Development of the DICOM-based Monte Carlo dose reconstruction system for a retrospective study on the secondary cancer risk in carbon ion radiotherapy

Furuta, Takuya; Koba, Yusuke*; Hashimoto, Shintaro; Chang, W.*; Yonai, Shunsuke*; Matsumoto, Shinnosuke*; Ishikawa, Akihisa*; Sato, Tatsuhiko

Physics in Medicine & Biology, 67(14), p.145002_1 - 145002_15, 2022/07

https://doi.org/10.1088/1361-6560/ac7998

Carbon ion radiotherapy has an advantage over conventional radiotherapy such that its superior dose concentration on the tumor helps to reduce unwanted dose to surrounding normal tissues. Nevertheless, a little dose to normal tissues, which is a potential risk of secondary cancer, is still unavoidable. The Monte Carlo simulation is a good candidate for the tool to assess secondary cancer risk, including the contributions of secondary particles produced by nuclear reactions. We therefore developed a new dose reconstruction system implementing PHITS as the engine. In this system, the PHITS input is automatically created from the DICOM data sets recorded in the treatment planning. The developed system was validated by comparing to experimental dose distribution in water and treatment plan on an anthropomorphic phantom. This system will be used for retrospective studies using the patient data in National Institute for Quantum and Science and Technology.

Oceanic dispersion of Fukushima-derived Cs-137 simulated by multiple oceanic general circulation models

Kawamura, Hideyuki; Furuno, Akiko; Kobayashi, Takuya; In, Teiji*; Nakayama, Tomoharu*; Ishikawa, Yoichi*; Miyazawa, Yasumasa*; Usui, Norihisa*

Journal of Environmental Radioactivity, 180, p.36 - 58, 2017/12

https://doi.org/10.1016/j.jenvrad.2017.09.020

This study simulates the oceanic dispersion of Fukushima-derived Cs-137 by an oceanic dispersion model and multiple oceanic general circulation models. The models relatively well reproduced the observed Cs-137 concentrations in the coastal, offshore, and open oceans. Multiple simulations in the coastal, offshore, and open oceans consistently suggested that Cs-137 dispersed along the coast in the north-south direction during the first few months post-disaster, and were subsequently dispersed offshore by the Kuroshio Current and Kuroshio Extension. Quantification of the Cs-137 amounts suggested that Cs-137 actively dispersed from the coastal and offshore oceans to the open ocean, and from the surface layer to the deeper layers in the North Pacific.

Development of ocean dispersion concentration maps of the contaminated water released from the Fukushima Dai-ichi Nuclear Power Plant

Kobayashi, Takuya; In, Teiji*; Ishikawa, Yoichi*

Journal of Nuclear Science and Technology, 52(6), p.769 - 772, 2015/06

https://doi.org/10.1080/00223131.2015.1011720

Ocean diffusion concentration maps were developed to gain an understanding of the migration behavior of contaminated water leaking from the Fukushima Dai-ichi Nuclear Power Plant. We used ensemble mean values to define the semi-climatological seasonal field in our calculations of the trajectories of the contaminated water. The maps were validated by conducting actual release events in two different seasons. The results showed that despite their simplicity, the proposed methods yield relatively good results.

Radiological characteristics of MRI-based VIP polymer gel under carbon beam irradiation

Maeyama, Takuya*; Fukunishi, Nobuhisa*; Ishikawa, Kenichi*; Furuta, Takuya; Fukasaku, Kazuaki*; Takagi, Shu*; Noda, Shigeho*; Himeno, Ryutaro*; Fukuda, Shigekazu*

Radiation Physics and Chemistry, 107, p.7 - 11, 2015/02

https://doi.org/10.1016/j.radphyschem.2014.09.001

We study the radiological characteristics of VIP polymer gel dosimeters under carbon beam irradiation with energy of 135 and 290 AMeV. To evaluate dose response of VIP polymer gels, the transverse relaxation rate R2 of the dosimeters measured by magnetic resonance imaging (MRI) as a function of linear energy transfer (LET), rather than penetration depth, as is usually done in previous reports. LET is evaluated by use of the particle transport simulation code PHITS. Our results reveal that the dose response decreases with increasing dose-averaged LET and that the response-LET relation also varies with incident carbon beam energy. The latter can be explained by taking into account the contribution from fragmentation products. Furthermore, as an application of the evaluated response-LET relation, we compare the measured and simulated R2 distribution in a VIP gel formed by heterogeneous irradiation and obtain agreement in overall distribution and range within an accuracy of 5% and 1-2 mm, respectively.

Intercomparison of numerical simulations on oceanic dispersion of the radioactive cesium released because of the Fukushima disaster

Kawamura, Hideyuki; Kobayashi, Takuya; Furuno, Akiko; Usui, Norihisa*; Kamachi, Masafumi*; Nishikawa, Shiro*; Ishikawa, Yoichi*

Proceedings of 19th Pacific Basin Nuclear Conference (PBNC 2014) (USB Flash Drive), 7 Pages, 2014/08

Numerical simulations on oceanic dispersion of the radioactive cesium in the North Pacific from March 2011 to September 2013 were conducted to clarify the concentration of the radioactive cesium released from the Fukushima Daiichi Nuclear Power Plant. We implemented the oceanic dispersion simulations with two independent ocean reanalysis dataset. It was suggested that the Cs concentration in the North Pacific was lower than the pre-Fukushima background level about two years after the Fukushima disaster. The intercomparison revealed that meso-scale eddies in the Kuroshio Extension region may have efficiently diluted the radioactive cesium concentration at the sea surface. In addition, it was suggested that the enhanced downward current accompanied by the meso-scale eddies played an important role in transporting the radioactive cesium into the intermediate layer.

Computer simulation of structural modifications induced by highly energetic ions in uranium dioxide

Sasajima, Yasushi*; Osada, Takuya*; Ishikawa, Norito; Iwase, Akihiro*

Nuclear Instruments and Methods in Physics Research B, 314, p.195 - 201, 2013/11

https://doi.org/10.1016/j.nimb.2013.04.068

The structural modification caused by the high-energy-ion irradiation of single-crystalline uranium dioxide was simulated by the molecular dynamics method. As the initial condition, high kinetic energy was supplied to the individual atoms within a cylindrical region of nanometer-order radius located in the center of the specimen. The potential proposed by Basak et al. was utilized to calculate interaction between atoms. The supplied kinetic energy was first spent to change the crystal structure into an amorphous one within a short period of about 0.3 ps, then it dissipated in the specimen. The amorphous track radius was determined as a function of the effective stopping power , i.e., the kinetic energy of atoms per unit length created by ion irradiation (: electronic stopping power, : energy transfer ratio from stopping power to lattice vibration energy).

Numerical experiments on dispersion of radionuclides in the ocean released from the Fukushima Daiichi Nuclear Power Plant

Kawamura, Hideyuki; Kobayashi, Takuya; Furuno, Akiko; In, Teiji*; Ishikawa, Yoichi*; Nakayama, Tomoharu*; Shima, Shigeki*; Awaji, Toshiyuki*

Reports of Research Institute for Applied Mechanics, Kyushu University, (143), p.111 - 117, 2012/09

Because of the Fukushima Dai-ichi Nuclear Power Plant disaster, some radionuclides were released into the ocean from the Fukushima Dai-ichi Nuclear Power Plant. In response to this situation, numerical experiments were carried out at Japan Atomic Energy Agency using an oceanic dispersion model and an ocean general circulation model to estimate an effect of the radionuclides on marine environment. It was suggested that the radionuclides deposited from the atmosphere mainly in the middle of March after the disaster spread over a comparatively wide area of the Pacific Ocean east of Japan. On the other hand the radionuclides directly released into the ocean from the Fukushima Dai-ichi Nuclear Power Plant were carried along the coast and then spread along the Kuroshio extension.

Preliminary numerical experiments on Oceanic dispersion of I and Cs discharged into the ocean because of the Fukushima Daiichi Nuclear Power Plant disaster

Kawamura, Hideyuki; Kobayashi, Takuya; Furuno, Akiko; In, Teiji*; Ishikawa, Yoichi*; Nakayama, Tomoharu*; Shima, Shigeki*; Awaji, Toshiyuki*

Journal of Nuclear Science and Technology, 48(11), p.1349 - 1356, 2011/11

AA2011-0314.pdf:0.68MB

https://doi.org/10.3327/jnst.48.1349

Numerical experiments were carried out to predict the spreading of I and Cs released into the ocean due to the Fukushima Daiichi Nuclear Power Plant incident. Results in the numerical experiments were in good agreement with the concentrations of I and Cs in the monitoring data. It was suggested that the high I concentration detected in the young lancefish caught off Kitaibaraki city was due to the deposition from the atmosphere. The numerical experiments suggest that the deposition of radionuclides released into the atmosphere in the middle March largely effected the concentrations of radionuclides east of Japan in the Pacific Ocean.

An Approach to DNA crystallization using the thermal reversible process of DNA duplexes

Chatake, Toshiyuki*; Sazaki, Gen*; Kikko, Tatsuhiko*; Fujiwara, Satoru; Ishikawa, Takuya*; Matsumoto, Osamu*; Morimoto, Yukio*

Crystal Growth & Design, 10(3), p.1090 - 1095, 2010/03

https://doi.org/10.1021/cg9007075

We propose a technique for DNA crystallization using the thermal reversible process of DNA: a conversion between a double-stranded DNA (dsDNA) and two single-stranded DNAs (ssDNAs) with temperatures. We investigated the solubility of the crystals of a DNA hexamer d(CGCGCG) and their melting temperature, at which the thermal conversion occurs. The results obtained suggest that the conversion from a dsDNA to ssDNAs results in an increase in solubility. It was shown that using this temperature-controlled technique, high-grade single crystals of the DNA hexamer could be obtained from a small amount of DNA samples. This easy-to-apply technique would be superior to the conventional vapor diffusion technique in that it allows the solubility of DNA crystals to be controlled with no need for expensive setups.

Development on Mo production technology by molybdenum solution irradiation method

Inaba, Yoshitomo; Ishikawa, Koji*; Ishida, Takuya; Tatenuma, Katsuyoshi*; Ishitsuka, Etsuo

JAEA-Conf 2008-010, p.259 - 267, 2008/12

https://jopss.jaea.go.jp/pdfdata/JAEA-Conf-2008-010-1.pdf

Tc for the medical diagnosis is the most widely used radioisotope in the world and it's demand is growing up year by year. In case of Japan, all Mo which is parent nuclide of Tc, is imported. However, the importance of the domestic production is pointed out from a viewpoint of the stable supply of Mo because of some troubles on transportation or the research reactor, and so on. Therefore, the (n,) method using solid molybdenum target had been planned in JMTR. However, it will be difficult to satisfy domestic demand because of the limited irradiation volumes of the hydraulic rabbit irradiation facility. In order to increase the amount of Mo production, the molybdenum solution irradiation method was proposed as a new production method. This method is based on the neutron irradiation of molybdenum solution, and several advantages can be pointed out such as a large irradiation volume, high efficient and low cost comparing with conventional methods using enriched U(n,f)Mo as the major method or using a solid molybdenum target of MoO as the minor (n,) method. Aiming at the realization of the molybdenum solution irradiation method, un-irradiated and ray irradiated tests of the molybdenum solution were carried out, and the data of chemical stability and compatibility with the structural materials were shown.