protons
and secondary electrons from the converters deposit theenergy in whole the thickness of 50 m. The efficiency ofthe energy deposition to be the IP signal will be higher
for the former, by possibly a few tens percents. Accordingly, the contribution of the epithermal neutron components to the IP signal is expected to be slightly higher
than the calculated sensitivities for the equation (1).
On the other hand, the time dependence of the fading of
the IP signal has been reported to be independent fromthe radiation type[2,4]. However, the results of investigation by Nakamura[5] showed that the IP signal producedby alpha particles reduces more rapidly than those by
X-rays. At 30 minutes or more after the irradiation, whichcorresponds to the experiment[1], the difference was reported to be about 30 to 40%.
These factors, i.e., the readout light attenuation and IP
signal fading, have opposite influences, i.e., the former
increases the sensitivity to the alpha particles, and thelatter decreases. In total, the type of radiation could double the IP signal, while it could be an overestimation. To
include its influence, the sensitivity aij should be adjusted.
For example, if the sensitivity for the secondary particlesof 10B(n,)7Li reaction that enhances the epithermal neutron component is  times, ai2 for all the IPs should be
replaced with ai2. Consequently, the solution will beepi’= epi/. This means that including the influence by
the radiation type does not change the relative distribution of the resultant fluences, which is what this study
aimed to assure. The analysis without considering thedependence of IP signal on radiation type will be enoughto assure the temporal change in the spatial distribution of
the irradiation field.
REFERENCES:[1] K. Tanaka et al., Appl. Rad. Isot. 106 (2015) 125-128.
[2] T. Thoms et al., Nucl. Instr. Meth. A. 378 (1996) 598-611.
[3] T. Bonnet et al., Rev. Sci. Instr., 84 (2013) 013508.
[4] S. Gunji et al., IEEE Tran. Cucl. Sci. 47 (2000) 865-869.
[5] S. Nakamura et al., Proc. 33 Rad. Rad. Res (1996) 158

27P8-25- 47 -

PR8-6Development and Evaluation of 3D Polymer Gel Dosimeter for
the Measurement of dose Distribution in BNCTS. Hayashi, Y. Sakurai1, M. Suzuki1, M. Narabayashi1,
T. Takata and R. Uchida1
Department of Clinical Radiology, Hiroshima International University
1
Research Reactor Institute, Kyoto University

INTRODUCTION:

Polymer gel dosimeters havebeen investigated for the three-dimensional (3D)
dose measurement of the complex conformal dose
distributions in the clinical applications [1]. These
devices utilize radiation-induced polymerization
reaction of vinyl monomer in the aqueous gel matrix to preserve information about the radiation dose.
The 3D absorbed dose distribution is deduced fromthe created polymer distribution measured by imaging modalities such as MRI and Optical CT.
Polymer gel dosimeter is also regarded as tissue
equivalent to neutron beam because the components
are mainly water and a small amount of otherchemicals consisting of carbon, nitrogen and oxygen. A further advantage of polymer gel dosimetersis that the interaction with neutron could be controlled by addition of some compounds with neutron-capture-nuclei such as 6Li and 10B. It meansthat each dose component might be distinguishedfrom complex dose due to various primary andsecondary radiations by the variety of elemental
composition.
In the previous work, we have investigated thatthe dose response of polymer gel dosimeter irradiated by thermal neutron beam was enhanced by addition of a very small amount of 10B (50 ppm) [2].
In this work, the influence of various lithium compounds on the dose response and the stability ofpolymer gel dosimeters was investigated byhigh-energy photon beam before the future experiments using neutron beam.
In this work, MAGAT-type
EXPERIMENTS:(methacrylic-acid-based) polymer gel dosimeter
was employed because of the high sensitivity. Various lithium salts (LiCl, LiNO3, LiOH, Li2SO4 andLi3-citrate, which have comparatively high solubility in water) containing 6Li in the natural ratio weremixed into the polymer gel in the concentration of

100 and 200 ppm of 6Li, respectively. The resulting
gels were subdivided by pouring into test tubes.
The irradiations were performed using 6 MV
X-ray from a medical linear accelerator (Novaris-TX, Varian/BrainLAB) and gamma ray from60
Co source. The doses upto 5 Gy were delivered toeach sample.
The read-out from the samples was performed
using a 1.5 T MRI scanner (SIGNA HDxt 1.5T, GE
Healthcare) with a head coil the day after irradiation.
A multiple spin-echo sequence was applied and thetransverse relaxation rate R2 (=1/T2) was obtained as
the function of absorbed dose.
RESULTS:In the results, the dose-R2 responses(sensitivities) of the polymer gel dosimeters containing LiNO3, LiOH and Li3-citrate decreased significantly (40-70% lower at 5 Gy) comparing withthat of the basic gel dosimeter without lithium salts.
Also, Li3-citrate did not dissolve enough in the gelsolution and the gel was translucent. On the other
hand, the gel dosimeters containing LiCl and Li2SO4
showed the comparable sensitivity to the basic gel
dosimeter and the rather sensitivity enhancement
was also observed.
From these results, it was suggested that LiCl or
Li2SO4 was a suitable additive to introduce lithium
to the polymer gel dosimeter. When lithium salts
containing the enriched 6Li could be used, theclearer enhancement due to 6Li would be expectedeven in a smaller amount of additive.
(These results would be presented at 17th International
Congress on Neutron Capture Therapy, ICNCT-17 inMissouri, USA.)
REFERENCES:[1]
C. Baldock et al., Phys. Med. Biol. 55 (2010)
R1–63
[2]
S. Hayashi et al., J. Phys.: Conf. Ser. 573 (2015)
012074 (4pp)27P8-26- 48 -

PR8-7

Patient-Position-Error Measuring System for BNCT Irradiation

T. Takata, Y. Sakurai, H. Tanaka and M. Suzuki
Research Reactor Institute, Kyoto University

INTRODUCTION: In boron neutron capture therapy(BNCT) irradiations carried out at Kyoto University Research Reactor, sitting position has been applied in manycases, considering a flexibility of patient positioning andstructural restriction of an irradiation facility. In thosecases, the patient position is sometimes unstable, resulting in a displacement from an initial set-up position determined by a treatment planning process. The displacement and motion during an irradiation period cause uncertainty in estimation of delivered dose.
Aiming to improve the dose estimation accuracy, we
have prepared a patient-position-error measuring systemusing a motion sensor. An outline of the measuring system and initial test operation are described.

quency component, related to a sensor bias, showed
time-dependent behavior, which resulted in abnormal
divergence of velocity obtained from integration of raw
accelerometer output. This phenomenon is well known as
velocity drift in general applications of motion sensor.
The velocity drift can be corrected at a resting state, atwhich velocity is adjusted to zero. The resting state need
to be detected based on the sensor outputs using appropriate threshold values. These filtration and correction are
under examination and need to be optimized to clinicalsituation of BNCT irradiation.

MATERIALS AND METHODS: An outline of themeasuring system is shown in Fig. 1. A MEMS motion
sensor module (IMU-Z 2, ZMP Inc., Tokyo) including
tri-axial accelerometer, gyroscope and magnetometer wasused to track a position and a rotation angle during anirradiation period. The sensor module (36×52×11 mm)
and a battery box (36×62×15 mm) are sufficiently small.
In addition, the module has a wireless data transmissionfunction. These features enable us to fix the sensor on
patient surface without interference in patient setup andirradiation process.
A displacement can be calculated by integrating accelerometer data twice with respect to time. Also, a rotation
angle can be calculated by integrating gyroscope datawith respect to time in motion phase and by direction ofgravitational acceleration and geomagnetic field at resting phase. The estimated displacement and rotation angle
are displayed and saved as a log data over an irradiation
period. The log data can be utilized for post-irradiationdose evaluation.
This system is considered to be useful for head cases,
where the measuring object is regarded as a rigid body.
For those cases such as brain tumor or head and necktumor, the sensor module and battery box are fixed on topof head so that the sensor coordinate system is aligned toanterior-to-posterior, left-to-right and inferior-to-superior
directions of the patient. The position and rotation angleof the head is measured in the reference coordinate system defined on the irradiation room.
RESULTS: An initial test operation of the motion sensor was conducted. Time fluctuations were observed in
the accelerometer output as well as the gyroscope andmagnetometer. High frequency component of the accelerometer output, related to a sensor noise, was observedin the amplitude range of about 0.3% with respect to thegravitational acceleration. This component can be removed by using an appropriate high-pass filter. Low fre-

27P8-28- 49 -

11mm

Wireless
Antenna
36mm

Motion Sensor

Irradiation Room
Position Estimator
Display
Data Logger
Magnetometer

Accelerometer

offsetoffset－Low-pass∫
velocity

－

Gyro
scope

offsetLow-pass－

Low-pass

Resting Phase
Detection
zero adj.
zero adj.

∫∫
positionrot. angle
at restrot. angle
in motion

Fig. 1. An outline of patient-position-error measuringsystem.