Tokushima University / Educator and Researcher Directory --- Kasai, Ryosuke

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https://researchmap.jp/ryosukek (researchmap)

https://orcid.org/0000-0002-4699-1642 (ORCID)

Field of Study

Subject of Study

Book / Paper

Academic Paper (Judged Full Paper):

1.	UEKI Yuya, Hideki Otsuka, Tamaki Otani, Ryosuke Kasai, Youichi Otomi, Daiki Ikemitsu, Shota Azane, Yamato Kunikane, Takanori Bandoh, NORITAKE Matsuda, Yasuyuki Okada, Tetsuji Takayama and Masafumi Harada : Combined visual and quantitative assessment of somatostatin receptor scintigraphy for staging and restaging of neuroendocrine tumors, Japanese Journal of Radiology, Vol.42, No.2, 2024. (Tokushima University Institutional Repository) ● Metadata: 118973 (Tokushima University Institutional Repository: 118973)
2.	Ryosuke Kasai and Hideki Otsuka : Noise Reduction Using Singular Value Decomposition with Jensen-Shannon Divergence for Coronary Computed Tomography Angiography, Diagnostics, Vol.13, No.6, 2023. (Summary) Coronary computed tomography angiography (CCTA) is widely used due to its improvements in computed tomography (CT) diagnostic performance. Unlike other CT examinations, CCTA requires shorter rotation times of the X-ray tube, improving the temporal resolution and facilitating the imaging of the beating heart in a stationary state. However, reconstructed CT images, including those of the coronary arteries, contain insufficient X-ray photons and considerable noise. In this study, we introduce an image-processing technique for noise reduction using singular value decomposition (SVD) for CCTA images. The threshold of SVD was determined on the basis of minimization of Jensen-Shannon (JS) divergence. Experiments were performed with various numerical phantoms and varying levels of noise to reduce noise in clinical CCTA images using the determined threshold value. The numerical phantoms produced 10% higher-quality images than the conventional noise reduction method when compared on a quantitative SSIM basis. The threshold value determined by minimizing the JS-divergence was found to be useful for efficient noise reduction in actual clinical images, depending on the level of noise. (Tokushima University Institutional Repository) ● Metadata: 118070 (Link to Publication Site) ● Publication site (DOI): 10.3390/diagnostics13061111 (Link to Search Site for Scientific Articles) ● PubMed @ National Institutes of Health, US National Library of Medicine (PMID): 36980419 ● Search Scopus @ Elsevier (PMID): 36980419 ● Search Scopus @ Elsevier (DOI): 10.3390/diagnostics13061111 (Tokushima University Institutional Repository: 118070, DOI: 10.3390/diagnostics13061111, PubMed: 36980419)
3.	Omar M. Abou Al-Ola, Ryosuke Kasai, Yusaku Yamaguchi, Takeshi Kojima and Tetsuya Yoshinaga : Image reconstruction algorithm using weighted mean of ordered-subsets EM and MART for computed tomography, Mathematics, Vol.10, No.22, 4277, 2022. (Tokushima University Institutional Repository) ● Metadata: 118919 (Link to Publication Site) ● Publication site (DOI): 10.3390/math10224277 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.3390/math10224277 (Tokushima University Institutional Repository: 118919, DOI: 10.3390/math10224277)
4.	Kanako Sakuragawa, Motoharu Sasaki, Takeshi Kamomae, Yokoishi Michihiro, Ryosuke Kasai, KAJINO Akimi and Hitoshi Ikushima : Differences in image density adjustment parameters on the image matching accuracy of a floor-mounted kV X-ray image-guided radiation therapy system, Journal of Applied Clinical Medical Physics, Vol.23, No.2, e13505, 2022. (Summary) This study aimed to investigate the effect of two different image density adjustment parameters on the results of image matching at six degrees of freedom using radiographic images generated by the ExacTrac X-ray system in brain stereotactic radiosurgery (SRS). This study comprised 32 patients who underwent brain SRS at our hospital from January 2020 to December 2020. In this study, (1) the default parameter (an image density parameter between "tissue" and "bone") was an image density parameter for digitally reconstructed radiograph (DRR) generation used at many facilities, and (2) the bone parameter was the steepest contrast parameter used at our hospital. Of the 32 patients, 24 (75%) had a couch angle of 0.5 mm or more in the translational direction or 0.5° or more in the rotational direction, and 10 (31%) had a couch angle of 1.0 mm or more in the translational direction or 1.0° or more in the rotational direction. Among the 131 cases of all couch angles, 46 (35%) cases had a translational direction of 0.5 mm or more or a rotational direction of 0.5° or more, and 15 (11%) had a translational direction of 1.0 mm or more or a rotational direction of 1.0° or more. The results of this study indicate the usefulness of using appropriate DRR parameters for each case, rather than using the default settings. The use of appropriate DRR parameters can lead to accurate position matching results, leading to fewer image-guided radiation therapy shots and a lower imaging dose. (Keyword) Stereotactic radiosurgery / digitally reconstructed radiograph / ExacTrac / brain metastasis (Tokushima University Institutional Repository) ● Metadata: 117228 (Link to Publication Site) ● Publication site (DOI): 10.1002/acm2.13505 (Link to Search Site for Scientific Articles) ● PubMed @ National Institutes of Health, US National Library of Medicine (PMID): 34931431 ● Summary page in Scopus @ Elsevier: 2-s2.0-85121471034 (Tokushima University Institutional Repository: 117228, DOI: 10.1002/acm2.13505, PubMed: 34931431, Elsevier: Scopus)
5.	Ryosuke Kasai, Yusaku Yamaguchi, Takeshi Kojima, Omar M. Abou Al-Ola and Tetsuya Yoshinaga : Noise-Robust Image Reconstruction Based on Minimizing Extended Class of Power-Divergence Measures, Entropy, Vol.23, No.8, 1-16, 2021. (Tokushima University Institutional Repository) ● Metadata: 116149 (Link to Publication Site) ● Publication site (DOI): 10.3390/e23081005 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.3390/e23081005 (Tokushima University Institutional Repository: 116149, DOI: 10.3390/e23081005)
6.	Ryosuke Kasai, Yusaku Yamaguchi, Takeshi Kojima and Tetsuya Yoshinaga : Hybrid Euler method for discretizing continuous-time tomographic dynamical system, Journal of Signal Processing, Vol.24, No.4, 183-186, 2020. (Link to Publication Site) ● Publication site (DOI): 10.2299/jsp.24.183 (Link to Search Site for Scientific Articles) ● CiNii @ National Institute of Informatics (CRID): 1390566775151534976 ● Search Scopus @ Elsevier (DOI): 10.2299/jsp.24.183 (DOI: 10.2299/jsp.24.183, CiNii: 1390566775151534976)
7.	Ryosuke Kasai, Yusaku Yamaguchi, Takeshi Kojima and Tetsuya Yoshinaga : Hybrid Euler method for discretizing continuous-time tomographic dynamical system, Proc. of NCSP'20, 73-76, 2020.
8.	Yusaku Yamaguchi, Moe Kudo, Ryosuke Kasai, Takeshi Kojima and Tetsuya Yoshinaga : Continuous-time image reconstruction based on Hellinger distance minimization for medical X-ray CT imaging, Basic & Clinical Pharmacology & Toxicology (Abstracts), Vol.125, No.S5, 30-31, 2019.
9.	Ryosuke Kasai, Yusaku Yamaguchi, Takeshi Kojima and Tetsuya Yoshinaga : Hybrid of ML-EM and MART algorithms for X-ray CT image reconstruction, Basic & Clinical Pharmacology & Toxicology (Abstracts), Vol.125, No.S5, 31-32, 2019.
10.	Ryosuke Kasai, Yusaku Yamaguchi, Takeshi Kojima and Tetsuya Yoshinaga : Hybrid algorithm of maximum-likelihood expectation-maximization and multiplicative algebraic reconstruction technique for iterative tomographic image reconstruction, Proceedings Volume 11049, International Workshop on Advanced Image Technology (IWAIT) 2019, No.110491F, 2019. (Link to Publication Site) ● Publication site (DOI): 10.1117/12.2521185 (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-85063894959 (DOI: 10.1117/12.2521185, Elsevier: Scopus)
11.	Hiroaki Hayashi, Emi Tomita, Sota Goto, Natsumi Kimoto, Keiji Tada, Ryosuke Kasai, Yuki Kanazawa, Yoshiki Mihara, Takashi Asahara, Tohru Okazaki, Takuya Hashizume and Vergil LE Cruz : Direct Dose Measurement of Patients during Pediatric Computed Tomography Examination, Progress in Nuclear Science and Technology, Vol.6, 18-21, 2019. (Link to Publication Site) ● Publication site (DOI): 10.15669/pnst.6.18 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.15669/pnst.6.18 (DOI: 10.15669/pnst.6.18)
12.	Ryosuke Kasai, Yusaku Yamaguchi, Takeshi Kojima and Tetsuya Yoshinaga : Tomographic image reconstruction based on minimization of symmetrized Kullback-Leibler divergence, Mathematical Problems in Engineering, Vol.2018, No.Article ID 8973131, 9-pages, 2018. (Tokushima University Institutional Repository) ● Metadata: 114383 (Link to Publication Site) ● Publication site (DOI): 10.1155/2018/8973131 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1155/2018/8973131 (Tokushima University Institutional Repository: 114383, DOI: 10.1155/2018/8973131)
13.	Ryosuke Kasai and Kenji Yamada : Application of Hamiltonian Monte Carlo Method to Metal Artifact Quantitative Evaluation in Computed Tomography (CT), Japanese Journal of Radiological Technology, Vol.73, No.8, 654-663, 2017. (Summary) In this study, we propose an evaluation method for Bayesian estimation of Gumbel distribution parameters by the Hamiltonian Monte Carlo method (HMC method), with changing the pixel size of the CT image to investigate streak artifacts, without using a significant difference test. Placed a titanium endcap in the center of the CT dose index (CTDI) measurement phantom and got the CT image by changing the display-field of view (D-FOV) to S, M, L, LL. We compared Gumbel distribution parameters with conventional estimation method and Bayesian estimation method using HMC method. In addition, we evaluated streak artifacts by Bayesian statistical analysis. The difference in streak artifact between D-FOV was more than 90% except between D-FOV M and L. The effect of streak artifacts is small as the pixel size was small. By using the HMC method, we can estimate the Gumbel distribution parameters accurately and objectively, and quantitatively evaluated that the streak artifacts differ in pixel size using Bayesian statistical analysis. (Keyword) computed tomography (CT) / Gumbel distribution / metal artifact / Bayesian statistics / Markov chain Monte Carlo (MCMC) method (Link to Publication Site) ● Publication site (DOI): 10.6009/jjrt.2017_JSRT_73.8.654 (Link to Search Site for Scientific Articles) ● PubMed @ National Institutes of Health, US National Library of Medicine (PMID): 28824089 ● Search Scopus @ Elsevier (PMID): 28824089 ● Search Scopus @ Elsevier (DOI): 10.6009/jjrt.2017_JSRT_73.8.654 (DOI: 10.6009/jjrt.2017_JSRT_73.8.654, PubMed: 28824089)
14.	Yoshiki Mihara, Hiroaki Hayashi, Kenji Yamada, Yuki Kanazawa, Kousaku Higashino, Kazuta Yamashita, Ryosuke Kasai, Tohru Okazaki and Takuya Hashizume : Basic study for internal dose evaluation during CT examination by means of small-type OSL dosimeter, European Congress of Radiology, C-0005-1-C-0005-22, 2017. (Summary) [Aims and objectives] We plan to manage the patient dose exposure during computed tomography (CT) examination using a small-type OSL dosimeter. The OSL dosimeter can measure entrance skin dose (ESD) directly, but the internal dose can't be measured. The aim of this study is to clarify the relationship between the ESD and internal dose during the CT examination. [Methods and materials] We constructed an abdominal phantom, in which OSL dosimeters can be implanted in, and used this phantom to measure external and internal doses during CT examination. The typical irradiation conditions were as follow, 64 rows of detectors, 120 kV, 600 mA, PF (pitch factor) = 1.484 in helical scan mode. Additionally, we analyzed the contribution of X-rays, which were generated from different angles to the dosimeter; namely, angular dependences of 0-360 degrees at 45 degree intervals were evaluated experimentally. [Results] The ESDs and internal doses showed similar values, however the deviations between them were completely different; maximum deviation of ESD was found to be 30% and that of internal dose was at the most 5%. The deviation in ESDs is explained by the phenomenon in which some dosimeters were irradiated by direct X-ray and others were not. However, the small deviation between internal doses was explained by the phenomenon in which dosimeters were mainly irradiated by scattered X-rays. [Conclusion] In this study, we analyzed the relationship between ESD and internal dose for direct dose measurement of patient dose undergoing CT examination. The ESDs show relatively large fluctuations, on the other hand, the internal doses show small deviations. (Link to Publication Site) ● Publication site (DOI): 10.1594/ecr2017/C-0005 (Link to Search Site for Scientific Articles) ● Search Scopus @ Elsevier (DOI): 10.1594/ecr2017/C-0005 (DOI: 10.1594/ecr2017/C-0005)
15.	Oyunbat Dashupuntsag, Midori Yoshida, Ryosuke Kasai, Naoki Maeda, Hidehiko Hosoki and Eiichi Honda : Numerical Evaluation of Image Contrast for Thicker and Thinner Objects among Current Intraoral Digital Imaging Systems., BioMed Research International, Vol.2017, 5215413, 2017. (Summary) The purpose is to evaluate the performance of current intraoral digital detectors in detail using a precise phantom and new method. Two aluminum step wedges in 0.5 mm steps were exposed by two photostimulable phosphor plate (PSP) systems-one with automatic exposure compensation (AEC) and the other without AEC-and a CCD sensor. Images were obtained with 3 doses at 60 kV. The effect of metallic material also was evaluated. The contrast-to-noise ratio (CNR) for thinner steps and the low contrast value (LCV) for thicker steps were obtained. The CCD system was the best under all conditions (P < 0.001), although the Gray value was sensitive to the dose, and the Gray value-dose relation varied greatly. The PSP system with AEC was superior to that without AEC for the LCV (P < 0.001) but was inferior to it regarding the CNR (P < 0.001). CNR and LCV in the PSP system without AEC were not affected by the metallic plate. Intraoral digital imaging systems should be chosen according to their diagnostic purpose. PSP system with AEC may be the best for detecting molar proximal caries, whereas the PSP system without AEC may be better for evaluating small bone regeneration in periodontal disease. The CCD system provided the best performance. (Tokushima University Institutional Repository) ● Metadata: 112388 (Link to Publication Site) ● Publication site (DOI): 10.1155/2017/5215413 (Link to Search Site for Scientific Articles) ● PubMed @ National Institutes of Health, US National Library of Medicine (PMID): 28497053 ● Summary page in Scopus @ Elsevier: 2-s2.0-85018836337 (Tokushima University Institutional Repository: 112388, DOI: 10.1155/2017/5215413, PubMed: 28497053, Elsevier: Scopus)

Academic Paper (Unrefereed Paper):

1.	Ryosuke Kasai, Kenji Yamada, 多田章久, Hidehiko Hosoki, Naoki Maeda, Midori Yoshida and Eiichi Honda : 口内法X線画像用DICOMファイルの規格化および歯科用Viewerの実用化, Dental Radiology, Vol.55, 58, 2015.
2.	ダシプンツァグオユンバト, Midori Yoshida, Ryosuke Kasai, Naoki Maeda, Hidehiko Hosoki and Eiichi Honda : 2種類のデジタル口内法イメージングシステムによるコントラストの比較, Dental Radiology, Vol.55, 88, 2015.

Proceeding of International Conference:

1.	Bollos Anne Christine L. Leah, Ryosuke Kasai, Shoichiro Takao, kawabata Yuka, Tetsuya Tanioka, Hitoshi Ikushima and Hideki Otsuka : Multimodal Image Analysis for Cardiac Sarcoidosis: A Narrative Review, 6TH SPUP INTERNATIONAL INTERDISCIPLINARY RESEARCH CONFERENCE, Tuguegarao City ,Philippines, Aug. 2023. (Keyword) 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET) / cardiac magnetic resonance (CMR) / cardiac sarcoidosis / PET/MRI
2.	Ryosuke Kasai, Yusaku Yamaguchi, Takeshi Kojima and Tetsuya Yoshinaga : Hybrid Euler method for discretizing continuous-time tomographic dynamical system, Proc. of NCSP'20, 73-76, Honolulu, Feb. 2020.
3.	Yusaku Yamaguchi, Moe Kudoh, Ryosuke Kasai, Takeshi Kojima and Tetsuya Yoshinaga : Continuous-time image reconstruction based on Hellinger distance minimization for medical X-ray CT imaging, Abstract Proceeding of the 8th International Conference on Biomedical Engineering and Biotechnology, 30-31, Seoul, Oct. 2019.
4.	Ryosuke Kasai, Yusaku Yamaguchi, Takeshi Kojima and Tetsuya Yoshinaga : Hybrid of ML-EM and MART algorithms for X-ray CT image reconstruction, Abstract Proceeding of the 8th International Conference on Biomedical Engineering and Biotechnology, 31-32, Seoul, Oct. 2019.
5.	Ryosuke Kasai, Yusaku Yamaguchi, Takeshi Kojima and Tetsuya Yoshinaga : Hybrid algorithm of maximum-likelihood expectation-maximization and multiplicative algebraic reconstruction technique for iterative tomographic image reconstruction, Proceedings of SPIE, Vol.11049, Singapore, Jan. 2019. (Link to Publication Site) ● Publication site (DOI): 10.1117/12.2521185 (Link to Search Site for Scientific Articles) ● Summary page in Scopus @ Elsevier: 2-s2.0-85063894959 (DOI: 10.1117/12.2521185, Elsevier: Scopus)
6.	Tohru OKAZAKI, Hiroaki Hayashi, Emi TOMITA, Sota GOTO, Keiji TADA, Yoshiki MIHARA, Natsumi KIMOTO, Ryosuke Kasai, Yuki Kanazawa, Vergil LE CRUZ, Takuya HASHIZUME, Cheng Wei Hsin and Ikuo KOBAYASHI : Practical phantom study using small-type OSL dosimeter toward direct dose measurement during pediatric CT examination, AOCMP-AMPICON 2017, Jaipur, Nov. 2017.
7.	Hiroaki Hayashi, Emi TOMITA, Sota GOTO, Natsumi KIMOTO, Keiji TADA, Ryosuke Kasai, Yuki Kanazawa, Yoshiki MIHARA, Takashi ASAHARA, Tohru OKAZAKI, Takuya HASHIZUME and Vergil LE CRUZ : Direct Dose Measurement of Patients during Pediatric Computed Tomography Examination, International Symposium On Radiation Safety and Detection Technology (ISORD-9), Nagoya, Jul. 2017.
8.	Yoshiki Mihara, Hiroaki Hayashi, Kenji Yamada, Yuki Kanazawa, Kousaku Higashino, Kazuta Yamashita, Ryosuke Kasai, Tohru Okazaki and Takuya Hashizume : Basic study for internal dose evaluation during CT examination by means of small-type OSL dosimeter, European Congress of Radiology, Vienna, Mar. 2017. (Summary) [Aims and objectives] We plan to manage the patient dose exposure during computed tomography (CT) examination using a small-type OSL dosimeter. The OSL dosimeter can measure entrance skin dose (ESD) directly, but the internal dose can't be measured. The aim of this study is to clarify the relationship between the ESD and internal dose during the CT examination. [Methods and materials] We constructed an abdominal phantom, in which OSL dosimeters can be implanted in, and used this phantom to measure external and internal doses during CT examination. The typical irradiation conditions were as follow, 64 rows of detectors, 120 kV, 600 mA, PF (pitch factor) = 1.484 in helical scan mode. Additionally, we analyzed the contribution of X-rays, which were generated from different angles to the dosimeter; namely, angular dependences of 0-360 degrees at 45 degree intervals were evaluated experimentally. [Results] The ESDs and internal doses showed similar values, however the deviations between them were completely different; maximum deviation of ESD was found to be 30% and that of internal dose was at the most 5%. The deviation in ESDs is explained by the phenomenon in which some dosimeters were irradiated by direct X-ray and others were not. However, the small deviation between internal doses was explained by the phenomenon in which dosimeters were mainly irradiated by scattered X-rays. [Conclusion] In this study, we analyzed the relationship between ESD and internal dose for direct dose measurement of patient dose undergoing CT examination. The ESDs show relatively large fluctuations, on the other hand, the internal doses show small deviations.
9.	Rurie Raina Shantiningsih, Midori Yoshida, Ryna Dwi Yanuaryska, Ryosuke Kasai and Eiichi Honda : Differences of image Quality among Intraoral Detectors, The 10th ACOMFR 2014 Bali Indonesia, Nov. 2014.

Proceeding of Domestic Conference:

1.	BANDOH Takanori, Ryosuke Kasai, Tamaki Otani, NAGAO Sana, MATSUDA Noritake, 智高志, Shota Azane and Hideki Otsuka : Attempt at quantitative evaluation using lutetium scintigraphy after peptide receptor radionuclide therapy, 第80回日本放射線技術学会総会学術大会, Apr. 2024.
2.	BOLLOS CHRISTINE ANNE LEAH LOCSIN, Ryosuke Kasai, Hideki Otsuka, Youichi Otomi, Tomomi Matsuura, Tamaki Otani, BANDOH Takanori, UEKI Yuya, MATSUDA Noritake, 高志智, Shota Azane, Yamato Kunikane, Shoichiro Takao, Shusuke Yagi, Masataka Sata, Hitoshi Ikushima and Masafumi Harada : Ventilation/Perfusion Mismatch in Pulmonary Vein Stenosis After Atrial Fibrillation Ablation, 第268回徳島医学会学術集会, Mar. 2024.
3.	Ryosuke Kasai and Hideki Otsuka : 生成モデルを用いた医用画像異常検出モデルの作成, 第268回徳島医学会学術集会, Mar. 2024.
4.	KAWABATA Yuka, Ryosuke Kasai, Tamaki Otani, Takanori Bandoh, NORITAKE Matsuda, Shota Azane, Satoru Takashi, Yamato Kunikane, Masafumi Amano and Hideki Otsuka : 心臓サルコイドーシスを対象とした画像検査 ∼ 18F-FDG PET の有用性を中心に∼, 第19回中四国放射線医療技術フォーラム CSFRT2023, Nov. 2023.
5.	翔平大喜多, Kenji Yamada, Ryosuke Kasai, 陸登清水, 直井上, 俊哉鹿重, 裕己矢野, 絢太北川, Kanako Sakuragawa and Masafumi Amano : 移動型術中イメージングシステムを用いた3次元画像撮影条件の検討, 第19回中四国放射線医療技術フォーラム CSFRT2023, Nov. 2023.
6.	裕己矢野, Kenji Yamada, Kanako Sakuragawa, Ryosuke Kasai, 陸登清水, 直井上, 俊哉鹿重, 翔平大喜多 and Masafumi Amano : ポジショニングの違いによる胸部X 線画像経時差分処理のDIR 精度の評価, 第19回中四国放射線医療技術フォーラム CSFRT2023, Nov. 2023.
7.	直井上, Ryosuke Kasai, Kenji Yamada, Kanako Sakuragawa, 陸登清水, 翔平大喜多, 裕己矢野, 絢太北川 and Masafumi Amano : 頭部CT 画像における再構成条件がRadiomics 特徴量に与える影響, 第19回中四国放射線医療技術フォーラム CSFRT2023, Nov. 2023.
8.	絢太北川, Ryosuke Kasai, Kenji Yamada, Kanako Sakuragawa, 陸登清水 and 直井上 : 画像解析ワークステーションの違いによるAgatston score 算出結果の検討, 第19回中四国放射線医療技術フォーラム CSFRT2023, Nov. 2023.
9.	Kenji Yamada, Masafumi Amano, Kanako Sakuragawa, Ryosuke Kasai, こころ南, 麻依山本 and 陸登清水 : 線量計の違いがデジタルブレストトモシンセシスの平均乳腺線量測定値に与える影響, 第19回中四国放射線医療技術フォーラム CSFRT2023, Nov. 2023.
10.	麻依山本, Kanako Sakuragawa, こころ南, Ryosuke Kasai, Kenji Yamada and Masafumi Amano : デジタルブレストトモシンセシスにおける深部位置の違いによる画像コントラストの検討, 第19回中四国放射線医療技術フォーラム CSFRT2023, Nov. 2023.
11.	こころ南, Kanako Sakuragawa, 麻依山本, Ryosuke Kasai, Kenji Yamada and Masafumi Amano : デジタルブレストトモシンセシスの画質と撮影条件の検討, 第19回中四国放射線医療技術フォーラム CSFRT2023, Nov. 2023.
12.	Bollos Leah, Ryosuke Kasai, Youichi Otomi, Shoichiro Takao, Hitoshi Ikushima, Hideki Otsuka and Masafumi Harada : Prediction model of coronary artery calcification risk basis for radiomics features of pericoronary fat in coronary computed tomography, 第59回日本医学放射線学会秋季臨床大会, Sep. 2023.
13.	直井上, Ryosuke Kasai, Kenji Yamada, Hideki Suito, Naoki Maeda, Hidehiko Hosoki, Midori Yoshida and Masafumi Amano : 歯科インプラント素材の違いによるCT金属アーチファクトの評価, 第18回中四国放射線医療技術フォーラムCSFRT2022, Oct. 2022.
14.	上野裕己, Kenji Yamada, Kanako Sakuragawa, Ryosuke Kasai, 直井上, 俊哉鹿重 and Masafumi Amano : 胸部CT再構成関数がCAD自動検出能に及ぼす影響の評価, 第18回中四国放射線医療技術フォーラムCSFRT2022, Oct. 2022.
15.	俊哉鹿重, Ryosuke Kasai, Kenji Yamada, Kanako Sakuragawa, 直井上, 上野裕己 and Masafumi Amano : 特異値分解を用いた臨床CT画像におけるノイズ低減, 第18回中四国放射線医療技術フォーラム, Oct. 2022.
16.	Ryosuke Kasai, Yusaku Yamaguchi, Takeshi Kojima and Tetsuya Yoshinaga : 拡張指数型ダイバージェンス測度族の最適化に基づく逐次CT画像再構成, 中四国放射線医療技術フォーラム, Oct. 2022.
17.	Hideki Suito, Naoki Maeda, Ryosuke Kasai, Tadashi Inoue, Masafumi Amano, Keiko Fujimoto, Tetsuo Ichikawa and Hidehiko Hosoki : ジルコニアインプラントの金属アーチファクト定量評価, 日本歯科放射線学会第3回秋季学術大会, Oct. 2022.
18.	翔平大喜多, 直井上, Yuki Ueno, Kenji Yamada, Kanako Sakuragawa, Ryosuke Kasai, 陸登清水, Motoharu Sasaki and Masafumi Amano : 撮影条件の違いによる経時的差分処理胸部X線画像の評価, 第17回中四国放射線医療技術フォーラム(WEB開催), Dec. 2021.
19.	Yuki Ueno, Kenji Yamada, 直井上, 翔平大喜多, Kanako Sakuragawa, Ryosuke Kasai, 陸登清水, Motoharu Sasaki and Masafumi Amano : 画像処理の違いによる経時差分処理胸部X線画像の評価, 第17回中国四国放射線医療技術フォーラム(WEB開催), Dec. 2021.
20.	直井上, Kenji Yamada, Kanako Sakuragawa, Ryosuke Kasai, 陸登清水, Motoharu Sasaki and Masafumi Amano : ポジショニングの違いによる経時差分処理胸部X線画像の評価, 第17回中国四国放射線医療技術フォーラム(WEB開催), Dec. 2021.
21.	Kanako Sakuragawa, Motoharu Sasaki, 横石道寛, Ryosuke Kasai, 川下徹也 and Masafumi Amano : Exactracシステムにおける画像照合精度に及ぼすDRR画像パラメータの違いに関する検討, 第17回中国四国放射線医療技術フォーラム(WEB開催), Dec. 2021.
22.	池光大貴, Kenji Yamada, Kanako Sakuragawa, 清水陸登 and Ryosuke Kasai : 三次元画像処理における閾値がCFD解析結果に与える影響, 第15回中四国放射線医療技術フォーラム CSFRT, Sep. 2019.
23.	Takuto Tomokawa, Kenji Yamada, Kanako Sakuragawa, 池光大貴 and Ryosuke Kasai : 移動型デジタル式汎用一体型X線透視診断装置の撮影モードの違いによる線量と画質の評価, 第15回中四国放射線医療技術フォーラム CSFRT, Sep. 2019.
24.	Ryosuke Kasai, Kenji Yamada, Toshiya Kanoshige, 清水陸登 and 池光大貴 : 機械学習を用いた孤立性小肺結節の画像分類, 第15回中四国放射線医療技術フォーラム CSFRT, Sep. 2019.
25.	Ryosuke Kasai, Yusaku Yamaguchi, Takeshi Kojima and Tetsuya Yoshinaga : 期待値最大化法と乗法的代数的再構成法を拡張した新しい逐次CT画像再構成法の特性, 中四国放射線医療技術フォーラム, Nov. 2018. (Summary) 【背景と目的】医用CT画像診断装置の画像再構成原理として，近年，多くの種類の逐次再構成(IR)法が提案され利用されている．最適化を導く評価関数の特性を反映して収束性能や画像の品質に特徴が生じる．種々の評価関数に基づき微分方程式系を構成し，系の離散化によりIR法を導出する接近法が提案されている．筆者らは，最近，期待値最大化(EM)法と乗法的代数的再構成法(MART)を混合して拡張したIR法を提案している．このときの数値離散には加法的および乗法的算法の混成による離散化法を考案して適用した．本報告では，提案したIR法の特長を実験により検証している．【方法】EM法とMARTの混合拡張系は，投影と順投影の対称カルバック・ライブラー距離(SKLD)を最適化の評価関数として導出した逐次法である．CT逆問題が適切性を満たすとき，微分方程式系にみられる平衡点の安定性を理論的に証明することが可能である．臨床例を模擬した数値実験および実際の画像診断装置から得られた投影データによる実験を通して，提案法の性能を評価する．【結果と結論】まず，ハイブリッド算法を用いた場合のみが数値演算の安定性が高いことを確認した．次に，適切性を満たす設定において，解に沿ったSKLDの時間変化が単調に減少することを検証した．さらに，複数の実験結果から，提案法はEM法とMARTよりも評価関数による定量的な性能が高いことがわかった．
26.	鹿重俊哉, Motoharu Sasaki, Kenji Yamada, Kanako Sakuragawa and Ryosuke Kasai : 畳み込み自己符号化器を用いた臨床CT画像におけるノイズ低減, 第46回日本放射線技術学会秋季学術大会, Oct. 2018.
27.	Yusaku Yamaguchi, Ryosuke Kasai, Takeshi Kojima and Tetsuya Yoshinaga : 連続時間断層画像再構成法の加法的・乗法的及びその混成による離散化, Proceedings of the 116th Scientific Meeting of JSMP, Vol.38, No.3, Sep. 2018. (Summary) 【目的】高品質な断層画像を高速に再構成する方法の開発を目指し，筆者らは，種々の評価関数に基づく微分方程式系とハイブリッド力学系を提案している(連続時間再構成法と呼ぶ)．これまでに提示した系は，断層逆問題が適切性を満たす場合，画素値としての制約を満たしながら理想解の漸近安定性が理論的に保証されている特長を持つ．本報告では，連続時間再構成法の離散化算法に着目し，精度の高い効果的な逐次再構成(IR)法を構成するアプローチを提案する．【方法】連続時間再構成法は非線形微分方程式系の初期値問題を用いる方法である．まず，方程式系にみられる平衡点の漸近安定性を非線形力学系理論の安定性定理を用いて証明する．次に，IR法を導出するための離散化を実施する．非適切な場合や雑音が測定に含まれる場合の逆問題設定に対する数値実験を通して，離散化算法の種類と系のパラメタに依存したIR法の性能を評価する．【結果】連続時間系にみられる平衡点の安定性証明はリアプノフ定理を用いた．加法系，乗法系だけでなく，加法と乗法の混成系に基づきIR法を構成する．数値実験により，系の特性に応じた適切な離散化算法が存在することがわかった．投影と順投影の比に係る冪指数を測定雑音に含まれる雑音の程度に応じて適切に選ぶことで，最も品質の高い画像を与える効果的な再構成を実現できることが明らかとなった．【結論】断層画像再構成法として望ましい最適化評価関数に基づく微分方程式系を構成し，乗法的・加法的算法，及び，それらの混成による離散化算法からIR法を導出する手順を提示した．品質の高い画像を高速に演算できるIR法の構成アプローチとして有効である．
28.	Ryosuke Kasai, Kenji Yamada, Motoharu Sasaki, Kanako Sakuragawa, 清水陸登, Tadashi Inoue, Toshiya Kanoshige and 湯浅将生 : CT画像におけるDeep Learningと局所特徴量による画像分類精度の検討, 第13回中四国放射線医療技術フォーラム CSFRT, Dec. 2017.
29.	Ryosuke Kasai : 逐次近似応用再構成法とSEMARにおける基礎検討, 第3回中四国東芝CTユーザ会 in 四国香川, Dec. 2017.
30.	Ryosuke Kasai, Kenji Yamada, Motoharu Sasaki, Kanako Sakuragawa, 清水陸登, Tadashi Inoue, Toshiya Kanoshige and 湯浅将生 : Convolutional Neural Networkを用いたディープラーニングによるCT画像認識精度の検討, 第45回日本放射線技術学会秋季学術大会, Nov. 2017.
31.	Kenji Yamada, Motokatsu Yasutomo, Motoharu Sasaki, Kanako Sakuragawa, Masahide Tominaga, Ryosuke Kasai, 井上直 and 鹿重俊哉 : 確率密度関数を用いたエッジ法におけるMTF測定時のLSF取得法, 第45回日本放射線技術学会秋季学術大会, Oct. 2017.
32.	Kanako Sakuragawa, Motokatsu Yasutomo, Kenji Yamada, Motoharu Sasaki, Masahide Tominaga, Ryosuke Kasai, 井上直 and 鹿重俊哉 : ディジタル乳房撮影装置の焦点のボケ関数から導かれる焦点サイズの推定法, 第45回日本放射線技術学会秋季学術大会, Oct. 2017.
33.	Toshiya Kanoshige, Ryosuke Kasai, Kenji Yamada, Motoharu Sasaki, Kanako Sakuragawa, 清水陸登, Tadashi Inoue and 湯浅将生 : ハミルトニアンモンテカルロ法を用いたCT金属アーチファクト定量評価, 第45回日本放射線技術学会秋季学術大会, Oct. 2017.
34.	Keita Terahara, Sadamitsu Nishihara, Takaaki Isayama, 湯浅将生, Ryosuke Kasai, 由井和茂 and Hideki Otsuka : 薄型CTファントムを用いたノンヘリカルスキャンで体軸方向のCT値を計測, Japanese Journal of Radiological Technology, Vol.73, No.9, 821, Oct. 2017.
35.	岡崎徹, 橋詰拓弥, Vergil Cruz, Hiroaki Hayashi, 冨田恵美, 後藤聡汰, Ryosuke Kasai, 紀本夏実, 三原由樹, 淺原孝, 多田佳司 and 小林育夫 : 小型OSL線量計を用いた新生児CT撮影時における入射表面線量の実測への検討, 日本保健物理学会第50回研究発表会日本放射線安全管理学会第16回学術大会合同大会, Jun. 2017.
36.	Oyunbat Dashupuntsag, Midori Yoshida, Ryosuke Kasai, Naoki Maeda, Hidehiko Hosoki and Eiichi Honda : デジタル口内法X線撮影における検出器の比較, 日本歯科放射線学会第58回学術大会講演抄録集, 81, Jun. 2017.
37.	Ryosuke Kasai : 当院における逐次近似応用再構成法の利用, 第2回中四国東芝CTユーザー会in四国愛媛, Dec. 2016.
38.	Ryosuke Kasai, 清水陸登, Kenji Yamada, Toshiya Kanoshige, Motoharu Sasaki, Tadashi Inoue, Kanako Sakuragawa and 川田直伸 : 再構成FOVとCTストリークアーチファクト低減処理の極値統計学を用いた定量評価, 第12回中四国放射線医療技術フォーラム CSFRT, Nov. 2016.
39.	Hiroaki Hayashi, 三原由樹, 淺原孝, 紀本夏実, Yuki Kanazawa, Kenji Yamada, Ryosuke Kasai, 岡崎徹, 橋詰拓弥 and 小林育夫 : 小型OSL線量計を用いた小児X線撮影における介助者被ばく実測に向けた現状と課題, 医用画像情報学会(MII)平成28年度秋季(第176回)大会, Oct. 2016.
40.	下窪康史, Masahide Tominaga, Ryosuke Kasai, Motoharu Sasaki, 田中翼, 佐川友啓, 本田道隆 and Hitoshi Ikushima : 子宮頸癌に対する腔内小線源治療計画時におけるCBCT画像の画質評価, 医用画像情報学会(MII), Oct. 2016.
41.	Ryosuke Kasai : 徳島大学病院における心臓CT撮影への取り組みと現状報告, 第17回中四国夏季学術大会広島, Jul. 2016.
42.	Ryosuke Kasai, 清水陸登, Kenji Yamada, Kanako Sakuragawa, 湯浅将生 and 川田直伸 : CTストリークアーチファクト低減処理に対する極値統計学を用いた定量評価, 第11回中四国放射線医療技術フォーラム CSFRT, Nov. 2015.
43.	ダシプンツァグオユンバト, Midori Yoshida, Ryosuke Kasai, Naoki Maeda, Hidehiko Hosoki and Eiichi Honda : 2種類のデジタル口内法イメージングシステムによるコントラストの比較, 日本歯科放射線学会第56回学術大会, Jun. 2015.
44.	Ryosuke Kasai, Kenji Yamada, 多田章久, Hidehiko Hosoki, Naoki Maeda, Midori Yoshida and Eiichi Honda : 口内法X線画像用DICOMファイルの規格化および歯科用Viewerの実用化, 日本歯科放射線学会第56回学術大会, Jun. 2015.
45.	Ryosuke Kasai, Kenji Yamada, 久米芳生, 多田章久, Hidehiko Hosoki, Naoki Maeda, Midori Yoshida and Eiichi Honda : 歯科用イメージングプレートの経年劣化とQA(品質保証), 中四国放射線医療技術フォーラム CSFRT 2013, 172, Nov. 2013.

Assistant Professor : Kasai, Ryosuke

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