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Piccini D.,Friedrich - Alexander - University, Erlangen - Nuremberg | Littmann A.,Siemens AG | Nielles-Vallespin S.,Cardiovascular MR unit | Zenge M.O.,Siemens AG
Magnetic Resonance in Medicine | Year: 2012

Free-breathing three-dimensional whole-heart coronary MRI is a noninvasive alternative to X-ray coronary angiography. However, the existing navigator-gated approaches do not meet the requirements of clinical practice, as they perform with suboptimal accuracy and require prolonged acquisition times. Self-navigated techniques, applied to bright-blood imaging sequences, promise to detect the position of the blood pool directly in the readouts acquired for imaging. Hence, the respiratory displacement of the heart can be calculated and used for motion correction with high accuracy and 100% scan efficiency. However, additional bright signal from the chest wall, spine, arms, and liver can render the isolation of the blood pool impossible. In this work, an innovative method based on a targeted combination of the output signals of an anterior phased-array surface coil is implemented to efficiently suppress such additional bright signal. Furthermore, an algorithm for the automatic segmentation of the blood pool is proposed. Robust self-navigation is achieved by cross-correlation. These improvements were integrated into a three-dimensional radial whole-heart coronary MRI sequence and were compared with navigator-gated imaging in vivo. Self-navigation was successful in all cases and the acquisition time was reduced up to 63%. Equivalent or slightly superior image quality, vessel length, and sharpness were achieved. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc. Copyright © 2011 Wiley Periodicals, Inc. Source

Torii R.,Imperial College London | Keegan J.,Cardiovascular MR unit | Wood N.B.,Imperial College London | Dowsey A.W.,Imperial College London | And 5 more authors.
Annals of Biomedical Engineering | Year: 2010

The aim of this study was to develop a fully subjectspecific model of the right coronary artery (RCA), including dynamic vessel motion, for computational analysis to assess the effects of cardiac-induced motion on hemodynamics and resulting wall shear stress (WSS). Vascular geometries were acquired in the right coronary artery (RCA) of a healthy volunteer using a navigator-gated interleaved spiral sequence at 14 time points during the cardiac cycle. A high temporal resolution velocity waveform was also acquired in the proximal region. Cardiac-induced dynamic vessel motion was calculated by interpolating the geometries with an active contour model and a computational fluid dynamic (CFD) simulation with fully subject-specific information was carried out using this model. The results showed the expected variation of vessel radius and curvature throughout the cardiac cycle, and also revealed that dynamic motion of the right coronary artery consequent to cardiac motion had significant effects on instantaneous WSS and oscillatory shear index. Subjectspecific MRI-based CFD is feasible and, if scan duration could be shortened, this method may have potential as a noninvasive tool to investigate the physiological and pathological role of hemodynamics in human coronary arteries. © 2010 Biomedical Engineering Society. Source

Canali E.,University of Rome La Sapienza | Masci P.,Cardiovascular MR unit | Masci P.,Cardiovascular Medicine Unit | Bogaert J.,University Hospitals Leuven | And 9 more authors.
European Heart Journal Cardiovascular Imaging | Year: 2012

Aims: There is conflicting evidence on the impact of gender on reperfusion after primary coronary angioplasty (PPCI), and on left ventricular (LV) remodelling (LVR). In a cohort of patients with reperfused ST elevation myocardial infarction (STEMI), gender-related differences on myocardial reperfusion, and sex-related differences on LVR were assessed by using a comprehensive cardiac magnetic resonance (CMR) approach. Methods and results: In four tertiary referral centres, 283 (238 males and 45 females) consecutive STEMI patients, treated with PPCI within 12 h from symptoms onset underwent CMR 3 ± 2 days after STEMI and at 4-month follow-up. By CMR, the area at risk, infarct size (IS), microvascular obstruction (MVO), and myocardial salvage index (MSI) were assessed. Women were older than men (P 0.014), more hypertensive (P < 0.001) and more frequently presented with pre-infarct angina (P 0.018). An MSI extent was significantly higher (P 0.013), IS was significantly smaller at both time points (acute P < 0.001, follow-up P < 0.001), and the MVO extent was significantly smaller (P < 0.001) in women. At multivariate analysis, Killip class and female sex were independently associated with a higher MSI (P 0.02, P 0.05, respectively). A similar incidence of LVR in both sexes was observed at follow-up (P 0.808). Conclusions: The better reperfusion pattern observed in women by CMR in our population of reperfused STEMI suggests sex-based differences exist. No gender differences were observed with respect to incidence of LV remodelling at the follow-up mainly occurring in the subset of patients with a larger IS. © The Author 2012. Source

Pennell D.J.,Cardiovascular MR unit | Porter J.B.,University College London | Cappellini M.D.,University of Milan | El-Beshlawy A.,Cairo University | And 12 more authors.
Blood | Year: 2010

Cardiac iron overload causes most deaths in β-thalassemia major. The efficacy of deferasirox in reducing or preventing cardiac iron overload was assessed in 192 patients with β-thalassemia in a 1-year prospective, multicenter study. The cardiac iron reduction arm (n = 114) included patients with magnetic resonance myocardial T2* from 5 to 20 ms (indicating cardiac siderosis), left ventricular ejection fraction (LVEF) of 56% or more, serum ferritin more than 2500 ng/mL, liver iron concentration more than 10 mg Fe/g dry weight, and more than 50 transfused blood units. The prevention arm (n = 78) included otherwise eligible patients whose myocardial T2* was 20 ms or more. The primary end point was the change in myocardial T2* at 1 year. In the cardiac iron reduction arm, the mean deferasirox dose was 32.6 mg/kg per day. Myocardial T2* (geometric mean ± coefficient of variation) improved from a baseline of 11.2 ms (± 40.5%) to 12.9 ms (± 49.5%) (+16%; P < .001). LVEF (mean ± SD) was unchanged: 67.4 (± 5.7%) to 67.0 (± 6.0%) (-0.3%; P = .53). In the prevention arm, baseline myocardial T2* was unchanged from baseline of 32.0 ms (± 25.6%) to 32.5 ms (± 25.1%) (±2%; P = .57) and LVEF increased from baseline 67.7 (± 4.7%) to 69.6 (± 4.5%) (+1.8%; P < .001). This prospective study shows that deferasirox is effective in removing and preventing myocardial iron accumulation. This study is registered at http:// clinicaltrials.gov as NCT00171821. © 2010 by The American Society of Hematology. Source

Yang G.,Cardiovascular MR unit | Yang G.,Imperial College London | Ye X.,University of Lincoln | Slabaugh G.,City University London | And 6 more authors.
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2016

Super-resolved image enhancement is of great importance in medical imaging. Conventional methods often require multiple low resolution (LR) images from different views of the same object or learning from large amount of training datasets to achieve success. However, in real clinical environments, these prerequisites are rarely fulfilled. In this paper, we present a self-learning based method to perform superresolution (SR) from a single LR input. The mappings between the given LR image and its downsampled versions are modeled using support vector regression on features extracted from sparse coded dictionaries, coupled with dual-tree complex wavelet transform based denoising. We demonstrate the efficacy of our method in application of cardiac MRI enhancement. Both quantitative and qualitative results show that our SR method is able to preserve fine textural details that can be corrupted by noise, and therefore can maintain crucial diagnostic information. © Springer International Publishing Switzerland 2016. Source

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