Japan Radioisotope Association

Bunkyō-ku, Japan

Japan Radioisotope Association

Bunkyō-ku, Japan
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Kessler C.,Bureau International des Poids et Mesures | Kurosawa T.,Japan National Institute of Advanced Industrial Science and Technology | Mikamoto T.,Japan Radioisotope Association
Metrologia | Year: 2016

An indirect comparison of the standards for reference air kerma rate for 192Ir high dose rate (HDR) brachytherapy sources of the National Metrology Institute of Japan (AIST-NMIJ), Japan, and of the Bureau International des Poids et Mesures (BIPM) was carried out at the Japan Radioisotope Association (JRIA) in April 2015. The comparison result, based on the calibration coefficients for a transfer standard and expressed as a ratio of the NMIJ and the BIPM standards for reference air kerma rate, is 1.0036 with a combined standard uncertainty of 0.0054.


Ishizu H.,Japan Radioisotope Association | Yamada T.,Japan Radioisotope Association
Applied Radiation and Isotopes | Year: 2017

When calibrating absolute peak efficiency and total efficiency functions for high efficient germanium detectors, single gamma-emitting nuclides are used in general to avoid coincidence summing effects. As another approach, Blaauw developed calibration technique using multiple gamma-emitting nuclides with least-square technique (). In the present study, we tried to calibrate efficiency functions of a well-type germanium detector based on Blaauw's approach using a home-made iteration calculation algorithm with the "Solver" add-in in Excel™. © 2017 Elsevier Ltd.


Yamada T.,Japan Radioisotope Association | Ishii K.,Tohoku University
Applied Radiation and Isotopes | Year: 2012

For diagnostic nuclear medicine, radiopharmaceuticals are labeled with γ-ray emitting nuclides. Routine activity measurements for these drugs are mainly performed with re-entrant ionization chambers. For radiotherapeutic applications, Β-ray emitting nuclides are also used. Since very few gamma transitions are involved in these nuclides, an ionization chamber responds only to weak bremsstrahlung. In order to apply the re-entrant chamber method to routine activity assay for these Β-ray emitting nuclides, detailed studies were carried out. It was determined that the response was strongly affected by the choice of thickness of the inner wall of the well in the measurement of high energy beta particle emitting nuclides. The geometrical dependences were successfully reduced. Accordingly, routine assay of radioactivity of 90Y therapeutic pharmaceuticals can be performed within an acceptable uncertainty with ordinary re-entrant dose calibrators that are commercially available and equipped in most hospitals. © 2012 Elsevier Ltd.


Yamada T.,Japan Radioisotope Association | Takano N.,Scarabs Corporation Co.
Applied Radiation and Isotopes | Year: 2014

A method has been studied for the analysis of the pulse-height spectrum of a mixed 134Cs and 137Cs source obtained with a NaI(Tl) scintillation spectrometer. A peak fitting technique using maximum likelihood estimation was used with a specially developed deconvolution computer program. The activities obtained by this program were compared with the reference value in order to validate the analysis algorithm. Peak-area determination for NaI(Tl) scintillation spectrometry was successfully carried out even for spectra that included peak doublet and were recorded with low statistics. The results obtained by the maximum likelihood estimation agreed with each reference value within their statistical uncertainties. © 2013 Elsevier Ltd.


Yamada T.,Japan Radioisotope Association | Ishizu H.,Japan Radioisotope Association | Kawada Y.,Japan National Institute of Advanced Industrial Science and Technology
Applied Radiation and Isotopes | Year: 2013

A simplified peak fitting technique for the analysis of the overlapped pulse-height spectra of 134Cs and 137Cs γ-rays obtained with a NaI(Tl) scintillation spectrometer was studied. In this analysis, nearly an upper half of 662keV 137Cs peak data was employed for fitting of the Gaussian peak using the least squares algorithm. Consistent results were obtained as compared with the reference value of test samples mixed with 134Cs and 137Cs standard solutions. © 2013 Elsevier Ltd.


Ishizu H.,Japan Radioisotope Association | Yamada T.,Japan Radioisotope Association | Kawada Y.,Japan National Institute of Advanced Industrial Science and Technology
Applied Radiation and Isotopes | Year: 2014

In the use of photon detectors having sensitivity to β-rays or internal conversion electrons (CEs), β-γ and/or X-CE coincidence summing may arise. In particular, an n-type germanium detector has a thin dead layer and window, causing considerably higher sensitivity to β-rays and/or CEs especially when sources are located at a small source-to-detector distance. In the present research, reduction of the photopeak area due to β-γ or X-CE coincidence summing has been studied for three germanium detectors. © 2013 Elsevier Ltd.


Hasegawa T.,Kitasato University | Sato Y.,Japan National Institute of Advanced Industrial Science and Technology | Oda K.,Tokyo Metropolitan University | Wada Y.,RIKEN | And 2 more authors.
Physics in Medicine and Biology | Year: 2011

The uncertainty of radioactivity concentrations measured with positron emission tomography (PET) scanners ultimately depends on the uncertainty of the calibration factors. A new practical calibration scheme using point-like 22Na radioactive sources has been developed. The purpose of this study is to theoretically investigate the effects of the associated 1.275 MeV γ rays on the calibration factors. The physical processes affecting the coincidence data were categorized in order to derive approximate semi-quantitative formulae. Assuming the design parameters of some typical commercial PET scanners, the effects of the γ rays as relative deviations in the calibration factors were evaluated by semi-quantitative formulae and a Monte Carlo simulation. The relative deviations in the calibration factors were less than 4%, depending on the details of the PET scanners. The event losses due to rejecting multiple coincidence events of scattered γ rays had the strongest effect. The results from the semi-quantitative formulae and the Monte Carlo simulation were consistent and were useful in understanding the underlying mechanisms. The deviations are considered small enough to correct on the basis of precise Monte Carlo simulation. This study thus offers an important theoretical basis for the validity of the calibration method using point-like 22Na radioactive sources. © 2011 Institute of Physics and Engineering in Medicine.


Ishizu H.,Japan Radioisotope Association | Yamada T.,Japan Radioisotope Association
Applied Radiation and Isotopes | Year: 2016

Radioactive impurities might cause significant error in the activity determination of a target nuclide using ionization chambers. In the present study, an impurity correction technique for 201Tl sources was performed by applying two different responses of an IG12A20 and IG11N20 ionization chamber. This technique can be extended to another method in which an attenuation filter made of tin was used to obtain different responses of an argon filled IG12A20. The results obtained with these techniques were very consistent with each other and with the reference value within their uncertainty after making the impurity correction. Examples of 64Cu activity determination were also shown. © 2015 Elsevier Ltd.


Yamada T.,Japan Radioisotope Association | Kawada Y.,Japan National Institute of Advanced Industrial Science and Technology | Sato Y.,Japan National Institute of Advanced Industrial Science and Technology
Applied Radiation and Isotopes | Year: 2016

We developed a 4πβ-4πγ counter composed of a 4π plastic scintillation detector and a well-type Ge detector, employing digital coincidence counting and data storage in list-mode. In both of the β- and γ-channels, the amplified pulses from a linear amplifier feed the input channel of the digitizer directly via delay circuits. A signal from the peak-hold of each channel is fed to a sliding scale ADC (14 bits, 200 MHz clock) after peak detection and converted into 13 bit digital data, registered along with a time stamp and event channel allowing various data analysis to be implemented offline. When employing multiple gamma window settings, a weighted average of each apparent efficiency might be introduced to improve the efficiency functions. This idea was investigated along with reasonable estimates of the weighing factors, and activity measurements of 59Fe using this system are presented. © 2015 Elsevier Ltd.


Ohshiro M.,Japan Radioisotope Association | Shiina T.,Japan Radioisotope Association | Yamada T.,Japan Radioisotope Association
Applied Radiation and Isotopes | Year: 2016

When conducting uniformity measurements of a wide area reference source with a detector having a window of a size similar to that of a gridded individual portion area on the source, it is important to carefully consider neighbor effects on measuring emission rates of the individual target portion resulting from the gap between the source and detector window. Optimization of the uniformity measurement conditions was studied for beta-emitting wide area reference sources in this study. A measurement system consisting of a PR-gas (Ar: 90%+CH4: 10%) flow type windowed proportional counter and a motorized XY stage was installed. This system is adapted to the uniformity measurement of two different types of 36Cl sources made by different manufacturers. Uniformity measurement of a 100 mm×100 mm source divided into 16 portions of 6.25 cm2 (25 mm squared) each could be conducted using our system under the present conditions with a neighbor effect of around 15% or less. The measurement results by use of this system were also compared with those using the imaging plate technique. © 2015 Elsevier Ltd.

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