Black-blood Imaging Research Articles

Effect of Angiotensin II Type I Receptor Blockade with Valsartan on Carotid Artery Atherosclerosis: A Double Blind Randomized Clinical Trial Comparing Valsartan and Placebo (EFFERVESCENT)

Progression of atherosclerosis is associated with a greater risk for adverse outcomes. Angiotensin II plays a key role in the pathogenesis and progression of atherosclerosis. We aimed to investigate the effects of angiotensin II type-1 receptor blockade with Valsartan on carotid wall atherosclerosis, with the hypothesis that Valsartan will reduce progression of atherosclerosis. Subjects (n = 120) with carotid intima-media thickness >0.65 mm by ultrasound were randomized (2:1) in a double-blind manner to receive either Valsartan or placebo for 2 years. Bilateral T2-weighted black-blood carotid magnetic resonance imaging was performed at baseline, 12 and 24 months. Changes in the carotid bulb vessel wall area and wall thickness were primary endpoints. Secondary endpoints included changes in carotid plaque thickness, plasma levels of aminothiols, C-reactive protein, fibrinogen, and endothelium-dependent and -independent vascular function. Over 2 years, the carotid bulb vessel wall area decreased with Valsartan (-6.7, 95% CI [-11.6, -1.9] mm(2)) but not with placebo (3.4, 95% CI [-2.8, 9.6] mm(2)), P = .01 between groups. Similarly, mean wall thickness decreased with Valsartan (-0.18, 95% CI [-0.30, -0.06] mm), but not with placebo (0.08, 95% CI [-0.07, 0.23] mm), P = .009 between groups. Furthermore, plaque thickness decreased with Valsartan (-0.35, 95% CI [-0.63, -0.08] mm) but was unchanged with placebo (+0.28, 95% CI [-0.11, 0.69] mm), P = .01 between groups. These findings were unaffected by statin therapy or changes in blood pressure. Notably, there were significant improvements in the aminothiol cysteineglutathione disulfide, and trends to improvements in fibrinogen levels and endothelium-independent vascular function. In subjects with carotid wall thickening, angiotensin II type-1 receptor blockade was associated with regression in carotid atherosclerosis. Whether these effects translate into improved outcomes in subjects with subclinical atherosclerosis warrants investigation.

Efficacy of early carotid endarterectomy for vulnerable plaque in the common carotid artery

Dear Editor Steno-occlusive disease in the common carotid artery (CCA) is relatively rare. Clinical and plaque features of CCA stenosis have thus seldom been investigated [6, 7]. We report here a case of refractory ischemia due to mild common carotid artery stenosis treated with carotid endarterectomy (CEA). A 59-year-old Japanese male developed mild right hemiparesis. Ischemic lesions in the left hemisphere due to mild left distal CCA stenosis with vulnerable plaque were revealed on diffusion-weighted imaging (DWI), time-of-flight imaging (TOF), and three-dimensional computed tomography angiography (3DCTA). Oral clopidgrel and rosuvastatin were initiated. Ten months later, symptoms recurred, and DWI revealed new ischemic lesions (Fig. 1a). Oral aspirin was added. TOF showed an increased plaque volume with retention of the lumen (Fig. 1b, c), indicating expansive remodeling. A fibrous cap (Fig. 1b) was disrupted, and the plaque was directly exposed to the lumen (Fig. 1c). The stenosis remained mild on 3DCTA (Fig. 1d, e upper). However, an intraluminal filling defect implied a mobile plaque (Fig. 1e lower). T1-weighted black-blood imaging showed protrusion of a high-intensity plaque into the lumen (Fig. 1f). Intravenous heparin was therefore started. Nevertheless, the third ischemic event occurred 4 days after the second onset. Six days after the third event, CEAwas performed without major perioperative complications. A large amount of fragile plaque with inner fibrous tissues was resected. A portion of the plaque was exposed directly to the lumen (Fig. 1g). No intraluminal thrombus was identified. Histopathological study showed fragile atheroma containing intraplaque hemorrhage. A portion of the inner fibrous tissues was disrupted (Fig. 1h). The patient has not developed further events after 12months of follow-up. Recently, plaque characteristics have been accurately evaluated using MRI [8, 10]. Intraplaque hemorrhage [1, 9], fibrous cap rupture [5, 9], expansive arterial remodeling [4], and a mobile plaque [2, 3] indicate plaque fragility and a higher risk of ischemic events. Steno-occlusive disease of the CCA is rare (1 %–5 % of stroke patients) because extracranial carotid atherosclerotic disease usually arises from the ICA [6, 7]. CCA lesions are supposed to frequently cause amaurosis fugax due to hemodynamic insufficiency [6]. In this case, the patient suffered repeated cerebral embolisms from mild CCA stenosis. A previous study reported that all CCA lesions showed less than 75 % stenosis [7]. However, from this case, we learned a lesson that an extent of stenosis in the CCA is not necessarily correlated with a risk of stroke as seen in the ICA. Although the vessel retains its lumen, the outer circumference might be increasing, which implies increasing plaque volume and vulnerability [4]. In this case, plaque imaging studies suggested plaque fragility and a higher * Yoshio Araki y.araki@med.nagoya-u.ac.jp

Diagnosis of deep vein thrombosis using 3D black-blood thrombus imaging (BTI): preliminary clinical experience

Background Deep vein thrombosis (DVT) is a common but elusive illness that can lead to fatal pulmonary embolism and sudden death. Effective treatment of DVT requires accurate evaluation of thrombus distribution and stage. MRI is one of diagnostic imaging modalities for DVT, and two conventional methods are MPRAGE[1] and CE-MRV[2]. Recently, 3D T1-weighted variable-flipangle turbo spin-echo (SPACE) was proposed as a black-blood technique that permits more direct visualization of DVT[3]. However, signal suppression of tremendously slow venous blood flow remains a challenge for SPACE. The unsuppressed blood signal could be a confounder in thrombus detection[3]. We hypothesized that the 3D black-blood thrombus imaging (BTI) technique[4] that combines SPACE with DANTE black-blood preparation[5] (DANTE-SPACE) might address the above issue. Methods Experiment The IRB-approved study was performed on a 3T scanner (Siemens TimTrio, Germany). DANTE-SPACE was first optimized on 8 healthy subjects (4 F 4 M, age 25 ± 4) and then tested on 12 patients (6 F 6 M, age 52 ± 13) with DVT. The optimized parameters for DANTE included: FA 15°, pulse trains 175, RF gap 1 ms, gradient 20 mT/m. The parameters for SPACE included: 3D coronal imaging with a resolution of 1.1 × 1.1 × (1.1-1.3) mm (interpolated to 0.55 × 0.55 × [0.55-0.65] mm),TR/ TE 650/9.8 ms, turbo factor 40, GRAPPA 2, scan time ~4 min. The scan was targeted to the thrombus region that was pre-determined by ultrasound within 3 days. Conventional SPACE, MPRAGE, and CE-MRV were conducted for comparison.

Utility of the signal intensity ratio of the spleen and myocardium (SMR) on T2-weighted short tau inversion recovery black-blood (T2-STIR BB) images compared to semi-quantitative analysis in patients with images with diffuse high T2 signal intensity, such as that with Takotsubo cardiomyopathy, cardiac amyloidosis, hypereosinophilic myocarditis, and apical hypertrophic cardiomyopathy

Utility of the signal intensity ratio of the spleen and myocardium (SMR) on T2-weighted short tau inversion recovery black-blood (T2-STIR BB) images compared to semi-quantitative analysis in patients with images with diffuse high T2 signal intensity, such as that with Takotsubo cardiomyopathy, cardiac amyloidosis, hypereosinophilic myocarditis, and apical hypertrophic cardiomyopathy Ryosuke Aoki, Takatomo Nakajima, Yosuke Nakano, Reina Tonegawa, Keiko Masuoka, Makoto Muto

An efficient fat suppression technique for stimulated-echo based CMR

Background Stimulated-echo acquisition mode (STEAM) is one of the key pulse sequences in CMR imaging, as it alleviates rapid magnetization decay with T2 relaxation. Fat suppression is frequently implemented in cardiac imaging to improve visualization and tissue characterization, albeit at the cost of reduced temporal resolution and signal-to-noise ratio (SNR), as well as possible increase of specific absorption rate (SAR). The purpose of this work is to develop an efficient fat suppression method (Spectrally-Presaturated Modulation (SPM)) for STEAM sequences to enable imaging at high temporal-resolution, with high SNR, and no increase in scan time. Methods The developed method is based on saturating the fat magnetization prior to applying the STEAM modulation; therefore, only the water-content of the tissues is modulated by the sequence, resulting in fat-suppressed images without the need to run the fat suppression module during image acquisition (Figure 1). The potential significance of the proposed method has been tested in two STEAM-based cardiac MRI applications: complementary spatial-modulation of magnetization (CSPAMM) tagging, and black-blood cine imaging. In vivo experiments were conducted to evaluate the developed technique and compare it to the commonly implemented chemical-shift selective (CHESS)

Myocardial imaging with 18F-fluoro-2-deoxyglucose positron emission tomography and T2-weighted short tau inversion recovery black-blood images of cardiac magnetic resonance in cardiac sarcoidosis

Myocardial imaging with 18F-fluoro-2-deoxyglucose positron emission tomography and T2-weighted short tau inversion recovery black-blood images of cardiac magnetic resonance in cardiac sarcoidosis Reina Tonegawa, Takatomo Nakajima, Hirotake Takahashi, Mitsuyoshi Mita, Keisuke Shirasaki, Shinya Fujii, Akimichi Murakami, Takeyukii Kubota, Teruhiko Suzuki, Yosuke Nakano, Kensuke Fujiwara, Takashi Miyamoto, Makoto Mutoh

Early Detection and Quantification of Cerebral Venous Thrombosis by Magnetic Resonance Black-Blood Thrombus Imaging.

Early diagnosis of cerebral venous thrombosis (CVT) is currently a major clinical challenge. We proposed a novel magnetic resonance black-blood thrombus imaging technique (MRBTI) for detection and quantification of CVT. MRBTI was performed on 23 patients with proven CVT and 24 patients with negative CVT confirmed by conventional imaging techniques. Patients were divided into 2 groups based on the duration of clinical onset: ≤7 days (group 1) and between 7 and 30 days (group 2). Signal/noise ratio was calculated for the detected thrombus, and contrast/noise ratio was measured between thrombus and lumen and also between thrombus and brain tissue. The feasibility of using MRBTI for thrombus volume measurement was explored, and total thrombus volume was calculated for each patient. In 23 patients with proven CVT, MRBTI correctly identified 113 of 116 segments with a sensitivity of 97.4%. Thrombus signal/noise ratio was 153±57 and 261±95 for group 1 (n=10) and group 2 (n=13), respectively (P<0.01). Thrombus to lumen contrast/noise ratio was 149±57 and 256±94 for group 1 and group 2, respectively. Thrombus to brain tissue contrast/noise ratio was 41±36 and 120±63 (P<0.01), respectively. Quantification of thrombus volume was successfully conducted in all patients with CVT, and mean volume of thrombus was 10.5±6.9 mL. The current findings support that with effectively suppressed blood signal, MRBTI allows selective visualization of thrombus as opposed to indirect detection of venous flow perturbation and can be used as a promising first-line diagnostic imaging tool.

Joint segmentation of lumen and outer wall from femoral artery MR images: Towards 3D imaging measurements of peripheral arterial disease

Three-dimensional (3D) measurements of peripheral arterial disease (PAD) plaque burden extracted from fast black-blood magnetic resonance (MR) images have shown to be more predictive of clinical outcomes than PAD stenosis measurements. To this end, accurate segmentation of the femoral artery lumen and outer wall is required for generating volumetric measurements of PAD plaque burden. Here, we propose a semi-automated algorithm to jointly segment the femoral artery lumen and outer wall surfaces from 3D black-blood MR images, which are reoriented and reconstructed along the medial axis of the femoral artery to obtain improved spatial coherence between slices of the long, thin femoral artery and to reduce computation time. The developed segmentation algorithm enforces two priors in a global optimization manner: the spatial consistency between the adjacent 2D slices and the anatomical region order between the femoral artery lumen and outer wall surfaces. The formulated combinatorial optimization problem for segmentation is solved globally and exactly by means of convex relaxation using a coupled continuous max-flow (CCMF) model, which is a dual formulation to the convex relaxed optimization problem. In addition, the CCMF model directly derives an efficient duality-based algorithm based on the modern multiplier augmented optimization scheme, which has been implemented on a GPU for fast computation. The computed segmentations from the developed algorithm were compared to manual delineations from experts using 20 black-blood MR images. The developed algorithm yielded both high accuracy (Dice similarity coefficients ≥ 87% for both the lumen and outer wall surfaces) and high reproducibility (intra-class correlation coefficient of 0.95 for generating vessel wall area), while outperforming the state-of-the-art method in terms of computational time by a factor of ≈ 20.

Improved black-blood imaging using DANTE-SPACE for simultaneous carotid and intracranial vessel wall evaluation.

The purpose of this study was to develop a three-dimensional black blood imaging method for simultaneously evaluating the carotid and intracranial arterial vessel walls with high spatial resolution and excellent blood suppression with and without contrast enhancement. The delay alternating with nutation for tailored excitation (DANTE) preparation module was incorporated into three-dimensional variable flip angle turbo spin echo (SPACE) sequence to improve blood signal suppression. Simulations and phantom studies were performed to quantify image contrast variations induced by DANTE. DANTE-SPACE, SPACE, and two-dimensional turbo spin echo were compared for apparent signal-to-noise ratio, contrast-to-noise ratio, and morphometric measurements in 14 healthy subjects. Preliminary clinical validation was performed in six symptomatic patients. Apparent residual luminal blood was observed in five (pre-contrast) and nine (post-contrast) subjects with SPACE and only two (post-contrast) subjects with DANTE-SPACE. DANTE-SPACE showed 31% (pre-contrast) and 100% (post-contrast) improvement in wall-to-blood contrast-to-noise ratio over SPACE. Vessel wall area measured from SPACE was significantly larger than that from DANTE-SPACE due to possible residual blood signal contamination. DANTE-SPACE showed the potential to detect vessel wall dissection and identify plaque components in patients. DANTE-SPACE significantly improved arterial and venous blood suppression compared with SPACE. Simultaneous high-resolution carotid and intracranial vessel wall imaging to potentially identify plaque components was feasible with a scan time under 6 min. Magn Reson Med 75:2286-2294, 2016. © 2015 Wiley Periodicals, Inc.

Optimized protocols for cardiac magnetic resonance imaging in patients with thoracic metallic implants.

Cardiac magnetic resonance (MR) imaging is a valuable tool in congenital heart disease; however patients frequently have metal devices in the chest from the treatment of their disease that complicate imaging. Methods are needed to improve imaging around metal implants near the heart. Basic sequence parameter manipulations have the potential to minimize artifact while limiting effects on image resolution and quality. Our objective was to design cine and static cardiac imaging sequences to minimize metal artifact while maintaining image quality. Using systematic variation of standard imaging parameters on a fluid-filled phantom containing commonly used metal cardiac devices, we developed optimized sequences for steady-state free precession (SSFP), gradient recalled echo (GRE) cine imaging, and turbo spin-echo (TSE) black-blood imaging. We imaged 17 consecutive patients undergoing routine cardiac MR with 25 metal implants of various origins using both standard and optimized imaging protocols for a given slice position. We rated images for quality and metal artifact size by measuring metal artifact in two orthogonal planes within the image. All metal artifacts were reduced with optimized imaging. The average metal artifact reduction for the optimized SSFP cine was 1.5+/-1.8mm, and for the optimized GRE cine the reduction was 4.6+/-4.5mm (P < 0.05). Quality ratings favored the optimized GRE cine. Similarly, the average metal artifact reduction for the optimized TSE images was 1.6+/-1.7mm (P < 0.05), and quality ratings favored the optimized TSE imaging. Imaging sequences tailored to minimize metal artifact are easily created by modifying basic sequence parameters, and images are superior to standard imaging sequences in both quality and artifact size. Specifically, for optimized cine imaging a GRE sequence should be used with settings that favor short echo time, i.e. flow compensation off, weak asymmetrical echo and a relatively high receiver bandwidth. For static black-blood imaging, a TSE sequence should be used with fat saturation turned off and high receiver bandwidth.

Characterization of Craniocervical Artery Dissection by Simultaneous MR Noncontrast Angiography and Intraplaque Hemorrhage Imaging at 3T.

Craniocervical artery dissection is the most common cause of ischemic stroke identified in young adults. For the diagnosis of craniocervical artery dissection, multisequence MR imaging is recommended but is time-consuming. Recently, investigators proposed a simultaneous noncontrast angiography and intraplaque hemorrhage imaging technique allowing simultaneous noncontrast MRA and vessel wall imaging in a single scan. This study sought to investigate the feasibility of 3D simultaneous noncontrast angiography and intraplaque hemorrhage MR imaging in the characterization of craniocervical artery dissection. Twenty-four symptomatic patients (mean age, 45.0 ± 16.1 years; 21 men) with suspected craniocervical artery dissection were recruited. The 3D simultaneous noncontrast angiography and intraplaque hemorrhage 3D TOF MRA and black-blood imaging sequences were performed on a 3T MR imaging scanner. The agreement between simultaneous noncontrast angiography and intraplaque hemorrhage imaging and multisequence MR imaging in evaluating arterial dissection was determined. Dissection was found to involve 1 artery in 22 patients and 2 arteries in 2 patients. The intramural hematoma and luminal occlusion were detected in 19 (79.2%) and 11 (45.8%) patients, respectively. In measuring stenosis, the Cohen κ value between 3D TOF MRA and simultaneous noncontrast angiography and intraplaque hemorrhage imaging was 0.82 (P < .001). All intramural hematomas on multisequence imaging were successfully identified by simultaneous noncontrast angiography and intraplaque hemorrhage imaging. 3D simultaneous noncontrast angiography and intraplaque hemorrhage imaging showed excellent agreement with multisequence MR imaging in evaluating luminal stenosis and intramural hematoma in patients with craniocervical artery dissection. The simultaneous noncontrast angiography and intraplaque hemorrhage imaging saved nearly 50% of scanning time compared with multisequence MR imaging. Our findings suggest that 3D simultaneous noncontrast angiography and intraplaque hemorrhage imaging might be an alternative, time-efficient diagnostic tool for craniocervical artery dissection.

Clinical value of black-blood high-resolution magnetic resonance imaging for intracranial atherosclerotic plaques.

The present study evaluated the value of black-blood high-resolution magnetic resonance imaging (HRMRI) for the visualization of intracranial atherosclerosis (ICAS) plaques. A total of 110 patients with cerebral artery or vertebrobasilar stenosis, vessel occlusion or a significantly weakened signal in black-blood magnetic resonance angiography (MRA; three-dimensional time-of-flight) were examined. Black-blood MRA was used to observe whether plaques were present in the abnormal vascular walls. Among the 110 patients with cerebral infarction, 16 cases presented with no significant abnormality of the lumen and walls, while plaques were observed in 94 cases. The plaques were categorized according to their signal characteristics, which resulted in the identification of four cases of type I and II plaques, 15 cases of type III, 26 cases of type IV and V, 23 cases of type VI, 11 cases of type VII, 14 cases of type VIII and one case of a mixed plaque. In summary, 3.0 T black-blood HRMRI was demonstrated to objectively exhibit characteristics of various types of ICAS plaques. Therefore, this imaging technique may be applied as a key method for the clinical non-invasive determination of ICAS plaques.

Three-dimensional quantitative T1 and T2 mapping of the carotid artery: Sequence design and in vivo feasibility.

A novel three-dimensional (3D) T1 and T2 mapping protocol for the carotid artery is presented. A 3D black-blood imaging sequence was adapted allowing carotid T1 and T2 mapping using multiple flip angles and echo time (TE) preparation times. B1 mapping was performed to correct for spatially varying deviations from the nominal flip angle. The protocol was optimized using simulations and phantom experiments. In vivo scans were performed on six healthy volunteers in two sessions, and in a patient with advanced atherosclerosis. Compensation for patient motion was achieved by 3D registration of the inter/intrasession scans. Subsequently, T1 and T2 maps were obtained by maximum likelihood estimation. Simulations and phantom experiments showed that the bias in T1 and T2 estimation was < 10% within the range of physiological values. In vivo T1 and T2 values for carotid vessel wall were 844 ± 96 and 39 ± 5 ms, with good repeatability across scans. Patient data revealed altered T1 and T2 values in regions of atherosclerotic plaque. The 3D T1 and T2 mapping of the carotid artery is feasible using variable flip angle and variable TE preparation acquisitions. We foresee application of this technique for plaque characterization and monitoring plaque progression in atherosclerotic patients.

Fast segmentation of the femoral arteries from 3D MR images: A tool for rapid assessment of peripheral arterial disease.

The peripheral arterial disease is a powerful indicator of coexistent generalized atherosclerosis. As plaques in femoral arteries are diffused and can span a length of 30 cm, a large coverage of the arteries is required to assess the full extent of atherosclerosis. Recent development of 3D black-blood magnetic resonance imaging sequences has allowed fast acquisition of images with an extended longitudinal coverage. Vessel wall volume quantification requires the segmentation of the lumen and outer wall boundaries, and conventional manual planimetry would be too time-consuming to be feasible for analyzing images with such a large coverage. To address this challenge in image analysis, this work introduces an efficient 3D algorithm to segment the lumen and outer wall boundaries for plaque and vessel wall quantification in the femoral artery. To generate the initial lumen surface, a user identified the location of the lumen centers manually on a set of transverse images with a user-specified interslice distance (ISD). A number of geometric operators were introduced to automatically adjust the initial lumen surface based on pixel intensity and gradient along the boundary and at the center of each transverse slice. The adjusted surface was optimized by a 3D deformable model driven by the local stiffness force and external force based on image gradient. The optimized lumen surface was expanded to obtain the initial outer wall surface, which was subsequently optimized by the 3D deformable model. The algorithm was executed with and without adjustment of the initial lumen surface and for three different selections of ISD: 10, 20, and 30 mm. The segmentation accuracy was improved in a statistically significant way with the introduction of initial lumen surface adjustment, but was insensitive to the ISD setting. When compared with the manual segmentation, the settings with adjustment have, on average, mean absolute differences (MADs) of 0.28 and 0.36 mm, respectively, for lumen and outer wall segmentations, which are significantly lower than those obtained when the adjustment operators were not applied (MAD = 0.43 and 0.59 mm for lumen and outer wall segmentations). The algorithm took about 1% of the time required for manual segmentation to complete segmenting the whole 3D femoral artery. The proposed semiautomatic algorithm generated accurate lumen and outer wall boundaries from 3D black-blood MR images with few user interactions, thereby allowing rapid and streamlined assessment of plaque burden in the femoral arteries.

Relaxation enhanced compressed sensing three-dimensional black-blood vessel wall MR imaging: Preliminary studies

ObjectiveIn this study, we sought to investigate the feasibility of a new technique termed relaxation enhanced compressed sensing three-dimensional motion-sensitizing driven equilibrium prepared 3D rapid gradient echo sequence (RECS-3D MERGE). Materials and methodsThe RECS-3D MERGE sequence consisted of a 3D MERGE sequence for imaging, a period of delay time (TD) for relaxation enhancement, and a pseudo-centric phase encoding order used for under-sampling acquisition to maintain scan efficiency. Seven healthy volunteers and six patients with 40% to 75% carotid artery stenosis were recruited in this study. Healthy subjects underwent 3D MERGE, RECS-3D MERGE and two-dimensional (2D) T1-weighted double inversion recovery fast spin echo (T1W DIR-FSE) scans. The signal ratio (SR) values of 21 RECS-3D MERGE scans were compared in order to determine the optimal scan parameter set of acceleration factor (AF) and delay time (TD) for RECS-3D MERGE sequence. Patients then underwent 3D MERGE, RECS-3D MERGE using the aforementioned optimal scan parameter set and 2D T1W DIR-FSE scans. Two radiologists, blinded to the imaging technique, qualitatively graded each image on a six-point ordinal scale. ResultsThe highest value of SR occurred with the scan parameter set of 3-fold AF and 800ms TD. Compared to 3D MERGE, RECS-3D MERGE with the parameter set significantly improved the image quality for both healthy subjects and patients experiments, while the scan efficiency was not sacrificed. And no significant differences were observed in the subjective scores of RECS-3D MERGE and 2D T1W DIR-FSE image qualities. ConclusionRECS-3D MERGE technique achieved significant improvement in black-blood image quality compared with 3D MERGE. And the image quality of this 3D rapid carotid black-blood imaging technique is comparable to 2D T1W DIR-FSE while it has much higher scan efficiency.

Automatic segmentation of myocardium from black-blood MR images using entropy and local neighborhood information.

By using entropy and local neighborhood information, we present in this study a robust adaptive Gaussian regularizing Chan–Vese (CV) model to segment the myocardium from magnetic resonance images with intensity inhomogeneity. By utilizing the circular Hough transformation (CHT) our model is able to detect epicardial and endocardial contours of the left ventricle (LV) as circles automatically, and the circles are used as the initialization. In the cost functional of our model, the interior and exterior energies are weighted by the entropy to improve the robustness of the evolving curve. Local neighborhood information is used to evolve the level set function to reduce the impact of the heterogeneity inside the regions and to improve the segmentation accuracy. An adaptive window is utilized to reduce the sensitivity to initialization. The Gaussian kernel is used to regularize the level set function, which can not only ensure the smoothness and stability of the level set function, but also eliminate the traditional Euclidean length term and re-initialization. Extensive validation of the proposed method on patient data demonstrates its superior performance over other state-of-the-art methods.

Fast 3D isotropic imaging of the aortic vessel wall by application of 2D spatially selective excitation and a new way of inversion recovery for black blood imaging.

Aortic vessel wall imaging requires large coverage and a high spatial resolution, which makes it prohibitively time-consuming for clinical use. This work explores the feasibility of imaging the descending aorta in acceptable scan time, using two-dimensional (2D) spatially selective excitation and a new way of inversion recovery for black blood imaging. The excitation pattern and field of view in a 3D gradient echo sequence are reduced in two dimensions, following the aorta's anisotropic geometry. Black blood contrast is obtained by partially inverting the blood's magnetization in the heart at the start of the cardiac cycle. Imaging is delayed until the inverted blood has filled the desired part of the aorta. The flip angle and delay are determined such that the blood signal is nulled upon arrival in the aorta. Experiments on eight volunteers showed that the descending aortic vessel wall could be imaged over more than 15 cm at a maximal resolution of 1.5 × 1.5 × 1.5 mm(3) in less than 5 min minimal scan time. This feasibility study demonstrates that time-efficient isotropic imaging of the descending aorta is possible by using 2D spatially selective excitation for motion artifact reduction and a new way of inversion recovery for black blood imaging.

Volumetric black-blood imaging of aortic dissection using T2 prepared inversion recovery

Background Aortic dissection is a life threatening condition, and the commonest presentation of the acute aortic syndrome, occurring in 80-90% of such cases. Identification of intimal tears is important to enable the success of an interventional procedure. MRI allows for black-blood contrast to depict the aortic vessel wall and intimal flap with positive contrast which help delineate tear and intimal anatomy. However, the conventional black-blood approach (double inversion recovery) is limited to single slice imaging with relatively low resolution in slice direction. In this study, we compare the usefulness of two approaches using T2 prepared inversion recovery (T2IR) and T2 prepared phase sensitive inversion recovery (T2PSIR) for volumetric high-resolution black-blood aortic imaging in healthy volunteers including a pilot study to optimize flow-independence.

3D high-resolution atrial wall thickness maps using black-blood PSIR

Background Atrial fibrillation (AF) is the most common cardiac arrhythmia. It is often treated using catheter ablation, which aims to isolate arrhythmogenic regions by delivering localized energy. Whereas an insufficient energy delivery can lead to AF recurrence, excessive power can cause potentially lethal complications. Knowledge of atrial wall thickness can help select an optimal amount of energy, but clinical imaging does not currently provide atrial wall thickness data for patients. Even ex-vivo studies have only measured the thickness of the atrial wall in discrete locations using CT or post-mortem samples. In this study, we apply black-blood MR imaging to reconstruct both epiand endocardial surfaces of the entire atria and compute wall thickness maps in healthy volunteers. To our knowledge, this is the first study to provide a complete 3D map of the wall thickness of both right and left atria.

Improved 2D slice-interleaved flow-independent cardiac black blood imaging using Ferumoxytol

Background Double inversion recovery (DIR) is the most commonly used black blood (BB) preparation method. However its single slice nature makes the acquisition inefficient and flow-dependence causes insufficient blood suppression when stagnant blood or in-plane blood flow is present. In this work, we propose to use ferumoxytol, an FDA approved iron oxide particle for treating iron deficiency anemia, as an MR contrast agent to achieve flow-independent BB imaging by taking advantage of its strong