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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

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.

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

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.

Oral presentation

Development of age and body size specific database of dose conversion coefficients 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, , 

JAEA is now developing CT dose calculator named WAZA-ARI in cooperation with the Oita University of Nursing and Health Sciences. WAZA-ARI has been opened to the public as trial uses on 21 December 2012. To upgrade dose calculation functions of WAZA-ARI for full-dress uses, we developed the dose coefficients database sets based on infant phantoms with 5 ages (0y, 1y, 5y, 10y, 15y) and adult phantoms with 3 body sizes (-2$$sigma$$, +2$$sigma$$, +5$$sigma$$). These database sets represent that organ doses are strongly dependent on body sizes of phantoms. Thus, it can be concluded that these dose coefficients database sets are very useful for dose assessment derived from CT scans against patients with various body sizes in Japan.

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