医療技術評価

臨床疫学

医療情報

放射線技術学

Life Science, Radiological sciences

Life Science, Medical technology assessment

Apr. 2026, 日本放射線技術学会 北海道支部, 学術賞

Apr. 2009, 日本放射線技術学会 北海道部会, 学術奨励賞

Apr. 2009, 日本放射線技術学会, 技術奨励賞

Overall Diagnostic Efficiency of a Noninvasive Diagnostic Strategy Aimed at Early Detection of Advanced Liver Fibrosis in Metabolic Dysfunction-Associated Steatotic Liver Disease Cases
Kunihiro Iwata; Naoto Mori; Katsuhiko Ogasawara
Cureus, Springer Science and Business Media LLC, 30 Sep. 2025, [Peer-reviewed], [Lead author]
Scientific journal

Investigation of optimal settings for deviceless respiratory synchronization in PET/CT examinations: effects of different reconstructions on image quality
Naoto Mori; Kunihiro Iwata; Takahiro Uno; Taku Uchibe; Atsutaka Okizaki
Radiological Physics and Technology, 18, 4, 1176, 1191, Springer Science and Business Media LLC, 26 Sep. 2025, [Peer-reviewed]
Scientific journal

Effect of Pulse Wave Synchronization on T1 Value in Cardiac T1 Mapping: Is Pulse Wave Synchronization a Substitute for Electrocardiogram Gating?
森直人, 中川貞弘, 岩田邦弘, 坂本央, 沖崎貴琢
Japanese Journal of Radiological Technology, 80, 10, 1026, 1036, Japanese Society of Radiological Technology, Oct. 2024, [Peer-reviewed]
Scientific journal

Evaluation of Right Ventricular Myocardial Properties Using Systolic Myocardial T1 Mapping
Yuki Sasaki; Hideharu Oka; Kouichi Nakau; Yuki Shibagaki; Keita Ito; Rina Imanishi; Sorachi Shimada; Yuki Akiho; Kazunori Fukao; Sadahiro Nakagawa; Kunihiro Iwata; Satoru Takahashi
Cureus, Springer Science and Business Media LLC, 26 Aug. 2024, [Peer-reviewed]
Scientific journal

Efficiency assessment of a two-stage diagnostic strategy combining CT angiography and fractional flow reserve derived from coronary CT angiography for the detection of myocardial ischemia: a simulation study
Kunihiro Iwata; Akira Yanagisawa; Katsuhiko Ogasawara
Egyptian Journal of Radiology and Nuclear Medicine, 55, 1, Springer Science and Business Media LLC, 17 Jun. 2024, [Peer-reviewed], [Lead author]
Scientific journal, Abstract

Background

The importance of a diagnostic strategy combining coronary computed tomography angiography (CCTA) with fractional flow reserve derived from CCTA (FFRCT) for detecting myocardial ischemia is increasing. However, sensitivity and specificity alone may be insufficient to understand the efficiency characteristics of a diagnostic strategy combining CCTA and FFRCT (DSCCF). Our study aimed to evaluate the overall efficiency of DSCCF in detecting myocardial ischemia and compare it with other diagnostic strategies to determine whether evaluation by DSCCF is currently appropriate.

Results

This simulation study included 1000 patients with stable chest pain and suspected myocardial ischemia. Using a decision tree analysis, assuming a diagnostic strategy of adding FFRCT to CCTA-positive patients, we calculated the following efficiency parameters of DSCCF: (1) true positive (TP), false positive (FP), net false negative (FN), and net true negative (TN) test results; (2) net sensitivity; (3) net specificity; (4) positive predictive value; (5) negative predictive value; (6) post-test probability; (7) diagnostic accuracy; (8) diagnostic odds ratio; and (9) number needed to diagnose. We also calculated the efficiency parameters of other diagnostic strategies and compared them with those of DSCCF. In the basic setting, regarding efficiency parameters (1), the number of TPs, FPs, net FNs, and net TNs were 254, 69, 46, and 631, respectively. Efficiency parameters (2)–(9) were 0.85 (95% confidence interval [CI], 0.80–0.89), 0.90 (95% CI 0.88–0.92), 0.79 (95% CI 0.74–0.83), 0.93 (95% CI 0.91–0.95), 0.07 (95% CI 0.05–0.09), 0.89 (95% CI 0.86–0.90), 50.50 (95% CI 33.83–75.37), and 1.34 (95% CI 1.24–1.48), respectively. Compared with other diagnostic strategies, DSCCF had good efficiency parameters. Moreover, the sensitivity analysis did not reveal any evidence to contradict the findings in the basic setting.

Conclusions

This study demonstrated the diagnostic ability characteristics of DSCCF by assessing various efficiency parameters. Compared with other diagnostic strategies, DSCCF had good efficiency. In terms of efficiency, evaluation using DSCCF for detecting myocardial ischemia appears to be appropriate.

Left atrial vortex flow and its relationship with left atrial functions in patients with congenital heart disease
Keita Ito; Hideharu Oka; Yuki Shibagaki; Yuki Sasaki; Rina Imanishi; Sorachi Shimada; Yuki Akiho; Kazunori Fukao; Sadahiro Nakagawa; Kunihiro Iwata; Kouichi Nakau; Satoru Takahashi
The Egyptian Heart Journal, 76, 1, Springer Science and Business Media LLC, 02 May 2024, [Peer-reviewed]
Scientific journal, Abstract

Background

Four-dimensional flow magnetic resonance imaging (MRI) enables blood flow visualization. The absence of left atrial vortex flow (LAVF) has been implicated in the development of thrombus formation and arrhythmias. However, the clinical relevance of this phenomenon in patients with congenital heart disease (CHD) remains unclear. This study aimed to unravel the relationship of LAVF with left atrial functions in patients with CHD.

Results

Twenty-five participants who underwent cardiac MRI examinations were included (8 postoperative patients with CHD aged 17–41 years and 17 volunteers aged 21–31 years). All participants were in sinus rhythm. Four-dimensional flow MRI (velocity encoding 100 cm/s) assessed the presence of LAVF, and its relationship with left atrial function determined by transthoracic echocardiography was explored. LAVF was detected in 16 patients. Upon classification of the participants based on the presence or absence of LAVF, 94% of participants in the LAVF group were volunteers, while 78% of those in the without LAVF group were postoperative patients. Participants without LAVF had a significantly lower left atrial ejection fraction (61% vs. 70%, p = 0.019), reservoir (32% vs. 47%, p = 0.006), and conduit (22% vs. 36%, p = 0.002) function than those with LAVF.

Conclusions

LAVF occurred during the late phase of ventricular systole, and left atrial reservoir function may have contributed to its occurrence. Many postoperative patients with CHD experienced a loss of LAVF. LAVF may indicate early left atrial dysfunction resulting from left atrial remodeling.

Evaluation of double-chambered right ventricle flow using 4D flow MRI: right ventricular helical flow may not disappear even after surgical intervention
Hideharu Oka; Keita Ito; Sadahiro Nakagawa; Kunihiro Iwata; Kouichi Nakau
European Heart Journal - Imaging Methods and Practice, 1, 2, Oxford University Press (OUP), 08 Sep. 2023, [Peer-reviewed]
Scientific journal

Four-Dimensional Flow Magnetic Resonance Imaging Can Visualize a Disturbed Pattern of Blood Flow in a Patient Without a Significant Pressure Gradient after Surgical Repair of Aortic Coarctation
Hideharu Oka; Sadahiro Nakagawa; Kouichi Nakau; Rina Imanishi; Sorachi Shimada; Yuki Mikami; Kazunori Fukao; Kunihiro Iwata; Satoru Takahashi
7, 1, 52, 53, Mar. 2023, [Peer-reviewed]

Assessment of the Efficiency of Non-Invasive Diagnostic Imaging Modalities for Detecting Myocardial Ischemia in Patients Suspected of Having Stable Angina
Kunihiro Iwata; Katsuhiko Ogasawara
Healthcare, 11, 1, 23, 23, MDPI AG, 22 Dec. 2022, [Lead author]
Scientific journal, This study aimed to assess and compare the efficiency of non-invasive imaging modalities in detecting myocardial ischemia in patients with suspected stable angina as easy-to-understand indices. Our study included 1000 patients with chest pain and possible stable myocardial ischemia. The modalities to be assessed were cardiac magnetic resonance imaging (CMRI), single-photon emission computed tomography, positron emission computed tomography (PET), stress echocardiography, and fractional flow reserve derived from coronary computed tomography angiography (FFRCT). As a simulation study, we assumed that all five imaging modalities were performed on these patients, and a decision tree analysis was conducted. From the results, the following efficiencies were assessed and compared: (1) number of true positive (TP), false positive (FP), false negative (FN), and true negative (TN) test results; (2) positive predictive value (PPV); (3) negative predictive value (NPV); (4) post-test probability; (5) diagnostic accuracy (DA); and (6) number needed to diagnose (NND). In the basic settings (pre-test probability: 30%), PET generated the highest TP (267) and NPV (95%, 95% confidence interval (CI): 93–96%). In contrast, CMRI produced the highest TN (616), PPV (76%, 95% CI: 71–80%), and DA (88%, 95% CI: 86–90%) and the lowest NND (1.33, 95% CI: 1.24–1.47). Although FFRCT generated the highest TP (267) and lowest FN (33), it generated the highest FP (168). In terms of detecting myocardial ischemia, compared with the other modalities, PET and CMRI were more efficient. The results of our study might be helpful for both patients and medical professionals associated with their examination.

Liver T1/T2 values with cardiac MRI during respiration
Hideharu Oka; Kouichi Nakau; Sadahiro Nakagawa; Rina Imanishi; Sorachi Shimada; Yuki Mikami; Kazunori Fukao; Kunihiro Iwata; Satoru Takahashi
Cardiology in the Young, 33, 10, 1859, 1865, Cambridge University Press (CUP), 25 Oct. 2022, [Peer-reviewed]
Scientific journal, Abstract

Background:

Assessing the hepatic status of children with CHD is very important in the post-operative period. This study aimed to assess the usefulness of paediatric liver T1/T2 values and to evaluate the impact of respiration on liver T1/T2 values.

Methods:

Liver T1/T2 values were evaluated in 69 individuals who underwent cardiac MRI. The mean age of the participants was 16.2 ± 9.8 years. Two types of imaging with different breathing methods were possible in 34 participants for liver T1 values and 10 participants for liver T2 values.

Results:

The normal range was set at 620–830 msec for liver T1 and 25–40 ms for liver T2 based on the data obtained from 17 healthy individuals. The liver T1/T2 values were not significantly different between breath-hold and free-breath imaging (T1: 769.4 ± 102.8 ms versus 763.2 ± 93.9 ms; p = 0.148, T2: 34.9 ± 4.0 ms versus 33.6 ± 2.4 ms; p = 0.169). Higher liver T1 values were observed in patients who had undergone Fontan operation, tetralogy of Fallot operation, or those with chronic viral hepatitis. There was a trend toward correlation between liver T1 values and liver stiffness (R = 0.65, p = 0.0004); and the liver T1 values showed a positive correlation with the shear wave velocity (R = 0.62, p = 0.0006).

Conclusions:

Liver T1/T2 values were not affected by breathing patterns. Because liver T1 values tend to increase with right heart overload, evaluation of liver T1 values during routine cardiac MRI may enable early detection of future complications.

Comparison of myocardial T1 mapping during breath-holding and free-breathing
Hideharu Oka; Kouichi Nakau; Sadahiro Nakagawa; Yuki Kobayashi; Rina Imanishi; Kunihiro Iwata; Hiroshi Azuma
Cardiology in the Young, 32, 6, 925, 929, Cambridge University Press (CUP), 09 Aug. 2021, [Peer-reviewed]
Scientific journal, Abstract

Background:

T1 mapping is a recently developed imaging analysis method that allows quantitative assessment of myocardial T1 values obtained using MRI. In children, MRI is performed under free-breathing. Thus, it is important to know the changes in T1 values between free-breathing and breath-holding. This study aimed to compare the myocardial T1 mapping during breath-holding and free-breathing.

Methods:

Thirteen patients and eight healthy volunteers underwent cardiac MRI, and T1 values obtained during breath-holding and free-breathing were examined and compared. Statistical differences were determined using the paired t-test.

Results:

The mean T1 values during breath-holding were 1211.1 ± 39.0 ms, 1209.7 ± 37.4 ms, and 1228.9 ± 52.5 ms in the basal, mid, and apical regions, respectively, while the mean T1 values during free-breathing were 1165.1 ± 69.0 ms, 1103.7 ± 55.8 ms, and 1112.0 ± 81.5 ms in the basal, mid, and apical regions, respectively. The T1 values were lower during free-breathing than during breath-holding in almost all segments (basal: p = 0.008, mid: p < 0.001, apical: p < 0.001). The mean T1 values in each cross section were 3.1, 7.8, and 7.7% lower during free-breathing than during breath-holding in the basal, mid, and apical regions, respectively.

Conclusions:

We found that myocardial T1 values during free-breathing were about 3–8% lower in all cross sections than those during breath-holding. In free-breathing, it may be difficult to assess myocardial T1 values, except in the basal region, because of underestimation; thus, the findings should be interpreted with caution, especially in children.

Optimization of External Driver Amplitude in Magnetic Resonance Elastography of the Liver: Relationship between Appropriate External Driver Amplitude and Indicators of Physical Constitution
Naoto Mori; Sadahiro Nakagawa; Kunihiro Iwata
Japanese Journal of Radiological Technology, 77, 3, 263, 271, Japanese Society of Radiological Technology, 2021, [Peer-reviewed], [Last author]
Scientific journal

Evaluation of Efficiencies on the Gadoxetic Acid-enhanced MRI for Preoperative Assessment of Liver Metastases from Colorectal Carcinoma
岩田 邦弘, 森谷 俊春, 中川 貞裕, 小笠原 克彦
Japanese Journal of Radiological Technology, 74, 1, 29, 38, Japanese Society of Radiological Technology, 2018, [Peer-reviewed], [Lead author]
Scientific journal

The Prognostic Value of Normal Stress Cardiovascular Magnetic Resonance Imaging
Kunihiro Iwata; Sadahiro Nakagawa; Katsuhiko Ogasawara
Journal of Computer Assisted Tomography, 38, 1, 36, 43, Ovid Technologies (Wolters Kluwer Health), 2014, [Peer-reviewed], [Lead author]
Scientific journal

Comparison of the cost-effectiveness of stress myocardial perfusion MRI and SPECT in patients with suspected coronary artery disease
Kunihiro Iwata; Katsuhiko Ogasawara
Radiological Physics and Technology, 6, 1, 28, 34, Springer Science and Business Media LLC, 18 Jul. 2012, [Peer-reviewed], [Lead author]
Scientific journal

Comparsion with myocardial perfusion MRI and myocardial perfusion SPECT in the diagnostic performance of coronary artery disease: A meta-analysis
Kunihiro Iwata; Makoto Kubota; Katsuhiko Ogasawara
Japanese Journal of Radiological Technology, 64, 2, 251, 258, Japanese Society of Radiological Technology, Feb. 2008, [Peer-reviewed], [Lead author]
Scientific journal

Evaluation of normal fatty replacement of the thymus with chemical‐shift MR imaging for identification of the normal thymus
Tsutomu Inaoka; Koji Takahashi; Kunihiro Iwata; Laurie Fajardo; Edwin vanBeek; Yutaka Sato; Tomonori Yamada; Kenichi Nagasawa; Noriyuki Shuke; Tamio Aburano
Journal of Magnetic Resonance Imaging, 22, 3, 341, 346, Wiley, 16 Aug. 2005, [Peer-reviewed]
Scientific journal, Abstract

Purpose

To clarify the influences of age and gender on normal fatty replacement of the thymus in childhood, adolescence, and early adulthood using chemical‐shift MRI.

Materials and Methods

A total of 95 normal subjects (52 males and 43 females, mean age = 15.6 years, range = 7–25 years) who underwent chemical‐shift MRI of the thymus were assessed prospectively. Signal intensity loss (SIL) of the thymus was determined by dividing the thymus/muscle ratio on the opposed‐phase image by that on the in‐phase image. We evaluated SIL for its correlation with age and gender, and assessed SIL of the thymus with uncommon morphological features.

Results

A significant correlation was found between SIL and age (r = 0.750, P < 0.001). There was no significant difference in SIL between the genders. No significant SIL was identified in any of the subjects aged 10 years or less. However, significant SIL was found in 70.8% of those aged 11–20 years, 100% of those aged 21 years or more, and 46.2% of subjects with uncommon morphological features of the thymus.

Conclusion

Chemical‐shift MRI can depict physiologic fatty infiltration within the normal thymus in subjects over 11 years of age. It is crucial to correlate these normal age‐related findings with clinical cases in order to avoid misinterpretation. J. Magn. Reson. Imaging 2005. © 2005 Wiley‐Liss, Inc.

Naturally Formed Coronary Arterial Thrombus Detected by In-111 Oxine Platelet Imaging
Chunlei Zhao; Noriyuki Shuke; Atsutaka Okizaki; Wakako Yamamoto; Junichi Sato; Kunihiro Iwata; Takayasu Kanno; Naoyuki Hasebe; Kenjiro Kikuchi; Tamio Aburano
Clinical Nuclear Medicine, 30, 7, 492, 495, Ovid Technologies (Wolters Kluwer Health), Jul. 2005, [Peer-reviewed]
Scientific journal

Characterization of the Normal and Hyperplastic Thymus on Chemical-Shift MR Imaging
Koji Takahashi; Tsutomu Inaoka; Noboru Murakami; Hatsune Hirota; Kunihiro Iwata; Kenichi Nagasawa; Tomonori Yamada; Masayuki Mineta; Tamio Aburano
American Journal of Roentgenology, 180, 5, 1265, 1269, American Roentgen Ray Society, May 2003, [Peer-reviewed]
Scientific journal

Detectability of liver metastases: comparison between Gd-EOB-DTPA-enhanced MRI and contrast-enhanced multi-detector CT
K. Iwata; T. Moriya; T. Tanikawa; K. Ogasawara, Mar. 2015, [Lead author]
English, Summary international conference

Cost-effectiveness analysis of the MRI with hepatocyte-specific contrast agent Gd-EOB-DTPA for the detection of metastatic liver tumor
K. Iwata; N. Murakami; K. Ogasawara, Mar. 2012, [Lead author]
English, Summary international conference

Cost-effectiveness analysis of the hepatocyte-specific MRI contrast agent Gd-EOB-DTPA in the patients with chronic hepatitis C
K. Iwata, K. Ogasawara, Mar. 2011, [Lead author]
English, Summary international conference

心筋血流MRIと心筋血流SPECTの冠動脈病変に対する診断能の比較と費用対効果
岩田 邦弘
第29回医療情報学連合大会, Nov. 2009, Japanese, Nominated symposium

Apr. 2026 - Present
日本医療情報学会

Jul. 2013 - Present
日本磁気共鳴医学会

Jan. 2011 - Present
欧州放射線学会

Jun. 1990 - Present
日本放射線技術学会

Feb. 2017
日本臨床疫学会

乳癌スクリーニングのためのAbbreviated MRIの財政影響分析と適正な検査費用の推定
科学研究費助成事業
01 Apr. 2026 - 31 Mar. 2027
岩田 邦弘
日本学術振興会, 奨励研究, 旭川医科大学, 26H00328