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39 results on '"Nishiyama, Hikaru"'

6. Analysis of volatile nuclides’ behavior in the atmosphere released due to the FDNPP accident

Author

Nishiyama, Hikaru, Kamida, Shunsuke, Moriizumi, Jun, Yamazawa, Hiromi, Nishiyama, Hikaru, Kamida, Shunsuke, Moriizumi, Jun, and Yamazawa, Hiromi

Abstract

The volatile nuclides, 131I, 132I, and 132Te, which were released in large quantities during the early stage of the Fukushima Dai-ichi Nuclear Power Plant accident, are the most dominant ones in determining the impact on the public and the environment. Since the behavior of these nuclides in the environment and their effects on human health differ depending on their physicochemical forms, it is necessary to understand more about the release fraction and the deposition process of each form. In this study, a behavior model was developed to calculate physical and chemical processes of organic, inorganic, and particulate 131I and 132I, and gaseous and particulate 132Te. This behavior model was used to estimate the physicochemical composition of iodine at the time of release, the 132Te/132I activity ratio at the time of release, and the dry deposition velocity of 132Te. The estimation was performed for five plumes transported during the period from March 14 to 21, 2011, and the estimated values were obtained by comparing with the values measured in previous studies. As a result of the estimation, the organic iodine fraction at the time of release was estimated to be 0.1 or less for most plumes, while a significantly higher value of 0.3 was estimated for the plume released in the night of March 14. This result implied that the possibility of formation and release of organic iodine in the liquid phase in Unit 3, which was considered to be the source of this plume. As for the 132Te/132I ratio at the time of release, it was estimated to be about 0.3–0.4 for most plumes, while it was about 1 in the plume released in the early morning of March 15, which is consistent with the release process in Unit 2 on the night of 14 and early morning of the 15. In addition, a remarkably high dry deposition velocity of 132Te was estimated in this plume, which was consistent with the existence of radiocaesium-bearing microparticles (CsMP) with a particle size of a few micrometers that had be

Published
2024

14. Visualization of pulmonary artery intimal sarcoma by color-coded iodine map using dual-energy computed tomography

Author

Uetani, Teruyoshi, Inaba, Shinji, Higashi, Haruhiko, Irita, Jun, Aono, Jun, Nishiyama, Hikaru, Tanabe, Yuki, Kitazawa, Riko, Kido, Teruhito, Ikeda, Shuntaro, and Yamaguchi, Osamu

Subjects
Case Report, Cardiology and Cardiovascular Medicine
Abstract

Pulmonary artery intimal sarcomas (PAIS) are often misdiagnosed as pulmonary embolisms (PE) as their clinical findings and imaging findings are similar. However, given the clinical outcome of both diseases is different in its prognosis, accurate and rapid diagnosis is mandatory. This is a case report of a histologically-proven PAIS which was initially treated as a PE. The color-coded iodine map using dual-energy computed tomography (dual-energy CT iodine map) well reflected the distribution of the tumor consistent with (18)fluoro-2-deoxyglucose-uptake region using positron emission tomography/CT. This case demonstrates the potential of using dual-energy CT iodine map to differentiate PAIS from PE. LEARNING OBJECTIVE: Use of a dual-energy computed tomography iodine map to visualize a pulmonary artery intimal sarcoma may provide useful diagnostic information.

Published
2022

19. A Novel Quantitative Parameter for Static Myocardial Computed Tomography: Myocardial Perfusion Ratio to the Aorta

Author

Kouchi, Takanori, primary, Tanabe, Yuki, additional, Takemoto, Takumasa, additional, Yoshida, Kazuki, additional, Yamamoto, Yuta, additional, Miyazaki, Shigehiro, additional, Fukuyama, Naoki, additional, Nishiyama, Hikaru, additional, Inaba, Shinji, additional, Kawaguchi, Naoto, additional, Kido, Tomoyuki, additional, Yamaguchi, Osamu, additional, and Kido, Teruhito, additional

Published
2022
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24. Dual-energy computed tomography for evaluation of breast cancer: value of virtual monoenergetic images reconstructed with a noise-reduced monoenergetic reconstruction algorithm

Author

Okada, Kanako, primary, Matsuda, Megumi, additional, Tsuda, Takaharu, additional, Kido, Teruhito, additional, Murata, Akihiro, additional, Nishiyama, Hikaru, additional, Nishiyama, Kanako, additional, Yamasawa, Haruna, additional, Kamei, Yoshiaki, additional, Kurata, Mie, additional, Fukushima, Mana, additional, Kitazawa, Riko, additional, and Mochizuki, Teruhito, additional

Published
2019
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29. Two-Phase Contrast Injection Protocol for Pediatric Cardiac Computed Tomography in Children with Congenital Heart Disease

Author

Fukuyama, Naoki, primary, Kurata, Akira, additional, Kawaguchi, Naoto, additional, Tashiro, Ryo, additional, Higaki, Takashi, additional, Yokoi, Takahiro, additional, Tanabe, Yuki, additional, Nishiyama, Hikaru, additional, Itoh, Toshihide, additional, Kido, Teruhito, additional, Miyagawa, Masao, additional, and Mochizuki, Teruhito, additional

Published
2017
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30. Peak enhancement ratio of myocardium to aorta for identification of myocardial ischemia using dynamic myocardial computed tomography perfusion imaging

Author

Tanabe, Yuki, primary, Kido, Teruhito, additional, Kurata, Akira, additional, Yokoi, Takahiro, additional, Fukuyama, Naoki, additional, Uetani, Teruyoshi, additional, Nishiyama, Hikaru, additional, Kawaguchi, Naoto, additional, Tahir, Enver, additional, Miyagawa, Masao, additional, and Mochizuki, Teruhito, additional

Published
2017
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31. Myocardial Segmentation of Area at Risk Based on Coronary Computed Tomography Angiography and Voronoi Diagram in Comparison with Magnetic Resonance Perfusion Imaging

Author

Fukuyama, Naoki, primary, Kido, Teruhito, additional, Kurata, Akira, additional, Tanabe, Yuki, additional, Kido, Tomoyuki, additional, Yokoi, Takahiro, additional, Ogawa, Ryo, additional, Nishiyama, Hikaru, additional, Uetani, Teruyoshi, additional, and Mochizuki, Teruhito, additional

Published
2017
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33. Optimal Scan Time for Single-Phase Myocardial Computed Tomography Perfusion to Detect Myocardial Ischemia – Derivation Cohort From Dynamic Myocardial Computed Tomography Perfusion –

Author

Tanabe, Yuki, primary, Kido, Teruhito, additional, Kurata, Akira, additional, Uetani, Teruyoshi, additional, Fukuyama, Naoki, additional, Yokoi, Takahiro, additional, Nishiyama, Hikaru, additional, Kido, Tomoyuki, additional, Miyagawa, Masao, additional, and Mochizuki, Teruhito, additional

Published
2016
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34. Separation of Pulmonary Artery and Pulmonary Vein Using 2-Phase Chest CT for Video-Assisted Thoracic Lobectomy

Author

Nishiyama, Hikaru

Subjects
Computer Applications-3D, Pulmonary vessels, Thorax, Contrast agent-intravenous, CT-Angiography, Lung, Cancer, CT
Abstract

Purpose Methods and Materials Results Conclusion References Personal Information, Purpose: Video-assisted thoracic surgery (VATS) lobectomy provides a minimally invasive approach for the treatment of early-stage lung cancer. For the safety ofVATSlobectomy, it is a key to get the anatomical information of the pulmonary artery (PA) and...

Published
2013
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37. The Feasibility of a Model-Based Iterative Reconstruction Technique Tuned for the Myocardium on Myocardial Computed Tomography Late Enhancement.

Author

Toritani H, Yoshida K, Hosokawa T, Tanabe Y, Yamamoto Y, Nishiyama H, Kido T, Kawaguchi N, Matsuda M, Nakano S, Miyazaki S, Uetani T, Inaba S, Yamaguchi O, and Kido T

Abstract

Objectives: This study evaluated the feasibility of a model-based iterative reconstruction technique (MBIR) tuned for the myocardium on myocardial computed tomography late enhancement (CT-LE)., Methods: Twenty-eight patients who underwent myocardial CT-LE and late gadolinium enhancement (LGE) magnetic resonance imaging (MRI) within 1 year were retrospectively enrolled. Myocardial CT-LE was performed using a 320-row CT with low tube voltage (80 kVp). Myocardial CT-LE images were scanned 7 min after CT angiography (CTA) without additional contrast medium. All myocardial CT-LE images were reconstructed with hybrid iterative reconstruction (HIR), conventional MBIR (MBIR&#95;cardiac), and new MBIR tuned for the myocardium (MBIR&#95;myo). Qualitative (5-grade scale) scores and quantitative parameters (signal-to-noise ratio [SNR] and contrast-to-noise ratio [CNR]) were assessed as image quality. The sensitivity, specificity, and accuracy of myocardial CT-LE were evaluated at the segment level using an American Heart Association (AHA) 16-segment model, with LGE-MRI as a reference standard. These results were compared among the different CT image reconstructions., Results: In 28 patients with 448 segments, 160 segments were diagnosed with positive by LGE-MRI. In the qualitative assessment of myocardial CT-LE, the mean image quality scores were 2.9 ± 1.2 for HIR, 3.0 ± 1.1 for MBIR&#95;cardiac, and 4.0 ± 1.0 for MBIR&#95;myo. MBIR&#95;myo showed a significantly higher score than HIR (P < 0.001) and MBIR&#95;cardiac (P = 0.018). In the quantitative image quality assessment of myocardial CT-LE, the median image SNR was 10.3 (9.1-11.1) for HIR, 10.8 (9.8-12.1) for MBIR&#95;cardiac, and 16.8 (15.7-18.4) for MBIR&#95;myo. The median image CNR was 3.7 (3.0-4.6) for HIR, 3.8 (3.2-5.1) for MBIR&#95;cardiac, and 6.4 (5.0-7.7) for MBIR&#95;myo. MBIR&#95;myo significantly improved the SNR and CNR of CT-LE compared to HIR and MBIR&#95;cardiac (P < 0.001). The sensitivity, specificity, and accuracy for the detection of myocardial CT-LE were 70%, 92%, and 84% for HIR; 71%, 92%, and 85% for MBIR&#95;cardiac; and 84%, 92%, and 89% for MBIR&#95;myo, respectively. MBIR&#95;myo showed significantly higher image quality, sensitivity, and accuracy than the others (P < 0.05)., Conclusions: MBIR tuned for myocardium improved image quality and diagnostic performance for myocardial CT-LE assessment., Competing Interests: Conflict of interest: Shota Nakano is an employee of Canon Medical Systems Corporation. The rest of the authors declare no conflict of interest., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Published
2024
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38. Active aneurysm thrombosis after Kawasaki disease in an adult: Insight into anticoagulation therapy.

Author

Akazawa Y, Inaba S, Sakaue T, Kurata M, Aono J, Yasugi T, Moritani T, Nishiyama H, Higaki T, Eguchi M, and Yamaguchi O

Abstract

The management of systemic artery aneurysms secondary to Kawasaki disease (KD) in adults remains a therapeutic challenge. KD guidelines recommend the use of anticoagulation therapy with warfarin in addition to antiplatelet therapy when a giant coronary aneurysm or a history of thrombosis is documented. However, long-term use of warfarin presents several concerns. This case reports acute thrombotic occlusion due to the giant arterial aneurysm in an adult KD. A surgical resection of the aneurysm was performed because of recurrent thrombotic events, despite anticoagulant therapy with warfarin. Pathological examinations revealed a layered thrombus with inflammation in the aneurysm and Factor Xa expression mainly in newly formed thrombus. This study provides an insight into the anticoagulation therapy for cardiovascular sequelae after KD. < Learning objective: This study, along with pathological evidence, illustrates that Factor Xa might contribute to thrombotic events after Kawasaki disease.>., Competing Interests: None., (© 2020 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.)

Published
2020
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39. [Investigation of reduction of exposure dose in digital mammography: relationship between exposure dose and image processing].

Author

Fujimura Y, Nishiyama H, Masumoto T, Kono S, Kitagawa Y, Ikeda T, Furukawa T, and Ishida T

Subjects
Image Interpretation, Computer-Assisted, Phantoms, Imaging, Mammography, Radiation Dosage, Radiographic Image Enhancement
Abstract

In digital mammograms, granularity is an important image property for the detection of microcalcifications and masses. Therefore, we investigated the relationship between the conditions of various exposure doses and the detectability of RMI156 phantom images with and without image processing for the reduction of exposure dose. The images are processed with Gaussian filter and unsharp-masking filters to evaluate the effects on image properties by using the digital Wiener spectrum (WS) presampled modulation transfer function (MTF). In addition, observer performance tests for the detectability of microcalcifications and masses are performed. With Gaussian filtering, the WS value decreased to 50% at 2.0 cycles/mm and the detectability score of masses increased 80% and 12%, on 1.34 mGy and 2.62 mGy, respectively (p<0.05). With unsharp-masking (7 x 7 pixels), the MTF value increased to 126% at 2.0 cycles/mm, and the detectability of microcalcification to 32% and 5%, on 1.34 mGy and 5.28 mGy, respectively (p<0.05) compared with the original image. The optimal dose of simulated lesions with unsharp masking became 5.25 mGy. The unsharp masking could reduce 37% of the exposure dose without a loss of detectability of microcalcifications and masses.

Published
2008
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