Motonori Nagata

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

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Publications (34)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: PURPOSE CT assessment of myocardial delayed enhancement (DE) is feasible but is not widely used due to relatively poor contrast-to-noise ratio (CNR) and artifacts associated with half scan reconstruction. Targeted spatial frequency filtration (TSFF) developed for dynamic myocardial perfusion imaging is a hybrid algorithm of half and full scan reconstruction that can achieve both high temporal resolution and improved stability of CT Hounsfield unit of the myocardium. The purpose of this study was to evaluate the feasibility and image quality of CTDE using TSFF in comparison with conventional half scan (CHS) reconstruction. METHOD AND MATERIALS Forty patients with suspected CAD underwent CTDE 7 minutes after administration of 120ml of contrast medium using dual-source CT. Images were reconstructed with TSFF and CHS. Two blinded readers independently determined the presence and size of DE. Signal-to-noise ratio (SNR) and CNR of DE lesions were also determined. Image artifact was assessed by a three-point scale (3=minimal, 2=not interfering with interpretation, and 1=substantial). The presence of DE was compared between CT and CMR in 12 patients. RESULTS TSFF demonstrated significantly reduced artifact on CTDE images compared with CHS (2.4±0.7 vs 3.0±0.0, P<0.01). In addition, inter-observer reproducibility of infarct size measurement was markedly improved by using TSFF instead of CHS (Intraclass Correlation Coefficient: 0.86 vs 0.50). The SNR and CNR of the DE lesions were 11.3±4.2 and 4.5±1.6 by TSFF, being significantly higher than those by CHS (7.9±2.9 and 3.3±1.8, P<0.01 for both). When CTDE was compared with delayed enhanced CMR, the kappa values for rater A and B in detecting DE segments were 0.81 and 0.85 by TSFF and 0.60 and 0.74 by CHS. CONCLUSION TSFF algorithm is highly effective in reducing artifacts on myocardial CTDE images and considerably improves inter-observer reproducibility of infarct sizing. Myocardial CTDE using TSFF allows for accurate infarct detection and reproducible infarct sizing in patients with known or suspected myocardial infarction. CLINICAL RELEVANCE/APPLICATION Myocardial CT delayed enhancement using TSFF algorithm markedly improves infarct detection and sizing, and is recommended for comprehensive assessment of CAD and myocardial infarction.
    Radiological Society of North America 2013 Scientific Assembly and Annual Meeting; 12/2013
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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: PURPOSE Identification of significant coronary artery stenoses on whole-heart coronary magnetic resonance angiography (MRA) is observer dependent. The purpose of this study was to develop a computer-aided diagnosis (CAD) scheme for detection of coronary artery stenoses on MRA images. METHOD AND MATERIALS Our database consisted of whole-heart coronary MRA images acquired with 32-channel cardiac coils in 30 patients (17 patients with 1.5 T and 13 patients with 3.0 T MR systems). All patients underwent X-ray coronary angiography and significant stenoses with luminal diameter reduction of >=50% were observed in 88 vessels. In our CAD scheme, coronary arteries were enhanced by a 3-D top-hat transformation and were then segmented by a region-growing technique. Based on the curvatures and the lengths from beginning and bifurcations, the segmented arteries were classified according to the American Heart Association (AHA) classifications. The signal intensity at each voxel of centerline of the segmented artery was defined by the maximum signal intensity within a circle with a radius of 3 voxels centered at the voxel in the original MRA image. While tracing the centerline, the voxel with which the signal intensity showed rapid reduction was finally detected as arterial stenosis. Threshold levels for this detection were selected empirically at each AHA classification by taking into account the variations in the signal intensities for normal coronary artery. RESULTS With our CAD scheme, RCA, LMT and LAD were correctly identified and segmented in all subjects. Segmentation of LCX was more difficult due to reduced signal to noise ratios of MRA in LCX territories. A sensitivity of artery stenoses for 1.5 T MRA was 83.9% (47/56) with 1.06 false positives (FPs) per image, whereas that for 3.0 T MRA was 81.3% (26/32) with 1.0 FPs per image. The sensitivity and the FPs per image were also 88.5% (23/26) and 0.33 for RCA, 100% (4/4) and 0.07 for LMT, 85.3% (29/34) and 0.13 for LAD, and 70.8% (17/24) and 0.5 for LCX, respectively. CONCLUSION Our CAD scheme achieved high sensitivities and low FPs for both 1.5 T MRA and 3.0 T MRA, and would have a great potential in assisting radiologists to identify coronary artery stenoses. CLINICAL RELEVANCE/APPLICATION Our CAD scheme would be useful in assisting radiologists for identifying coronary artery stenoses on whole-heart coronary MRA and for reducing the interpretation time.
    Radiological Society of North America 2012 Scientific Assembly and Annual Meeting; 11/2012
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    ABSTRACT: PURPOSE In spite of the advancement of multi-detector row computed tomography (MDCT) technology, non-invasive detection of Adamkiewicz artery using MDCT is still very challenging especially in patients with aortic diseases. The purpose of this study was to investigate if model based iterative reconstruction (MBIR) can improve MDCT assessment of the Adamkiewicz artery by comparing with adaptive statistical iterative reconstruction (ASIR) and filtered back projection (FBP). METHOD AND MATERIALS This study was performed in thirty-three patients who underwent contrast enhanced 64-slice MDCT for the assessment of aortic aneurysm or dissection. The helical data were reconstructed using FBP, ASIR and MBIR (Veo). Signal-to-noise ratio (SNR) of the aorta and contrast-to-noise (CNR) of the anterior spinal artery relative to the spinal cord were measured on multiplanar reformation images. Visualization of the Adamkiewicz artery and its continuity with the intercostal or lumbar artery were evaluated by consensus of two radiologists using a 4 point scale (1: not visible; 2: visible but branching level is unknown, 3: visible with continuous delineation from the intercostal artery except at the intervertebral foramen, 4: visible and full length of the arterial course is traceable). RESULTS MBIR showed significantly improved SNR of the aorta (33.7±5.6) and CNR of the anterior spinal artery (4.1±1.7) in comparison with those by ASIR (19.9±5.0 and 2.8±1.0) and FBP (14.6±3.2 and 2.6±0.9) (p<0.001 for all comparisons). The visualization score of the Adamkiewicz artery was also significantly improved by using MBIR (3.0±1.0) as compared with those by ASIR (2.4±1.2, p=0.001) and FBP (2.3±1.2, p<0.001). As a result, the level and the side from which the Adamkiewicz artery originated was identified in 85% (28/33) of the patients by using MBIR compared with 52%(17/33) and 39%(13/33) of the patients, respectively, by using ASIR and FBP. CONCLUSION The MBIR algorithm improved the MDCT visualization of the Adamkiewicz artery when compared with ASIR and FBP. This reconstruction method may therefore be helpful in planning surgical or endovascular treatment of aortic diseases. CLINICAL RELEVANCE/APPLICATION MBIR dramatically improved the detection rate of the branching level of Adamkiewicz artery in patients with aortic aneurysm or dissection.
    Radiological Society of North America 2012 Scientific Assembly and Annual Meeting; 11/2012
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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
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    ABSTRACT: PURPOSE The purpose of this study is to determine the effect of raw-data-based iterative reconstruction on signal, noise, and image quality of cardiac computed tomography. METHOD AND MATERIALS We evaluated 20 consecutive patients (M:F=14:6, mean age 72±10 years) who underwent clinically indicated CTA using 64-MDCT scanner (SOMATOM Definition AS+, Siemens, Germany). Images were reconstructed using filtered back projection (FBP) and sinogram affirmed iterative reconstruction (SAFIRE) of different strength (1 to 5). The signal and noise were measured in the aortic root and left main artery and right coronary artery. Image sharpness of coronary arteries was assessed by comparing with FBP images (1=worse, 2=slightly worse, 3=comparable to FBP, 4=slightly better, 5=better). Presence of seemingly artificial texture which is caused by the process of removing image noise was evaluated by two blinded readers using 4-point scale (1=not noticeable, 2=mild, 3=moderate, 4=unacceptable). RESULTS In comparison with FBP, the use of SAFIRE strength 1, 2, 3, 4, and 5 resulted in reduced noise (-9±2%, -17±3%, -25±5%, -32±7%, and -39±8%, respectively; p<0.001) and increased contrast-to-noise in the coronary arteries (+8±2%, +18±7%, +28±9%, +40±14%, and +54±22%, respectively; p<0.001), while no differences were observed in aortic signal (487±76HU, 487±76HU, 487±76HU, 487±76HU, and 487±76HU, respectively; p=ns) and image sharpness of coronary arteries (3.00±0.00, 3.00±0.00, 3.00±0.00, 2.99±0.12 and 2.98±0.14, respectively, p=ns). Artificial texture increased as SAFIRE strength increased (1.1±0.2, 1.3±0.5, 2.2±0.7, 3.1±0.7, and 3.6±0.5, respectively; p<0.001). However, the artificial texture did not compromise image interpretation as far as SAFIRE strength 3 or less is used for reconstruction. CONCLUSION Raw-data-based iterative reconstruction resulted in noise reduction without degradation of image sharpness. For cardiac computed tomography, SAFIRE of strength 3 provided the best image quality offering 25% less noise with limited artificial texture. CLINICAL RELEVANCE/APPLICATION Raw-data-based iterative reconstruction significantly reduces the image noise without compromising the image sharpness and texture of coronary CT angiography and will help to reduce radiation exposure
    Radiological Society of North America 2011 Scientific Assembly and Annual Meeting; 12/2011
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    ABSTRACT: PURPOSE/AIM 1. To understand why accurate quantification of myocardial blood flow (MBF) and perfusion reserve (MPR) is important in therapeutic decision making in patients with coronary artery disease (CAD). 2. To explain existing and new techniques and modeling for quantitative analysis of myocardial perfusion MRI and their benefits and pitfalls. CONTENT ORGANIZATION 1. Importance of objective assessment of MBF and MPR in patients with CAD. 2. Property of gadolinium contrast medium as a perfusion tracer. 3. Principles of quantitative analysis of MBF:(a) deconvolution methods, (b) compartment model approaches. 4. Pitfall of MBF quantification: (a) linearity of arterial input and myocardial output functions, (b) mathematical modeling and assumptions. 5. Clinical applications: (a) detection of CAD and subclinical disease, (b) indication of revascularization. SUMMARY Quantitative analysis of myocardial perfusion MRI allows for the absolute quantification of MBF by employing pharmacokinetic modeling. With this exhibit, the viewers will understand (1) principles of MBF quantification with pharmacokinetics of gadolinium contrast medium, (2) advantages and pitfalls in quantitative analysis of myocardial perfusion MRI, and (3) importance of accurate quantification of MBF and MPR in managing patients with CAD.
    Radiological Society of North America 2011 Scientific Assembly and Annual Meeting; 12/2011
  • 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: PURPOSE Coronary endothelial dysfunction can provide detection of early state of atherosclerosis and has been assessed with acetylcholine test during coronary angiography or PET measurements of myocardial blood flow (MBF) at rest and during cold pressor test (CPT). The purposes of this study were to evaluate the feasibility and reproducibility of noninvasive MR measurement of endothelium-dependent blood flow increase during CPT in the coronary sinus by using 3T MR imager, and to determine if MR CPT test can detect altered coronary endothelial function in young smokers. METHOD AND MATERIALS Ten control subjects (age: 28±5years) and age-matched 10 smokers (smoking duration ≥5 years, age: 29±4 years) without cardiovascular risk factors were studied with a 3T MR imager and 32 channel coils. Breath hold phase contrast cine MR images of coronary sinus were obtained at rest and during CPT by immersing the foot in ice water (TR/TE = 7.3/4.4 msec, Venc = ±50 cm/sec). LV mass was determined on short axis cine MRI. MBF was calculated as coronary sinus blood flow divided by LV myocardial mass. To evaluate inter-study, intra- and inter-observer reproducibilities, rest and CPT studies were repeated by two independent operators and were analyzed by two independent observers. RESULTS In control subjects, MBF was 0.96±0.28 ml/min/g in the resting state and increased to 1.28±0.35 ml/min/g during CPT (p=0.038), with an averaged increase of 34±11%. Inter-operator, intra- and inter-observer variability for measuring the increase in MBF was low, with a mean difference of -3.0% (95% limit of agreement; -16.1 to 10.1%), -0.3% (-9.7 to 9.1%), and -2.8% (-12.1 to 6.6%), respectively. In smokers, rest MBF (0.85±0.28 ml/min/g) was not significantly different from that in control subjects. However, the average increase in MBF was significantly reduced in smokers in compared with control subjects (0±27% vs 34±11%, p=0.003). CONCLUSION MBF response to CPT can be quantified by using 3T phase contrast cine MRI with higher reproducibilities in comparison to those reported in previous studies using PET. Impaired coronary endothelial function in young smokers was clearly demonstrated with a MR CPT method. CLINICAL RELEVANCE/APPLICATION CPT test using 3T MRI is a feasible and reproducible method for the non-invasive assessment of coronary endothelial function, and may provide an early detection of diffuse coronary atherosclerosis.
    Radiological Society of North America 2010 Scientific Assembly and Annual Meeting; 11/2010
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    ABSTRACT: PURPOSE Comprehensive cardiac MR (CMR) study at 3T may offer accurate detection of myocardial ischemia and infarction as well as delineation of luminal narrowing in the coronary artery. The purpose of this study was to evaluate the feasibility and diagnostic performance of 3T CMR study including stress and rest myocardial perfusion MRI, late gadolinium enhanced MRI (LGE) and whole-heart coronary MR angiography (CMRA) for the detection of significant coronary artery disease (CAD). METHOD AND MATERIALS Fifty patients (50±9 years old, 38 men) with suspected CAD who were scheduled for X-ray coronary angiography underwent CMR study by using a 3T MRI with 32 channel cardiac coils. Stress and rest perfusion MR images are acquired with a k-t-SENSE accelerated TFE sequence with B1-insensitive saturation pulse. After acquiring LGE MRI, free-breathing CMRA was obtained by employing a navigator-echo gated 3D TFE sequence with T2 preparation, SPIR fat saturation and SENSE factor of 4. Two observers qualitatively determined presence of myocardial ischemia and luminal narrowing in the coronary arteries on CMR. Significant coronary arterial stenosis was defined as a reduction in luminal diameter of ≥50% on X-ray coronary angiography. RESULTS CMR study including CMRA was successfully completed in all patients with an averaged total study time of 67±10 minutes. LGE was observed in 23 (46%) patients. On a patient based analysis, sensitivity, specificity, positive and negative predictive values (PPV and NPV) of stress perfusion MRI for predicting CAD on X-ray angiography were 91% (21/23), 89% (24/27), 88% (21/24) and 92% (24/26). These values by CMRA were 87% (20/23), 93% (25/27), 91% (20/22), 89% (25/28). Combined stress perfusion MRI and CMRA study demonstrated sensitivity of 96% (22/23), specificity of 85% (23/27), PPV of 85% (22/26) and NPV of 96% (23/24). CONCLUSION The results in current study demonstrated that the comprehensive 3T CMR study has high success rate in patients with suspected CAD and allows for noninvasive assessments of myocardial ischemia and luminal narrowing in the coronary arteries. High sensitivity (96%) and high NPV (96%) indicate that 3T comprehensive CMR study can accurately rule out CAD. CLINICAL RELEVANCE/APPLICATION 3T comprehensive CMR can play a pivotal role in managing patients with suspected CAD since this approach permits assessment of myocardial ischemia in addition to reliable detection of significant CAD.
    Radiological Society of North America 2010 Scientific Assembly and Annual Meeting; 11/2010