Kyushu University Academic Staff Educational and Research Activities Database
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Tsukasa Kojima Last modified date:2024.05.20

 Reseacher Profiling Tool Kyushu University Pure
Academic Degree
Country of degree conferring institution (Overseas)
Field of Specialization
CT, Medical Image Analysis
Total Priod of education and research career in the foreign country
Academic Activities
1. Tsukasa Kojima, Yuzo Yamasaki, Yuko Matsuura, Ryoji Mikayama, Takashi Shirasaka, Masatoshi Kondo, Takeshi Kamitani, Toyoyuki Kato, Kousei Ishigami, Hidetake Yabuuchi, The Feasibility of Deep Learning-Based Reconstruction for Low-Tube-Voltage CT Angiography for Transcatheter Aortic Valve Implantation., Journal of computer assisted tomography, 10.1097/RCT.0000000000001525, 2023.08, OBJECTIVE: The purpose of this study is to evaluate the efficacy of deep learning reconstruction (DLR) on low-tube-voltage computed tomographic angiography (CTA) for transcatheter aortic valve implantation (TAVI). METHODS: We enrolled 30 patients who underwent TAVI-CT on a 320-row CT scanner. Electrocardiogram-gated coronary CTA (CCTA) was performed at 100 kV, followed by nongated aortoiliac CTA at 80 kV using a single bolus of contrast material. We used hybrid-iterative reconstruction (HIR), model-based IR (MBIR), and DLR to reconstruct these images. The contrast-to-noise ratios (CNRs) were calculated. Five-point scales were used for the overall image quality analysis. The diameter of the aortic annulus was measured in each reconstructed image, and we compared the interobserver and intraobserver agreements. RESULTS: In the CCTA, the CNR and image quality score for DLR were significantly higher than those for HIR and MBIR (P 0.89). CONCLUSIONS: In low tube voltage TAVI-CT, DLR provides higher image quality than HIR, and DLR provides higher image quality than MBIR in CCTA and is visually comparable to MBIR in aortoiliac CTA..
2. Tsukasa Kojima, Takashi Shirasaka, Yuzo Yamasaki, Masatoshi Kondo, Hiroshi Hamasaki, Ryoji Mikayama, Yuki Sakai, Toyoyuki Kato, Akihiro Nishie, Kousei Ishigami, Hidetake Yabuuchi, Importance of the heart rate in ultra-high-resolution coronary CT angiography with 0.35 s gantry rotation time, JAPANESE JOURNAL OF RADIOLOGY, 10.1007/s11604-022-01265-2, 2022.04, Purpose We investigated the effects of the heart rate (HR) on the motion artifact in coronary computed tomography angiography (CCTA) with ultra-high-resolution-CT (U-HRCT), and we clarified the upper limit of optimal HR in CCTA with U-HRCT in a comparison with conventional-resolution-CT (CRCT) on a cardiac phantom and in patients with CCTA.Materials and methods A pulsating cardiac phantom equipped with coronary models was scanned at static and HR simulations of 40-90 beats/min (bpm) at 10-bpm intervals using U-HRCT and CRCT, respectively. The sharpness and lumen diameter of the coronary model were quantitatively compared between U-HRCT and CRCT stratified by HR in the phantom study. We also assessed the visual inspections of clinical images in CCTA with U-HRCT.Results At the HRs 60 bpm, the inverse was shown. For the image sharpness, the U-HRCT was significantly superior to the CRCT (p
3. Tsukasa Kojima, Michinobu Nagao, Hidetake Yabuuchi, Yuzo Yamasaki, Takashi Shirasaka, Masateru Kawakubo, Kenji Fukushima, Toyoyuki Kato, Atsushi Yamamoto, Risako Nakao, Akiko Sakai, Eri Watanabe, Shuji Sakai, New transluminal attenuation gradient derived from dynamic coronary CT angiography: diagnostic ability of ischemia detected by(13)N-ammonia PET, HEART AND VESSELS, 10.1007/s00380-020-01712-y, 36, 4, 433-441, 2021.04, Coronary computed tomography angiography (CCTA) has low specificity for detecting significant functional coronary stenosis. We developed a new transluminal attenuation gradient (TAG)-derived dynamic CCTA with dose modulation, and we investigated its diagnostic performance for myocardial ischemia depicted by(13)N-ammonia positron emission tomography (PET). Data from 48 consecutive patients who had undergone both dynamic CCTA and(13)N-ammonia PET were retrospectively analyzed. Dynamic CCTA was continuously performed in mid-diastole for five cardiac cycles with prospective electrocardiography gating after a 10-s contrast medium injection. One scan of the dynamic CCTA was performed as a boost scan for conventional CCTA at the peak phase of the ascending aorta. Absolute TAG values at five phases around the boost scan were calculated. The dynamic TAG index (DTI) was defined as the ratio of the maximum absolute TAG to the standard deviation of five TAG values. We categorized the coronary territories as non-ischemia or ischemia based on the(13)N-ammonia PET results. A receiver operating characteristic (ROC) analysis was performed to determine the optimal cutoff of the DTI for identifying ischemia. The DTI was significantly higher for ischemia compared to non-ischemia (8.8 +/- 3.9 vs. 4.6 +/- 2.0,p
4. Tsukasa Kojima, Takashi Shirasaka, Masatoshi Kondo, Toyoyuki Kato, Akihiro Nishie, Kousei Ishigami, Hidetake Yabuuchi, A novel fast kilovoltage switching dual-energy CT with deep learning: Accuracy of CT number on virtual monochromatic imaging and iodine quantification, PHYSICA MEDICA-EUROPEAN JOURNAL OF MEDICAL PHYSICS, 10.1016/j.ejmp.2020.12.018, 81, 253-261, 2021.01, Purpose: A novel fast kilovoltage switching dual-energy CT with deep learning [Deep learning based-spectral CT (DL-Spectral CT)], which generates a complete sinogram for each kilovolt using deep learning views that complement the measured views at each energy, was commercialized in 2020. The purpose of this study was to evaluate the accuracy of CT numbers in virtual monochromatic images (VMIs) and iodine quantifications at various radiation doses using DL-Spectral CT.Materials and methods: Two multi-energy phantoms (large and small) using several rods representing different materials (iodine, calcium, blood, and adipose) were scanned by DL-Spectral CT at varying radiation doses. Images were reconstructed using three reconstruction parameters (body, lung, bone). The absolute percentage errors (APEs) for CT numbers on VMIs at 50, 70, and 100 keV and iodine quantification were compared among different radiation dose protocols.Results: The APEs of the CT numbers on VMIs were
5. Tsukasa Kojima, Yuzo Yamasaki, Takeshi Kamitani, Hidetake Yabuuchi, Takashi Shirasaka, Yamato Shimomiya, Masatoshi Kondo, Hiroshi Hamasaki, Toyoyuki Kato, Michinobu Nagao, Hiroshi Honda, Dynamic Coronary 320-Row CT Angiography Using Low-Dose Contrast and Temporal Maximum Intensity Projection: A Comparison with Standard Coronary CT Angiography, Cardiovascular Imaging Asia,, 2019.04.
6. Tsukasa Kojima, Masateru Kawakubo, Mari K. Nishizaka, Anita Rahmawati, Shin-ichi Ando, Akiko Chishaki, Yasuhiko Nakamura, Michinobu Nagao, Assessment by airway ellipticity on cine-MRI to differentiate severe obstructive sleep apnea, CLINICAL RESPIRATORY JOURNAL, 10.1111/crj.12598, 12, 3, 878-884, 2018.03, IntroductionThe severity of obstructive sleep apnea (OSA) is assessed by the apnea-hypopnea index (AHI) determined from polysomnography (PSG). However, PSG requires a specialized facility with well-trained specialists and takes overnight. Therefore, simple tools, which could distinguish severe OSA, have been needed before performing PSG.ObjectivesWe propose the new index using cine-MRI as a screening test to differentiate severe OSA patients, who would need PSG and proper treatment.MethodsThirty-six patients with suspected OSA (mean age 54.6 y, mean AHI 52.6 events/h, 33 males) underwent airway cine-MRI at the fourth cervical vertebra level during 30 s of free breathing and PSG. The minimum airway ellipticity (AE) in 30 s duration was measured, and was defined as the severity of OSA. Patients were divided into severe OSA, not-severe OSA, and normal groups, according to PSG results. The comparison of AE between any two of the three groups was performed by Wilcoxon rank-sum test. Receiver operating characteristic (ROC) curve analysis was performed to determine the optimal cut-off of AE for identifying severe OSA patients.ResultsThe minimum AE for severe OSA was significantly lower than that for not-severe OSA and normal (severe, 0.170.16; not severe, 0.31 +/- 0.17; normal, 0.38 +/- 0.19, P<.05 roc analysis revealed that the optimal cutoff of minimum ae identified severe osa patients with an area under curve sensitivity and specificity.conclusionae is a feasible quantitative index promising screening test for detecting patients.. id="gencho_ronbuns10265098" class="qir_handle_link">
7. Tsukasa Kojima, Hidetake Yabuuchi, Hiroshi Narita, Seiji Kumazawa, Yuzo Yamasaki, Yuki Yano, Noriyuki Sakai, Yoichi Kurihara, Kiyoshi Hisada, Masafumi Masaki, Hiroshi Kimura, Efficacy of the radial acquisition regime (RADAR) for acquiring head and neck MR images ,, 2016.05.