CO7-1

A Fundamental Experiment for the Measure Against the Activation of theIrradiation-room Concrete at BNCT facility (II)Y. Sakurai, T. Takata, K. Kimura1, H. Tanaka, K. Takamiya

found that the generation of the secondary thermal neutrons was a little larger for Resin B than for Resin A. Also,it was found that the generation of the secondary thermal
neutrons was decreased to almost one fifth for the resinwith B4C.

Research Reactor Institute, Kyoto UniversityFujita Corporation

1INTRODUCTION: At present time, the research anddevelopment into several types of accelerator-based neutron sources for boron neutron capture therapy (BNCT)
are underway by several research groups in the world,with Cyclotron-based BNCT Epi-thermal Neutron Source(C-BENS) at the head of the list [1]. In near future,
BNCT using the accelerator-based neutron sources may
be carried out at several places in the world. Unlike thefacilities for radiation therapy and charged-particle therapy, the neutron yield is larger at BNCT facility. Then,the activation of concrete, which is a main structure of
the irradiation room, is larger. The use of low-activation
concrete is prefer in the viewpoints of the decrease ofexposure under the work in the irradiation room, the decommissioning of the irradiation room, etc.. This research is intended to perform the characteristic estimation
for low-activation concrete and confirm its usability at
BNCT facility. In 2015, Kyoto University Reactor (KUR)
was not operated. Then, a characteristic estimation wasperformed for the measure against the activation due to aneutron shield for concrete using an Am-Be neutron
source, as the same manner in 2014.

CONCLUSION: When the KUR operation is restarted,the estimations for the important characteristics oflow-activation concrete are planned, such as the shielding
effect for neutrons and gamma rays, the generation of thesecondary gamma rays, etc., using Heavy Water Neutron
Irradiation Facility [2]. Also, the estimations for thecharacteristics are planned for short-life activation andlong-life activation using Pneumatic Tubes.

METHODS: A characteristic estimation was performed
for two kinds of resins such as Resin A and Resin B, andalso Resin A containing B4C, which are under development. As nine resin sheets of 10-cm side, 10-cm long and
2-mm thickness were stacked on the concrete surface, theshielding performance against the Am-Be neutron source
was estimated by foil activation method. Indium foil wasused as an activation foil. The shielding characteristic forfast neutrons was estimated by the activity change forIn-113(n,n’)In-113m reaction, and the generating characteristic for the secondary thermal neutrons was estimatedby the activity change for In-115(n,γ)In-116m reaction.
RESULTS: Figure 1 shows the radioactivity changes
dependent on the neutron-shield thickness for theIn-113(n,n’)In-113m reaction. Figure 2 shows the radioactivity changes dependent on the thickness for theIn-115(n,γ)In-116m reaction. In these figures, the radioactivity changes for Resin A, Resin B and Resin A withB4C are drawn. From the comparison for the radioactivity
changes for the In-113(n,n’)In-113m reaction, it wasfound that the shielding effect for fast neutrons was alittle larger for Resin B than for Resin A. Also, it wasfound that the shielding effect for fast neutrons was alittle smaller for the resin with B4C, as its hydrogen density was smaller. From the comparison for the radioactivity changes for the In-115(n,γ)In-116m reaction, it wasFig. 1. Radioactivity changes dependent on thethickness for the In-113(n,n’)In-113m reaction.

Fig. 2. Radioactivity changes dependent on thethickness for the In-115(n,γ)In-116m reaction.
REFERENCES:[1] H. Tanaka et al., Nucl. Instr. Meth. B 267 (2009)
1970-1977.
[2] Y. Sakurai et al., Nucl. Instr. Meth. A 453 (2000)
569-596.

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Antitumor Effectivity by Gd-neutron Capture Therapy
Using Gd-DTPA-incorporated Calcium Phosphate Nanoparticles

N. Dewi1, P. Mi2,3, H. Yanagie1,4,5, Y. Sakurai4, H.
Cabral2 , N. Nishiyama3, K. Kataoka2,6, Y. Sakurai7, H.
Tanaka7, M. Suzuki7, S. Masunaga7, K. Ono7,
and H. Takahashi1,41Dept of Nuclear Engineering & Management, Univ ofTokyo, 2Bioengineering Dept, Univ of Tokyo, 3Polymer
chemistry division, Chemical Resource Laboratory, Tokyo
Institute of Technology, 4Cooperative Unit of Medicine &Engineering, Univ of Tokyo Hospital, 5Dept of InnovativeCancer Therapeutics, Meiji Pharmaceutical University,
6Materials Engineering Dept, The University of Tokyo,
7
Research Reactor Institute, Kyoto University
INTRODUCTION: Gadolinium-157 has been getting
attention as alternative for neutron capture therapy (NCT)
agent because of its high thermal neutron cross section(255 000 barns), which the highest among all stableelements. Gadolinium neutron capture reaction (Gd-NCR)
results in release of gamma rays, which reduce thelocalization effect of the treatment, which on the other side
is increasing the possible additional effect if Gd-157 isaccumulated to a bulk tumor cluster [1].
In this work, we performed histo-pathological examinations to evaluate the effects of Gd-NCT according totumor growth suppression on multiple-injections GdDTPA/CaP nanoparticles in vivo.
EXPERIMENTS: In vivo evaluation was performed oncolon-26 tumor-bearing mice irradiated for 60 minutes atnuclear reactor facility of Kyoto University Research
Reactor Institute with average neutron fluence of 1.8 ×1012 n/cm2[2,3]. Antitumor effect was evaluated on thebasis of the change in histopathological examinations
using HE staining & TUNEL staining.
RESULTS: Tumor growth was suppressed until aroundfour times of the non-treated group. Possibility of neutron
depression for higher gadolinium concentration, there
might be not sufficient amount of neutron reached deeper
tumor site. Higher accumulation of gadolinium on tumor
surface might reduce cancer cells killing effect at thetumor core[2,3].
Multiple-injection irradiated of bare Gd-DTPA groupshows slightly better tumor growth suppression compared
to control irradiated group. This proves low toxicity of Gd-DTPA/CaP nanoparticles, because all mice survived forboth single and multiple injection groups.
Tumor cells were destroyed after NCT and changed into
granulation tissue. Number of cells killed after treatment
were similar for single and multiple injection groups ofGd-DTPA/CaP nanoparticles. Non-treated group shows
normal histology with clear cytoplasm andnucleus(Fig.1)[3].
Evaluation of possible apoptosis occurred on cancer
cells by detecting the DNA fragmentation following
GdNCT treatment. Negative control for both irradiatedand non-irradiated groups was also prepared during theapoptotic assay. Number of cells undergoing stained byTUNEL, which correlates to the number of apoptosis, washigher on GdNCT treated group compared to the nonirradiated ones(Fig.2)[3].

Gd-DTPA/CaP multiple
injections + Irradiation

Gd-DTPA/CaP multiple
injections

Figure 1. Evaluation of Antitumor Effectivity (H&EStaining)

Gd-DTPA/CaP multiple
injections + Irradiation

Gd-DTPA/CaP multiple
injections

Figure 2. Evaluation of Antitumor Effectivity(TUNEL Staining)
REFERENCES:[1] Dewi N et al., Biomed & Pharmacother (2013) 67:451-457.
[2] Mi P, et al.: ACS Nano (2015) 23;9(6):5913-5921[3] Dewi N et al., J Can.Res.Clin.Oncol. (2016) 142(4):767-775.

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