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Journal Articles

Numerical analysis of organ doses delivered during computed tomography examinations using Japanese adult phantoms with the WAZA-ARI dosimetry system

Takahashi, Fumiaki; Sato, Kaoru; Endo, Akira; Ono, Koji*; Ban, Nobuhiko*; Hasegawa, Takayuki*; Katsunuma, Yasushi*; Yoshitake, Takayasu*; Kai, Michiaki*

Health Physics, 109(2), p.104 - 112, 2015/08

 Times Cited Count:4 Percentile:51.6(Environmental Sciences)

A dosimetry system, named WAZA-ARI, is developed to assess accurately radiation doses to persons from Computed Tomography (CT) examination patients in Japan. Organ doses were prepared to application to dose calculations in WAZA-ARI by numerical analyses using average adult Japanese human models with the Particle and Heavy Ion Transport code System (PHITS). Experimental studies clarified the radiation configuration on the table for some multi-detector row CT (MDCT) devices. Then, a source model in PHITS could specifically take into account for emissions of X-ray in each MDCT device based on the experiment results. Numerical analyses with PHITS revealed a concordance of organ doses with human body size. The organ doses by the JM phantoms were compared with data obtained using previously developed systems. In addition, the dose calculation in WAZA-ARI were verified with previously reported results by realistic NUBAS phantoms and radiation dose measurement using a physical Japanese model. The results implied that analyses using the Japanese phantoms and PHITS including source models can appropriately give organ dose data with consideration of the MDCT device and physiques of typical Japanese adults.

Journal Articles

WAZA-ARI; A Dose assessment system for patients in CT scan

Sato, Kaoru; Takahashi, Fumiaki; Endo, Akira; Ono, Koji*; Hasegawa, Takayuki*; Katsunuma, Yasushi*; Yoshitake, Takayasu*; Ban, Nobuhiko*; Kai, Michiaki*

RIST News, (58), p.25 - 32, 2015/01

The Japan Atomic Energy Agency (JAEA) are now developing WAZA-ARI for improvement of management of exposure doses due to CT examination under the joint research with the Oita University of Nursing and Health Sciences. The trial version of WAZA-ARI has been released on 21 December 2012. In trial version, users can perform dose assessment by using organ dose database based on the average adult Japanese male (JM-103) and female (JF-103) voxel phantoms and a 4 years old female voxel phantom (UFF4). The homepage of WAZA-ARI has been accessed over 1000 times per month and 28421 times by the end of September 2014. We are developing WAZA-ARI version 2 as the extension version of dose calculation functions of WAZA-ARI. WAZA-ARI version 2 will be released by the end of March 2015. In WAZA-ARI version 2. Users can upload dose calculation results to WAZA-ARI version 2 server, and utilize improvement of the dose management of patients and the optimization of CT scan conditions.

Journal Articles

Evaluation of soft X-ray laser with ${it in situ}$ imaging device of high spatial resolution ZnO scintillator

Nakazato, Tomoharu*; Shimizu, Toshihiko*; Yamanoi, Kohei*; Sakai, Kohei*; Takeda, Kohei*; Nishi, Ryosuke*; Minami, Yuki*; Cadatal-Raduban, M.*; Sarukura, Nobuhiko*; Nishimura, Hiroaki*; et al.

Japanese Journal of Applied Physics, 50(12), p.122202_1 - 122202_4, 2011/12

 Times Cited Count:7 Percentile:63.59(Physics, Applied)

We demonstrate the potential of a hydrothermal method-grown ZnO as a high-spatial resolution imaging device for in-situ soft X-ray laser diagnostics by characterizing the exciton emission patterns. By plotting the emission pattern radii at each position, we estimated the evolution of the beam radius around the focal point. The beam profile of the Ni-like Ag ion plasma laser was estimated from the waist radii as 29 and 21$$mu$$m, the divergence angle as 7.2 and 11 mrad and the M2 factor as 47 and 50 in the horizontal- and vertical-axis, respectively. Spatial resolution of the magnifier was estimated to be 6$$mu$$m and is expected to improve by optimizing the optics of the magnifier and using a telescope. Our results would enhance the use of ZnO as an imaging device that would play a crucial role in the development and application of soft X-ray light sources.

Journal Articles

Effects of human model configuration in Monte Carlo calculations for organ doses from CT examinations

Takahashi, Fumiaki; Sato, Kaoru; Endo, Akira; Ono, Koji*; Yoshitake, Takayasu*; Hasegawa, Takayuki*; Katsunuma, Yasushi*; Ban, Nobuhiko*; Kai, Michiaki*

Progress in Nuclear Science and Technology (Internet), 2, p.153 - 159, 2011/10

Computed Tomography (CT) is one of the most useful tools for medical diagnosis, and is becoming a major source of medical exposure in developed countries. Appropriate radiation protection in CT examinations is emphasized by international organizations, such as the International Atomic Energy Agency (IAEA), because the patients receive higher radiation doses than in conventional radiography. Medical staffs can acquire dose information on the conditions of some CT examinations with available dosimetry systems, which had been already developed. These systems utilize datasets of organ and tissue doses, which were derived with Monte Carlo calculations. Methods in computational analyses, however, have been improved, since these calculations had been performed. Then, our new dosimetry system for CT examination, WAZA-ARI, is being developed to estimate radiation dose based upon the state-of-art numerical analyses. Our analysis adopts Particle and Heavy Ion Transport code System (PHITS) coupled with a voxel-type phantom, JM phantom, for the organ dose calculation. PHITS has advantageous to define the model of photon emission from X-ray tube in a CT device for radiation transport calculations. The physique and mass of organs for JM phantom are similar to those for average Japanese male adults. Since the goal of WAZA-ARI is to provide dosimetric information of arbitrary patient, it is important to evaluate uncertainty due to different configurations in human bodies between JM phantom and individual patients. For this purpose, the organ doses are calculated and compared for different human models; another Japanese male adult voxel phantom and the ICRP reference voxel phantom, which is constructed on the basis of Caucasian data.

Journal Articles

Development of a web-based CT dose calculator; WAZA-ARI

Ban, Nobuhiko*; Takahashi, Fumiaki; Sato, Kaoru; Endo, Akira; Ono, Koji*; Hasegawa, Takayuki*; Yoshitake, Takayasu*; Katsunuma, Yasushi*; Kai, Michiaki*

Radiation Protection Dosimetry, 147(1-2), p.333 - 337, 2011/09

 Times Cited Count:16 Percentile:17.24(Environmental Sciences)

A web-system of WAZA-ARI is being developed to assess radiation dose to a patient in a Computed Tomography (CT) examination. The databases of organ doses for WAZA-ARI were derived by the Japanese adult Male phantom (JM phantom) combined with the Particle and Heavy Ion Transport code System, PHITS. In the Monte Carlo simulation, the phantoms were irradiated with a 5 mm-thick fan-shaped photon beam, which was moved every 5 mm along the body axis from the upper leg to the top of head. The attenuation by the beam-shaping filter (bow-tie filter) was also taken into account here. The MIRD-type phantom was also applied to the calculations. The MIRD phantom sometimes showed step changes for organ doses, while smoother curves were obtained for JM phantom. The dose data by JM phantom were incorporated into the WAZA-ARI system, which has been implemented on a Linux server. With regard to the system implementation, the system has achieved a high degree of flexibility without commercial software.

Journal Articles

WAZA-ARI; Computational dosimetry system for X-ray CT examinations, 1; Radiation transport calculation for organ and tissue doses evaluation using JM phantom

Takahashi, Fumiaki; Sato, Kaoru; Endo, Akira; Ono, Koji*; Yoshitake, Takayasu*; Hasegawa, Takayuki*; Katsunuma, Yasushi*; Ban, Nobuhiko*; Kai, Michiaki*

Radiation Protection Dosimetry, 146(1-3), p.241 - 243, 2011/07

 Times Cited Count:14 Percentile:20.5(Environmental Sciences)

A web-system of WAZA-ARI is being developed to assess radiation dose to a patient in a Computed Tomography (CT) examination. WAZA-ARI utilizes a set of organ and tissue doses in a database for the dose assessment, according to the given resources with a consideration of the examination condition. The organ and tissue doses in the database have been derived with the Particle and Heavy Ion Transport code System, PHITS. Modeling of the patient was a significant issue in the radiation transport calculation. JM phantom, whose height (171 cm) and weight (65 kg) are near to those averaged over Japanese male adults, was incorporated to PHITS as a human model. Since JM phantom consisted of about 1 mm$$^{3}$$ size voxel, the shapes could be realistically reproduced even for small organs such as thyroid, adrenals. Masses of most organs could be also adjusted to the averaged values of Japanese male adults. In addition, our calculations introduced a new phantom without arms based upon JM phantom, because the patient usually puts arms toward the head direction in a torso examination. Some of organ doses calculated by JM phantom were compared with results, which were derived with a MIRD-type phantom. Differences could be seen in some organ doses between the phantoms, if photon attenuations in a shaping (Bow-tie) filter were taken into account to a source model in PHITS.

Journal Articles

WAZA-ARI; Computational dosimetry system for X-ray CT examinations, 2; Development of web-based system

Ban, Nobuhiko*; Takahashi, Fumiaki; Ono, Koji*; Hasegawa, Takayuki*; Yoshitake, Takayasu*; Katsunuma, Yasushi*; Sato, Kaoru; Endo, Akira; Kai, Michiaki*

Radiation Protection Dosimetry, 146(1-3), p.244 - 247, 2011/07

 Times Cited Count:14 Percentile:20.5(Environmental Sciences)

We are developing a web-based system, WAZA-ARI, for the dose calculation of patients undergoing X-ray CT examinations. Tissue doses were calculated in a Japanese adult male phantom (JM phantom) using a Monte Carlo code, PHITS, and the normalized dose coefficient data are stored as XML files. The system is implemented in Java on a Linux server running Apache Tomcat, which is accessed via a web browser over a network. Users are requested to choose scanning options and to input parameters in the data entry screen. The corresponding dose data are called upon input, and they are summed over the scan range specified by the user to estimate unit tissue doses. Tissue doses are computed based on the radiographic exposure (mAs), the beam pitch and air kerma at the beam center on the axis of rotation. Users can also use their own air kerma, CTDI vol and DLP values for the dose computation instead of the default setting. Although the dose coefficients are prepared for only limited CT scanner models currently, our system has achieved high usability and easy maintenance without commercial software. Possibility of further expansion for the practical application is also discussed.

Journal Articles

Analysis of organ doses from Computed Tomography (CT) examination by the radiation transport calculation to develop the dosimetry system, WAZA-ARI

Takahashi, Fumiaki; Endo, Akira; Sato, Kaoru; Hasegawa, Takayuki*; Katsunuma, Yasushi*; Ono, Koji*; Yoshitake, Takayasu*; Ban, Nobuhiko*; Kai, Michiaki*

Progress in Nuclear Science and Technology (Internet), 1, p.517 - 520, 2011/02

Several dose assessment system were developed to avoid unnecessary exposure for a patient in a Computed Tomography (CT) examination. Most of these systems contain datasets of organ doses, which had been calculated with mathematical phantoms. The numerical analyses for radiation dosimetry and CT machines have progressed in recent years. Thus, a project is being carried out to develop a new dosimetry system, named WAZA-ARI. The basic data of organ doses are calculated with a male voxel phantom (JM phantom), which defines configurations of the human body more precisely than the mathematical model. The radiation transports in CT examination can be simulated with the Particle and Heavy Ion Transport code System, PHITS. A source model can be set up for emissions of photons from the X-ray tube with a subroutine, including the helical scanning. Thus, the WAZA-ARI system can assess radiation dose based upon the organ doses, which are calculated with the appropriate source and human models.

Journal Articles

Initiation of systems radiation biology in Japan

Sakashita, Tetsuya; Suzuki, Michiyo; Ouchi, Noriyuki; Ban, Nobuhiko*

Hoshasen Seibutsu Kenkyu, 45(4), p.379 - 395, 2010/12

Recently, systems radiation biology (SRB) has been studied and developed in Europe and USA. Also, Japanese researchers in radiation biology are interested in this research field, gradually. In this review, four scientists shortly review SRB in each stand points.

Oral presentation

Development of dose assessment system for CT examination with a Japanese voxel phantom, 2; Dose assessment of CT examination using a radiation transport calculation code

Takahashi, Fumiaki; Endo, Akira; Sato, Kaoru; Hasegawa, Takayuki*; Katsunuma, Yasushi*; Ono, Koji*; Yoshitake, Takayasu*; Ban, Nobuhiko*; Kai, Michiaki*

no journal, , 

no abstracts in English

Oral presentation

Development of dose assessment system for CT examination with a Japanese voxel phantom, 1; Aim of our development and its overall plan

Kai, Michiaki*; Ono, Koji*; Hasegawa, Takayuki*; Katsunuma, Yasushi*; Yoshitake, Takayasu*; Ban, Nobuhiko*; Takahashi, Fumiaki; Sato, Kaoru; Endo, Akira

no journal, , 

no abstracts in English

Oral presentation

Interaction between glass dosimeters in a measueremnt of organ doses

Hasegawa, Takayuki*; Katsunuma, Yasushi*; Takahashi, Fumiaki; Ban, Nobuhiko*; Kai, Michiaki*

no journal, , 

no abstracts in English

Oral presentation

Construction of an adult Japanese female voxel phantom used for assessment of organ doses due to CT examination

Sato, Kaoru; Takahashi, Fumiaki; Endo, Akira; Ono, Koji*; Hasegawa, Takayuki*; Katsunuma, Yasushi*; Yoshitake, Takayasu*; Ban, Nobuhiko*; Kai, Michiaki*

no journal, , 

no abstracts in English

Oral presentation

Numerical analyses of organ dose in MSCT examination by using Japanese male and female human models

Takahashi, Fumiaki; Sato, Kaoru; Endo, Akira; Ono, Koji*; Hasegawa, Takayuki*; Katsunuma, Yasushi*; Yoshitake, Takayasu*; Ban, Nobuhiko*; Kai, Michiaki*

no journal, , 

no abstracts in English

Oral presentation

Experimental validation of dose assessment system for CT scans "WAZA-ARI"

Ono, Koji*; Yoshitake, Takayasu*; Hasegawa, Takayuki*; Katsunuma, Yasushi*; Takahashi, Fumiaki; Sato, Kaoru; Endo, Akira; Ban, Nobuhiko*; Kai, Michiaki*

no journal, , 

A computed tomography (CT) dose calculation system, WAZA-ARI, evaluates organ doses by CT examination using dose coefficients calculated in voxel type Japanese adult male and female phantoms. AEC (Auto Exposure Control) is an essential function in order to optimize the relationship between radiation dose and quality of image of CT scan. Therefore, a method for dose estimation under the AEC operation is being developed for WAZA-ARI. The presentation reports comparison of organ doses between calculation by WAZA-ARI and measurement for various CT scanner equip with AEC for validation of WAZA-ARI.

Oral presentation

The Experience obtained by risk communication activity with radiation question and answer in life website after Fukushima Daiichi Nuclear Power Plant Accident

Kono, Takahiko; Ogino, Haruyuki*; Hayakawa, Hironobu*; Shimo, Michikuni*; Taniguchi, Kazufumi*; Ban, Nobuhiko*

no journal, , 

no abstracts in English

Oral presentation

The Experience of risk communication activities using the Q&A web site concerning about radiation in life after Fukushima Daiichi Nuclear Power Plant accident

Kono, Takahiko; Ogino, Haruyuki*; Hayakawa, Hironobu*; Shimo, Michikuni*; Taniguchi, Kazufumi*; Ban, Nobuhiko*

no journal, , 

After Fukushima Daiichi Nuclear Power Plant accident happened on 11 March 2011, we have been providing the right information about radiation and radioactivity via a Q&A website. Immediately after the accident, volunteers of Japan Health Physics Society (JHPS) built up a website named Questions and Answers about Radiation in Daily Life. They carefully answered all of the questions posted on the website. In August, Steering Committee of the Q&A site was officially established in JHPS. Since then, the Committee has been engaged in the risk communication activities to the public. We have analyzed characteristics of questioners and question contents of about 1,500 posted on our web site so far. It has been found that mothers of small children form the major portion of the questioners all through the period.

Oral presentation

Validation of dose assessment system for CT diagnosis

Yoshitake, Takayasu*; Ono, Koji*; Hasegawa, Takayuki*; Katsunuma, Yasushi*; Sato, Kaoru; Takahashi, Fumiaki; Endo, Akira; Ban, Nobuhiko*; Kai, Michiaki*

no journal, , 

Since 2000s, computed tomography (CT) examination has significantly increased at medical treatment in Japan. Therefore, it is very interested in radiation exposure doses derived from CT examinations. We started development of a web-based system, named WAZA-ARI, which can assess radiation doses more accurately now in Japan in 2007. So far a beam-shaping (bow-tie) filter was newly constructed for the X-ray source model of CT device by using PHITS code. In this study, CTDI phantom, which dosimeter was placed in center or periphery, was irradiated with X-ray of CT device. In order to validate WAZA-ARI, measured values were compared with calculated values by PHITS code. The dose differences of center in CTDI phantom between measurement and calculation were within 2-5%.

Oral presentation

Development of deformation method of body shapes in adult Japanese phantoms used for assessment of organ doses due to CT examination

Sato, Kaoru; Takahashi, Fumiaki; Endo, Akira; Ono, Koji*; Hasegawa, Takayuki*; Katsunuma, Yasushi*; Yoshitake, Takayasu*; Ban, Nobuhiko*; Kai, Michiaki*

no journal, , 

no abstracts in English

Oral presentation

WAZA-ARI2; Web-based CT dose calculator for Asian physiques

Ono, Koji*; Sato, Kaoru; Takahashi, Fumiaki; Hasegawa, Takayuki*; Katsunuma, Yasushi*; Kamei, Osamu*; Yoshitake, Takayasu*; Ban, Nobuhiko*; Endo, Akira; Lee, C.*; et al.

no journal, , 

We developed a web-based CT dosimetry system, WAZA-ARI, which calculates doses to average-sized Japanese adults (male and female) as well as a four-year-old girl. The system is being upgraded to a new version, WAZA-ARI 2, incorporating several new features. To enable the dose calculation for a wider range of subjects, WAZA-ARI 2 utilizes voxelized hybrid phantoms developed by Florida University (0, 1, 5, 10 and 15 years old, both sexes) in addition to the JAEA voxel phantoms of the average-sized Japanese male and female. It is also capable of calculating doses to adults with small, large and extra-large body sizes. The system computes tissue doses on user's request referring to the dose coefficient datasets that have been calculated using the Particle and Heavy Ion Transport code System (PHITS). As the phantoms used represent physiques of Asian population, WAZA-ARI 2 is appropriate to calculate patient doses in Asian countries.

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