Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Masateru Kawakubo Last modified date:2024.06.03

Assistant Professor / Department of Health Sciences / Faculty of Medical Sciences

1. Kawakubo M, Nagao M*, Kaimoto Y, Nakao R, Yamamoto A, Kawasaki H, Iwaguchi T, Matsuo Y, Kaneko K, Sakai A, Sakai S. *Corresponding author., Deep learning approach using SPECT-to-PET translation for attenuation correction in CT-less myocardial perfusion SPECT imaging., Annals of Nuclear Medicine, 10.1007/s12149-023-01889-y, 38, 3, 199-209, 2024.03, [URL].
2. Arai H*, Kawakubo M, Sanui K, Nishimura H, Kadokami T., Differentiation between mild and severe myocarditis using multiparametric cardiac magnetic resonance, Radiology Case Reports, doi: 10.1016/j.radcr.2023.07.048, 18, 10, 3710-3715, 2023.08, The pathophysiology of myocarditis is associated with mild inflammation and may progress silently, or in severe cases such as fulminant myocarditis, may lead to sudden hemodynamic compromise. An invasive myocardial biopsy is generally required for a definitive myocarditis diagnosis. Alternatively, cardiac magnetic resonance (CMR), which evaluates myocardial characteristics and cardiac function, can be used as a noninvasive tool for diagnosing myocarditis. We describe the cases of a 49-year-old woman with mild acute eosinophilic myocarditis and a 48-year-old man with severe acute lymphocytic myocarditis. CMR was performed during the acute and convalescent phases in both cases. Compared with mild myocarditis, CMR in severe myocarditis showed higher T2 values and decreased left ventricular and atrial volumes and strains; however, the right ventricular strain was preserved. Late gadolinium enhancement showed faint contrast enhancement in the whole and strong enhancement in the local myocardium. Follow-up CMR showed recovery from myocardial inflammation and cardiac function. Some late gadolinium enhancement persisted whereas acute inflammation-associated enhancement disappeared. This case report highlights the differences between the cardiac parameters of patients with mild and severe myocarditis. Severe myocardial inflammation can be caused by severe heart failure owing to the concurrent reduction of cardiac function and compliance. Additionally, preserved right ventricular strain may predict cardiac function recovery in acute myocarditis. Noninvasive and repeatable CMR provides information on myocardial characteristics, cardiac function, and hemodynamics in a single scan at that time, which is useful not only for diagnosis but also for severity assessment and patient management in acute myocarditis..
3. Shirasaka T, Kojima T, Yamane S, Mikayama R, Kawakubo M, Funatsu R, Kato T, Ishigami K, Funama Y., Effect of iodine concentration and body size on iodine subtraction in virtual non-contrast imaging: A phantom study, Radiography (Lond)., 10.1016/j.radi.2023.03.003, 29, 3, 557-563, 2023.03.
4. 河窪 正照、長尾 充展、山本 篤志、中尾 梨沙子、松尾 有香、金子 恒一郎、渡邊 絵里、坂井 晶子、佐々木 雅之、坂井 修二. *責任著者, 高解像13N-アンモニアPET画像の feature-trackingによる右心室ストレインと心筋虚血との関連, 心臓核医学,, 23, 1, 13-17, 2023.03.
5. Yamamoto A, Nagao M, Kawakubo M, Ando K, Nakao R, Matsuo Y, Sakai A, Kaneko K, Momose M, Sakai S, Yamaguchi J., Prediction of cardiovascular events using myocardial strain ratio derived from N-13-ammonia positron emission tomography, Eur Radiol., 10.1007/s00330-022-09359-1, 2022.12.
6. Kawakubo M*,**, Waki H**, Shirasaka T, Kojima T, Mikayama R, Hamasaki H, Akamine H, Kato T, Baba S, Ushiro S, Ishigami K. *Corresponding author, **Equal contribution., A deep learning model based on fusion images of chest radiography and X-ray sponge images supports human visual characteristics of retained surgical items detection., Int J Comput Assist Radiol Surg., 10.1007/s11548-022-02816-8, 2022.12.
7. Michinobu Nagao, Masateru Kawakubo, Risako Nakao, Eri Watanabe, Masami Yoneyama, Nobuhisa Hagiwara, and Shuji Sakai., Myocardial Strain Derived from 13N-ammonia Positron Emission Tomography: Detection of Ischemia-Related Wall Motion Abnormality, Annals of Nuclear Cardiology,, 2022.11, [URL].
8. Sato T, Sakamoto I, Hiasa K, Kawakubo M, Ishikita A, Umemoto S, Kang JM, Sawatari H, Chishaki A, Shigeto H, Tsutui H., High-echoic line tracing of transthoracic echocardiography accurately assesses right ventricular enlargement in adult patients with atrial septal defect, The International Journal of Cardiovascular Imaging,, 2022.08.
9. Wibowo A, Triadyaksa P, Sugiharto A, Sarwoko A E, Nugroho A F, Arai H, Kawakubo M., Cardiac Disease Classification Using Two-Dimensional Thickness and Few-Shot Learning Based on Magnetic Resonance Imaging Image Segmentation, Journal of Imaging,, 8, 7, 194, 2022.07, Cardiac cine magnetic resonance imaging (MRI) is a widely used technique for the noninvasive assessment of cardiac functions. Deep neural networks have achieved considerable progress in overcoming various challenges in cine MRI analysis. However, deep learning models cannot be used for classification because limited cine MRI data are available. To overcome this problem, features from cine image settings are derived by handcrafting and addition of other clinical features to the classical machine learning approach for ensuring the model fits the MRI device settings and image parameters required in the analysis. In this study, a novel method was proposed for classifying heart disease (cardiomyopathy patient groups) using only segmented output maps. In the encoder–decoder network, the fully convolutional EfficientNetB5-UNet was modified to perform the semantic segmentation of the MRI image slice. A two-dimensional thickness algorithm was used to combine the segmentation outputs for the 2D representation of images of the end-diastole (ED) and end-systole (ES) cardiac volumes. The thickness images were subsequently used for classification by using a few-shot model with an adaptive subspace classifier. Model performance was verified by applying the model to the 2017 MICCAI Medical Image Computing and Computer-Assisted Intervention dataset. High segmentation performance was achieved as follows: the average Dice coefficients of segmentation were 96.24% (ED) and 89.92% (ES) for the left ventricle (LV); the values for the right ventricle (RV) were 92.90% (ED) and 86.92% (ES). The values for myocardium were 88.90% (ED) and 90.48% (ES). An accuracy score of 92% was achieved in the classification of various cardiomyopathy groups without clinical features. A novel rapid analysis approach was proposed for heart disease diagnosis, especially for cardiomyopathy conditions using cine MRI based on segmented output maps..
10. Kawakubo M*, **, Moriyama D**, Yamasaki Y, Abe K, Hosokawa K, Moriyama T, Triadyaksa P, Wibowo A, Nagao M, Arai H, Nishimura H, Kadokami T. *Corresponding author, **Equal contribution., Right ventricular strain and volume analyses through deep learning‐based fully automatic segmentation based on radial long‐axis reconstruction of short‐axis cine magnetic resonance images, Magnetic Resonance Materials in Physics, Biology and Medicine,, 2022.05, Objective We propose a deep learning-based fully automatic right ventricle (RV) segmentation technique that targets radially reconstructed long-axis (RLA) images of the center of the RV region in routine short axis (SA) cardiovascular magnetic resonance (CMR) images. Accordingly, the purpose of this study is to compare the accuracy of deep learning-based fully automatic segmentation of RLA images with the accuracy of conventional deep learning-based segmentation in SA orientation in terms of the measurements of RV strain parameters.
Materials and methods We compared the accuracies of the above-mentioned methods in RV segmentations and in measuring RV strain parameters by Dice similarity coefficients (DSCs) and correlation coefficients.
Results DSC of RV segmentation of the RLA method exhibited a higher value than those of the conventional SA methods (0.84 vs. 0.61). Correlation coefficient with respect to manual RV strain measurements in the fully automatic RLA were superior to those in SA measurements (0.5–0.7 vs. 0.1–0.2).
Discussion Our proposed RLA realizes accurate fully automatic extraction of the entire RV region from an available CMR cine image without any additional imaging. Our findings overcome the complexity of image analysis in CMR without the limitations of the RV visualization in echocardiography..
11. Masateru Kawakubo, Michinobu Nagao, Risako Nakao, Eri Watanabe, Masami Yoneyama, Nobuhisa Hagiwara, and Shuji Sakai., Decelerated Dark Flow Measured Using Steady-State Free Precession Magnetic Resonance Imaging for Specific Detection of Left Ventricular Myocardial Strain and Dyssynchrony in Dilated Cardiomyopathy, Cardiovascular Imaging Asia,, 6, 1, 4-12, 2022.01, [URL], Objective
In steady-state free precession (SSFP) cine imaging, signal loss can be observed as accelerated dark flow in patients with valvular disease and decelerated dark flow (DDF) in patients with severe left ventricular (LV) dysfunction. In our study, we measured DDF with optical flow calculations and investigated the relationship between DDF and myocardial strain or intraventricular dyssynchrony.
Materials and Methods
Fifty-seven consecutive patients with heart failure were retrospectively enrolled. In the short-axis orientation, the optical flow magnitude vector of the DDF was calculated over a cardiac cycle. The maximum value of the mean magnitude vector in the LV blood region was defined as the DDF index. The systolic circumferential strain (CS) of the LV free-wall, as well as the absolute difference in systolic timing of the LV free-wall and interventricular septum (LV dyssynchrony, LVD), was measured using the feature-tracking method. Spearman’s correlation coefficients (ρ) were calculated between DDF and CS or LVD.
Median and interquartile ranges (25th to 75th percentile) of measured DDF, CS, and LVD in 57 patients were 14.0 (10.3 to 20.4), -8.0% (-13.3 to -3.2), and 40 ms (21 to 99), respectively. There were statistically significant correlations between the values of DDF and CS as well as LVD (0.60 and 0.48; pConclusion
Measurement of DDF may provide a specific clinical picture of myocardial strain and intraventricular dyssynchrony. Furthermore, it is possible to cost-effectively measure DDF without additional image acquisition during routine MR examination.
12. Hideo Arai, Masateru Kawakubo*, Kenichi Sanui, Ryoji Iwamoto, Hiroshi Nishimura, Toshiaki Kadokami. *Corresponding author, Assessment of Bi-Ventricular and Bi-Atrial Areas Using Four-Chamber Cine Cardiovascular Magnetic Resonance Imaging: Fully Automated Segmentation with a U-Net Convolutional Neural Network, International Journal of Environmental Research and Public Health,, 19, 3, 1401, 2022.01, [URL], Four-chamber (4CH) cine cardiovascular magnetic resonance imaging (CMR) facilitates simultaneous evaluation of cardiac chambers; however, manual segmentation is time-consuming and subjective in practice. We evaluated deep learning based on a U-Net convolutional neural network (CNN) for fully automated segmentation of the four cardiac chambers using 4CH cine CMR. Cine CMR datasets from patients were randomly assigned for training (1400 images from 70 patients), validation (600 images from 30 patients), and testing (1000 images from 50 patients). We validated manual and automated segmentation based on the U-Net CNN using the dice similarity coefficient (DSC) and Spearman’s rank correlation coefficient (ρ); p
13. Kawakubo M, Nagao M, Yamamoto A, Nakao R, Matsuo Y, Kaneko K, Watanabe E, Sakai A, Sasaki M, Sakai S, 13 N-ammonia PET-derived right ventricular longitudinal strain and myocardial flow reserve in right coronary artery disease, Eur J Nucl Med Mol Imaging., 10.1007/s00259-021-05647-y, 2021.12.
14. Kawakubo M, Nagao M, Kikuchi N, Yamamoto A, Nakao R, Matsuo Y, Kaneko K, Watanabe E, Sasaki M, Nunoda S, Sakai S, 13N-ammonia positron emission tomography-derived left-ventricular strain in patients after heart transplantation validated using cardiovascular magnetic resonance feature tracking as reference, Ann Nucl Med., 10.1007/s12149-021-01686-5, 36, 1, 70-81, 2022.01, Objective: Heart transplant rejection leads to cardiac allograft vasculopathy (CAV). 13N-ammonia positron emission tomography (PET) can be useful in detecting CAV, as it can evaluate both epicardial vessels and microvasculature. In this study, we evaluated the regional wall motion in heart transplant patients using our PET-specific feature-tracking (FT) algorithm for myocardial strain calculation and validated it using a cardiovascular magnetic resonance (CMR) FT strain as a reference.
Methods: A total of 15 heart transplant patients who underwent both 13N-ammonia PET and CMR within 3 months were retrospectively enrolled. The same slice position of short-axis cine images of the middle slice of left ventricle (LV) and the same slice position of horizontal long-axis cine images were selected for the two modalities to measure the circumferential strain (CS) and longitudinal strain (LS), respectively. Based on the FT technique, time-strain curves were calculated by semi-automatic tracking of the endocardial contour on cine images throughout a cardiac cycle. The peak value in the time-strain curve was defined as the representative value. Correlations of CS and LS between PET and CMR were analyzed using Pearson correlation coefficients. The inter-modality error of strain measurements was evaluated using intraclass correlation coefficients (ICCs) with two-way random single measures.
Results: Excellent correlations of CS and LS between PET and CMR were observed (CS: r = 0.80; p Conclusions: We propose the first PET strain showing an excellent agreement with the CMR strain and high reproducibility in measurement..
15. Kawakubo M*, Yamasaki Y, Toyomura D, Yamamura K, Sakamoto I, Moriyama T, Yabuuchi H, Ishigami K, *Corresponding author, Unchanged right ventricular strain in repaired tetralogy of Fallot after pulmonary valve replacement with radial long-axis cine magnetic resonance images, Scientific Reports, 10.1038/s41598-021-98464-0, 11, 1, 2021.09.
16. Masateru Kawakubo, Michinobu Nagao, Atsushi Yamamoto, Risako Nakao, Yuka Matsuo, Kenji Fukushima, Eri Watanabe, Akiko Sakai, Masayuki Sasaki, and Shuji Sakai, 13N-ammonia positron emission tomography-derived endocardial strain for the assessment of ischemia using feature-tracking in high-resolution cine imaging, Journal of Nuclear Cardiology. Picked up in Editorial (, 10.1007/s12350-021-02677-9, 2021.06, Background: Assessing endocardial strain using a single 13N-ammonia positron emission tomography (PET) scan would be clinically useful, given the association between ischemia and myocardial deformation. However, no software has been developed for strain analysis using PET. We evaluated the clinical potential of feature tracking-derived strain values measured using PET, based on associations
with the myocardial flow reserve (MFR).
Methods and Results: This retrospective study included 95 coronary artery disease patients who underwent myocardial 13N-ammonia PET. Semi-automatic measurements were made using a feature-tracking technique during myocardial cine imaging, and values were calculated using a 16-segment model. Adenosine-stressed global circumferential strain (CS) and global longitudinal strain (LS) values were compared with global MFR values. Stressed and resting global strain values were also compared. Global strain values were significantly lower in 39 patients with abnormal MFRs [Conclusions: This study applied endocardial feature-tracking to 13N-ammonia PET, and the results suggested that blood flow and myocardial motility could be clinically assessed in ischemic patients using a single PET scan..
17. Kanatani R, Shirasaka T, Kojima T, Kato T, Kawakubo M*. *Corresponding author, Influence of beam hardening in dual- energy CT imaging: phantom study for iodine mapping, virtual monoenergetic imaging, and virtual non-contrast imaging, European Radiology Experimental,, 5, 18, 2021.04.
18. Shiina Y, Kawakubo M, Inai K, Asagai S, Nagao M., Dual VENC 4D flow magnetic resonance imaging demonstrates arterial-pulmonary collaterals in an adult with tetralogy of Fallot, Eur Heart J Cardiovasc Imaging., 10.1093/ehjci/jeaa343., Online ahead of print., 2020.12.
19. T Kojima, M Nagao, H Yabuuchi, Y Yamasaki, T Shirasaka, M Kawakubo, K Fukushima, T Koto, A Yamamoto, R Nakao, A Sakai, E Watanabe, and S Sakai, New transluminal attenuation gradient derived from dynamic coronary CT angiography: diagnostic ability of ischemia detected by 13N-ammonia PET, Heart and Vessels, In Press, 2020.10.
20. Hideo Arai, Masateru Kawakubo*, Kenichi Sanui, Hiroshi Nishimura, Toshiaki Kadokami. *Corresponding author, Assessing myocardial circumferential strain using cardiovascular magnetic resonance after magnetic resonance-conditional cardiac resynchronization therapy, Radiology Case Reports,, 15, 10, 1954-1959, 2020.08, Nondrug therapy for arrhythmia patients had been developed dramatically until recent years. Cardiac resynchronization therapy (CRT), a nondrug therapy for arrhythmia, is especially utilized for the treatment of left ventricular (LV) severe heart failure caused by cardiac dyssynchrony. Prolonged QRS duration (≥130 ms) is strongly used as a CRT indication criterion, but QRS is not the direct clinical index of mechanical contraction delay of the LV myocardium. Therefore, identifying the presence of dyssynchrony by diagnostic imaging is necessary. Echocardiography is widely used for the assessment of dyssynchrony as a standard diagnostic imaging. Several studies have addressed the efficacy of cardiovascular magnetic resonance feature tracking (CMR-FT) in the diagnosis of dyssynchrony for arry- thmia patients. In addition, cardiac implantable electronic devices (CIEDs) were not avail- able to examine CMR until recent years; however, new MR-conditional CIEDs have become available for use before and after CRT. Recently, diagnostic imaging using CMR-FT has been attracting attention for the assessment of dyssynchrony. However, a strong metal artifact caused by CIEDs may make the analysis difficult after CRT implantation. Strain analysis us- ing short-axis (SA) cine CMR overcame this issue of artifact by enabling slice selection by avoiding artifact. Moreover, circumferential strain has superiority over other strain methods with respect to sensitivity, and we focused on these advantages. This case illustrates that circumferential strain with CMR-FT using SA cine CMR is useful in the assessment of improvement of myocardial motion after CRT and can provide useful additional information with imaging to determine the responders of CRT..
21. Yamasaki Y, Abe K, Kamitani T, Hosokawa K, Kawakubo M, Sagiyama K, Hida T, Matsuura Y, Murayama Y, Funatsu R, Tsutsui H, Yabuuchi H., Balloon pulmonary angioplasty improves right atrial reservoir and conduit functions in chronic thromboembolic pulmonary hypertension., European Heart Journal Cardiovascular Imaging, 10.1093/ehjci/jeaa064, 2020.05.
22. Shiina Y, Taniguchi K, Nagao M, Takahashi T, Niwa K, Kawakubo M, and Inai K., The relationship between extracellular volume fraction in symptomatic adults with tetralogy of Fallot and adverse cardiac events., Journal of Cardiology, DOI: 10.1016/j.jjcc.2019.09.009., 75, 4, 424-431, 2020.04.
23. Arai H, Kawakubo M*, Abe K, Hatashima H, Sanui K, Nishimura H, and Kadokami T. *Corresponding author, Quantification of intramyocardial hemorrhage volume using magnetic resonance imaging with three-dimensional T1-weighted sequence in patients with ischemia-reperfusion injury—a semi-automated image processing technique, The International Journal of Cardiovascular Imaging, 10.1007/s10554-019-01697-4, 36, 1, 111-119, 2020.01.
24. M Kawakubo, M Nagao, U Ishizaki, Y Shina, K Inai, Y Yamasaki, M Yoneyama, S Sakai., Feature-Tracking MRI Fractal Analysis of Right Ventricular Remodeling in Adults with Congenitally Corrected Transposition of the Great Arteries, Radiology: Cardiothoracic Imaging, 10.1148/ryct.2019190026, 1, 4, 2019.10.
25. R Nakao, M Nagao, K Fukushima, A Sakai, E Watanabe, M Kawakubo, S Sakai, N Hagiwara., Prediction of Cardiac Resynchronization Therapy Response in Dilated Cardiomyopathy Using Vortex Flow Mapping on Cine Magnetic Resonance Imaging, Circulation Reports, 10.1253/circrep.CR-18-0024, 1, 8, 333-341, 2019.08.
26. Kawakubo M*, Yamasaki Y, Kamitani T, Sagiyama K, Matsuura Y, Hino T, Abe K, Hosokawa K, Yabuuchi H, and Honda H. *Corresponding author, Clinical usefulness of right ventricular 3D area strain in the assessment of treatment effects of balloon pulmonary angioplasty in chronic thromboembolic pulmonary hypertension: comparison with 2D feature-tracking MRI, European Radiology,, 29, 9, 4583-4592, 2019.09.
27. Arai H, Kawakubo M, Sanui K, Nishimura H, Kadokami T., Accurate and robust systolic myocardial T1 mapping using saturation recovery with individualized delay time: Comparison with diastolic T1 mapping, Radiol Phys Technol.,, 11, 4, 415-422, 2018.09.
28. Kawakubo M*, Arai H, Nagao M, Yamasaki Y, Sanui K, Nishimura H, Kadokami T. *Corresponding author, Global left ventricular area strain using standard two-dimensional cine MR imaging with inter-slice interpolation, Cardiovascular Imaging: Asia,, 2, 4, 187-193, 2018.10.
29. Kojima T, Kawakubo M, Nishizaka MK, Rahmawati A, Ando S, Chishaki SA, Nakamura Y, Nagao M, 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.
30. Kawakubo M*, Akamine H, Yamasaki Y, Takemura A, Abe K, Hosokawa K, Morishita J, Nagao M. *Corresponding author, Three-dimensional phase contrast magnetic resonance imaging validated to assess pulmonary artery flow in patients with chronic thromboembolic pulmonary hypertension., Radiological Physics and Technologies, 2016.10.
31. Kawakubo M*, Yamasaki Y, Sakamoto I, Yamamura K, Nagao M. *Corresponding author, Clinical Impact of Interventricular Dyssynchrony in Repaired Tetralogy of Fallot: Myocardial Strain Analysis Using Semi-automatic Tracking of Cine Magnetic Resonance Imaging., Journal of Adult Congenital Heart Disease, Vol. 4, No. 2, 69-73, 2015.12.
32. Kawakubo M*, Nagao M, Kumazawa S, Yamasaki Y, Chishaki AS, Nakamura Y, Honda H, Morishita J. *Corresponding author, Evaluation of ventricular dysfunction using semi-automatic longitudinal strain analysis of four-chamber cine MR imaging., The International Journal of Cardiovascular Imaging., 32, 2, 283-9, 2016.02.
33. Kawakubo M*, Nagao M, Kumazawa S, Chishaki AS, Mukai Y, Nakamura Y, Honda H, Morishita J. *Corresponding author, Evaluation of cardiac dyssynchrony with longitudinal strain analysis in 4-chamber cine MR imaging., European Journal of Radiology, 82, 12, 2212-2216, 2013.12.
34. Kudomi S, Ueda K, Ueda Y, Kawakubo M, Sanada T, Evaluation of the spatial resolution of multiplanar reconstruction images., Radiological Physics and Technologies, 1, 2, 229-233, 2008.07.