Publications

PURPOSE: To assess the efficacy and robustness of motion sensitized driven equilibrium (MSDE) for blood suppression in volumetric 3D whole-heart cardiac MR. MATERIALS AND METHODS: To investigate the efficacy of MSDE on blood suppression and myocardial signal-to-noise ratio (SNR) loss on different imaging sequences, seven healthy adult subjects were imaged using 3D electrocardiogram (ECG)-triggered MSDE-prep T(1) -weighted turbo spin echo (TSE), and spoiled gradient echo (GRE), after optimization of MSDE parameters in a pilot study of five subjects. Imaging artifacts, myocardial and blood SNR were assessed. Subsequently, the feasibility of isotropic spatial resolution MSDE-prep black-blood was assessed in six subjects. Finally, 15 patients with known or suspected cardiovascular disease were recruited to be imaged using a conventional multislice 2D double inversion recovery (DIR) TSE imaging sequence and a 3D MSDE-prep spoiled GRE. RESULTS: The MSDE-prep yielded significant blood suppression (75%-92%), enabling a volumetric 3D black-blood assessment of the whole heart with significantly improved visualization of the chamber walls. The MSDE-prep also allowed successful acquisition of black-blood images with isotropic spatial resolution. In the patient study, 3D black-blood MSDE-prep and DIR resulted in similar blood suppression in left ventricle and right ventricle walls but the MSDE-prep had superior myocardial signal and wall sharpness. CONCLUSION: MSDE-prep allows volumetric black-blood imaging of the heart.

We sought to evaluate the efficacy of prospective random undersampling and low-dimensional-structure self-learning and thresholding reconstruction for highly accelerated contrast-enhanced whole-heart coronary MRI. A prospective random undersampling scheme was implemented using phase ordering to minimize artifacts due to gradient switching and was compared to a randomly undersampled acquisition with no profile ordering. This profile-ordering technique was then used to acquire contrast-enhanced whole-heart coronary MRI in 10 healthy subjects with 4-fold acceleration. Reconstructed images and the acquired zero-filled images were compared for depicted vessel length, vessel sharpness, and subjective image quality on a scale of 1 (poor) to 4 (excellent). In a pilot study, contrast-enhanced whole-heart coronary MRI was also acquired in four patients with suspected coronary artery disease with 3-fold acceleration. The undersampled images were reconstructed using low-dimensional-structure self-learning and thresholding, which showed significant improvement over the zero-filled images in both objective and subjective measures, with an overall score of 3.6 ± 0.5. Reconstructed images in patients were all diagnostic. Low-dimensional-structure self-learning and thresholding reconstruction allows contrast-enhanced whole-heart coronary MRI with acceleration as high as 4-fold using clinically available five-channel phased-array coil.

A respiratory navigator with a fixed acceptance gating window is commonly used to reduce respiratory motion artifacts in cardiac MR. This approach prolongs the scan time and occasionally yields an incomplete dataset due to respiratory drifts. To address this issue, we propose an adaptive gating window approach in which the size and position of the gating window are changed adaptively during the acquisition based on the individual's breathing pattern. The adaptive gating window tracks the breathing pattern of the subject throughout the scan and adapts the size and position of the gating window such that the gating efficiency is always fixed at a constant value. To investigate the image quality and acquisition time, free breathing cardiac MRI, including both targeted coronary MRI and late gadolinium enhancement imaging, was performed in 67 subjects using the proposed navigator technique. Targeted coronary MRI was acquired from eleven healthy adult subjects using both the conventional and proposed adaptive gating window techniques. Fifty-six patients referred for cardiac MRI were also imaged using late gadolinium enhancement with the proposed adaptive gating window technique. Subjective and objective image assessments were used to evaluate the proposed method. The results demonstrate that the proposed technique allows free-breathing cardiac MRI in a relatively fixed time without compromising imaging quality due to respiratory motion artifacts.

A mean respiratory navigator tracking factor of 0.6 is commonly used to estimate the respiratory motion of the heart from the displacement of the right hemi-diaphragm. A constant tracking factor can generate significant residual error in estimation of the respiratory motion of the heart for the cases where the actual tracking factor highly deviates from 0.6. In this study, we implemented and evaluated a robust method to calculate a subject-specific tracking factor for free-breathing high resolution cardiac MR. The subject-specific tracking factor was calculated from two consecutive navigator signals placed on the right hemi-diaphragm and the basal left ventricle in a training phase. To verify the accuracy of the estimated subject-specific tracking factor, nineteen subjects were recruited for comparing the estimated tracking factor in real-time with an image-based tracking factor, calculated off-line. Subsequently, in seven adult subjects, whole-heart or targeted coronary artery MR images were acquired using the estimated subject-specific tracking factor and visually compared with those acquired using a constant (0.6) tracking factor. It was shown that the proposed method can accurately estimate the subject-specific tracking factor and improve the quality of coronary images when the subject-specific tracking factor differs from 0.6.

BACKGROUND: Resveratrol has been shown to reverse some of the detrimental effects of metabolic syndrome (MetS). We sought to define the impact of supplemental resveratrol on normal myocardium remote from an ischemic territory in a swine model of MetS and chronic myocardial ischemia. STUDY DESIGN: Yorkshire swine were fed a normal diet (control), a high cholesterol diet (HCD), or a high cholesterol diet with orally supplemented resveratrol (HCD-R; 100 mg/kg/day). Four weeks after diet modification, myocardial ischemia was induced by ameroid constrictor placement. Seven weeks later, myocardial tissue from a territory remote from the ischemia was harvested. Animals in the HCD and HCD-R groups underwent functional cardiac MRI before ischemia and before sacrifice. Tissue was harvested for protein expression analysis. RESULTS: After 7 weeks of ischemia, regional left ventricular systolic function was significantly increased in HCD-R as compared with HCD animals. During ventricular pacing the HCD group had significantly decreased flow (p = 0.03); perfusion in the HCD-R was preserved as compared with the control. There was no difference in microvascular relaxation. Expression of metabolic proteins Sirt-1 (p = 0.002), AMPkinase (p = 0.02), and carnitine palmitoyltransferase-I (p = 0.002) were upregulated in the HCD-R group. Levels of protein oxidative stress were significantly increased in the HCD and HCD-R groups, as compared with the controls (p = 0.003). Activated endothelial nitric oxide synthase (eNOS) was increased in the HCD-R group (p = 0.01). There was no difference in myocardial endothelial cell density between the groups; however, dividing endothelial cells were decreased in the HCD and HCD-R groups (p = 0.006). CONCLUSIONS: Resveratrol supplementation improves regional left ventricular function and preserves perfusion to myocardium remote from an area of ischemia in an animal model of metabolic syndrome and chronic myocardial ischemia.

PURPOSE: To evaluate the use of low-dimensional-structure self-learning and thresholding (LOST) compressed sensing acquisition and reconstruction in the assessment of left atrial (LA) and left ventricular (LV) scar by using late gadolinium enhancement (LGE) magnetic resonance (MR) imaging with isotropic spatial resolution. MATERIALS AND METHODS: The study was approved by the local institutional review board and was compliant with HIPAA. All subjects provided written informed consent. Twenty-eight patients (eight women; mean age, 58.0 years ± 10.1) with a history of atrial fibrillation were recruited for the LA LGE study, and 14 patients (five women; mean age, 54.2 years ± 18.6) were recruited for assessment of LV myocardial infarction. With use of a pseudorandom k-space undersampling pattern, threefold accelerated three-dimensional (3D) LGE data were acquired with isotropic spatial resolution and reconstructed off-line by using LOST. For comparison, subjects were also imaged by using standard 3D LGE protocols with nonisotropic spatial resolution. Images were compared qualitatively by three cardiologists with regard to diagnostic value, presence of enhancement, and image quality. The signed rank test and Wilcoxon unpaired two-sample test were used to test the hypothesis that there would be no significant difference in image quality ratings with different resolutions. RESULTS: Interpretable images were obtained in 26 of the 28 patients (93%) in the LA LGE study. LGE was seen in 17 of 30 cases (57%) with nonisotropic resolution and in 18 cases (60%) with isotropic resolution. Diagnostic quality scores of isotropic images were significantly higher than those of nonisotropic images with coronal views (median, 3 vs 2, respectively [25th and 75th percentiles: 3, 3 vs 2, 3]; P < .001) and sagittal views (median, 3 vs 2 [25th and 75th percentiles: 3, 4 vs 2, 3]; P < .001) but lower with axial views (median, 4 vs 3 [25th and 75th percentiles: 3, 4 vs 3, 3]; P < .001). For the LV LGE study, all patients had interpretable images. LGE was seen in six of 14 patients (43%), with 100% agreement between both data sets. Diagnostic quality scores of high-isotropic-resolution LV images were higher than those of nonisotropic images with short-axis views (median, 4 vs 3 [25th and 75th percentiles: 3, 4 vs 2, 3]; P = .014) and two-chamber views (median, 4 vs 3 [25th and 75th percentiles: 3, 4 vs 2, 3]; P = .001). CONCLUSION: An accelerated LGE acquisition with LOST enables imaging with high isotropic spatial resolution for improved assessment of LV, LA, and pulmonary vein scar.