Development of guidelines on radiation protection for the lens of the eye in Japan

Yokoyama, Sumi*; Iwai, Satoshi*; Tsujimura, Norio; Hashimoto, Makoto; Yoshitomi, Hiroshi; Kato, Masahiro*; Kurosawa, Tadahiro*; Tatsuzaki, Hideo*; Sekiguchi, Hiroshi*; Koguchi, Yasuhiro*; et al.

Proceedings of 15th International Congress of the International Radiation Protection Association (IRPA-15) (Internet), 8 Pages, 2022/00

https://irpa.net/irpa15/T3.1-O0124.pdf

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

https://doi.org/10.1097/HP.0000000000000299

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.

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

https://doi.org/10.15669/pnst.2.153

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.

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

https://doi.org/10.1093/rpd/ncr160

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 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.

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

https://doi.org/10.15669/pnst.1.517

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.

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

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

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%.

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.

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, +2, +5). 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.