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324 results on '"Inaba, Yohei"'

7. Effectiveness of third vaccine dose for coronavirus disease 2019 during the Omicron variant pandemic: a prospective observational study in Japan

Author

Akaishi, Tetsuya, Kushimoto, Shigeki, Katori, Yukio, Sugawara, Noriko, Egusa, Hiroshi, Igarashi, Kaoru, Fujita, Motoo, Kure, Shigeo, Takayama, Shin, Abe, Michiaki, Kikuchi, Akiko, Ohsawa, Minoru, Ishizawa, Kota, Abe, Yoshiko, Imai, Hiroyuki, Inaba, Yohei, Iwamatsu-Kobayashi, Yoko, Nishioka, Takashi, Onodera, Ko, and Ishii, Tadashi

Published
2022
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8. Evaluation of Radiation Doses Received by Physicians during Permanent 198 Au Grain Implant Brachytherapy for Oral Cancer.

Author

Inaba, Yohei, Jingu, Keiichi, Fujisawa, Masaki, Otomo, Kazuki, Ishii, Hiroki, Kato, Toshiki, Murabayashi, Yuuki, Suzuki, Masatoshi, Zuguchi, Masayuki, and Chida, Koichi

Subjects
MEDICAL personnel, RADIATION doses, RADIATION protection, TONGUE cancer, CRYSTALLINE lens
Abstract

Featured Application: Importance of the evaluation of the physician's eye exposure to radiation during 198Au grain brachytherapy, given that the eye dose limit has been reduced drastically from 150 to 20 mSv/year. Brachytherapy is a practical, effective procedure for the local treatment of cancer; it delivers a high radiation dose to a limited tissue volume while sparing the surrounding normal tissues. Although the clinical benefit of brachytherapy is clear, there have been very few studies on the radiation dose received by physicians during the procedure. Furthermore, no study has investigated the eye radiation dose received by physicians performing 198Au grain (seed) brachytherapy, using an eye dosimeter. Recently, the International Commission on Radiological Protection (ICRP) recommended significantly reducing the occupational lens dose limit, from 150 to 20 mSv/yr (100 mSv/5 years). Therefore, it has become essential to evaluate the eye radiation doses of medical workers. We evaluated the eye radiation dose of a brachytherapy physician performing 198Au permanent grain implantation for tongue cancer; this is the first study on this topic. The maximum eye dose was ~0.1 mSv/procedure, suggesting that it is unlikely to exceed the ICRP limit (20 mSv/yr) for the lens, unless many procedures are performed with inappropriate radiation protection. To reduce the dose of radiation received by 198Au grain brachytherapy physicians, it is necessary to use additional lead shielding equipment when preparing the treatment needles, i.e., when loading the grains. This study provides useful information on radiation exposure of physicians conducting 198Au permanent grain brachytherapy. [ABSTRACT FROM AUTHOR]

Published
2024
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9. Effect of backscatter radiation on the occupational eye-lens dose.

Author

Ohno, Saya, Konta, Satoe, Shindo, Ryota, Yamamoto, Keisuke, Isobe, Rio, Inaba, Yohei, Suzuki, Masatoshi, Zuguchi, Masayuki, and Chida, Koichi

Subjects
PROTECTIVE eyeglasses, RADIATION protection, BACKSCATTERING, RADIATION measurements, CRYSTALLINE lens
Abstract

We quantified the level of backscatter radiation generated from physicians' heads using a phantom. We also evaluated the shielding rate of the protective eyewear and optimal placement of the eye-dedicated dosimeter (skin surface or behind the Pb-eyewear). We performed diagnostic X-rays of two head phantoms: Styrofoam (negligible backscatter radiation) and anthropomorphic (included backscatter radiation). Radiophotoluminescence glass dosimeters were used to measure the eye-lens dose, with or without 0.07-mm Pb-equivalent protective eyewear. We used tube voltages of 50, 65 and 80 kV because the scattered radiation has a lower mean energy than the primary X-ray beam. The backscatter radiation accounted for 17.3–22.3% of the eye-lens dose, with the percentage increasing with increasing tube voltage. Furthermore, the shielding rate of the protective eyewear was overestimated, and the eye-lens dose was underestimated when the eye-dedicated dosimeter was placed behind the protective eyewear. We quantified the backscatter radiation generated from physicians' heads. To account for the effect of backscatter radiation, an anthropomorphic, rather than Styrofoam, phantom should be used. Close contact of the dosimeter with the skin surface is essential for accurate evaluation of backscatter radiation from physician's own heads. To assess the eye-lens dose accurately, the dosimeter should be placed near the eye. If the dosimeter is placed behind the lens of the protective eyewear, we recommend using a backscatter radiation calibration factor of 1.2–1.3. [ABSTRACT FROM AUTHOR]

Published
2024
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23. Internal organ dose rate conversion coefficients of Japanese macaques to 134Cs,137Cs and 131I.

Author

Takamura, Yuta, Kajimoto, Tsuyoshi, Tanaka, Kenichi, Yamamoto, Tomoya, Suzuki, Masatoshi, Inaba, Yohei, Chida, Koichi, Fukumoto, Manabu, Rangacharyulu, Chary, and Endo, Satoru

Abstract

The purpose of this study was to estimate the internal dose of radiation in Japanese macaques (aka Nihonzaru or snow monkey) due to the Fukushima nuclear power plant accident. Images of a male Japanese macaque weighing ~10 kg were acquired using a multi-slice computed tomography (CT) scan with a 64-row segment detector. The CT images were used to create voxel phantoms of the bones, bone marrow, brain, eyes, heart, lungs, stomach, liver, spleen, pancreas, kidneys, intestines, bladder, testes, thyroid and miscellaneous tissue. The Particle and Heavy Ion Transport System (PHITS) Monte Carlo code was used to calculate the internal exposure rate conversion factors for 134Cs, 137Cs and 131I isotopes for the created voxel phantoms with a statistical precision higher than 1%. The PHITS-calculated energy deposits were compared with those for rhesus monkeys. The results showed that the fractions of energy deposits for β-radiation in different organs were almost identical between the two species. For γ-radiation, there was excellent agreement in the self-absorption rate with the approximate curve of the Japanese macaque, with an average deviation of 2%. The maximum deviation of 12% was for the kidney, which has two organs, so the error with the approximate curve is slightly larger due to the energy loss created between organs. [ABSTRACT FROM AUTHOR]

Published
2023
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27. Analysis of whole-blood antioxidant capacity after chronic and localized irradiation using the i-STrap method

Author

Sun, Lue, Inaba, Yohei, Sogo, Yu, Morikawa, Kumi, Kunugita, Naoki, Chida, Koichi, Moritake, Takashi, Naoki, Kunugita, and Takashi, Moritake

Abstract

Ionizing radiation exposure affects the redox state in vivo. Recently, whole-blood antioxidant capacity (WBAC) has been reported to decrease in a dose-dependent manner after acute total body irradiation (TBI). However, changes in WBAC after localized and chronic irradiations have not been reported. This study analyzed changes to WBAC in mice after either localized irradiation (irradiation of the left hind leg only) or chronic TBI using the i-STrap method. Leg-localized irradiation exerted limited effects on WBAC, while WBAC decreased in a dose rate-dependent manner after TBI. Further, the WBAC reached the minimum value in a shorter period at a smaller dose rate. Our results suggest that changes in WBAC do not directly reflect absorbed dose, but may reflect radiation-induced biological damage at the systemic level. This study will contribute to the understanding of radiation-induced injuries and diseases, and will facilitate the establishment of biomarkers for radiation exposure.

Published
2022

33. SVOC Concentrations in House dust and Residential Environment in Japanese Houses

Author

KIM Hoon, INABA Yohei, BEKKI Kanae, HAYASHI Motoya, AZUMA Kenichi, and KUNUGITA Naoki

Subjects
Environmental sciences, GE1-350
Abstract

This study aims to investigate the relevance of between SVOC concentrations in house dust and living environments. Using the newly proposed dust collecting and SVOC analysis method, we determined concentrations of the nine SVOC substances by dust size and made simultaneously the questionnaire about residential environments. Collected dusts were screened with sieves and then analyzed on nine components (DEP, DMP, BBP, DEHP, DINP, DBP, DNOP, DIDP, DIBP) by LC/MS/MS method. The results leaded to selecting less than 100μm and 100-250μm as the target size of dusts to be investigated intensively by considering the concentration distribution and the oral intake of humans. DEHP and DINP accounted for 96 to 97% of determined amount of SVOC and only the small amounts in the other seven components were detected. There was no significant difference in the component ratio depending on particle size. Significant difference was obtained between a few substances of SVOC and several living environment items.

Published
2019
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39. COVID-19-Related Symptoms during the SARS-CoV-2 Omicron (B.1.1.529) Variant Surge in Japan

Author

Akaishi, Tetsuya, primary, Kushimoto, Shigeki, additional, Katori, Yukio, additional, Sugawara, Noriko, additional, Egusa, Hiroshi, additional, Igarashi, Kaoru, additional, Fujita, Motoo, additional, Kure, Shigeo, additional, Takayama, Shin, additional, Abe, Michiaki, additional, Kikuchi, Akiko, additional, Ohsawa, Minoru, additional, Ishizawa, Kota, additional, Abe, Yoshiko, additional, Imai, Hiroyuki, additional, Inaba, Yohei, additional, Iwamatsu-Kobayashi, Yoko, additional, Nishioka, Takashi, additional, Onodera, Ko, additional, and Ishii, Tadashi, additional

Published
2022
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41. Effectiveness of mRNA COVID-19 Vaccines in Japan during the Nationwide Pandemic of the Delta Variant

Author

Akaishi, Tetsuya, primary, Kushimoto, Shigeki, additional, Katori, Yukio, additional, Sugawara, Noriko, additional, Igarashi, Kaoru, additional, Fujita, Motoo, additional, Kure, Shigeo, additional, Takayama, Shin, additional, Abe, Michiaki, additional, Kikuchi, Akiko, additional, Ishizawa, Kota, additional, Abe, Yoshiko, additional, Imai, Hiroyuki, additional, Inaba, Yohei, additional, Iwamatsu-Kobayashi, Yoko, additional, Nishioka, Takashi, additional, Onodera, Ko, additional, and Ishii, Tadashi, additional

Published
2022
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47. Discriminatory Value of Self-reported Olfactory Dysfunction in the Prediction of Coronavirus Disease 2019

Author

Akaishi, Tetsuya, primary, Kushimoto, Shigeki, additional, Katori, Yukio, additional, Kure, Shigeo, additional, Igarashi, Kaoru, additional, Fujita, Motoo, additional, Takayama, Shin, additional, Abe, Michiaki, additional, Kikuchi, Akiko, additional, Tanaka, Junichi, additional, Abe, Yoshiko, additional, Imai, Hiroyuki, additional, Inaba, Yohei, additional, Iwamatsu-Kobayashi, Yoko, additional, Nishioka, Takashi, additional, Onodera, Ko, additional, and Ishii, Tadashi, additional

Published
2021
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