Interstudy reproducibility of dark blood high-resolution MRI in evaluating basilar atherosclerotic plaque at 3 Tesla

PURPOSE:We aimed to evaluate the interscan, intraobserver, and interobserver reproducibility of basilar atherosclerotic plaque employing dark blood high-resolution magnetic resonance imaging (HR-MRI) at 3 Tesla.METHODS:Sixteen patients (14 males and 2 females) with >30% basilar stenosis as identified by conventional magnetic resonance angiography were prospectively recruited for scan and rescan examinations on a 3 Tesla MRI system using T2-weighted turbo spin-echo protocol. Two observers independently measured the areas of vessels and lumens. Wall area was derived by subtracting the lumen area from the vessel area. Areas of vessels, lumens and walls were compared for the evaluation of interscan variability of basilar plaque. To assess the intraobserver variability, one observer reevaluated all the images of the first scan after a 4-week interval.RESULTS:Fourteen patients were included in the final analysis. No clinically significant difference was observed for interscan, intraobserver, and interobserver measurements. The intraclass correlations for vessel, lumen, and wall areas were excellent and ranged from 0.973 to 0.981 for the interscan measurements, 0.997 to 0.998 for the intraobserver measurements and 0.979 to 0.985 for the interobserver measurements. The coefficients of variation for quantitative basilar morphology measurements were 4.31%–10.35% for the interscan measurements, 1.41%–4.62% for the intraobserver measurements and 3.79%–8.46% for the interobserver measurements. Compared with the interscan and interobserver measurements, narrow intervals of the scatterplots were observed for the intraobserver measurements by Bland-Altman plots.CONCLUSION:Basilar atherosclerotic plaque imaging demonstrates excellent reproducibility at 3 Tesla. The study proves that dark blood HR-MRI may serve as a reliable tool for clinical studies focused on the progression and treatment response of basilar atherosclerosis

Ultra High Field (7T) Magnetic Resonance Imaging of Intracranial Vessel Wall

Intracranial vessel wall imaging may be accomplished with high-field (7T) magnetic resonance (MRI). To determine its feasibility, a 7T MR protocol was defined using Polyvinyl-alcohol cryogel (PVA-C) phantom vessels and healthy subjects. A 2D matrix construct of PVA-C vessel phantoms of different diameters and wall thicknesses was scanned. Three observers measured the phantom images, one of which three times. Physical measurements were performed using a digital caliper. Ten volunteers were scanned using three different MRI sequences (TSE-3D, FLAIR, MPRAGE). Imaging assessment was performed in different circle of Willis (COW) segments. Reliability and accuracy of the measurements was analyzed by inter and intraobserver correlation and by comparison to physical measurements. Phantom measurements showed overall high inter and intraobserver reliability and accuracy (ICC≅0.9). However, precision diminished for smaller vessels (\u3c3mm). TSE was superior on vessel wall definition compared with FLAIR on both, phantoms and volunteers. On healthy subjects, vessel wall was recognized consistently, but precise definition of distal COW segments was not achieved. Vessel wall was significantly overestimated (p\u3c0.05) when comparing to intracranial vessel diameters from prior studies due to partial volume effects. Vessel wall imaging is feasible with 7T MR. However, precision and definition decreases consistently with the vessel caliber. PVA adequately mimics 7T MR vessel wall imaging properties

Diagnosis of Symptomatic Intracranial Atherosclerotic Disease

Intracranial atherosclerotic stroke differs from extracranial atherosclerotic stroke in many aspects, including risk factors and stroke patterns. It occurs in association with in situ thrombotic occlusion, artery-to-artery embolism, branch occlusion, and hemodynamic insufficiency. Intracranial atherosclerotic stenosis (ICAS) could have only been diagnosed by transcranial Doppler (TCD) and transcranial color-coded sonography (TCCS), which are burdened by a risk of bias, or catheter angiography (DSA), which, on the contrary, is very precise, but rarely it is done in clinical practice due to its invasiveness. Computed tomography angiography (CT-A) and magnetic resonance imaging angiography (MR-A) have increased the identification of ICAS in a wider stroke population

Vessel-Wall Magnetic Resonance Imaging of Intracranial Atherosclerotic Plaque and Ischemic Stroke: A Systematic Review and Meta-Analysis

Introduction: Vessel-wall magnetic resonance imaging (MRI) has been suggested as a valuable tool for assessing intracranial arterial stenosis with additional diagnostic features. However, there is limited conclusive evidence on whether vessel-wall MR imaging of intracranial atherosclerotic plaques provides valuable information for predicting vulnerable lesions. We conducted this systematic review and meta-analysis to evaluate which characteristics of intracranial-plaque on vessel-wall MRI are markers of culprit lesions.Methods: The MEDLINE, EMBASE, and Cochrane Library of Clinical Trials databases were searched for studies reporting the association between vessel-wall MRI characteristics of intracranial plaque and corresponding stroke events. Odds ratios (ORs) for the prevalence of stroke with intracranial-plaque MRI characteristics were pooled in a meta-analysis using a random-effects model.Results: Twenty studies were included in this review. We found a significant association between plaque enhancement (OR, 10.09; 95% CI, 5.38–18.93), positive remodeling (OR, 6.19; 95% CI, 3.22–11.92), and plaque surface irregularity (OR, 3.94; 95% CI, 1.90–8.16) with stroke events. However, no significant difference was found for the presence of eccentricity (OR, 1.22; 95% CI, 0.51–2.91).Conclusion: Based on current evidence, intracranial plaque contrast enhancement, positive remodeling, and plaque irregularity on MRI are associated with increased risk of stroke events. Our findings support the design of future studies on intracranial-plaque MRI and decision making for the management of intracranial atherosclerotic plaques

Quantitative magnetic resonance angiography for flow quantification of carotid and intracranial stenosis

Carotid and intracranial stenosis are responsible for stroke, which is the third leading cause of death globally. Carotid and intracranial stenting are used in management of stenosis. In-stent stenosis occurs in 25-35% of patients. Stent related artifacts and artificial lumen narrowing are problems during MRI scanning. A potential solution is estimate the flow profile across stenosis. The goal of this project is to optimize and implement quantitative magnetic resonance angiography (QMRA) for flow encoding and flow velocity estimation for better characterizing stenosis and assessing its degrees. We conducted multiple phantom measurements (mimicking normal carotid and middle cerebral anatomy) using phase contrast sequence with implementing different degrees of stenosis. Subsequent volunteer and patients measurements were conducted. In 8 mm tubes, flow was stable till 75 % stenosis while in 4 mm tubes, decline starts at 65% stenosis. In subject measurements, there is flow asymmetry between paired ICAs and MCAs that is not pathologic but within certain range. Patients had reduced flow in stenotic vessels compared to the other side and compared to mean flow in our volunteer subjects. QMRA results demonstrated reduced flow on the exact side detected with conventional MRA, with a strong correlation between QMRA and conventional MRA (R2 =0.7942). The percentage of flow difference between sides varied with the degree of stenosis. QMRA can be used for non-invasive diagnosis of suspected stenosis even if the stenosis itself cannot be visualized

Acute cerebral infarcts in multiple arterial territories : The Bergen NORSTROKE study

Introduction The majority of acute cerebral infarcts results from an occlusion of one single cerebral artery followed by loss of blood supply to the respective arterial territory. However, several independent arterial territories may be affected if more than one cerebral artery is occluded simultaneously. Acute cerebral infarcts in multiple arterial territories (MACI) account for 10 to 20 % of all ischemic strokes. MACI may have distinct pathophysiological and clinical features differing from acute cerebral infarct(s) in a single arterial territory (SACI). Aims In this dissertation, we sought to give a broad description of patients with MACI. The aim of the first two papers was to clarify pathophysiological mechanisms in regards to the etiology. In the third paper, we assessed short-term outcome and complications within the first week after the hospital admission. The fourth paper sheds light on the clinical manifestation on admission. Methods We used data from the Bergen NORSTROKE registry. We included only patients with acute cerebral infarct(s) (ACI) confirmed by diffusion-weighted magnetic resonance imaging (DWI-MRI) consecutively admitted to the stroke unit at Haukeland University Hospital. The first two papers are based on a cohort of 2125 patients admitted from 2006 to 2013. The last two papers are based on a cohort of 3343 patients admitted in an extended time frame from 2006 to 2016. MACI was defined as more than one non-continuous ischemic lesion in more than one arterial cerebral territory; either left and/or right carotid artery territory and/or basilar artery territory. Results The proportion of patients with MACI was approximately 9% of all ACI patients. The paper-I confirmed that cardiogenic embolism (CE), as defined by TOAST criteria, is the most frequent underlying etiology of MACI. The paper-II showed a positive correlation between the time from stroke onset to MRI examination and frequency of large artery atherosclerosis (LAA)-associated MACI. There was no correlation between the time from stroke onset to MRI examination and frequency of CE- 6 associated MACI. These findings suggest that CE-associated MACI occur simultaneously as a shower of emboli, while LAA-associated MACI happens rather successively over time. The paper-III showed that patients with MACI have a worse short-term outcome within the first week after the admission compared to patients with SACI. Moreover, MACI was associated with more in-hospital complications, namely deep venous thrombosis and myocardial infarction. The paper-IV showed that 72% of patients diagnosed with MACI presented with a single-territory clinical manifestation (MACI-S) on admission. MACI-S was associated with less than five ischemic lesions on DWI-MRI, involvement of the left hemisphere, and a partial anterior cerebral infarct stroke syndrome (PACI) as defined by the Oxfordshire Community Stroke Project (OCSP) classification. This finding emphasizes the essential role of MRI examination for final diagnosis of MACI. Conclusion The data presented in this dissertation show that patients with MACI differ in many clinical aspects from patients with SACI. Our findings add new knowledge to this less documented field of stroke medicine and may help to improve the diagnostic and therapeutic approaches in these patients

Characterization of Carotid Plaques with Ultrasound Non-Invasive Vascular Elastography (NIVE) : Feasibility and Correlation with High-Resolution Magnetic Resonance Imaging

L’accident vasculaire cérébral (AVC) est une cause principale de décès et de morbidité dans le monde; une bonne partie des AVC est causée par la plaque d’athérosclérose carotidienne. La prévention de l’AVC chez les patients ayant une plaque carotidienne demeure controversée, vu les risques et bénéfices ambigus associés au traitement chirurgical ou médical. Plusieurs méthodes d’imagerie ont été développées afin d’étudier la plaque vulnérable (dont le risque est élevé), mais aucune n’est suffisamment validée ou accessible pour permettre une utilisation comme outil de dépistage. L’élastographie non-invasive vasculaire (NIVE) est une technique nouvelle qui cartographie les déformations (élasticité) de la plaque afin de détecter les plaque vulnérables; cette technique n’est pas encore validée cliniquement. Le but de ce projet est d’évaluer la capacité de NIVE de caractériser la composition de la plaque et sa vulnérabilité in vivo chez des patients ayant des plaques sévères carotidiennes, en utilisant comme étalon de référence, l’imagerie par résonance magnétique (IRM) à haute-résolution. Afin de poursuivre cette étude, une connaissance accrue de l’AVC, l’athérosclérose, la plaque vulnérable, ainsi que des techniques actuelles d’imagerie de la plaque carotidienne, est requise. Trente-et-un sujets ont été examinés par NIVE par ultrasonographie et IRM à haute-résolution. Sur 31 plaques, 9 étaient symptomatiques, 17 contenaient des lipides, et 7 étaient vulnérables selon l’IRM. Les déformations étaient significativement plus petites chez les plaques contenant des lipides, avec une sensibilité élevée et une spécificité modérée. Une association quadratique entre la déformation et la quantité de lipide a été trouvée. Les déformations ne pouvaient pas distinguer les plaques vulnérables ou symptomatiques. En conclusion, NIVE par ultrasonographie est faisable chez des patients ayant des sténoses carotidiennes significatives et peut détecter la présence d’un coeur lipidique. Des études supplémentaires de progression de la plaque avec NIVE sont requises afin d’identifier les plaques vulnérables.Stroke is a leading cause of death and morbidity worldwide, and a significant proportion of strokes are caused by carotid atherosclerotic plaque rupture. Prevention of stroke in patients with carotid plaque poses a significant challenge to physicians, as risks and benefits of surgical or medical treatments remain equivocal. Many imaging techniques have been developed to identify and study vulnerable (high-risk) atherosclerotic plaques, but none is sufficiently validated or accessible for population screening. Non-invasive vascular elastography (NIVE) is a novel ultrasonic technique that maps carotid plaque strain (elasticity) characteristics to detect its vulnerability; it has not been clinically validated yet. The goal of this project is to evaluate the ability of ultrasound NIVE strain analysis to characterize carotid plaque composition and vulnerability in vivo in patients with significant plaque burden, as determined by the reference standard, high resolution MRI. To undertake this study, a thorough understanding of stroke, atherosclerosis, vulnerable plaque, and current non-invasive carotid plaque imaging techniques is required. Thirty-one subjects underwent NIVE and high-resolution MRI of internal carotid arteries. Of 31 plaques, 9 were symptomatic, 17 contained lipid and 7 were vulnerable on MRI. Strains were significantly lower in plaques containing a lipid core compared to those without lipid, with high sensitivity and moderate specificity. A quadratic fit was found between strain and lipid content. Strains did not discriminate symptomatic patients or vulnerable plaques. In conclusion, ultrasound NIVE is feasible in patients with significant carotid stenosis and can detect the presence of a lipid core. Further studies of plaque progression with NIVE are required to identify vulnerable plaques

New Insight into Cerebrovascular Diseases

“Brain circulation is a true road map that consists of large extended navigation territories and a number of unimagined and undiscovered routes.” Dr. Patricia Bozzetto Ambrosi This book combines an update on the review of cerebrovascular diseases in the form of textbook chapters, which has been carefully reviewed by Dr. Patricia Bozzetto Ambrosi, Drs. Rufai Ahmad and Auwal Abdullahi and Dr. Amit Agrawal, high-performance academic editors with extensive experience in neurodisciplines, including neurology, neurosurgery, neuroscience, and neuroradiology, covering the best standards of neurological practice involving basic and clinical aspects of cerebrovascular diseases. Each topic was carefully revised and prepared using smooth, structured vocabulary, plus superb graphics and scientific illustrations. In emphasizing the most common aspects of cerebrovascular diseases: stroke burden, pathophysiology, hemodynamics, diagnosis, management, repair, and healing, the book is comprehensive but concise and should become the standard reference guide for this neurological approach