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Taitō-ku, Japan

Tachi Y.,Japan Atomic Energy Agency | Ebina T.,NESI Inc. | Takeda C.,Tokyo Nuclear Service Co. | Saito T.,Tokyo Nuclear Service Co. | And 3 more authors.
Journal of Contaminant Hydrology | Year: 2015

Matrix diffusion and sorption are important processes controlling radionuclide transport in crystalline rocks. Such processes are typically studied in the laboratory using borehole core samples however there is still much uncertainty on the changes to rock transport properties during coring and decompression. It is therefore important to show how such laboratory-based results compare with in situ conditions. This paper focuses on laboratory-scale mechanistic understanding and how this can be extrapolated to in situ conditions as part of the Long Term Diffusion (LTD) project at the Grimsel Test Site, Switzerland. Diffusion and sorption of 137Cs+, 22Na+, 125I- and tritiated water (HTO) in Grimsel granodiorite were studied using through-diffusion and batch sorption experiments. Effective diffusivities (De) of these tracers showed typical cation excess and anion exclusion effects and their salinity dependence, although the extent of these effects varied due to the heterogeneous pore networks in the crystalline rock samples. Rock capacity factors (α) and distribution coefficients (Kd) for Cs+ and Na+ were found to be sensitive to porewater salinity. Through-diffusion experiments indicated dual depth profiles for Cs+ and Na+ which could be explained by a near-surface Kd increment. A microscopic analysis indicated that this is caused by high porosity and sorption capacities in disturbed biotite minerals on the surface of the samples. The Kd values derived from the dual profiles are likely to correspond to Kd dependence on the grain sizes of crushed samples in the batch sorption experiments. The results of the in situ LTD experiments were interpreted reasonably well by using transport parameters derived from laboratory data and extrapolating them to in situ conditions. These comparative experimental and modelling studies provided a way to extrapolate from laboratory scale to in situ condition. It is well known that the difference in porosity between laboratory and in situ conditions is a key factor to scale laboratory-derived De to in situ conditions. We also show that cation excess diffusion is likely to be a key mechanism in crystalline rocks and that high Kd in the disturbed surfaces is critically important to evaluate transport in both laboratory and in situ tests. © 2015 Elsevier B.V.

Hayashi K.,Japan National Institute of Radiological Sciences | Hayashi K.,RIKEN | Furutsuka K.,Japan National Institute of Radiological Sciences | Furutsuka K.,SHI Accelerator Service Co. | And 8 more authors.
Applied Radiation and Isotopes | Year: 2011

The aim of this study was to develop an efficient fully automated synthesis method to achieve a high radiochemical yield of [18F]FAZA with a small amount of precursor. A small cartridge containing 25mg of the QMA resin was prepared and evaluated to obtain [18F]F- in a small quantity of base (K2CO3), which might allow the use of a small amount of precursor. The labeling and hydrolyzing conditions for [18F]FAZA synthesis were also investigated manually. No-carrier-added [18F]F- was trapped on the small QMA cartridge and eluted with a mixture of Krytofix 222 (2.26mg, 6.0γmol) and K2CO3 (0.69mg, 5.0γmol) in 70% MeCN (0.4mL). The automated synthesis of [18F]FAZA was optimally performed with a modified NIRS original synthesis system for clinical use, by labeling 2.5mg (5.2γmol) of the precursor in DMSO (0.4mL) at 120°C for 10min, and then by hydrolyzing the 18F-labeled intermediate with 0.1M NaOH (0.5mL) at room temperature for 3min. Using the above condition, the [18F]FAZA injection was obtained with a high radiochemical yield of 52.4±5.3% (decay-corrected, n=8) within 50.5±1.5min. © 2011 Elsevier Ltd.

Kumata K.,Japan National Institute of Radiological Sciences | Takei M.,Japan National Institute of Radiological Sciences | Takei M.,Tokyo Nuclear Service Co. | Ogawa M.,Japan National Institute of Radiological Sciences | And 5 more authors.
Journal of Labelled Compounds and Radiopharmaceuticals | Year: 2010

Recent studies revealed that thalidomide (1) has unique and broad pharmacological effects on multi-targets although the application of 1 in therapy is still controversial. In this study, we synthesized nitrogen-13-labeled thalidomide ([13N]1) as a potential positron emission tomography (PET) probe using no-carrier-added [13N]NH 3 as a labeling agent. By use of an automated system, [ 13N]1 was prepared by reacting N-phthaloylglutamic anhydride (2) with [13N]NH3, following by cyclization with carbonyldiimidazole in a radiochemical yield of 56±12% (based on [ 11N]NH3, corrected for decay) and specific activity of 49±24GBq/μmol at the end of synthesis (EOS). At EOS, 570-780MBq (n=7) of [13N]1 was obtained at a beam current of 15 μA after 15 min proton bombardment with a synthesis time of 14 min from the end of bombardment. Using a small animal PET scanner, preliminary biodistribution of [ 13N]1 in mice was examined. Copyright © 2010 John Wiley & Sons, Ltd.

Yanamoto K.,Japan National Institute of Radiological Sciences | Kumata K.,Japan National Institute of Radiological Sciences | Fujinaga M.,Japan National Institute of Radiological Sciences | Nengaki N.,Japan National Institute of Radiological Sciences | And 12 more authors.
Nuclear Medicine and Biology | Year: 2010

Introduction: The translocator protein (18 kDa) (TSPO) is widely expressed in peripheral tissues, including the heart, lung, and kidney. Our laboratory developed N-benzyl-N-methyl-2-[7,8-dihydro-7-(2-[18F]fluoroethyl)-8-oxo-2-phenyl-9H-purin-9-yl]acetamide ([18F]FEDAC) as a TSPO positron emission tomography (PET) ligand. Here, using small-animal PET with [18F]FEDAC, we performed TSPO imaging and quantitative analysis of TSPO binding in rat peripheral tissues. Methods: The in vivo distribution and kinetics of [18F]FEDAC were measured in rat peripheral tissues (heart, lung and kidney). Using the in vivo pseudo-equilibrium method, TSPO binding parameters [TSPO density (Bmax), dissociation constant (KD)] and receptor occupancy were estimated in these peripheral tissues. Results: [18F]FEDAC was highly distributed in the lung, heart and kidney, and these TSPO-enriched tissues could be clearly visualized. The kinetics of this radioligand in these tissues was rapid, which is suitable for the determination of in vivo TSPO binding parameters and receptor occupancy. The Bmax value of TSPO in the heart, lung, and kidney was 393, 141, and 158 pmol/ml, respectively. The KD value of the radioligand in the heart, lung, and kidney was 119, 36 and 123 nM, respectively. By pretreatment with 5 mg/kg Ro 5-4864 (a TSPO ligand), about 90% of binding sites for TSPO in the heart and lung were occupied. In the kidney, the binding sites were completely occupied by 5 mg/kg Ro 5-4864. Conclusions: [18F]FEDAC is a suitable PET ligand for TSPO imaging and quantitative analysis of TSPO binding in rat peripheral tissues. The utilization of [18F]FEDAC-PET and the pseudo-equilibrium method can contribute to the study of the TSPO function and evaluate the in vivo binding parameters and receptor occupancy of TSPO therapeutic compounds. © 2010 Elsevier Inc.

Yanamoto K.,Japan National Institute of Radiological Sciences | Konno F.,Japan National Institute of Radiological Sciences | Odawara C.,Japan National Institute of Radiological Sciences | Yamasaki T.,Japan National Institute of Radiological Sciences | And 9 more authors.
Nuclear Medicine and Biology | Year: 2010

Introduction: Developing positron emission tomography (PET) ligands for imaging metabotropic glutamate receptor type 1 (mGluR1) is important for studying its role in the central nervous system. N-cyclohexyl-6-{[N-(2-methoxyethyl)-N-methylamino]methyl}-N-methylthiazolo[3,2-a]benzimidazole-2-carboxamide (YM-202074) exhibited high binding affinity for mGluR1 (Ki=4.8 nM), and selectivity over other mGluRs in vitro. The purpose of this study was to label YM-202074 with carbon-11 and to evaluate in vitro and in vivo characteristics of [11C]YM-202074 as a PET ligand for mGluR1 in rodents. Methods: [11C]YM-202074 was synthesized by N-[11C]methylation of its desmethyl precursor with [11C]methyl iodide. The in vitro and in vivo brain regional distributions were determined in rats using autoradiography and PET, respectively. Results: [11C]YM-202074 (262-630 MBq, n=5) was obtained with radiochemical purity of >98% and specific activity of 27-52 GBq/Αmol at the end of synthesis, starting from [11C]CO2 of 19.3-21.5 GBq. In vitro autoradiographic results showed that the high specific binding of [11C]YM-202074 for mGluR1 was presented in the cerebellum, thalamus and hippocampus, which are known as mGluR1-rich regions. In ex vivo autoradiography and PET studies, the radioligand was specifically distributed in the cerebellum, although the uptake was low. Furthermore, the regional distribution was fairly uniform in the whole brain by pretreatment with JNJ16259685 (a mGluR1 antagonist). However, radiometabolite(s) was detected in the brain. Conclusions: From these results, especially considering the low brain uptake and the influx of radiometabolite(s) into brain, [11C]YM-202074 may not be a useful PET ligand for in vivo imaging of mGluR1 in the brain. © 2010 Elsevier Inc.

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