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Purpose: Many diseases can simultaneously involve renal arteries and the adjacent abdominal aorta. This study proposed a free‐breathing three‐dimensional (3D) isotropic‐resolution magnetic resonance sequence for simultaneous vessel wall imaging (VWI) of bilateral renal arteries and adjacent abdominal aorta. Methods: A respiratory‐triggered isotropic‐resolution sequence that combined the improved motion‐sensitized driven‐equilibrium (iMSDE) preparation with the spoiled gradient recalled (SPGR) readout (iMSDE‐SPGR) was proposed for simultaneous VWI of renal arteries and abdominal aorta. The proposed iMSDE‐SPGR sequence was optimized by positioning spatial saturation pulses (i.e., REST slabs) elaborately to further alleviate respiratory and gastrointestinal motion artifacts and selecting appropriate first‐order gradient moment (m1) of the iMSDE preparation. Thirteen healthy subjects and 13 patients with renal artery stenosis underwent simultaneous VWI with the optimized iMSDE‐SPGR sequence at 3.0 T. Signal‐to‐noise ratio (SNR), contrast‐to‐noise ratio (CNR), and morphology of renal arterial wall and aortic wall were measured. Reproducibility of intra‐observer, inter‐observer, and scan–rescan (n = 13 healthy subjects) in measuring SNR, CNR, and morphology was evaluated. For the reproducibility test, the agreement was determined using intraclass correlation coefficients (ICC), and the differences were compared using paired t‐test or nonparametric Wilcoxon test when appropriate. Bland–Altman plots were used to calculate the bias between observers and between scans. Results: The proposed iMSDE‐SPGR sequence was feasible for simultaneous VWI both in the healthy subjects and the patients. The sequence showed good to excellent inter‐observer (ICC: 0.615‐0.999), excellent intra‐observer (ICC: 0.801‐0.998), and scan–rescan (ICC: 0.768‐0.998) reproducibility in measuring morphology, SNR, and CNR. There were no significant differences in SNR, CNR, and morphology measurements between observers and between scans (all p > 0.05). Bland–Altman plots showed small bias in assessing SNR, CNR, and morphology. Data conclusion: The proposed free‐breathing 3D isotropic‐resolution iMSDE‐SPGR technique is feasible and reproducible for simultaneous VWI of bilateral renal arteries and adjacent abdominal aorta. [ABSTRACT FROM AUTHOR]

To evaluate the feasibility and reproducibility of 2D and 3D black-blood sequences in measuring morphology of renal arterial wall. The 2D and 3D imaging sequences used variable-refocusing-flip-angle and constant-low-refocusing-flip-angle turbo spin echo (TSE) readout respectively, with delicately selected black-blood scheme and respiratory motion trigger for free-breathing imaging. Fourteen healthy subjects and three patients with Takayasu arteritis underwent renal artery wall imaging with 3D double inversion recovery (DIR) TSE and 2D Variable Flip Angle-TSE (VFA-TSE) black-blood sequences at 3.0 T. Four healthy subjects were randomly selected for scan-rescan reproducibility experiments. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and morphology of arterial wall were measured and compared using paired- t- test or Wilcoxon signed-rank test between 2D and 3D sequences. The inter-observer, intra-observer and scan-rescan agreements of above measurements were determined using intraclass correlation coefficient (ICC). The 2D and 3D imaging sequences showed similar morphological measurements (lumen area, wall area, mean wall thickness and maximum wall thickness) of renal arterial wall (all P > 0.05) and excellent agreement (ICC: 0.853–0.954). Compared to 2D imaging, 3D imaging exhibited significantly lower SNR lumen (P < 0.01) and SNR wall (P = 0.037), similar contrast-to-noise ratio (CNR) (P = 0.285), and higher CNR efficiency (CNR eff) (P < 0.01). Both 2D and 3D imaging showed good to excellent inter-observer (ICC: 0.723–0.997), intra-observer (ICC: 0.749–0.996) and scan-rescan (ICC: 0.710–0.992) reproducibility in measuring renal arterial wall morphology, SNR and CNR, respectively. Both high-resolution free-breathing 2D VFA-TSE and 3D DIR TSE black-blood sequences are feasible and reproducible in high-resolution renal arterial wall imaging. The 2D imaging has high SNR, whereas 3D imaging has high imaging efficiency. • Free-breathing 2D VFA-TSE and 3D DIR TSE black-blood sequences provide feasible and reproducible renal arterial imaging. • Free-breathing 2D VFA-TSE and 3D DIR TSE black-blood sequences show similar morphology, image quality and CNR in renal arterial wall imaging. • For different clinical settings, 2D VFA-TSE black-blood imaging has high SNR, whereas 3D DIR TSE black-blood imaging has high imaging efficiency. [ABSTRACT FROM AUTHOR]

To determine the usefulness of multiparametric magnetic resonance (MR) quantitative imaging in characterizing the kidneys in systemic sclerosis (SSc) patients. Forty-six SSc patients (47.9 ± 12.8 years, 40 females) and 22 age- and sex- matched healthy volunteers (46.1 ± 13.8 years, 20 females) were recruited and underwent renal MR imaging by acquiring blood oxygen level dependent and saturated multi-delay renal arterial spin labeling (SAMURAI) sequences. The T2* value, T1 value, renal blood flow (RBF), arterial bolus arrival time (aBAT), and tissue bolus arrival time (tBAT) of renal cortex were measured and compared among diffuse cutaneous SSc (dcSSc) and limited cutaneous SSc (lcSSc) groups and healthy controls using One-way ANOVA and analyzed by logistic regression. Compared to healthy volunteers, SSc patients with normal estimated glomerular filtration rate (n = 40) had significantly lower T2* value (P = 0.026) in the left renal cortex, longer T1 value (right: P = 0.015; left: P = 0.023), lower RBF (right: P < 0.001; left: P < 0.001), and shorter tBAT (right: P < 0.001; left: P = 0.005) in both right and left renal cortex after adjusting for demographics. The dcSSc patients (n = 23) had significantly lower RBF in both right (226.7 ± 65.2 mL/100 g/min vs. 278.2 ± 73.5 mL/100 g/min, P = 0.022) and left (194.5 ± 71.5 mL/100 g/min vs. 252.7 ± 84.4 mL/100 g/min, P = 0.020) renal cortex compared to the lcSSc patients (n = 23) after adjusting for demographics, but the significance of the difference was attenuated after further adjusting for modified Rodnan skin score and digital ulcers. Multi-parametric MR quantitative imaging, particularly multi-delay ASL perfusion imaging, is a useful technique for characterizing the kidneys and classification of SSc patients. • Multiparametric MR quantitative imaging was utilized to characterize the impairment of renal microstructure and function in SSc patients. • Compared to the healthy volunteers, the SSc patients were more likely to have significantly lower T2*, longer T1, lower RBF, and shorter tBAT. • The dcSSc patients were found to have significantly lower RBF than the lcSSc patients. [ABSTRACT FROM AUTHOR]

Image registration is one of the most important processes for the generation of remote sensing image mosaics. This paper focuses on the special problems related to remote sensing data registration, and multi-temporal data mosaic applications in the domain of forestry. It proposes an image registration method based on hierarchical convolutional features, and applies it to improve the efficiency of large scale forestry image mosaic generation. This method uses a deep learning architecture to adaptively obtain image features from deep convolutional neural networks. The features derived from different images at different depth are sent to a correlation filter to compute the similarity between them; then the locations of the feature points are computed precisely. Based on this method, we study forestry image registration and the mosaic framework. We apply our approach to remote sensing images under different weather and seasonal conditions, and compare the results with those generated using the traditional SIFT image mosaic method. The experimental result shows that our method can detect and match the image feature points with significant spectral difference, and effectively extract feature points to generate accurate image registration and mosaic results. This demonstrates the effectiveness and robustness of the proposed approach. [ABSTRACT FROM AUTHOR]

Segmentation of cerebral vasculature on MR vascular images is of great significance for clinical application and research. However, the existing cerebrovascular segmentation approaches are limited due to insufficient image contrast and complicated algorithms. This study aims to explore the potential of the emerging four-dimensional arterial spin labeling magnetic resonance angiography (4D ASL-MRA) technique for fast and accurate cerebrovascular segmentation with a simple machine-learning approach. Nine temporal features were extracted from the intensity-time signal of each voxel, and eight spatial features from the neighboring voxels. Then, the unsupervised outlier detection algorithm, i.e. Isolation Forest, is used for segmentation of the vascular voxels based on the extracted features. The total length of the centerlines of the intracranial arterial vasculature, the dice similarity coefficient (DSC), and the average Hausdorff Distance (AVGHD) on the cross-sections of small- to large-sized vessels were calculated to evaluate the performance of the segmentation approach on 4D ASL-MRA of 18 subjects. Experiments show that the temporal information on 4D ASL-MRA can largely improve the segmentation performance. In addition, the proposed segmentation approach outperforms the traditional methods that were performed on the 3D image (i.e. the temporal average intensity projection of 4D ASL-MRA) and the previously proposed frame-wise approach. In conclusion, this study demonstrates that accurate and robust segmentation of cerebral vasculature is achievable on 4D ASL-MRA by using a simple machine-learning approach with appropriate features. [ABSTRACT FROM AUTHOR]

We compared plaque characteristics between symptomatic and asymptomatic sides in patients with bilateral carotid vulnerable plaques using magnetic resonance imaging (MRI). Participants (n = 67; mean age: 65.8 ± 7.7 years, 61 males) with bilateral carotid vulnerable plaques were included. Vulnerable plaques were characterized by intraplaque hemorrhage (IPH), large lipid-rich necrotic core (LRNC), or fibrous cap rupture (FCR) on MRI. Symptomatic vulnerable plaques showed greater plaque burden, LRNC volume (median: 221.4 vs 134.8 mm3, P =.003), IPH volume (median: 32.2 vs 22.5 mm3, P =.030), maximum percentage (Max%) LRNC (median: 51.3% vs 41.8%, P =.002), Max%IPH (median: 13.4% vs 9.5%, P =.022), cumulative slices of LRNC (median: 10 vs 8, P =.005), and more juxtaluminal IPH and/or thrombus (29.9% vs 6.0%, P =.001) and FCR (37.3% vs 16.4%, P =.007) than asymptomatic ones. After adjusting for plaque burden, differences in juxtaluminal IPH and/or thrombus (odds ratio [OR]: 5.49, 95% CI: 1.61-18.75, P =.007) and FCR (OR: 2.90, 95% CI: 1.16-7.24, P =.022) between bilateral sides remained statistically significant. For patients with bilateral carotid vulnerable plaques, symptomatic plaques had greater burden, more juxtaluminal IPH and/or thrombus, and FCR compared with asymptomatic ones. The differences in juxtaluminal IPH and/or thrombus and FCR between bilateral sides were independent of plaque burden. [ABSTRACT FROM AUTHOR]

• The carotid plaque calcification is independently associated with the WMHs. • Intracranial artery atherosclerotic stenosis was not associated with the WMHs. • Carotid plaque characteristics may have closer association with the WMHs. This study aimed to investigate the associations of atherosclerotic plaque characteristics in intracranial and extracranial carotid arteries with severity of white matter hyperintensities (WMHs) in symptomatic patients using magnetic resonance (MR) imaging. Patients with cerebrovascular symptoms and carotid plaque were recruited from the cross-sectional, multicenter study of CARE-II. Luminal stenosis of intracranial and extracranial carotid arteries, carotid plaque compositional features, and WMHs were evaluated by brain structural and vascular MR imaging. The atherosclerotic plaque characteristics in intracranial and extracranial carotid arteries were compared between patients with and without moderate-to-severe WMHs (Fazekas score > 2), and their associations with severity of WMHs were analyzed using logistic regression. Of the recruited 622 patients (mean age, 58.7 ± 10.9 years; 422 males), 221 (35.5 %) had moderate-to-severe WMHs with higher prevalence of moderate-to-severe luminal stenosis (17.0 % vs. 10.4 %), intraplaque hemorrhage (15.7 % vs. 9.0 %), thin/ruptured fibrous cap (30.2 % vs. 20.4 %), calcification (44.4 % vs. 22.2 %) and lipid-rich necrotic core (63.8 % vs. 51.1 %) in carotid artery compared to those without (all P < 0.05). Multivariate logistic regression showed that carotid calcification (OR, 1.854; 95 % CI, 1.187–2.898; P = 0.007) was independently associated with moderate-to-severe WMHs after adjusting for confounding factors. No significant association was found between intracranial atherosclerotic stenosis and moderate-to-severe WMHs (P > 0.05). Carotid atherosclerotic plaque features, particularly presence of calcification, were independently associated with severity of WMHs, but such association was not found in intracranial atherosclerotic stenosis, suggesting that carotid atherosclerotic plaque characteristics may have closer association with severity of WMHs compared to intracranial atherosclerosis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Performance of HZSM-5 in glycerol dehydration was greatly improved by phosphoric acid impregnation. • The acid strength of HZSM-5 zeolite was weakened by P incorporation. • Weakened acid strength suppressed coke formation and prolonged the catalytic lifetime. • 1.0P-NZ showed excellent performance in glycerol dehydration. • Product diffusion restriction played a crucial role in promoting acrolein selectivity over HZSM-5. HZSM-5 zeolites modified by simple and economical impregnation with phosphoric acid were applied to acrolein production from glycerol. After 68 h on stream, the glycerol conversion was still maintained at 100 % with an acrolein selectivity of 89.6 % on phosphorus modified nanosheet HZSM-5, which ranks among the best catalytic performance in glycerol dehydration catalyzed by zeolites. Besides, improvement in catalytic stability was further confirmed by the lowered deactivation rate on phosphorus modified HZSM-5 zeolite. Characterization results revealed that the acidity of HZSM-5 zeolite was adjusted by phosphorus incorporation. More importantly, the regulative mechanism was thoroughly discussed basing on a comprehensive consideration of the 27Al MAS NMR and Py-IR results. Further investigation with in situ FT-IR indicated that products or intermediates in glycerol dehydration could be more easily desorbed from phosphorus modified HZSM-5 zeolite with weaker acidity, which dramatically suppressed coke formation and greatly prolonged the lifetime of catalyst. Moreover, for the first time, diffusivity calculation and experimental results illustrated that product diffusion restriction played a crucial role in producing acrolein with ultrahigh selectivity over HZSM-5 apart from acidity. [ABSTRACT FROM AUTHOR]

• Slice-based and time-specific metrics were proposed for carotid hemodynamics. • Hemodynamic metrics are associated with presence of vulnerable plaque features. • Combining hemodynamics with plaque burden could better discriminate presence of IPH. Hemodynamic patterns play key roles in progression of carotid vulnerable plaques. However, most of previous studies utilized maximum or averaged value of hemodynamic measurements which is not an ideal representative of hemodynamic patterns. This study aimed to investigate the association of slice-based and time-specific hemodynamic measurements with carotid vulnerable plaque using magnetic resonance (MR) vessel wall imaging and histology. Thirty-two patients (mean age: 63.9±8.1 years; 25 males) with carotid atherosclerotic stenosis (≥50% stenosis) referred to carotid endarterectomy were recruited and underwent MR vessel wall imaging. Carotid plaque burden was evaluated on MR images and vulnerable plaque features including calcification, lipid-rich necrotic core, and intra-plaque hemorrhage (IPH) were identified by histology. The slice-based and time-specific hemodynamic measurements were extracted from computational fluid dynamics simulation of 3D carotid arterial model. Correlation coefficients between hemodynamic measurements and carotid plaque features were calculated and the logistic regressions with generalized estimating equation (GEE) were conducted. The value in discriminating carotid vulnerable plaque features was determined by receiver-operating-characteristic analysis. Of 102 MR-histology matched slices from 32 patients, time-averaged wall shear stress (TAWSS) (r=0.263, p=0.008), oscillatory shear index (OSI) (r=-0.374, p<0.001), and peakWSS (r=0.232, p=0.019) were significantly associated with carotid IPH. The logistic regression with GEE revealed that peakWSS (OR, 1.206; 95% CI, 1.026-1.418; p, 0.023) and TAWSS (OR, 0.364, 95% CI, 0.138-0.959; p, 0.041) were significantly associated with presence of IPH after adjusting for age and BMI. In discriminating carotid IPH, the AUC of TAWSS, OSI, combined TAWSS with maximum wall thickness (MWT) and combined OSI with MWT was 0.656, 0.722, 0.761, and 0.764, respectively. Slice-based and time-specific hemodynamic characteristics could effectively discriminate carotid IPH. Combination of hemodynamic measurements with carotid plaque burden might be a stronger indicator for carotid vulnerable plaque features than each measurement alone. [ABSTRACT FROM AUTHOR]