Showing papers by "Matthias Stuber published in 2019"

Time-Dependent Deep Image Prior for Dynamic MRI

Abstract: We propose a novel unsupervised deep-learning-based algorithm for dynamic magnetic resonance imaging (MRI) reconstruction. Dynamic MRI requires rapid data acquisition for the study of moving organs such as the heart. Existing reconstruction methods suffer from restrictions either in the model design or in the absence of ground-truth data, resulting in low image quality. We introduce a generalized version of the deep-image-prior approach, which optimizes the network weights to fit a sequence of sparsely acquired dynamic MRI measurements. Our method needs neither prior training nor additional data. In particular, for cardiac images, it does not require the marking of heartbeats or the reordering of spokes. The key ingredients of our method are threefold: 1) a fixed low-dimensional manifold that encodes the temporal variations of images; 2) a network that maps the manifold into a more expressive latent space; and 3) a convolutional neural network that generates a dynamic series of MRI images from the latent variables and that favors their consistency with the measurements in k-space. Our method outperforms the state-of-the-art methods quantitatively and qualitatively in both retrospective and real fetal cardiac datasets. To the best of our knowledge, this is the first unsupervised deep-learning-based method that can reconstruct the continuous variation of dynamic MRI sequences with high spatial resolution.

An automated approach to fully self-gated free-running cardiac and respiratory motion-resolved 5D whole-heart MRI.

Abstract: PURPOSE To develop a previously reported, electrocardiogram (ECG)-gated, motion-resolved 5D compressed sensing whole-heart sparse MRI methodology into an automated, optimized, and fully self-gated free-running framework in which external gating or triggering devices are no longer needed. METHODS Cardiac and respiratory self-gating signals were extracted from raw image data acquired in 12 healthy adult volunteers with a non-ECG-triggered 3D radial golden-angle 1.5 T balanced SSFP sequence. To extract cardiac self-gating signals, central k-space coefficient signal analysis (k0 modulation), as well as independent and principal component analyses were performed on selected k-space profiles. The procedure yielding triggers with the smallest deviation from those of the reference ECG was selected for the automated protocol. Thus, optimized cardiac and respiratory self-gating signals were used for binning in a compressed sensing reconstruction pipeline. Coronary vessel length and sharpness of the resultant 5D images were compared with image reconstructions obtained with ECG-gating. RESULTS Principal component analysis-derived cardiac self-gating triggers yielded a smaller deviation ( 17.4±6.1ms ) from the reference ECG counterparts than k0 modulation ( 26±7.5ms ) or independent component analysis ( 19.8±5.2ms ). Cardiac and respiratory motion-resolved 5D images were successfully reconstructed with the automated and fully self-gated approach. No significant difference was found for coronary vessel length and sharpness between images reconstructed with the fully self-gated and the ECG-gated approach (all P≥.06 ). CONCLUSION Motion-resolved 5D compressed sensing whole-heart sparse MRI has successfully been developed into an automated, optimized, and fully self-gated free-running framework in which external gating, triggering devices, or navigators are no longer mandatory. The resultant coronary MRA image quality was equivalent to that obtained with conventional ECG-gating.

Simultaneous Evaluation of Lung Anatomy and Ventilation Using 4D Respiratory-Motion-Resolved Ultrashort Echo Time Sparse MRI.

Abstract: BACKGROUND Computed tomography (CT) and spirometry are the current standard methods for assessing lung anatomy and pulmonary ventilation, respectively. However, CT provides limited ventilation information and spirometry only provides global measures of lung ventilation. Thus, a method that can enable simultaneous examination of lung anatomy and ventilation is of clinical interest. PURPOSE To develop and test a 4D respiratory-resolved sparse lung MRI (XD-UTE: eXtra-Dimensional Ultrashort TE imaging) approach for simultaneous evaluation of lung anatomy and pulmonary ventilation. STUDY TYPE Prospective. POPULATION In all, 23 subjects (11 volunteers and 12 patients, mean age = 63.6 ± 8.4). FIELD STRENGTH/SEQUENCE 3T MR; a prototype 3D golden-angle radial UTE sequence, a Cartesian breath-hold volumetric-interpolated examination (BH-VIBE) sequence. ASSESSMENT All subjects were scanned using the 3D golden-angle radial UTE sequence during normal breathing. Ten subjects underwent an additional scan during alternating normal and deep breathing. Respiratory-motion-resolved sparse reconstruction was performed for all the acquired data to generate dynamic normal-breathing or deep-breathing image series. For comparison, BH-VIBE was performed in 12 subjects. Lung images were visually scored by three experienced chest radiologists and were analyzed by two observers who segmented the left and right lung to derive ventilation parameters in comparison with spirometry. STATISTICAL TESTS Nonparametric paired two-tailed Wilcoxon signed-rank test; intraclass correlation coefficient, Pearson correlation coefficient. RESULTS XD-UTE achieved significantly improved image quality compared both with Cartesian BH-VIBE and radial reconstruction without motion compensation (P < 0.05). The global ventilation parameters (a sum of the left and right lung measures) were in good correlation with spirometry in the same subjects (correlation coefficient = 0.724). There were excellent correlations between the results obtained by two observers (intraclass correlation coefficient ranged from 0.8855-0.9995). DATA CONCLUSION Simultaneous evaluation of lung anatomy and ventilation using XD-UTE is demonstrated, which have shown good potential for improved diagnosis and management of patients with heterogeneous lung diseases. LEVEL OF EVIDENCE 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:411-422.

Flexible water excitation for fat-free MRI at 3 Tesla using lipid insensitive binomial off-resonant RF excitation (LIBRE) pulses

Abstract: Purpose: To develop a robust and flexible low power water excitation pulse that enables effective fat suppression at high magnetic field strength. Methods: A water excitation method that uses spatially non-selective pulses was optimized in numerical simulations, and implemented and tested in phantoms and healthy volunteers at 3T. The lipid insensitive binomial off-resonant excitation (LIBRE) pulse comprises two low power rectangular sub-pulses that have a variable frequency offset, phase offset and duration. The capability and extent of LIBRE fat suppression was quantitatively compared with conventional fat saturation (FS) and water excitation (WE) techniques. Results: LIBRE enables simultaneous water excitation and near complete fat suppression in large volumes at 3T as demonstrated by numerical simulations, and experiments. In phantoms and in human subjects, the frequency responses matched well with those from the numerical simulation. Comparing FS and WE, LIBRE demonstrated an improved robustness to magnetic field inhomogeneities, and a much more effectively suppressed fat signal. This applied for a range of pulse durations and pulses as short as 1.4 ms. Conclusion: A flexible water excitation method was developed that shows robust, near complete fat suppression at 3T.

Short-term changes in dietary sodium intake influence sweat sodium concentration and muscle sodium content in healthy individuals.

Abstract: OBJECTIVE There is increasing evidence that sodium can be stored in the skin and muscles without being osmotically active, yet whether acute changes in dietary sodium intake alter sweat and muscle sodium content has not been investigated previously. METHODS In a cross-over design, we assessed muscle sodium content by Na-MRI in 38 healthy normotensive volunteers (aged 33.5 ± 11.1 years, 76.3% women) after 5 days of high-sodium diet (6 g of salt added to their normal diet) and 5 days of a low-sodium diet. In a subgroup of 18 participants (72.2% women) we conducted quantitative pilocarpine iontophoretic sweat collections and measured the sodium concentration in sweat. Plasma aldosterone and plasma renin activity levels were measured in all participants. RESULTS Under high-sodium diet conditions urinary sodium excretion, muscle sodium content and sweat sodium concentration all increased significantly. Muscle sodium content (rm = 0.47, P = 0.03) and sodium sweat concentration (rm = 0.72, P < 0.001) correlated positively with salt intake as estimated by 24-h urine sodium excretion. Age, sex or the phase of the menstrual cycle did not influence muscle or sweat sodium concentrations or their changes. In contrast, plasma aldosterone levels were negatively associated with both muscle sodium (rs = -0.42, P = 0.0001) and sweat sodium content (rs = -0.52, P = 0.002). Plasma renin activity correlated negatively with sweat sodium (rs = -0.43, P = 0.012) and muscle sodium levels (rs = -0.42, P < 0.001). CONCLUSION Muscle and sweat sodium concentrations are significantly higher on a high-salt intake in healthy male and female individuals, suggesting that muscle and sweat play a role in regulating sodium balance in humans.

Noncontrast free-breathing respiratory self-navigated coronary artery cardiovascular magnetic resonance angiography at 3 T using lipid insensitive binomial off-resonant excitation (LIBRE).

Abstract: Robust and homogeneous lipid suppression is mandatory for coronary artery cardiovascular magnetic resonance (CMR) imaging since the coronary arteries are commonly embedded in epicardial fat. However, effective large volume lipid suppression becomes more challenging when performing radial whole-heart coronary artery CMR for respiratory self-navigation and the problem may even be exacerbated at increasing magnetic field strengths. Incomplete fat suppression not only hinders a correct visualization of the coronary vessels and generates image artifacts, but may also affect advanced motion correction methods. The aim of this study was to evaluate a recently reported lipid insensitive CMR method when applied to a noncontrast self-navigated coronary artery CMR acquisitions at 3 T, and to compare it to more conventional fat suppression techniques. Lipid insensitive binomial off resonant excitation (LIBRE) radiofrequency excitation pulses were included into a self-navigated 3D radial GRE coronary artery CMR sequence at 3 T. LIBRE was compared against a conventional CHESS fat saturation (FS) and a binomial 1–180°-1 water excitation (WE) pulse. First, fat suppression of all techniques was numerically characterized using Matlab and experimentally validated in phantoms and in legs of human volunteers. Subsequently, free-breathing self-navigated coronary artery CMR was performed using the LIBRE pulse as well as FS and WE in ten healthy subjects. Myocardial, arterial and chest fat signal-to-noise ratios (SNR), as well as coronary vessel conspicuity were quantitatively compared among those scans. The results obtained in the simulations were confirmed by the experimental validations as LIBRE enabled near complete fat suppression for 3D radial imaging in vitro and in vivo. For self-navigated whole-heart coronary artery CMR at 3 T, fat SNR was significantly attenuated using LIBRE compared with conventional FS. LIBRE increased the right coronary artery (RCA) vessel sharpness significantly (37 ± 9% (LIBRE) vs. 29 ± 8% (FS) and 30 ± 8% (WE), both p < 0.05) and led to a significant increase in the measured RCA vessel length to (83 ± 31 mm (LIBRE) vs. 56 ± 12 mm (FS) and 59 ± 27 (WE) p < 0.05). Applied to a respiratory self-navigated noncontrast 3D radial whole-heart sequence, LIBRE enables robust large volume fat suppression and significantly improves coronary artery image quality at 3 T compared to the use of conventional FS and WE.

Natively Fat-Suppressed 5D Whole-Heart MRI with a Radial Free-Running Fast-Interrupted Steady-State (FISS) Sequence at 1.5T and 3T

Abstract: Purpose: To implement, optimize and test fast interrupted steady-state (FISS) for natively fat-suppressed free-running 5D whole-heart MRI at 1.5T and 3T. Methods: FISS was implemented for fully self-gated free-running cardiac- and respiratory-motion-resolved radial imaging of the heart at 1.5T and 3T. Numerical simulations and phantom scans were performed to compare fat suppression characteristics and to determine parameter ranges (readouts per FISS module (NR) and repetition time (TR)) for effective fat suppression. Subsequently, free-running FISS data were collected in ten healthy volunteers. All acquisitions were compared with a continuous bSSFP version of the same sequence, and both fat suppression and scan times were analyzed. Results: Simulations demonstrate a variable width and location of suppression bands in FISS that was dependent on TR and NR. For a fat suppression bandwidth of 100Hz and NR below 8, simulations demonstrated that a TR between 2.2ms and 3.0ms is required at 1.5T while a range of 3.0ms to 3.5ms applies at 3T. Fat signal increases with NR. These findings were corroborated in phantom experiments. In volunteers, fat SNR was significantly decreased using FISS compared with bSSPF at both field strengths. After protocol optimization, high-resolution (1.1mm x 1.1mm x 1.1mm) 5D whole-heart free-running FISS can be performed with effective fat suppression in under 8 min at 1.5T and 3T at a modest scan time increase compared to bSSFP.Conclusion: An optimal FISS parameter range was determined enabling natively fat-suppressed 5D whole-heart free-running MRI with a single continuous scan at 1.5T and 3T, demonstrating potential for cardiac imaging and noncontrast angiography.

Ultrashort echo time imaging of the lungs under high-frequency noninvasive ventilation: A new approach to lung imaging.

Abstract: Although ultrashort echo time (UTE) sequences allow excellent assessment of lung parenchyma, image quality remains lower than that of computed tomography (CT). To investigate a high-frequency noninvasive ventilation (HF-NIV) technique allowing a stabilized inspiration and to compare image quality with current dedicated MR sequences. Prospective. Ten healthy volunteers. 3D radial UTE sequence at 1.5T. UTE-HF-NIV sequence was compared with UTE-free-breathing (UTE-FB), reconstructed at end expiration (UTE-Exp) and average (UTE-Avg), and breath-hold VIBE sequences. The distance from lung apex to the dome of the right hemidiaphragm was measured. Visual assessment of the visibility and sharpness of normal anatomical structures was carried out. Dedicated software also quantitatively evaluated vessel-lung and right lung-liver interface sharpness. Apparent signal ratio (Sr) and contrast ratios (Cr) were quantitatively evaluated. Wilcoxon signed rank test for visual scores, paired t-test for continuous variables, significance at P < 0.05. The distance between apex and the right hemidiaphragmatic dome was significantly larger (P < 0.001) with UTE-HF-NIV compared with UTE-FB and VIBE acquisitions. Vessel and airway visibility had identical median visual scores with all UTE methods. Median visual scores for sharpness of vessels and airways were significantly higher (P < 0.001) with HF-NIV (vessels = 3; airways = 2) than in UTE-FB (vessels = 2; airways = 1) and VIBE (vessels = 1; airways = 1). Software-based vessel sharpness evaluation resulted in larger values in 8/10 volunteers with UTE-HF-NIV (67.3 ± 9.8) compared with UTE-Avg (62.3 ± 12.6) but the average difference was not significant (P = 0.28). The sharpness of the lung-liver interface was significantly higher (P < 0.001) with HF-NIV (17.3 ± 5.3) compared with UTE-Avg (14.1 ± 3.9). Significantly higher values (P < 0.01) of Sr and Cr were observed with UTE-HF-NIV compared with UTE-FB and VIBE. HF-NIV allowing acquisition at full inspiration significantly improves image quality for lung imaging. This could offer the option to alternate some follow-up CT studies by using this technique. 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;50:1789-1797.

In vitro optimization and comparison of CT angiography versus radial cardiovascular magnetic resonance for the quantification of cross-sectional areas and coronary endothelial function.

Abstract: Our objectives were first to determine the optimal coronary computed tomography angiography (CTA) protocol for the quantification and detection of simulated coronary artery cross-sectional area (CSA) differences in vitro, and secondly to quantitatively compare the performance of the optimized CTA protocol with a previously validated radial coronary cardiovascular magnetic resonance (CMR) technique. 256-multidetector CTA and radial coronary CMR were used to obtain images of a custom in vitro resolution phantom simulating a range of physiological responses of coronary arteries to stress. CSAs were automatically quantified and compared with known nominal values to determine the accuracy, precision, signal-to-noise ratio (SNR), and circularity of CSA measurements, as well as the limit of detection (LOD) of CSA differences. Various iodine concentrations, radiation dose levels, tube potentials, and iterative image reconstruction algorithms (ASiR-V) were investigated to determine the optimal CTA protocol. The performance of the optimized CTA protocol was then compared with a radial coronary CMR method previously developed for endothelial function assessment under both static and moving conditions. The iodine concentration, dose level, tube potential, and reconstruction algorithm all had significant effects (all p < 0.001) on the accuracy, precision, LOD, SNR, and circularity of CSA measurements with CTA. The best precision, LOD, SNR, and circularity with CTA were achieved with 6% iodine, 20 mGy, 100 kVp, and 90% ASiR-V. Compared with the optimized CTA protocol under static conditions, radial coronary CMR was less accurate (− 0.91 ± 0.13 mm2 vs. -0.35 ± 0.04 mm2, p < 0.001), but more precise (0.08 ± 0.02 mm2 vs. 0.21 ± 0.02 mm2, p < 0.001), and enabled the detection of significantly smaller CSA differences (0.16 ± 0.06 mm2 vs. 0.52 ± 0.04 mm2; p < 0.001; corresponding to CSA percentage differences of 2.3 ± 0.8% vs. 7.4 ± 0.6% for a 3-mm baseline diameter). The same results held true under moving conditions as CSA measurements with CMR were less affected by motion. Radial coronary CMR was more precise and outperformed CTA for the specific task of detecting small CSA differences in vitro, and was able to reliably identify CSA changes an order of magnitude smaller than those reported for healthy physiological vasomotor responses of proximal coronary arteries. However, CTA yielded more accurate CSA measurements, which may prove useful in other clinical scenarios, such as coronary artery stenosis assessment.

MR Volumetry of Lung Nodules: A Pilot Study.

Abstract: Introduction: Computed tomography (CT) is currently the reference modality for the detection and follow-up of pulmonary nodules. While 2D measurements are commonly used in clinical practice to assess growth, increasingly 3D volume measurements are being recommended. The goal of this pilot study was to evaluate preliminarily the capabilities of 3D MRI using ultra-short echo time for lung nodule volumetry, as it would provide a radiation-free modality for this task. Material and Methods: Artificial nodules were manufactured out of Agar and measured using an ultra-short echo time MRI sequence. CT data were also acquired as a reference. Image segmentation was carried out using an algorithm based on signal intensity thresholding (SIT). For comparison purposes, we also performed manual slice by slice segmentation. Volumes obtained with MRI and CT were compared. Finally, the volumetry of a lung nodule was evaluated in one human subject in comparison with CT. Results: Using the SIT technique, minimal bias was observed between CT and MRI across the entire range of volumes (2%) with limits of agreement below 14%. Comparison of manually segmented MRI and CT resulted in a larger bias (8%) and wider limits of agreement (-23% to 40%). In vivo, nodule volume differed of <16% between modalities with the SIT technique. Conclusion: This pilot study showed very good concordance between CT and UTE-MRI to quantify lung nodule volumes, in both a phantom and human setting. Our results enhance the potential of MRI to quantify pulmonary nodule volume with similar performance to CT.

A black-blood ultra-short echo time (UTE) sequence for 3D isotropic resolution imaging of the lungs.

Abstract: PURPOSE Ultra-short echo time MRI is a promising alternative to chest CT for cystic fibrosis patients. Black-blood imaging in particular could help discern small-sized anomalies, such as mucoid plugging, which may otherwise be confused with neighboring blood vessels, particularly when contrast agent is not used. We, therefore, implemented and tested an ultra-short echo time sequence with black-blood preparation. Additionally, this sequence may also be used to generate bright-blood angiograms. METHODS Using this sequence, data was acquired during free breathing in 10 healthy volunteers to obtain respiratory-motion-resolved 3D volumes covering the entire thorax with an isotropic resolution of (1 mm)3 . The magnitude of signal suppression relative to a bright-blood reference acquisition was quantified and compared with that obtained with a turbo-spin echo (TSE) acquisition. Bright-blood angiograms were also generated by subtraction. Finally, an initial feasibility assessment was performed in 2 cystic fibrosis patients, and images were visually compared with contrast-enhanced images and with CT data. RESULTS Black-blood preparation significantly decreased the average normalized signal intensity in the vessel lumen (-66%; P < 0.001). Similarly, blood signal was significantly lowered (-60%; P = 0.001) compared with the TSE acquisition. In patients, mucoid plugging could be emphasized in the black-blood datasets. An intercostal artery could also be visualized in the subtraction angiograms. CONCLUSION Black-blood free-breathing ultra-short echo time imaging was successfully implemented and motion-resolved full volumetric coverage of the lungs with high spatial resolution was achieved, while obtaining an angiogram without contrast agent injection. Encouraging initial results in patients prompt further investigations in a larger cohort.

Towards Quantification of Inflammation in Atherosclerotic Plaque in the Clinic - Characterization and Optimization of Fluorine-19 MRI in Mice at 3 T.

Abstract: Fluorine-19 (19F) magnetic resonance imaging (MRI) of injected perfluorocarbons (PFCs) can be used for the quantification and monitoring of inflammation in diseases such as atherosclerosis. To advance the translation of this technique to the clinical setting, we aimed to 1) demonstrate the feasibility of quantitative 19F MRI in small inflammation foci on a clinical scanner, and 2) to characterize the PFC-incorporating leukocyte populations and plaques. To this end, thirteen atherosclerotic apolipoprotein-E-knockout mice received 2 × 200 µL PFC, and were scanned on a 3 T clinical MR system. 19F MR signal was detected in the aortic arch and its branches in all mice, with a signal-to-noise ratio of 11.1 (interquartile range IQR = 9.5–13.1) and a PFC concentration of 1.15 mM (IQR = 0.79–1.28). Imaging flow cytometry was used on another ten animals and indicated that PFC-labeled leukocytes in the aortic arch and it branches were mainly dendritic cells, macrophages and neutrophils (ratio 9:1:1). Finally, immunohistochemistry analysis confirmed the presence of those cells in the plaques. We thus successfully used 19F MRI for the noninvasive quantification of PFC in atherosclerotic plaque in mice on a clinical scanner, demonstrating the feasibility of detecting very small inflammation foci at 3 T, and advancing the translation of 19F MRI to the human setting.

Noncontrast free-breathing respiratory self-navigated coronary artery cardiovascular magnetic resonance angiography at 3 T using lipid insensitive binomial off-resonant excitation (LIBRE)

Abstract: Robust and homogeneous lipid suppression is mandatory for coronary magnetic resonance angiography (MRA) since coronary arteries are commonly embedded in fat. However, effective large volume lipid suppression becomes challenging when performing radial whole-heart coronary MRA and the problem may even be exacerbated at increasing magnetic field strengths. Incomplete fat suppression also generates artifacts, and may affect advanced motion correction methods. The aim was to evaluate a recently reported lipid insensitive MRI method for self-navigated coronary MRA at 3T. Lipid insensitive binomial off resonant excitation (LIBRE) radiofrequency (RF) excitation pulses were included into a self-navigated 3D radial GRE coronary MRA sequence at 3T. LIBRE was compared against conventional fat saturation (FS) and binomial 1-180{\deg}-1 water excitation (WE). First, fat suppression of all techniques was numerically characterized using Matlab and experimentally validated in phantoms and in legs of human volunteers. Subsequently, free-breathing self-navigated coronary MRA was performed using the LIBRE pulse as well as FS and WE in ten volunteers. Results obtained in the simulations were confirmed by the experimental validations as LIBRE enabled near complete fat suppression for 3D radial imaging in vitro and in vivo. For self-navigated whole-heart coronary MRA at 3T, fat SNR was significantly attenuated using LIBRE compared with conventional FS. LIBRE increased the RCA vessel sharpness significantly (37 +/- 9% (LIBRE) vs. 29 +/- 8% (FS) and 30 +/- 8% (WE), both p<0.05) and led to a significant increase in the measured RCA vessel length to (83 +/- 31 mm (LIBRE) vs. 56 +/- 12 mm (FS) and 59 +/- 27 (WE) p<0.05). LIBRE enables robust large volume fat suppression and significantly improves coronary artery image quality at 3T compared to the use of conventional fat suppression and water excitation.

Noncontrast free-breathing respiratory self-navigated coronary MR angiography at 3T using lipid insensitive binomial off-resonant excitation (LIBRE)

Abstract: Robust and homogeneous lipid suppression is mandatory for coronary magnetic resonance angiography (MRA) since coronary arteries are commonly embedded in fat. However, effective large volume lipid suppression becomes challenging when performing radial whole-heart coronary MRA and the problem may even be exacerbated at increasing magnetic field strengths. Incomplete fat suppression also generates artifacts, and may affect advanced motion correction methods. The aim was to evaluate a recently reported lipid insensitive MRI method for self-navigated coronary MRA at 3T. Lipid insensitive binomial off resonant excitation (LIBRE) radiofrequency (RF) excitation pulses were included into a self-navigated 3D radial GRE coronary MRA sequence at 3T. LIBRE was compared against conventional fat saturation (FS) and binomial 1-180°-1 water excitation (WE). First, fat suppression of all techniques was numerically characterized using Matlab and experimentally validated in phantoms and in legs of human volunteers. Subsequently, free-breathing self-navigated coronary MRA was performed using the LIBRE pulse as well as FS and WE in ten volunteers. Results obtained in the simulations were confirmed by the experimental validations as LIBRE enabled near complete fat suppression for 3D radial imaging in vitro and in vivo. For self-navigated whole-heart coronary MRA at 3T, fat SNR was significantly attenuated using LIBRE compared with conventional FS. LIBRE increased the RCA vessel sharpness significantly (37 +/- 9% (LIBRE) vs. 29 +/- 8% (FS) and 30 +/- 8% (WE), both p<0.05) and led to a significant increase in the measured RCA vessel length to (83 +/- 31 mm (LIBRE) vs. 56 +/- 12 mm (FS) and 59 +/- 27 (WE) p<0.05). LIBRE enables robust large volume fat suppression and significantly improves coronary artery image quality at 3T compared to the use of conventional fat suppression and water excitation.

Cardiovascular Magnetic Resonance Tagging for Assessment of Left Ventricular Diastolic Function

Abstract: Left ventricular (LV) diastolic function has been recognized as an important factor in the pathophysiology of many common cardiovascular diseases. Dilated and hypertrophic cardiomyopathies, coronary artery disease, and systemic hypertension are all associated with abnormal LV filling dynamics. Diastolic dysfunction has also been increasingly appreciated as a major cause of heart failure, especially in the elderly. Although invasive hemodynamic measures/assessment of diastole are considered the gold standard, echocardiographic methods, including tissue Doppler imaging, have gained greater use in the clinical assessment of LV diastolic function because of their noninvasive acquisition, which greatly facilitates serial assessments. In cardiovascular magnetic resonance (CMR) imaging, with the advent of parallel imaging, three-dimensional data collection, spiral and balanced steady-state free precession imaging, and higher magnetic field strength, the prolonged tag persistence permits easier access to diastole. Together with rapid state-of-the-art software analysis tools, quantification of LV diastolic wall motion can now be readily performed using CMR.