MRI in the Evaluation of Cryptogenic Stroke and Embolic Stroke of Undetermined Source.

Cryptogenic stroke refers to a stroke of undetermined etiology. It accounts for approximately one-fifth of ischemic strokes and has a higher prevalence in younger patients. Embolic stroke of undetermined source (ESUS) refers to a subgroup of patients with nonlacunar cryptogenic strokes in whom embolism is the suspected stroke mechanism. Under the classifications of cryptogenic stroke or ESUS, there is wide heterogeneity in possible stroke mechanisms. In the absence of a confirmed stroke etiology, there is no established treatment for secondary prevention of stroke in patients experiencing cryptogenic stroke or ESUS, despite several clinical trials, leaving physicians with a clinical dilemma. Both conventional and advanced MRI techniques are available in clinical practice to identify differentiating features and stroke patterns and to determine or infer the underlying etiologic cause, such as atherosclerotic plaques and cardiogenic or paradoxical embolism due to occult pelvic venous thrombi. The aim of this review is to highlight the diagnostic utility of various MRI techniques in patients with cryptogenic stroke or ESUS. Future trends in technological advancement for promoting the adoption of MRI in such a special clinical application are also discussed.

MR Multitasking-based multi-dimensional assessment of cardiovascular system (MT-MACS) with extended spatial coverage and water-fat separation.

PURPOSE: To extend the MR MultiTasking-based Multidimensional Assessment of Cardiovascular System (MT-MACS) technique with larger spatial coverage and water-fat separation for comprehensive aortocardiac assessment. METHODS: MT-MACS adopts a low-rank tensor image model for 7D imaging, with three spatial dimensions for volumetric imaging, one cardiac motion dimension for cine imaging, one respiratory motion dimension for free-breathing imaging, one T2-prepared inversion recovery time dimension for multi-contrast assessment, and one T2*-decay time dimension for water-fat separation. Nine healthy subjects were recruited for the 3T study. Overall image quality was scored on bright-blood (BB), dark-blood (DB), and gray-blood (GB) contrasts using a 4-point scale (0-poor to 3-excellent) by two independent readers, and their interreader agreement was evaluated. Myocardial wall thickness and left ventricular ejection fraction (LVEF) were quantified on DB and BB contrasts, respectively. The agreement in these metrics between MT-MACS and conventional breath-held, electrocardiography-triggered 2D sequences were evaluated. RESULTS: MT-MACS provides both water-only and fat-only images with excellent image quality (average score = 3.725/3.780/3.835/3.890 for BB/DB/GB/fat-only images) and moderate to high interreader agreement (weighted Cohen's kappa value = 0.727/0.668/1.000/1.000 for BB/DB/GB/fat-only images). There were good to excellent agreements in myocardial wall thickness measurements (intraclass correlation coefficients [ICC] = 0.781/0.929/0.680/0.878 for left atria/left ventricle/right atria/right ventricle) and LVEF quantification (ICC = 0.716) between MT-MACS and 2D references. All measurements were within the literature range of healthy subjects. CONCLUSION: The refined MT-MACS technique provides multi-contrast, phase-resolved, and water-fat imaging of the aortocardiac systems and allows evaluation of anatomy and function. Clinical validation is warranted.

An Ultrasmall Fe3 O4 -Decorated Polydopamine Hybrid Nanozyme Enables Continuous Conversion of Oxygen into Toxic Hydroxyl Radical via GSH-Depleted Cascade Redox Reactions for Intensive Wound Disinfection.

Nanozyme-based chemodynamic therapy (CDT) for fighting bacterial infections faces several major obstacles including low hydrogen peroxide (H2 O2 ) level, over-expressed glutathione (GSH) in infected sites, and inevitable damage to healthy tissue with abundant nonlocalized nanozymes. Herein, a smart ultrasmall Fe3 O4 -decorated polydopamine (PDA/Fe3 O4 ) hybrid nanozyme is demonstrated that continuously converts oxygen into highly toxic hydroxyl radical (•OH) via GSH-depleted cascade redox reactions for CDT-mediated bacterial elimination and intensive wound disinfection. In this system, photonic hyperthermia of PDA/Fe3 O4 nanozymes can not only directly damage bacteria, but also improve the horseradish peroxidase-like activity of Fe3 O4 decorated for CDT. Surprisingly, through photothermal-enhanced cascade catalytic reactions, PDA/Fe3 O4 nanozymes can consume endogenous GSH for disrupting cellular redox homeostasis and simultaneously provide abundant H2 O2 for improving •OH generation, ultimately enhancing the antibacterial performance of CDT. Such PDA/Fe3 O4 can bind with bacterial cells, and reveals excellent antibacterial property against both Staphylococcus aureus and Escherichia coli. Most interestingly, PDA/Fe3 O4 nanozymes can be strongly retained in infected sites by an external magnet for localized long-term in vivo CDT and show minimal toxicity to healthy tissues and organs. This work presents an effective strategy to magnetically retain the therapeutic nanozymes in infected sites for highly efficient CDT with good biosafety.

Vessel Wall Magnetic Resonance Imaging Biomarkers of Symptomatic Intracranial Atherosclerosis: A Meta-Analysis.

BACKGROUND AND PURPOSE: Intracranial atherosclerotic disease is a common cause of stroke worldwide. Intracranial vessel wall magnetic resonance imaging may be able to identify imaging biomarkers of symptomatic plaque. We performed a meta-analysis to evaluate the strength of association of imaging features of symptomatic plaque leading to downstream ischemic events. Effects on the strength of association were also assessed accounting for possible sources of bias and variability related to study design and magnetic resonance parameters. METHODS: PubMed, Scopus, Web of Science, EMBASE, and Cochrane databases were searched up to October 2019. Two independent reviewers extracted data on study design, vessel wall magnetic resonance imaging techniques, and imaging end points. Per-lesion odds ratios (OR) were calculated and pooled using a bivariate random-effects model. Subgroup analyses, sensitivity analysis, and evaluation of publication bias were also performed. RESULTS: Twenty-one articles met inclusion criteria (1750 lesions; 1542 subjects). Plaque enhancement (OR, 7.42 [95% CI, 3.35-16.43]), positive remodeling (OR, 5.60 [95% CI, 2.23-14.03]), T1 hyperintensity (OR, 2.05 [95% CI, 1.27-3.32]), and surface irregularity (OR, 4.50 [95% CI, 1.39-8.57]) were significantly associated with downstream ischemic events. T2 signal intensity was not significant (P=0.59). Plaque enhancement was significantly associated with downstream ischemic events in all subgroup analyses and showed stronger associations when measured in retrospectively designed studies (P=0.02), by a radiologist as a rater (P<0.001), and on lower vessel wall magnetic resonance imaging spatial resolution sequences (P=0.02). CONCLUSIONS: Plaque enhancement, positive remodeling, T1 hyperintensity, and surface irregularity emerged as strong imaging biomarkers of symptomatic plaque in patients with ischemic events. Plaque enhancement remained significant accounting for sources of bias and variability in both study design and instrument. Future studies evaluating plaque enhancement as a predictive marker for stroke recurrence with larger sample sizes would be valuable.

Motion-compensated 3D turbo spin-echo for more robust MR intracranial vessel wall imaging.

PURPOSE: (1) To investigate the effect of internal localized movement on 3DMR intracranial vessel wall imaging and (2) to develop a novel motion-compensation approach combining volumetric navigator (vNav) and self-gating (SG) to simultaneously compensate for bulk and localized movements. METHODS: A 3D variable-flip-angle turbo spin-echo (ie, SPACE) sequence was modified to incorporate vNav and SG modules. The SG signals from the center k-space line are acquired at the beginning of each TR to detect localized motion-affected TRs. The vNavs from low-resolution 3D EPI are acquired to identify bulk head motion. Fifteen healthy subjects and 3 stroke patients were recruited in this study. Overall image quality (0-poor to 4-excellent) and vessel wall sharpness were compared among the scenarios with and without bulk and/or localized motion and/or the proposed compensation strategies. RESULTS: Localized motion reduced wall sharpness, which was significantly mitigated by SG (ie, outer boundary of basilar artery: 0.68 ± 0.27 vs 0.86 ± 0.17; P = .037). When motion occurred, the overall image quality and vessel wall sharpness obtained with vNav-SG SPACE were significantly higher than those obtained with conventional SPACE (ie, basilarartery outer boundary sharpness: 0.73 ± 0.24 vs 0.94 ± 0.24; P = .033), yet comparable to those obtained in motion-free scans (ie, basilarartery outer boundary sharpness: 0.94 ± 0.24 vs 0.96 ± 0.31; P = .815). CONCLUSION: Localized movements can induce considerable artifacts in intracranial vessel wall imaging. The vNav-SG approach is capable of compensating for both bulk and localized motions.

Plaque Morphologic Quantification Reliability of 3D Whole-Brain Vessel Wall Imaging in Patients With Intracranial Atherosclerotic Disease: A Comparison With Conventional 3D Targeted Vessel Wall Imaging.

BACKGROUND: Three-dimensional (3D) whole-brain vessel wall imaging (VWI) has demonstrated exquisite image quality for delineating intracranial atherosclerotic disease (ICAD) and reliability for quantifying normal vessel dimensions. However, its reliability in quantifying plaque morphology remains unknown. PURPOSE: To evaluate the plaque morphologic quantification reliability of 3D whole-brain VWI in patients via comparison with 3D targeted VWI and 2D turbo spin-echo (TSE). STUDY TYPE: Prospective. POPULATION: Thirty-three patients with symptomatic ICAD. FIELD STRENGTH/SEQUENCE: A 3D and 2D TSE acquired at 3.0 T. ASSESSMENT: Each participant underwent two VWI sessions with an interval of 7-10 days. Three readers identified in consensus all the plaques on both whole-brain and targeted 3D VWI. Their lumen and vessel wall area and volume, plaque burden, percent stenosis, and vessel wall remodeling were measured for by two independent readers. At each culprit plaque determined by a radiologist, the lumen and vessel wall area, plaque burden, plaque-to-wall contrast ratio (CR), and plaque enhancement ratio (ER) were measured for 2D and 3D VWI methods. STATISTICAL TESTS: Intra-class correlation coefficient (ICC) was used to evaluate for 3D VWI's interobserver/intraobserver agreement, interscan repeatability, and agreement with 2D TSE in each plaque morphologic measurements. Paired t test was performed for detecting the differences in plaque-to-wall CR and plaque ER between the two 3D methods. RESULTS: Eighty-four plaques were detected by both 3D VWI methods. Whole-brain VWI provided excellent interobserver/intraobserver agreement (ICCs: 0.79-0.99/0.95-0.99), interscan repeatability (ICCs: 0.85-0.99), agreement with 2D TSE (ICC: 0.80-0.94) in all morphologic measurements. ICCs of whole-brain VWI (0.79-0.99) were higher or equal to those of targeted VWI (0.76-0.99). The plaque-to-wall CR and plaque ER were significantly higher on whole-brain VWI than on targeted VWI. DATA CONCLUSION: The 3D whole-brain VWI provides excellent interobserver/intraobserver agreement, interscan repeatability, and agreement with 2D TSE in plaque morphologic quantification of ICAD and outperforms 3D targeted VWI. LEVEL OF EVIDENCE: 2 TECHNICAL EFFICACY STAGE: 2.

Imaging endpoints of intracranial atherosclerosis using vessel wall MR imaging: a systematic review.

PURPOSE: The vessel wall MR imaging (VWI) literature was systematically reviewed to assess the criteria and measurement methods of VWI-related imaging endpoints for symptomatic intracranial plaque in patients with ischemic events. METHODS: PubMed, Scopus, Web of Science, EMBASE, and Cochrane databases were searched up to October 2019. Two independent reviewers extracted data from 47 studies. A modified Guideline for Reporting Reliability and Agreement Studies was used to assess completeness of reporting. RESULTS: The specific VWI-pulse sequence used to identify plaque was reported in 51% of studies. A VWI-based criterion to define plaque was reported in 38% of studies. A definition for culprit plaque was reported in 40% of studies. Frequently scored qualitative imaging endpoints were plaque quadrant (21%) and enhancement (21%). Frequently measured quantitative imaging endpoints were stenosis (19%), lumen area (15%), and remodeling index (14%). Reproducibility for all endpoints ranged from good to excellent (range: ICCT1 hyperintensity = 0.451 to ICCstenosis = 0.983). However, rater specialty and years of experience varied among studies. CONCLUSIONS: Investigators are using different criteria to identify and measure VWI-imaging endpoints for culprit intracranial plaque. Early awareness of these differences to address methods of acquisition and measurement will help focus research resources and efforts in technique optimization and measurement reproducibility. Consensual definitions to detect plaque will be important to develop automatic lesion detection tools particularly in the era of radiomics.

Magnetic resonance multitasking for multidimensional assessment of cardiovascular system: Development and feasibility study on the thoracic aorta.

PURPOSE: To develop an MR multitasking-based multidimensional assessment of cardiovascular system (MT-MACS) with electrocardiography-free and navigator-free data acquisition for a comprehensive evaluation of thoracic aortic diseases. METHODS: The MT-MACS technique adopts a low-rank tensor image model with a cardiac time dimension for phase-resolved cine imaging and a T2 -prepared inversion-recovery dimension for multicontrast assessment. Twelve healthy subjects and 2 patients with thoracic aortic diseases were recruited for the study at 3 T, and both qualitative (image quality score) and quantitative (contrast-to-noise ratio between lumen and wall, lumen and wall area, and aortic strain index) analyses were performed in all healthy subjects. The overall image quality was scored based on a 4-point scale: 3, excellent; 2, good; 1, fair; and 0, poor. Statistical analysis was used to test the measurement agreement between MT-MACS and its corresponding 2D references. RESULTS: The MT-MACS images reconstructed from acquisitions as short as 6 minutes demonstrated good or excellent image quality for bright-blood (2.58 ± 0.46), dark-blood (2.58 ± 0.50), and gray-blood (2.17 ± 0.53) contrast weightings, respectively. The contrast-to-noise ratios for the three weightings were 49.2 ± 12.8, 20.0 ± 5.8 and 2.8 ± 1.8, respectively. There were good agreements in the lumen and wall area (intraclass correlation coefficient = 0.993, P < .001 for lumen; intraclass correlation coefficient = 0.969, P < .001 for wall area) and strain (intraclass correlation coefficient = 0.947, P < .001) between MT-MACS and conventional 2D sequences. CONCLUSION: The MT-MACS technique provides high-quality, multidimensional images for a comprehensive assessment of the thoracic aorta. Technical feasibility was demonstrated in healthy subjects and patients with thoracic aortic diseases. Further clinical validation is warranted.

Visualization of the lenticulostriate arteries at 3T using black-blood T1-weighted intracranial vessel wall imaging: comparison with 7T TOF-MRA.

OBJECTIVES: The objective of this study was to explore the feasibility of using intracranial T1-weighted vessel wall imaging (VWI) to visualize the lenticulostriate arteries (LSAs) at 3T. MATERIAL AND METHODS: Thirteen healthy volunteers were examined with VWI at 3T and TOF-MRA at 7T during the same day. On the vascular skeletons obtained by manual tracing, the number of stems and branches of LSAs were counted. On the most prominent branch in every hemisphere, the contrast-to-noise ratio (CNR), the full length and the local length (5-15 mm above MCAs) were measured and compared between the two methods. Nine stroke patients with intracranial artery stenosis were also recruited into the study. The branches of LSAs were compared between the symptomatic and asymptomatic side. RESULTS: The extracted vascular trees were in good agreement between 7T TOF-MRA and 3T VWI. The two acquisitions showed similar numbers of the LSA stems. The number of branches revealed by 3T VWI was slightly lower than 7T TOF. The full lengths were slightly lower by VWI at 3T (p = 0.011, ICC = 0.917). The measured local lengths (5-15 mm from MCAs) showed high coherence between VWI and TOF-MRA (p = 0.098, ICC = 0.970). In stroke patients, 12 plaques were identified on MCA segments, and nine plaques were located on the symptomatic side. The average numbers of LSA visualized by 3T VWI were 4.3±1.3 on the symptomatic side and 5.0±1.1 on the asymptomatic side. CONCLUSION: 3T VWI is capable of depicting LSAs, particularly the stems and the proximal segments, with comparable image quality to that of 7T TOF-MRA. KEY POINTS: • T1-weighted intracranial VWI at 3T allows for black-blood MR angiography of lenticulostriate artery. • 3T intracranial VWI depicts the stems and proximal segments of the lenticulostriate arteries comparable to 7T TOF-MRA. • It is feasible to assess both large vessel wall lesions and lenticulostriate vasculopathy in one scan.

Hyperintense Plaque on Intracranial Vessel Wall Magnetic Resonance Imaging as a Predictor of Artery-to-Artery Embolic Infarction.

BACKGROUND AND PURPOSE: The aim of the present study was to investigate atherosclerotic plaque characteristics in patients with artery-to-artery (A-to-A) embolic infarction by whole-brain high-resolution magnetic resonance imaging. METHODS: Seventy-four patients (mean age, 54.7±12.1 years; 59 men) with recent stroke in the territory of middle cerebral artery because of intracranial atherosclerotic disease were prospectively enrolled. Whole-brain high-resolution magnetic resonance imaging was performed in all the patients both precontrast and postcontrast administration by using a 3-dimensional T1-weighted vessel wall magnetic resonance imaging technique known as inversion-recovery prepared sampling perfection with application-optimized contrast using different flip angle evolutions. Patients were divided into A-to-A embolic infarction and non-A-to-A embolic infarction groups based on diffusion-weighted imaging findings. The characteristics of the intracranial atherosclerotic plaques were compared between groups. RESULTS: A total of 74 intracranial atherosclerotic plaques were analyzed (36 in A-to-A embolism group and 38 in non-A-to-A embolism group). Hyperintense plaques (HIPs) were more frequently observed in A-to-A embolism group (75.0% versus 21.1%; P<0.001). Eighteen of the 27 HIPs (66.7%) demonstrated hyperintense spots or areas located adjacent to the lumen versus 9 HIPs (33.3%) located within the plaque in A-to-A embolism group. Furthermore, a higher prevalence of plaque surface irregularity was also observed in A-to-A embolism group (41.7% versus 18.4%; P=0.029). Logistic regression analysis showed that HIP was the most powerful independent predictor of A-to-A embolic infarction (P<0.001), with the odds ratio of 11.2 (95% confidence interval, 3.5-36.2). CONCLUSIONS: A-to-A embolic infarction has distinct vulnerable plaque characteristics compared with non-A-to-A embolic infarction. HIP and plaque surface irregularity may predict A-to-A embolic infarction.

A Novel Fast Mobile-Window Small Incision Technique for Hip Arthroplasty in the Elderly and Comparison with Conventional Incision.

BACKGROUND We deeloped a novel technique - fast mobile-window small incision (FMWSI) - a modification of minimally invasive surgery for total hip arthroplasty, which we believe is particularly suited to elderly patients with hip fractures. The present article aimed to introduce this technique and compare the clinical effects between the FMWSI technique and conventional incision (CI) for hip arthroplasty in elderly patients. MATERIAL AND METHODS This study included 240 consecutive patients who underwent hip arthroplasty. Half received total hip arthroplasty and half received hemi hip arthroplasty. The 120 patients in each group were further divided into FMWSI and CI groups. The following parameters were compared between the FMWSI and CI groups: length of incision, operation time, bleeding volume, drainage volume, postoperative ambulation time, and Harris score. RESULTS Compared with the CI group, the FMWSI group had a significantly shorter incision length, operation time, and postoperative ambulation time, as well as lower bleeding and drainage volumes, irrespective of whether the treatment was total or hemi hip arthroplasty (P<0.05). However, no significant difference was found in the Harris score between the FMWSI and CI groups (P>0.05). CONCLUSIONS The novel FMWSI technique introduced in this study is a useful method for hip arthroplasty, especially for elderly patients with poor constitutions or tolerance to surgery.

Post-Traumatic Cerebral Infarction: A Narrative Review of Pathophysiology, Diagnosis, and Treatment.

Traumatic brain injury (TBI) is a common diagnosis requiring acute hospitalization. Long-term, TBI is a significant source of health and socioeconomic impact in the United States and globally. The goal of clinicians who manage TBI is to prevent secondary brain injury. In this population, post-traumatic cerebral infarction (PTCI) acutely after TBI is an important but under-recognized complication that is associated with negative functional outcomes. In this comprehensive review, we describe the incidence and pathophysiology of PTCI. We then discuss the diagnostic and treatment approaches for the most common etiologies of isolated PTCI, including brain herniation syndromes, cervical artery dissection, venous thrombosis, and post-traumatic vasospasm. In addition to these mechanisms, hypercoagulability and microcirculatory failure can also exacerbate ischemia. We aim to highlight the importance of this condition and future clinical research needs with the goal of improving patient outcomes after TBI.

VWI-APP: Vessel wall imaging-dedicated automated processing pipeline for intracranial atherosclerotic plaque quantification.

BACKGROUND: Quantitative plaque assessment based on 3D magnetic resonance (MR) vessel wall imaging (VWI) has been shown to provide valuable numerical markers of the burden and risk of intracranial atherosclerotic disease (ICAD). However, plaque quantification is currently time-consuming and observer-dependent due to the demand for heavy manual effort. A VWI-dedicated automated processing pipeline (VWI-APP) is desirable. PURPOSE: To develop and evaluate a VWI-APP for end-to-end quantitative analysis of intracranial atherosclerotic plaque. METHODS: We retrospectively enrolled 91 subjects with ICAD (80 for pipeline development, 10 for an end-to-end pipeline evaluation, and 1 for demonstrating longitudinal plaque assessment) who had undergone VWI and MR angiography. In an end-to-end evaluation, diameter stenosis (DS), normalized wall index (NWI), remodeling ratio (RR), plaque wall contrast ratio (CR), and total plaque volume (TPV) were quantified at each culprit lesion using the developed VWI-APP and a computer-aided manual approach by a neuroradiologist, respectively. The time consumed in each quantification approach was recorded. Two-sided paired t-tests and intraclass correlation coefficient (ICC) were used to determine the difference and agreement in each plaque metric between VWI-APP and manual quantification approaches. RESULTS: There was no significant difference between VWI-APP and manual quantification in each plaque metric. The ICC was 0.890, 0.813, 0.827, 0.891, and 0.991 for DS, NWI, RR, CR, and TPV, respectively, suggesting good to excellent accuracy of the pipeline method in plaque quantification. Quantitative analysis of each culprit lesion on average took 675.7 s using the manual approach but shortened to 238.3 s with the aid of VWI-APP. CONCLUSIONS: VWI-APP is an accurate and efficient approach to intracranial atherosclerotic plaque quantification. Further clinical assessment of this automated tool is warranted to establish its utility in the risk assessment of ICAD lesions.

Underactuated Humanoid Peeling Approach for Pickled Mustard Tuber Based on Metamorphic Constraints.

Pickled mustard tuber (PMT), also known as Brassica juncea var. tumida, is a conical tuberous vegetable with a scaly upper part and a coarse fiber skin covering the lower part. Due to its highly distorted and complex heterogeneous fiber network structure, traditional manual labor is still used for peeling and removing fibers from pickled mustard tuber, as there is currently no effective, fully automated method or equipment available. In this study, we designed an underactuated humanoid pickled mustard tuber peeling robot based on variable configuration constraints that emulate the human "insert-clamp-tear" process via probabilistic statistical design. Based on actual pickled mustard tuber morphological cluster analysis and statistical features, we constructed three different types of pickled mustard tuber peeling tool spectral profiles and analyzed the modular mechanical properties of three different tool configurations to optimize the variable configuration constraint effect and improve the robot's end effector trajectory. Finally, an ADAMS virtual prototype model of the pickled mustard tuber peeling robot was established, and simulation analysis of the "insert-clamp-tear" process was performed based on the three pickled mustard tuber statistical classification selection. The results showed that the pickled mustard tuber peeling robot had a meat loss rate of no more than 15% for each corresponding category of pickled mustard tuber, a theoretical peeling rate of up to 15 pieces per minute, and an average residual rate of only about 2% for old fibers. Based on reasonable meat loss, the efficiency of peeling was greatly improved, which laid the theoretical foundation for fully automated pickled mustard tuber peeling.

Intracranial vessel wall segmentation with deep learning using a novel tiered loss function incorporating class inclusion.

PURPOSE: To develop an automated vessel wall segmentation method on T1-weighted intracranial vessel wall magnetic resonance images, with a focus on modeling the inclusion relation between the inner and outer boundaries of the vessel wall. METHODS: We propose a novel method that estimates the inner and outer vessel wall boundaries simultaneously, using a network with a single output channel resembling the level-set function height. The network is driven by a unique tiered loss that accounts for data fidelity of the lumen and vessel wall classes and a length regularization to encourage boundary smoothness. RESULTS: Implemented with a 2.5D UNet with a ResNet backbone, the proposed method achieved Dice similarity coefficients (DSC) in 2D of 0.925 ± 0.048, 0.786 ± 0.084, Hausdorff distance (HD) of 0.286 ± 0.436, 0.345 ± 0.419 mm, and mean surface distance (MSD) of 0.083 ± 0.037 and 0.103 ± 0.032 mm for the lumen and vessel wall, respectively, on a test set; compared favorably to a baseline UNet model that achieved DSC 0.924 ± 0.047, 0.794 ± 0.082, HD 0.298 ± 0.477, 0.394 ± 0.431 mm, and MSD 0.087 ± 0.056, 0.119 ± 0.059 mm. Our vessel wall segmentation method achieved substantial improvement in morphological integrity and accuracy compared to benchmark methods. CONCLUSIONS: The proposed method provides a systematic approach to model the inclusion morphology and incorporate it into an optimization infrastructure. It can be applied to any application where inclusion exists among a (sub)set of classes to be segmented. Improved feasibility in result morphology promises better support for clinical quantification and decision.

Imaging of left heart intracardiac thrombus: clinical needs, current imaging, and emerging cardiac magnetic resonance techniques.

Intracardiac thrombus in the left atrium and atrial appendage (LA/LAA) and left ventricle (LV) increases the risk of systemic thromboembolism and causes potentially devastating diseases such as ischemic stroke and acute ischemia in abdominal organs and lower extremities. Detecting the presence and monitoring the resolution of left heart intracardiac thrombus are of vital importance for stratifying patients and guiding treatment decisions. Currently, echocardiography is the most frequently used method for the above clinical needs, followed by computed tomography. An increasing number of studies have been performed to investigate the value of cardiac magnetic resonance (CMR) as an alternative imaging modality given its several unique strengths. This article provides an overview of the clinical relevance of the LA/LAA and LV thrombus as well as the diagnostic performance of the current imaging modalities and emerging CMR techniques.

Spatial Bridge Locking Fixator versus Traditional Locking Plates in Treating AO/OTA 32-A3.2 Fracture: Finite Element Analysis and Biomechanical Evaluation.

OBJECTIVE: To compare the biomechanical behaviors of the spatial bridge locking fixator (SBLF), single locking plate (SP), and double locking plate (DP) for AO/OTA 32-A3.2 fractures using finite element analysis and biomechanical tests. METHODS: Axial loading of 700 N was conducted on the AO/OTA 32-A3.2 model via finite element analysis. The von Mises stress and the interfragmentary movement (IFM) were comparatively analyzed in the three configurations above. On the mechanical tester, axial and torsional loading of 30 synthetic femurs (five specimens of each configuration for each test at random) was performed, and the interfragmentary movement, torsion angle, stiffness, and ultimate load were recorded and analyzed. RESULTS: The finite element analysis (FEA) results showed that the von Mises stress of the spatial bridge locking fixator (SBLF) was lower than that of the single locking plate (SP) and higher than that of the double locking plate (DP). At 700 N, the axial IFMs were 0.15-0.38 mm (SBLF), 0.03-0.84 mm (SP), and 0.02-0.07 mm (DP). The biomechanical experiment indicated that the axial interfragmentary movements (IFMs) were 0.44 ± 0.23 mm (SBLF), 1.02 ± 0.40 mm (SP), and 0.07 ± 0.07 mm (DP) (p < 0.001). The axial IFM of the SBLF group had the highest probability (79.26%) of falling within the ideal range (0.2-0.8 mm), and the SP and DP groups had probabilities of 27.10% and 3.14%, respectively. The axial stiffness in the SBLF group (1586 ± 130 N/mm) was significantly lower than that in the DP group (10,264 ± 2671 N/mm) (p < 0.001) but greater than that in the SP group (725 ± 178 N/mm) (p = 0.396). The range of axial loads to ultimate failure was 3385-4527 N (SBLF), 3377-4664 N (SP), and 3780-4804 N (DP). The shear motion of the fracture end was 0.35 ± 0.14 mm (SBLF), 0.16 ± 0.10 mm (SP), and 0.08 ± 0.04 mm (DP) (p < 0.001). The torsional stiffness was 1.68 ± 0.14 Nm/degree (SBLF), 2.32 ± 0.29 Nm/degree (SP) (SBLF&SP, p < 0.001), and 3.53 ± 0.73 Nm/degree (DP) (SBLF&DP, p < 0.001). CONCLUSIONS: The SBLF structure may exhibit a better biomechanical performance compared with the SP and DP in providing the best quantity and more symmetrical interfragmentary movement for AO/OTA 32-A3.2 fractures.

MRA-free intracranial vessel localization on MR vessel wall images.

Analysis of vessel morphology is important in assessing intracranial atherosclerosis disease (ICAD). Recently, magnetic resonance (MR) vessel wall imaging (VWI) has been introduced to image ICAD and characterize morphology for atherosclerotic lesions. In order to automatically perform quantitative analysis on VWI data, MR angiography (MRA) acquired in the same imaging session is typically used to localize the vessel segments of interest. However, MRA may be unavailable caused by the lack or failure of the sequence in a VWI protocol. This study aims to investigate the feasibility to infer the vessel location directly from VWI. We propose to synergize an atlas-based method to preserve general vessel structure topology with a deep learning network in the motion field domain to correct the residual geometric error. Performance is quantified by examining the agreement between the extracted vessel structures from the pair-acquired and alignment-corrected angiogram, and the estimated output using a cross-validation scheme. Our proposed pipeline yields clinically feasible performance in localizing intracranial vessels, demonstrating the promise of performing vessel morphology analysis using VWI alone.

The Clinical Utility of High-Resolution Vessel Wall Imaging in Screening for Meningovascular Neurosyphilis.

Meningovascular neurosyphilis is a common cause of stroke in young adults, particularly when HIV co-infection is present. Contemporary screening for neurosyphilis relies on invasive testing. High resolution vessel wall imaging (HR-VW) is an emerging non-invasive tool to detect intracranial vessel wall inflammation. We report a case of multifocal acute cerebral infarctions from meningovascular neurosyphillis in which HR-VWI was instrumental in leading to the etiological diagnosis. A 32-year-old man with history of untreated HIV and polysubstance abuse presented with sudden onset vertigo. CT angiogram of the head and neck showed non-dominant left extracranial vertebral artery occlusion in the V1 segment, and multifocal areas of stenoses in V2 through V4 segments. Non-contrast brain MRI demonstrated multiple small acute infarcts in the left cerebellum, left brachium pontis, medulla and occipital lobe. Rapid plasma reagin was reactive. 3D whole-brain HR-VWI revealed concentric vessel wall contrast enhancement in the left V4 segment, suggestive of inflammation. This HR-VWI finding prompted further investigation with cerebrospinal fluid analysis that revealed reactive fluorescent treponemal antibody absorption test. The patient received high-dose intravenous Penicillin G, was restarted on highly active antiretroviral therapy, and remained neurologically stable to-date. With high spatial resolution and signal-to-noise ratio, HR-VWI allows for visualization of vessel wall inflammation in co-morbid HIV and neurosyphilis.

Sex Differences in Intracranial Atherosclerosis in Patients With Hypertension With Acute Ischemic Stroke.

Background Studies suggest the presence of sex differences in hypertension prevalence and its associated outcomes in atherosclerosis and stroke. We hypothesized a higher intracranial atherosclerosis burden among men with hypertension and acute ischemic stroke compared with women. Methods and Results A multicenter retrospective study was performed from a prospective database identifying patients with hypertension presenting with intracranial atherosclerosis-related acute ischemic stroke and imaged with intracranial vessel wall magnetic resonance imaging. Proximal and distal plaques on vessel wall magnetic resonance imaging were scored. Negative binomial models assessed the associations between plaque-count and sex and the interaction between sex and treatment. Covariates were selected by a least absolute shrinkage and selection operator procedure. Sixty-one patients (n=42 men) were included. There were no significant differences in demographic or cardiovascular risk factors except for smoking history (P=0.002). Adjusted total and proximal plaque counts for men were 1.6 (95% CI, 1.2-2.1; P<0.01) and 1.4 (95% CI, 1.0-1.9; P=0.03) times as high as women, respectively. Female sex was more protective for proximal plaque if treated for hypertension. The risk ratio of men versus women was 1.5 (95% CI, 1.0-2.1) for treated patients. The risk ratio of men versus women was 0.7 (95% CI, 0.4-1.3) for untreated patients. The relative difference between these 2 risk ratios was 2.0 (95% CI, 1.1-3.9), which was statistically significant from the interaction test, P=0.04. Conclusions Men with hypertension with acute ischemic stroke have significantly higher total and proximal plaque burdens than women. Women with hypertension on anti-hypertensive medication showed a greater reduction in proximal plaque burden than men. Further confirmation with a longitudinal cohort study is needed and may help evaluate whether different treatment guidelines for managing hypertension by sex can help reduce intracranial atherosclerosis burden and ultimately acute ischemic stroke risk.