Diffusion- and perfusion-weighted MRI. The DWI/PWI mismatch region in acute stroke.

BACKGROUND AND PURPOSE: Diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) are relatively new MR techniques increasingly used in acute stroke. During the first hours of stroke evolution, the regions with abnormal perfusion are typically larger than the DWI lesions, and this mismatch region has been suggested to be "tissue at risk." The aim of this study was to evaluate the PWI/DWI mismatch region in acute stroke patients and find parameters indicative of both infarct progression and functional impairment. METHODS: Twenty patients with nonlacunar ischemic stroke were imaged with DWI, PWI, and conventional MRI within 24 hours of symptom onset and after 1 week; in addition, the European Stroke Scale (ESS) score was recorded. With PWI, the volumes of regions with "time-to-peak" (TTP) delays of >/=2, 4, 6, 8, and 10 seconds were measured; these volumes were compared with the acute DWI lesion volumes, final infarct size, and ESS score. RESULTS: In 80% of patients the acute DWI lesion was surrounded by regions with abnormal TTP delays (PWI>DWI lesion). A TTP delay of >/=6 s in the mismatch region was found to be associated with lesion enlargement between the initial and follow-up MRI scans. Lesions increased in 9 of 12 patients (75%) in whom the area with TTP delay >/=6 s was larger than the DWI lesion, but they increased in only 1 of 8 (12.5%) of the remaining patients, in whom the area with a TTP delay >/=6 s was smaller than the DWI lesion. The volume of the regions with TTP delays of >/=4 s correlated better with ESS (r=-0.88, P<0.001) than other PWI (or DWI) volumes, which indicated that a TTP delay of approximately 4 s might be the threshold for functional impairment of brain tissue. CONCLUSIONS: Only patients with severe perfusion deficits in the PWI/DWI mismatch (TTP delays of >/=6 s) are at high risk of lesion enlargement. Functionally, more moderate perfusion deficits (TTP delays >/=4 and <6 s) appear to also contribute to the acute clinical deficit.     

弥散加权和灌注加权在缺血性中风的应用

目的　观察缺血性中风早期病灶的部位及程度,评价病灶的微循环状态。方法　ＤＷＩ和ＰＷＩ是一 种新的磁共振成像技术,ＤＷＩ通过测定水分子的布朗运动而获得;ＰＷＩ通过静脉团注造影剂而得到。结果　ＤＷＩ 能明确早期急性缺血性病灶的部位,ＰＷＩ证实病灶区微循环不良的范围。结论　有助于对缺血性中风患者治疗方 法的选择,并提供了一种高度敏感的评价治疗效果的方法。     

Diffusion- and perfusion-weighted MRI: influence of severe carotid artery stenosis on the DWI/PWI mismatch in acute stroke

BACKGROUND AND PURPOSE: Diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) have been used increasingly in recent years to evaluate acute stroke in the emergency setting. In the present study, we compared DWI and PWI findings in acute stroke patients with and without severe extracranial internal carotid artery (ICA) disease. METHODS: Twenty-seven patients with nonlacunar ischemic stroke were selected for this analysis. DWI, PWI, and conventional MRI were performed in all patients within 24 hours of symptom onset and after 1 week. To exclude patients with partial or complete reperfusion, we included only patients with a PWI deficit larger than the DWI lesion. Severe ICA disease (>70% stenosis) was present unilaterally in 9 and bilaterally in 2 patients. Acute DWI lesion volume, the size of the acute PWI/DWI mismatch, and final infarct size (on T2-weighted images) were determined. RESULTS: The PWI/DWI mismatch was significantly larger in patients with severe ICA disease than in patients without extracranial carotid stenosis, both when time-to-peak and mean transit time maps (P<0.01) were used to calculate the mismatch. Quantitative analysis of the time-to-peak delay in the mismatch indicated that a relatively smaller fraction of the total mismatch was critically ischemic in patients with carotid stenosis than in those without. Average lesion volume increased less in the stenosis group (P=0.14), despite the larger PWI/DWI mismatch, and final infarct size was smaller in the stenosis group (P<0.05). In the 2 patients with bilateral ICA disease, variable hemodynamic involvement of the contralateral hemisphere was found in addition to the ipsilateral PWI deficit. CONCLUSIONS: In most acute stroke patients with severe ICA stenosis, a considerably smaller fraction of the total PWI/DWI mismatch is at risk than in patients without carotid disease.     

PWI-ASPECTS/DWI-ASPECTS不匹配与PWI/DWI不匹配相关性研究

目的探讨大脑中动脉闭塞的急性脑卒中患者PWI-ASPECTS/DWI-ASPECTS不匹配与PWI/DWI不匹配间的相关性。方法回顾性分析2017年1月～2019年6月在本院就诊且行血管再通治疗的急性脑卒中患者65例,所有患者均于血管再通前行MRI(DWI、PWI)检查。计算所有患者PWI体积、DWI体积、PWI/DWI不匹配体积及PWI-ASPECTS、DWI-ASPECTS、PWI-ASPECTS/DWI-ASPECTS不匹配评分。Spearman等级相关分析体积与ASPECTS间的相关性,ROC分析PWI-ASPECTS/DWI-ASPECTS不匹配预测PWI/DWI不匹配的价值。结果 PWI体积、DWI体积及PWI/DWI不匹配体积分别为(25. 01±23. 11) ml、(75. 90±48. 99) ml、(50. 73±27. 14) ml。DWIASPECTS、PWI-ASPECTS及PWI-ASPECTS/DWI-ASPECTS不匹配评分分别为5. 95±2. 32、3. 52±2. 57、2. 43±0. 75。Spearman等级相关分析显示PWI体积与PWI-ASPECTS、DWI体积与DWI-ASPECTS、PWI/DWI不匹配体积与PWI-ASPECTS/DWI-ASPECTS不匹配间具有较强的相关性(r=-0. 767; P=0. 000、r=-0. 817; P=0. 000、r=-0. 643; P=0. 000)。ROC分析显示当PWI-ASPECTS/DWI-ASPECTS不匹配≥2时,PWI-ASPECTS/DWI-ASPECTS不匹配预测PWI/DWI不匹配的其敏感性和特异性分别为87. 90%、100%。当PWI-ASPECTS/DWI-ASPECTS不匹配≥3时,PWI-ASPECTS/DWI-ASPECTS不匹配预测PWI/DWI不匹配的敏感性和特异性分别为93. 80%、63. 64%。结论临床工作中PWI-ASPECTS/DWI-ASPECTS不匹配可替代PWI/DWI不匹配评估缺血半暗带。     

Penumbra detection using PWI/DWI mismatch MRI in a rat stroke model with and without comorbidity: comparison of methods

Perfusion-diffusion (perfusion-weighted imaging (PWI)/diffusion-weighted imaging (DWI)) mismatch is used to identify penumbra in acute stroke. However, limitations in penumbra detection with mismatch are recognized, with a lack of consensus on thresholds, quantification and validation of mismatch. We determined perfusion and diffusion thresholds from final infarct in the clinically relevant spontaneously hypertensive stroke-prone (SHRSP) rat and its normotensive control strain, Wistar-Kyoto (WKY) and compared three methods for penumbra calculation. After permanent middle cerebral artery occlusion (MCAO) (WKY n=12, SHRSP n=15), diffusion-weighted (DWI) and perfusion-weighted (PWI) images were obtained for 4 hours post stroke and final infarct determined at 24 hours on T₂ scans. The PWI/DWI mismatch was calculated from volumetric assessment (perfusion deficit volume minus apparent diffusion coefficient (ADC)-defined lesion volume) or spatial assessment of mismatch area on each coronal slice. The ADC-derived lesion growth provided the third, retrospective measure of penumbra. At 1 hour after MCAO, volumetric mismatch detected smaller volumes of penumbra in both strains (SHRSP: 31±50 mm³, WKY: 22±59 mm³, mean±s.d.) compared with spatial assessment (SHRSP: 36±15 mm³, WKY: 43±43 mm³) and ADC lesion expansion (SHRSP: 41±45 mm³, WKY: 65±41 mm³), although these differences were not statistically significant. Spatial assessment appears most informative, using both diffusion and perfusion data, eliminating the influence of negative mismatch and allowing the anatomical location of penumbra to be assessed at given time points after stroke.     

Comparison of automated and visual DWI ASPECTS in acute ischemic stroke

Background and purposeTo assess intra-and inter-rater agreement of the ASPECTS (Alberta Stroke Program Early CT Score) based on diffusion-weighted MRI and to compare it with fully – automated methods (eASPECTS).MethodsDWI-ASPECTS of scans of 96 patients with acute ischemic stroke was rated by 2 experts. Automated methods based on thresholding the affected volumes of a coregistered atlas, and a regression tree learning method were established. Intra-rater, inter-rater and human-rater vs. automated methods agreements were investigated based on the intraclass correlation coefficients (ICC) and Bland Altman plots.ResultsIntra-rater agreement was good for both raters (ICC of 0.91 and 0.93). Inter-rater agreement was worse (ICC = 0.86) indicating a slight bias between both raters. Agreement with automated methods ranged from 0.81 to 0.87. Root-mean-squared deviation was 0.89 and 0.69 for the human raters and ranged from 0.95 to 1.24 for the automated methods.ConclusionsAgreement values are on the same order or higher compared to a literature review of CT-based ASPECTS. Automated methods perform slightly worse than human expert ratings, but they still have enough power to determine the DWI-ASPECTS with good precision in a clinical setting.     

磁共振血管成像-弥散成像不匹配对预测急性缺血性脑卒中缺血半暗带的价值

目的研究急性缺血性脑卒中（AIS）超早期磁共振血管成像（MRA）一弥散成像（DWI）不匹配对预测缺血半暗带的价值。方法选择在发病6h内完成MRA、DWI及灌注成像（PWI）检查的大脑中动脉供血区脑梗死患者，MRA—DWI桓Ⅱ体女不匹配定义为MRA示大脑中动脉M1段闭塞，DWI的梗死体积〈25ml；MRA—DWI梗Ⅱ部＆不匹配定义为M1段闭塞，DWI的梗死部位评分（以Alberta梗死早期CT评分评价）≥7。结果共入选78例患者，MRA—DWI梗死体积不匹配预测：PWI—DWI不匹配的特异度为100％，灵敏度仅为46％。MRA—DWI梗Ⅱ部＆不匹配预测：PWI—DWI不匹配的特异度为100％，灵敏度为42．9％。结论AIS超早期MRA．DWI不匹配预测缺血半暗带有很高的特异度，可作为筛选进行溶栓治疗患者的手段。     

Application of hidden Markov random field approach for quantification of perfusion/diffusion mismatch in acute ischemic stroke

The perfusion/diffusion 'mismatch model' in acute ischemic stroke provides the potential to more accurately understand the consequences of thrombolytic therapy on an individual patient basis. Few methods exist to quantify mismatch extent (ischemic penumbra) and none have shown a robust ability to predict infarcted tissue outcome. Hidden Markov random field (HMRF) approaches have been used successfully in many other applications. The aim of the study was to develop a method for rapid and reliable identification and quantification of perfusion/diffusion mismatch using an HMRF approach. An HMRF model was used in combination with automated contralateral identification to segment normal tissue from non-infarcted tissue with perfusion abnormality. The infarct was used as a seed point to initialize segmentation, along with the contralateral mirror tissue. The two seeds were then allowed to compete for ownership of all unclassified tissue. In addition, a novel method was presented for quantifying tissue salvageability by weighting the volume with the degree of hypoperfusion, allowing the penumbra voxels to contribute unequal potential damage estimates. Simulated and in vivo datasets were processed and compared with results from a conventional thresholding approach. Both simulated and in vivo experiments demonstrated a dramatic improvement in accuracy with the proposed technique. For the simulated dataset, the mean absolute error decreased from 171.9% with conventional thresholding to 2.9% for the delay-weighted HMRF approach. For the in vivo dataset, the mean absolute error decreased from 564.6% for thresholding to 34.2% for the delay-weighted HMRF approach. The described method represents a significant improvement over thresholding techniques.     

Chitotriosidase in patients with acute ischemic stroke

BACKGROUND: Following an acute brain ischemia, local endothelia allow monocyte chemoattraction into the lesion site which contributes to brain damage through a group of neurotoxic factors. A relationship exists between the extent of brain damage and the plasma level of monocyte products, including chitotriosidase, though usually strictly related to preexisting infectious-inflammatory diseases. PURPOSE: Since chitotriosidase activity is also elevated in pathogen-free conditions, we tested whether chitotriosidase upregulation might be specifically related to stroke and unrelated to clinically relevant infectious diseases. METHODS: We studied the plasma level of chitotriosidase activity, TNF-alpha and IL-6 in 44 consecutive patients with acute brain ischemia without concomitant symptoms or signs of inflammatory-infectious diseases. Results were compared with stroke severity and outcome as detected by brain CT and NIH scale. Blood samples were collected, on average, 11 h after stroke onset. RESULTS: Chitotriosidase activity positively correlates with stroke severity, as measured by NIH scale (r = 0.69, p < 0.01), to the extent of brain damage as documented by CT (r = 0.75, p < or = 0.001) and the TNF-alpha level (r = 0.76, p < 0.001); it also inversely correlates with the IL-6 level (r = -0.43, p < or = 0.05). CONCLUSION: Our results indicate that chitotriosidase is a specific marker of macrophage activation occurring in stroke which directly correlates with stroke severity independently of preexisting inflammatory or infectious conditions.     

Interleukin-12 in acute ischemic stroke patients

Cytokines are important mediators of stroke-induced immunological/inflammatory reaction which contributes to brain infarct progression as well as to the disease severity and outcome. The aim of the study was to evaluate the levels of the proinflammatory and immunomodulatory cytokine interleukin-12 (IL-12) in serum of acute ischemic stroke patients, and to investigate the relation between these levels and demographic, laboratory, neuroimaging, and clinical data. The study comprised 23 first-ever ischemic stroke patients and 15 age- and sex-matched controls. Blood sampling for the determination of IL-12 and such peripheral markers of inflammation as erythrocyte sedimentation rate (ESR) and leukocyte count, together with cranial CT were performed within 24 h of stroke, while neurological and functional deficits were estimated, respectively, with the Scandinavian Stroke Scale (SSS) and Barthel Index (BI) within the same period and two weeks later. Stroke patients displayed significantly higher serum IL-12 levels in comparison with controls. The serum IL-12 levels in stroke patients correlated significantly with the ESR values, the volume of early brain CT hypodense areas, and with the SSS and BI scores calculated within both studied times. The results indirectly suggest that IL-12 may play a role in the pathophysiology of ischemic stroke.     

Microalbuminuria in patients with acute ischemic stroke

ABSTRACT

Objective: Microalbuminuria could be detected in patients with acute stroke. However, the association between microalbuminuria and the severity of ischemic stroke has not been systematically investigated. This study aimed to systematically explore the prevalence of microalbuminuria in ischemic stroke patients, and the association of microalbuminuria with the severity of ischemic stroke, as well as the prognostic value of microalbuminuria in cerebral infarction patients.

Methods: 160 ischemic stroke patients and 54 controls were enrolled and clinical characteristics were recorded. Severity of stroke was assessed by NIHSS score at admission, and outcome was measured using mRS score. The concentration of urinary microalbumin was collected for each participant. Multiple linear regression analysis was performed to evaluate the relationship between microalbuminuria and the severity of ischemic stroke, and logistic regression analysis was employed to identify the prognostic value of microalbuminuria in ischemic stroke patients.

Results: The incidence of microalbuminuria in ischemic stroke patients was 36.88%. The concentration of urinary microalbumin increased with the increasing of cerebral infarction size, and was independently correlated with NIHSS score at admission and mRS score at 3 months after onset. In multivariate logistic regression analyses, microalbuminuria was one of the independent risk factors for poor prognosis of cerebral infarction patients.

Conclusions: MAU?was?found?in?approximately?one-third of patients with acute ischemic stroke. It was correlated with the severity of cerebral infarction at admission and clinical outcomes at 3 months after onset and could be used as a potential indicator of poor prognosis in ischemic stroke patients.