Influence of distant scatterer on air kerma measurement in the evaluation of diagnostic X-rays using Monte Carlo simulation

Tominaga, Masahide*; Nagayasu, Yukari*; Sasaki, Motoharu*; Furuta, Takuya; Hayashi, Hiroaki*; Oita, Masataka*; Nishiyama, Yuichi*; Haga, Akihiro*

Radiological Physics and Technology, 14(4), p.381 - 389, 2021/12

https://doi.org/10.1007/s12194-021-00641-3

Due to recent advance of diagnostic radiology, the increase of diagnostic radiation exposure to patient becomes problem. Diagnostic Reference Levels has been released to optimized the radiation exposure to patients in Japan recently. The evaluation of entrance surface dose (ESD) is recommended to assess the dose level for general X-ray examination. The ESD can be easily evaluated by multiplying the backscatter factor of the patient body on the free-in-air air kerma. The air kerma free-in-air value used to estimate ESD may contain X-rays scattered from obstacles located at the time of measurement, which may induce non-minor error in assessments. We therefore studied the influence of scattered X-rays on air kerma measurement under various environments (distances, field sizes, and materials). It was found that the dependence on the X-ray energy and field size was different for different materials. The X-ray contamination can be ignored for all the materials when the distance to the scatterer exceeds 35 cm.

Animal study on biological responses by radon inhalation making use of waste rock which contains feeble activity of uranium (Joint research)

Ishimori, Yuu; Sakoda, Akihiro; Tanaka, Hiroshi; Mitsunobu, Fumihiro*; Yamaoka, Kiyonori*; Kataoka, Takahiro*; Yamato, Keiko*; Nishiyama, Yuichi*

JAEA-Research 2013-005, 60 Pages, 2013/06

JAEA-Research-2013-005.pdf:4.49MB

Okayama University and the Japan Atomic Energy Agency (JAEA) have carried out the collaborative study of physiological effects of inhaled radon for the low-dose range. From 2007 to 2011, the following results were obtained. (1) Literature on effects of radon for the low-dose range was surveyed to determine the present tasks. (2) The first Japanese large-scale facility was developed for radon inhalation experiments with small animals. (3) Relationships between radon concentration and inhalation time were widely examined to understand the change in antioxidative functions due to radon, which are the most basic parameters. (4) Inhibitory effects of radon on oxidative damages were observed using model mice with reactive oxygen- or free radical-related diseases like alcohol-induced oxidative damages and type I diabetes. (5) In order to discuss biological responses quantitatively following radon inhalation, the biokinetics of inhaled radon was examined and the model for calculation of absorbed doses for organs and tissues was obtained.

Study of the response of superoxide dismutase in mouse organs to radon using a new large-scale facility for exposing small animals to radon

Kataoka, Takahiro*; Sakoda, Akihiro; Ishimori, Yuu; Toyota, Teruaki*; Nishiyama, Yuichi*; Tanaka, Hiroshi; Mitsunobu, Fumihiro*; Yamaoka, Kiyonori*

Journal of Radiation Research, 52(6), p.775 - 781, 2011/11

https://doi.org/10.1269/jrr.10072

We examined dose-dependent or dose rate-dependent changes of superoxide dismutase (SOD) activity using a new large-scale facility for exposing small animals to radon. Mice were exposed to radon at a concentration of 250, 500, 1000, 2000, or 4000 Bq/m for 0.5, 1, 2, 4, or 8 days. When mice were exposed to radon at 2000 day Bq/m, activation of SOD activities in plasma, liver, pancreas, heart, thymus, and kidney showed dose-rate effects. Our results also suggested that continuous exposure to radon increased SOD activity, but SOD activity transiently returned to normal levels at around 2 days. Moreover, we classified the organs into four groups ((1) plasma, brain, lung (2) heart, liver, pancreas, small intestine (3) kidney, thymus (4) stomach) based on changes in SOD activity. Thymus had the highest responsiveness and stomach had lowest. These data provide useful baseline measurements for future studies on radon effects.

Differences of natural radioactivity and radon emanation fraction among constituent minerals of rock or soil

Sakoda, Akihiro*; Nishiyama, Yuichi*; Hanamoto, Katsumi*; Ishimori, Yuu; Yamamoto, Yuki*; Kataoka, Takahiro*; Kawabe, Atsushi*; Yamaoka, Kiyonori*

Applied Radiation and Isotopes, 68(6), p.1180 - 1184, 2010/06

https://doi.org/10.1016/j.apradiso.2009.12.036

We examined differences in the radioactive characteristics among the main minerals forming granite materials. Using a non-toxic high-density agent, minerals were separated from rock (granite-gneiss) and soil (weathered granite) samples. The natural radioactivity (U and Ra) and radon emanation fraction of the minerals were then studied by -ray spectrometry. The radon emanation fractions (27-43%) of the minerals from the soil were much higher than those (0.6-4.6%) of the rock minerals. Additionally, the emanation fractions differed greatly among the minerals separated from both the bulk rock and soil. These results were discussed in terms of the differences of surface area and radium distribution in the mineral grains. It was noticeable that a higher emanation fraction than expected for quartz was commonly observed in the rock and soil samples. We then estimated the contribution of each constituent mineral to the total radon exhalation from the bulk samples. The result depended not only on the radon emanation fraction, but also on the Ra activity and the mineral content. Furthermore, using the obtained data, we also discussed the effect of grain size on radon emanation and why this has been reported to vary markedly in previous studies.

The New large-volume high P-T apparatus for in situ X-ray observation,

Katsura, Tomoo*; Funakoshi, Kenichi*; Nishiyama, Norimasa*; Kubo, Atsushi*; Tange, Yoshinori*; Sueda, Yuichiro*; Kubo, Tomoaki*; Utsumi, Wataru

Hoshako, 16(6), p.352 - 357, 2003/11

http://ci.nii.ac.jp/naid/80016306561

no abstracts in English