Motonori Nagata

Mie University, Tsu-shi, Mie-ken, Japan

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Publications (21)85.13 Total impact

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    ABSTRACT: Background Clinical utility of myocardial delayed enhancement CT is currently limited due to relatively poor contrast-to-noise ratio (CNR) and artifacts. Targeted spatial frequency filtration (TSFF) is a hybrid algorithm of half and full scan reconstruction that can achieve both high temporal resolution and improved stability of myocardial signal. Objective The purpose of this study was to evaluate image quality of delayed enhancement CT using TSFF with image averaging and its reproducibility in infarct assessment in comparison with conventional half scan reconstruction (HALF). Methods Forty patients with suspected coronary artery disease underwent delayed enhancement CT with HALF and TSFF using dual-source CT. Two blinded readers independently determined the presence and size of delayed enhancement. Image quality, signal-to-noise ratio (SNR) and CNR were assessed. The presence of delayed enhancement on CT was compared with MRI in 12 patients. Results TSFF with averaging of 4 image stacks acquired during one breath-hold demonstrated significantly better image quality compared with HALF. Good LV lumen-myocardium contrast was consistently achieved with TSFF in patients who received iodine dose of >600mgI/kg. The SNR and CNR were 11.3±4.2 and 4.5±1.6 by TSFF, being significantly higher than those by HALF (7.9±2.9 and 3.3±1.8, P<0.01 for both). Inter-observer reproducibility of infarct sizing was markedly improved by using TSFF instead of HALF (ICC: 0.86 vs 0.50). Agreement with MRI by kappa statistics was 0.85 with TSFF and 0.74 with HALF. Conclusions TSFF with image averaging can significantly improve image quality of delayed enhancement CT and considerably enhances inter-observer reproducibility of infarct sizing.
    Journal of Cardiovascular Computed Tomography. 01/2014;
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    ABSTRACT: Purpose To develop a method to determine significant stenosis at whole-heart coronary magnetic resonance (MR) angiography and to evaluate the accuracy and reproducibility of this approach. Materials and Methods The institutional review board approved the study, and all participants provided written informed consent. Sixty-two patients who were suspected of having coronary artery disease (CAD) and were scheduled for conventional coronary angiography were included. Coronary MR angiography was performed by using a 1.5-T imager with 32-channel coils. Luminal narrowing was evaluated with quantitative analysis (QA) of coronary MR angiograms on the basis of the signal intensity profile along the vessel. Percentage stenosis with QA of coronary MR angiograms was calculated as [1 - (SImin/SIref)] × 100, where SImin is minimal signal intensity and SIref is corresponding reference signal intensity. Diagnostic performance of QA of coronary MR angiograms for predicting at least a 50% reduction in diameter was evaluated by using quantitative coronary angiography (QCA), with conventional angiography findings serving as the reference standard. Receiver operating characteristic (ROC) analysis, Spearman rank correlation, Bland-Altman analysis, and Cohen κ analysis were used. Results The areas under the ROC curve in a segment-based analysis for detecting significant CAD were 0.96 (95% confidence interval [CI]: 0.94, 0.98) with QA of coronary MR angiograms and 0.93 (95% CI: 0.88, 0.98) with visual assessment. The correlation coefficients between percentage stenosis with QA of coronary MR angiograms and percentage stenosis with QCA were 0.84 (P < .001), 0.80 (P < .001), and 0.66 (P < .001) in the patient-, vessel-, and segment-based analyses, respectively. Conclusion QA of coronary MR angiograms with use of a signal intensity profile along the vessel permits detection of CAD. This method had a diagnostic performance approximately equal to that of visual analysis of coronary MR angiograms with high inter- and intraobserver reliability, allowing for more objective interpretation of coronary MR angiography findings. © RSNA, 2013 Online supplemental material is available for this article.
    Radiology 12/2013; · 6.34 Impact Factor
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    ABSTRACT: To determine the effect of reduced 80-kV tube voltage with increased 370-mAs tube current on radiation dose, image quality and estimated myocardial blood flow (MBF) of dynamic CT stress myocardial perfusion imaging (CTP) in patients with a normal body mass index (BMI) compared with a 100-kV and 300-mAs protocol. Thirty patients with a normal BMI (<25 kg/m(2)) with known or suspected coronary artery disease underwent adenosine-stress dual-source dynamic CTP. Patients were randomised to 80-kV/370-mAs (n = 15) or 100-kV/300-mAs (n = 15) imaging. Maximal enhancement and noise of the left ventricular (LV) cavity, contrast-to-noise ratio (CNR) and MBF of the two groups were compared. Imaging with 80-kV/370-mAs instead of 100-kV/300-mAs was associated with 40 % lower radiation dose (mean dose-length product, 359 ± 66 vs 628 ± 112 mGy[Symbol: see text]cm; P < 0.001 ) with no significant difference in CNR (34.5 ± 13.4 vs 33.5 ± 10.4; P = 0.81) or MBF in non-ischaemic myocardium (0.95 ± 0.20 vs 0.99 ± 0.25 ml/min/g; P = 0.66). Studies obtained using 80-kV/370-mAs were associated with 30.9 % higher maximal enhancement (804 ± 204 vs 614 ± 115 HU; P < 0.005), and 31.2 % greater noise (22.7 ± 3.5 vs 17.4 ± 2.6; P < 0.001). Dynamic CTP using 80-kV/370-mA instead of 100-kV/300-mAs allowed 40 % dose reduction without compromising image quality or MBF. Tube voltage of 80-kV should be considered for individuals with a normal BMI. • CT stress perfusion imaging (CTP) is increasingly used to assess myocardial function. • Dynamic CTP is feasible at 80-kV in patients with normal BMI. • An 80-kV/370-mAs protocol allows 40 % dose reduction compared with 100-kV/300-mAs. • Contrast-to-noise ratio and myocardial blood flow of the two protocols were comparable.
    European Radiology 11/2013; · 4.34 Impact Factor
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    ABSTRACT: Purpose:To determine if model-based iterative reconstruction (MBIR) can improve visualization of the Adamkiewicz artery on multi-detector row computed tomographic (CT) images compared with adaptive statistical iterative reconstruction (ASIR) and filtered back projection (FBP).Materials and Methods:This retrospective study was approved by the institutional review board, and written informed consent for the CT examination was obtained. Thirty-three patients underwent contrast material-enhanced 64-section multi-detector row CT for assessment of aortic aneurysm or dissection. Helical data were reconstructed by using FBP, ASIR, and MBIR. The signal-to-noise ratio of the aorta and contrast-to-noise ratio of the anterior spinal artery relative to the spinal cord were measured on multiplanar reformatted images. Visualization of the Adamkiewicz artery and its continuity with the intercostal or lumbar artery were evaluated by using a four-point scale. All image analyses were performed by two blinded, independent observers. The one-way analysis of variance and the Wilcoxon signed-rank test were used for statistical analysis.Results:MBIR showed significantly better signal-to-noise and contrast-to-noise ratios than did ASIR and FBP (P < .05 for all comparisons) with good interobserver agreement (intraclass correlation coefficient of 0.93 for signal-to-noise ratio and 0.75 for contrast-to-noise ratio). The visualization score of the Adamkiewicz artery was also significantly better when MBIR was used (3.4 ± 0.8 and 3.6 ± 0.7 for observers A and B, respectively) than when ASIR (2.7 ± 1.1 and 3.0 ± 1.0, respectively) or FBP (2.5 ± 1.2 and 3.1 ± 0.9, respectively) was used.Conclusion:Use of the MBIR algorithm led to improved multi-detector row CT visualization of the Adamkiewicz artery when compared with the use of ASIR and FBP.© RSNA, 2013.
    Radiology 08/2013; · 6.34 Impact Factor
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    ABSTRACT: To determine the diagnostic performance and reproducibility of strain assessment with displacement encoding with stimulated echoes (DENSE) cardiovascular magnetic resonance (CMR) in identifying contractile abnormalities in myocardial segments with late gadolinium enhancement (LGE). DENSE CMR was obtained on short-axis planes of the left ventricle (LV) in 24 patients with suspected coronary artery disease. e1 and e2 strains of LV wall were quantified. Cine MRI was acquired to determine percent systolic wall thickening (%SWT), followed by (LGE) CMR. The diagnostic performance of e1, e2 and %SWT for predicting the presence of LGE was evaluated by receiver operating characteristics (ROC) analysis. Myocardial scar on LGE CMR was observed in 91 (24 %) of 384 segments. The area under ROC curve for predicting the segments with LGE was 0.874 by e1, 0.916 by e2 and 0.828 by %SWT (p = 0.001 between e2 and %SWT). Excellent inter-observer reproducibility was found for strain [Intraclass correlation coefficient (ICC) = 0.962 for e1, 0.955 for e2] as compared with %SWT (ICC = 0.790). DENSE CMR can be performed as a part of routine CMR study and allows for quantification of myocardial strain with high inter-observer reproducibility. Myocardial strain, especially e2 is useful in detecting altered abnormal systolic contraction in the segments with myocardial scar.
    The international journal of cardiovascular imaging 08/2013; · 2.15 Impact Factor
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    ABSTRACT: Recent studies have demonstrated that chronic obstructive pulmonary disease (COPD) is associated with cardiovascular disease (CVD). However, the association between COPD and coronary microcirculatory dysfunction is unknown. We sought to assess whether myocardial perfusion reserve (MPR) is impaired in patients with COPD, even in the absence of regional myocardial ischaemia or infarction, by using quantitative myocardial perfusion cardiovascular magnetic resonance (CMR). We recruited 60 subjects with a normal CMR study: 20 individuals with mild-to-moderate COPD; 20 age-matched control smokers, and 20 age-matched control-never smokers. Individuals with established CVD and diabetes mellitus were excluded. Stress-rest myocardial blood flow (MBF) was quantified in 16 myocardial segments by using a Patlak plot method. There were no significant differences in the rest MBF among COPD patients, control smokers, and control-never smokers. However, the mean MPR was significantly lower in COPD patients than in control smokers and control-never smokers (1.76 ± 0.58, 2.57 ± 1.30, and 3.56 ± 1.27, respectively). Univariate associations with MPR were smoking (r = -0.44, P < 0.001), forced expiratory volume in 1 s (FEV1) (r = 0.30, P = 0.02), haematocrit (r = 0.25, P = 0.04), and C-reactive protein (CRP; r = -0.46, P < 0.001). On multivariable analysis, the levels of CRP, FEV1, and renal dysfunction were independent predictors of the impaired MPR. The presence of COPD was associated with a five-fold increased risk of MPR <1.5 (95% confidence interval, 1.4-19.0; P = 0.01). The MPR, which was independently associated with systemic inflammation and airflow limitation, was impaired in patients with COPD. The presence of COPD was a powerful predictor of impaired MPR in patients without regional myocardial ischaemia or infarction.
    European heart journal cardiovascular Imaging. 07/2013;
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    Journal of Cardiovascular Magnetic Resonance 01/2013; 15(1). · 4.44 Impact Factor
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    ABSTRACT: Purpose The purposes of this study were to evaluate the reproducibility for measuring the cold pressor test (CPT)-induced myocardial blood flow (MBF) alteration using phase-contrast (PC) cine MRI, and to determine if this approach could detect altered MBF response to CPT in smokers. Materials and methods After obtaining informed consent, ten healthy male non-smokers (mean age: 28 ± 5 years) and ten age-matched male smokers (smoking duration ≥ 5 years, mean age: 28 ± 3 years) were examined in this institutional review board approved study. Breath-hold PC cine MR images of the coronary sinus were obtained 3T MR imager with 32 channel coils at rest and during a CPT performed after immersing one foot in ice water. MBF was calculated as coronary sinus flow divided by the left ventricular (LV) mass which was given as a total LV myocardial volume measured on cine MRI multiplied by the specific gravity (1.05 g/mL). Results In non-smokers, MBF was 0.86 ± 0.25 mL/min/g at rest, with a significant increase to 1.20 ± 0.36 mL/min/g seen during CPT (percentage change of MBF (∆MBF (%)); 39.2 ± 14.4%, p < 0.001). Inter-study reproducibility for ∆MBF (%) measurements by different MR technologist was good, as indicated by the intraclass correlation coefficient of 0.93 and reproducibility coefficient of 10.5%. There was no significant difference between smokers and non-smokers for resting MBF (0.85 ± 0.32 mL/min/g, p = 0.91). However, ∆MBF (%) in smokers was significantly reduced (-4.0 ± 32.2% vs. 39.2 ± 14.4%, p = 0.011). Conclusion PC cine MRI can be used to reproducibly quantify MBF response to CPT and to detect impaired flow response in smokers. This MR approach may be useful for monitoring the sequential change of coronary blood flow in various potentially pathologic conditions and for investigating its relationship with cardiovascular risk.
    Magnetic Resonance Imaging 01/2013; · 2.06 Impact Factor
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    ABSTRACT: Background: The purpose of this study was to determine whether the presence of fatty liver is associated with an alteration in myocardial perfusion reserve (MPR). Methods and Results: A retrospective analysis of 65 asymptomatic subjects who underwent both plain abdominal computed tomography and cardiac magnetic resonance imaging (MRI), and who had normal left ventricular wall motion, no regional myocardial ischemia and no myocardial scar on MRI was performed. Stress and rest myocardial perfusion MRI were analyzed by Patlak plot method to quantify myocardial blood flow (MBF) and MPR in 16 myocardial segments. Fatty liver was detected in 18 (28%) of the 65 subjects. No significant difference was found in rest-MBF between subjects with and without fatty liver (1.2±0.75 vs. 1.1±0.67ml·min(-1)·g(-1), P=0.59). However, MPR was significantly lower in subjects with fatty liver than the non-fatty liver subjects (2.3±0.74 vs. 3.3±1.4, P<0.001). Subjects with fatty liver had a higher prevalence of MPR <2.5 (78% vs. 38%, P<0.005) and higher triglyceride levels (206±61 vs. 92±37mg/dl, P<0.001). Multivariate analysis revealed the presence of fatty liver as a significant predictor of reduced MPR with an odds ratio of 8.2 (P<0.01). Conclusions: Nonalcoholic fatty liver disease is related to reduced MPR, suggesting impaired coronary microcirculation.  (Circ J 2012; 76: 2234-2240).
    Circulation Journal 06/2012; 76(9):2234-40. · 3.58 Impact Factor
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    Journal of Cardiovascular Magnetic Resonance 02/2012; 14 Suppl 1:O88. · 4.44 Impact Factor
  • Motonori Nagata, Hajime Sakuma
    Nippon rinsho. Japanese journal of clinical medicine 09/2011; 69 Suppl 7:233-8.
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    ABSTRACT: For the absolute quantification of myocardial blood flow (MBF), Patlak plot-derived K1 need to be converted to MBF by using the relation between the extraction fraction of gadolinium contrast agent and MBF. This study was conducted to determine the relation between extraction fraction of Gd-DTPA and MBF in human heart at rest and during stress. Thirty-four patients (19 men, mean age of 66.5 ± 11.0 years) with normal coronary arteries and no myocardial infarction were retrospectively evaluated. First-pass myocardial perfusion MRI during adenosine triphosphate stress and at rest was performed using a dual bolus approach to correct for saturation of the blood signal. Myocardial K1 was quantified by Patlak plot method. Mean MBF was determined from coronary sinus flow measured by phase contrast cine MRI and left ventricle mass measured by cine MRI. The extraction fraction of Gd-DTPA was calculated as the K1 divided by the mean MBF. The extraction fraction of Gd-DTPA was 0.46 ± 0.22 at rest and 0.32 ± 0.13 during stress (P < 0.001). The relationship between extraction fraction (E) and MBF in human myocardium can be approximated as E = 1 - exp(-(0.14 × MBF + 0.56)/MBF). The current results indicate that MBF can be accurately quantified by Patlak plot method of first-pass myocardial perfusion MRI by performing a correction of extraction fraction.
    Magnetic Resonance in Medicine 04/2011; 66(5):1391-9. · 3.27 Impact Factor
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    ABSTRACT: To compare the imaging time and image quality obtained with whole-heart coronary magnetic resonance (MR) angiography performed with five- and 32-channel coils in healthy subjects and determine the accuracy of MR angiography performed with 32-channel coils in the detection of obstructive coronary artery disease (CAD). The institutional review board approved the study protocol, and all participants provided written informed consent. The authors studied 10 healthy subjects and 67 patients suspected of having CAD who were scheduled for coronary angiography. Unenhanced 1.5-T coronary MR angiography was performed with five- and 32-channel coils in healthy subjects and with 32-channel coils in patients. Clinically significant CAD was defined as a diameter reduction of at least 50% at coronary angiography. The sensitivity and specificity of coronary MR angiography were calculated. The mean imaging time was substantially reduced from 12.3 minutes ± 4.2 (standard deviation) with five-channel coils to 6.3 minutes ± 2.2 with 32-channel coils, with equivalent image quality scores. Acquisition of MR angiograms was completed in all 67 patients, with a mean imaging time of 6.2 minutes ± 2.8. The prevalence of CAD in the study population was 58% (39 of the 67 patients). The areas under the receiver operating characteristic curves as determined at vessel- and patient-based analyses were 0.91 and 0.90, respectively; the sensitivity and specificity at vessel-based analysis were 86% and 93%, respectively. Whole-heart coronary MR angiography performed at 1.5 T with 32-channel coils permits noninvasive detection of CAD with substantially reduced imaging time. This noninvasive approach can be an alternative to multidetector computed tomographic coronary angiography for ruling out obstructive CAD in patients who have a contraindication to contrast material and in young subjects who are at higher risk from ionizing radiation. Supplemental material: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11101323/-/DC1.
    Radiology 03/2011; 259(2):384-92. · 6.34 Impact Factor
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    ABSTRACT: Quantitative analysis of myocardial perfusion MRI can provide noninvasive assessments of myocardial perfusion reserve (MPR), which is associated with endothelial function. Endothelial function is influenced by various factors, including hypertension, diabetes, dyslipidemia, renal dysfunction and anemia. The purpose of this study was to evaluate which risk factor is the strongest effector of MPR in subjects without regional myocardial ischemia. We studied 110 patients (66 years ±10, male 68%, hypertension 76%, diabetes mellitus (DM) 40% and dyslipidemia 65%) without regional myocardial ischemia. Adenosine triphosphate (ATP) stress and rest first-pass perfusion magnetic resonance (MR) images were acquired with a 1.5-T MR system, and MPR was calculated as the ratio of stress to rest myocardial blood flow (MBF). Average rest MBF in 110 patients was 1.07±0.62 ml min⁻¹ g⁻¹, whereas stress MBF was 3.15±1.93 ml min⁻¹ g⁻¹ and the MPR was 3.33±1.82. Rest MBF correlated significantly with hematocrit, whereas stress MBF showed a strong correlation with estimated glomerular filtration rate (e-GFR). MPR was associated with hypertension, age, e-GFR, hematocrit and left ventricular mass index (LVMI). In multiple regression analysis, hypertension (P=0.003, β=-0.274) showed the strongest correlation with MPR among other risk factors, such as diabetes (P=ns), dyslipidemia (P=ns), e-GFR (P=ns), LVMI (P=0.007, β=-0.248) and hematocrit (P=ns) after adjusting age and gender. Hypertension is the most important effector of MPR in subjects without myocardial ischemia.
    Hypertension Research 11/2010; 33(11):1144-9. · 2.79 Impact Factor
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    ABSTRACT: This national multicenter study determined the diagnostic performance of 1.5-T whole-heart coronary magnetic resonance angiography (MRA) in patients with suspected coronary artery disease (CAD). Whole-heart coronary MRA using steady-state free precession allows noninvasive detection of CAD without the administration of contrast medium. However, the accuracy of this approach has not been determined in a multicenter trial. Using a 1.5-T magnetic resonance imaging unit, free-breathing steady-state free precession whole-heart coronary MRA images were acquired for 138 patients with suspected CAD at 7 hospitals. The accuracy of MRA for detecting a ≥ 50% reduction in diameter was determined using X-ray coronary angiography as the reference method. Acquisition of whole-heart coronary MRA images was performed in 127 (92%) of 138 patients with an average imaging time of 9.5 ± 3.5 min. The areas under the receiver-operator characteristic curve from MRA images according to vessel- and patient-based analyses were 0.91 (95% confidence interval [CI]: 0.87 to 0.95) and 0.87 (95% CI: 0.81 to 0.93), respectively. The sensitivity, specificity, positive and negative predictive values, and accuracy of MRA according to a patient-based analysis were 88% (49 of 56, 95% CI: 75% to 94%), 72% (51 of 71, 95% CI: 60% to 82%), 71% (49 of 69, 95% CI: 59% to 81%), 88% (51 of 58, 95% CI: 76% to 95%), and 79% (100 of 127, 95% CI: 72% to 86%), respectively. Non-contrast-enhanced whole-heart coronary MRA at 1.5-T can noninvasively detect significant CAD with high sensitivity and moderate specificity. A negative predictive value of 88% indicates that whole-heart coronary MRA can rule out CAD.
    Journal of the American College of Cardiology 09/2010; 56(12):983-91. · 14.09 Impact Factor
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    Journal of Cardiovascular Magnetic Resonance 01/2010; 12:1-1. · 4.44 Impact Factor
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    ABSTRACT: In experimental animal models and human autopsy studies, hemorrhagic infarction caused by microvascular injury has been detected after coronary reperfusion. The purpose of this study was to determine whether detection of myocardial edema with T2-weighted MRI is influenced by the presence of microvascular obstruction. Thirty-seven patients underwent black-blood fat-suppressed T2-weighted, rest perfusion, and late gadolinium-enhanced MRI 5.4 +/- 3.1 days after the onset of acute myocardial infarction. On T2-weighted MR images, the signal intensity in relation to that of remote myocardium was determined in the late gadolinium-enhanced and periinfarction areas. Segment-based analysis was performed to determine whether the presence of microvascular obstruction influences the detection of myocardial edema. The averaged signal intensity in the late gadolinium-enhanced area without microvascular obstruction was significantly higher than the signal intensity in remote normal myocardium (relative signal intensity, 1.83 +/- 0.50; p < 0.001). In contrast, the signal intensity in the microvascular obstruction area on T2-weighted images was not significantly different from the signal intensity in remote myocardium (relative signal intensity, 1.14 +/- 0.26). The percentages of late gadolinium-enhanced segments with high signal intensity on T2-weighted MR images were 95% (73/77) without microvascular obstruction and 30% (22/73) with microvascular obstruction. With T2-weighted MRI, infarction-associated edema can be reliably detected in infarct lesions without microvascular obstruction. Microvascular obstruction, however, does not necessarily exhibit high signal intensity on T2-weighted MRI. Careful attention is required in interpretation of cardiac MR images of patients who have experienced acute myocardial infarction and undergone percutaneous coronary intervention. The findings on T2-weighted MR images can be substantial underestimates of the extent of acute myocardial infarction.
    American Journal of Roentgenology 10/2009; 193(4):W321-6. · 2.90 Impact Factor
  • Journal of Cardiovascular Magnetic Resonance 01/2009; · 4.44 Impact Factor
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    ABSTRACT: The aim of this study was to determine the diagnostic performance of stress and rest perfusion magnetic resonance imaging (MRI) and late gadolinium-enhanced (LGE) MRI for identifying patients with obstructive coronary artery disease (CAD). A total of 50 patients with suspected CAD underwent stress-rest perfusion MRI, followed by LGE MRI with a 1.5-T system. Stress-rest perfusion MRI resulted in an area under the receiver-operating characteristic curve (AUC) of 0.92 for observer 1 and 0.84 for observer 2 with sensitivity and specificity of 89% (32/36) and 79% (11/14) by observer 1, 83% (30/36) and 71% (10/14) by observer 2, respectively, showing a moderate interobserver agreement (Cohen's kappa = 0.49). While combination of stress-rest perfusion and LGE MRI did not result in improved accuracy for the prediction of flow-limiting obstructive CAD (AUC 0.81 for observer 1 and 0.80 for observer 2), the sensitivity was increased to 92% in both observers with a substantial interobserver agreement (kappa = 0.70). Stress-rest myocardial perfusion MRI is an accurate diagnostic test for identifying patients with obstructive CAD.
    European Radiology 12/2008; 18(12):2808-16. · 4.34 Impact Factor
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    Journal of Cardiovascular Magnetic Resonance 01/2008; · 4.44 Impact Factor