Dark blood cardiovascular magnetic resonance of the heart, great vessels, and lungs using electrocardiographic-gated three-dimensional unbalanced steady-state free precession.

BACKGROUND: Recently, we reported a novel neuroimaging technique, unbalanced T1 Relaxation-Enhanced Steady-State (uT1RESS), which uses a tailored 3D unbalanced steady-state free precession (3D uSSFP) acquisition to suppress the blood pool signal while minimizing bulk motion sensitivity. In the present work, we hypothesized that 3D uSSFP might also be useful for dark blood imaging of the chest. To test the feasibility of this approach, we performed a pilot study in healthy subjects and patients undergoing cardiovascular magnetic resonance (CMR). MAIN BODY: The study was approved by the hospital institutional review board. Thirty-one adult subjects were imaged at 1.5 T, including 5 healthy adult subjects and 26 patients (44 to 86 years, 10 female) undergoing a clinically indicated CMR. Breath-holding was used in 29 subjects and navigator gating in 2 subjects. For breath-hold acquisitions, the 3D uSSFP pulse sequence used a high sampling bandwidth, asymmetric readout, and single-shot along the phase-encoding direction, while 3 shots were acquired for navigator-gated scans. To minimize signal dephasing from bulk motion, electrocardiographic (ECG) gating was used to synchronize the data acquisition to the diastolic phase of the cardiac cycle. To further reduce motion sensitivity, the moment of the dephasing gradient was set to one-fifth of the moment of the readout gradient. Image quality using 3D uSSFP was good-to-excellent in all subjects. The blood pool signal in the thoracic aorta was uniformly suppressed with sharp delineation of the aortic wall including two cases of ascending aortic aneurysm and two cases of aortic dissection. Compared with variable flip angle 3D turbo spin-echo, 3D uSSFP showed improved aortic wall sharpness. It was also more efficient, permitting the acquisition of 24 slices in each breath-hold versus 16 slices with 3D turbo spin-echo and a single slice with dual inversion 2D turbo spin-echo. In addition, lung and mediastinal lesions appeared highly conspicuous compared with the low blood pool signals within the heart and blood vessels. In two subjects, navigator-gated 3D uSSFP provided excellent delineation of cardiac morphology in double oblique multiplanar reformations. CONCLUSION: In this pilot study, we have demonstrated the feasibility of using ECG-gated 3D uSSFP for dark blood imaging of the heart, great vessels, and lungs. Further study will be required to fully optimize the technique and to assess clinical utility.

Reverse double inversion-recovery: Improving motion robustness of cardiac T2 -weighted dark-blood turbo spin-echo sequence.

BACKGROUND: Cardiac dark-blood turbo spin-echo (TSE) imaging is sensitive to through-plane motion, resulting in myocardial signal reduction. PURPOSE: To propose and validate reverse double inversion-recovery (RDIR)-a dark-blood preparation with improved motion robustness for the cardiac dark-blood TSE sequence. STUDY TYPE: Prospective. POPULATION: Healthy volunteers (n = 10) and patients (n = 20). FIELD STRENGTH: 1.5T (healthy volunteers) and 3T (patients). ASSESSMENT: Compared to double inversion recovery (DIR), RDIR swaps the two inversion pulses in time and places the slice-selective 180° in late-diastole of the previous cardiac cycle to minimize slice misregistration. RDIR and DIR were performed in the same left-ventricular basal short-axis slice. Healthy subjects were imaged with two preparation slice thicknesses, 110% and 200%, while patients were imaged using a 200% slice thickness only. Images were assessed quantitatively, by measuring the myocardial signal heterogeneity and the extent of dropout, and also qualitatively on a 5-point scale. STATISTICAL TESTS: Quantitative and qualitative data were assessed with Student's t-test and Wilcoxon signed-rank test, respectively. RESULTS: In healthy subjects, RDIR with 110% slice thickness significantly reduced signal heterogeneity in both the left ventricle (LV) and right ventricle (RV) (LV: P = 0.006, RV: P < 0.0001) and the extent of RV dropout (P < 0.0001), while RDIR with 200% slice thickness significantly reduced RV signal heterogeneity (P = 0.001) and the extent of RV dropout (P = 0.0002). In patients, RDIR significantly reduced RV myocardial signal heterogeneity (0.31 vs. 0.43; P = 0.003) and the extent of RV dropout (24% vs. 46%; P = 0.0005). LV signal heterogeneity exhibited a trend towards improvement with RDIR (0.12 vs. 0.16; P = 0.06). Qualitative evaluation showed a significant improvement of LV and RV visualization in RDIR compared to DIR (LV: P = 0.04, RV: P = 0.0007) and a significantly improved overall image quality (P = 0.03). DATA CONCLUSION: RDIR TSE is less sensitive to through-plane motion, potentiating increased clinical utility for black-blood TSE. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:1498-1508.

Improved dark blood imaging of the heart using radial balanced steady-state free precession.

BACKGROUND: Dark blood imaging of the heart is conventionally performed using a breath-hold, dual-inversion Cartesian fast spin-echo pulse sequence. Our aim was to develop a faster, more flexible approach that would be less motion-sensitive and provide better image quality. For this purpose, we implemented a prototype radial balanced steady-state free precession (bSSFP) pulse sequence. METHODS: The study was approved by the institutional review board. Six healthy volunteers and 27 subjects undergoing clinically-indicated cardiovascular magnetic resonance (CMR) were imaged using dark blood Cartesian fast spin-echo and radial bSSFP. For patient studies, overall image quality, fat suppression and blood nulling were scored on a 5-point Likert scale. The quality of visualization of the right and left ventricular free walls and septum were individually scored. Streaking and ghosting artifacts were noted, as well as signal dropout in the free wall of the left ventricle. RESULTS: In volunteer studies, radial bSSFP showed less degradation by cardiac or respiratory motion than fast spin-echo as indicated by visual analysis and calculation of the temporal signal-to-noise ratio. The least motion sensitivity and maximal imaging efficiency were achieved with a single-shot radial bSSFP acquisition using only 35 views (temporal resolution = 95 ms). In patient studies, radial bSSFP images showed fewer motion artifacts and were judged to provide better myocardial visibility, including depiction of the right ventricular free wall, than fast spin-echo. CONCLUSIONS: Dual-inversion radial bSSFP provides the benefits of diminished sensitivity to image artifacts from respiratory or cardiac motion, better myocardial visibility, and improved imaging efficiency compared with standard-of-care Cartesian fast spin-echo for dark blood imaging of the heart.

Atypical clinical and novel radiological findings in Susac syndrome: Experience from a large monocentric cohort.

Susac syndrome (SuS) is a rare immune-mediated endotheliopathy that affects the brain, retina and inner ear and is characterised by the variable clinical triad of encephalopathy, visual and vestibulocochlear dysfunction. Here, we present clinical and paraclinical data of 19 SuS patients followed at Ghent University Hospital and highlight some atypical clinical and novel radiological findings. Our findings suggest that spinal involvement expands the clinical phenotype of SuS. We further introduce dark blood sequences as a more sensitive technique to detect radiological disease activity in SuS. Our data add to the current understanding of the diagnosis, monitoring and treatment of SuS.

Anatomical assessment of intrathoracic cardiovascular structures using fast spin-echo double inversion recovery and steady-state free precession magnetic resonance imaging in a normal cat.

In human medicine, non-contrast cardiac magnetic resonance imaging (CMRI) is routinely used to assess the cardiovascular system. In this study, using non-contrast CMRI, we provide a thorough description of the normal appearance of the intrathoracic cardiovascular structures in one healthy cat using a magnet operating at a field of 1.5-Tesla. The CMRI protocol was based on the use of fast spin-echo double inversion recovery and steady-state free precession pulse sequences in oblique short-axis, vertical long-axis, and horizontal long-axis imaging planes. After imaging the feline heart, four cadaver cats injected with latex substance into their arterial and venous systems were sectioned to facilitate interpretation of the intrathoracic cardiovascular structures to the corresponding CMRI. The fast spin-echo double inversion recovery images showed the best evaluation of gross intrathoracic anatomy, giving excellent contrast of the myocardium and vessels walls as they appeared with intermediate signal intensity compared to the lumen that appeared with low signal intensity. By contrast, steady-state free precession images showed details of the heart cavities and vascular lumen due to the high signal intensity of fast-flowing blood. The results of this study provide some anatomic detail for the heart and associated vessels as seen by non-contrast CMRI in the domestic cat.

A fast screening protocol for carotid plaques imaging using 3D multi-contrast MRI without contrast agent.

PURPOSE: To implement a fast (~15min) MRI protocol for carotid plaque screening using 3D multi-contrast MRI sequences without contrast agent on a 3Tesla MRI scanner. MATERIALS AND METHODS: 7 healthy volunteers and 25 patients with clinically confirmed transient ischemic attack or suspected cerebrovascular ischemia were included in this study. The proposed protocol, including 3D T1-weighted and T2-weighted SPACE (variable-flip-angle 3D turbo spin echo), and T1-weighted magnetization prepared rapid acquisition gradient echo (MPRAGE) was performed first and was followed by 2D T1-weighted and T2-weighted turbo spin echo, and post-contrast T1-weighted SPACE sequences. Image quality, number of plaques, and vessel wall thicknesses measured at the intersection of the plaques were evaluated and compared between sequences. RESULTS: Average examination time of the proposed protocol was 14.6min. The average image quality scores of 3D T1-weighted, T2-weighted SPACE, and T1-weighted magnetization prepared rapid acquisition gradient echo were 3.69, 3.75, and 3.48, respectively. There was no significant difference in detecting the number of plaques and vulnerable plaques using pre-contrast 3D images with or without post-contrast T1-weighted SPACE. The 3D SPACE and 2D turbo spin echo sequences had excellent agreement (R=0.96 for T1-weighted and 0.98 for T2-weighted, p<0.001) regarding vessel wall thickness measurements. CONCLUSION: The proposed protocol demonstrated the feasibility of attaining carotid plaque screening within a 15-minute scan, which provided sufficient anatomical coverage and critical diagnostic information. This protocol offers the potential for rapid and reliable screening for carotid plaques without contrast agent.