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1.
Relationship between severity of MR perfusion deficit and DWI lesion evolution   总被引:10,自引:0,他引:10  
OBJECTIVE: To assess whether a quantitative analysis of the severity of the early perfusion deficit on MRI in acute ischemic stroke predicts the evolution of the perfusion/diffusion mismatch and to determine thresholds of hypoperfusion that can distinguish between critical and noncritical hypoperfusion. METHODS: Patients with acute ischemic stroke were studied in whom perfusion-weighted imaging (PWI) and diffusion-weighted imaging (DWI MRI) were performed within 7 hours of symptom onset and again after 4 to 7 days. Patients with early important decreases in points on the NIH Stroke Scale were excluded. Maps of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) were created. These hemodynamic parameters were correlated with the degree of recruitment of the baseline PWI lesion by the DWI lesion. RESULTS: Twelve patients had an initial PWI > DWI mismatch of >20%. A linear relationship was observed between the initial MTT and the degree of recruitment of the baseline PWI lesion by the DWI lesion at follow-up (R(2) = 0.9, p < 0.001). Higher CBV values were associated with higher degrees of recruitment (rho = 0.732, p < 0.007). The volume of MTT of >4 (R(2) = 0.86, p < 0.001) or >6 seconds (R(2) = 0.85, p < 0.001) predicted final infarct size. CONCLUSION: Among patients who have had an acute stroke with PWI > DWI, who do not have dramatic early clinical improvement, the degree of expansion of the initial DWI lesion correlates with the severity of the initial perfusion deficit as measured by the mean transit time and the cerebral blood volume.  相似文献   

2.
The aim of this study is to investigate whether different spatial perfusion-deficit patterns, which indicate differing compensatory mechanisms, can be recognized and used to predict recanalization success of intravenous fibrinolytic therapy in acute stroke patients. Twenty-seven acute stroke data sets acquired within 6 hours from symptom onset including diffusion- (DWI) and perfusion-weighted magnetic resonance (MR) imaging (PWI) were analyzed and dichotomized regarding recanalization outcome using time-of-flight follow-up data sets. The DWI data sets were used for calculation of apparent diffusion coefficient (ADC) maps and subsequent infarct core segmentation. A patient-individual three-dimensional (3D) shell model was generated based on the segmentation and used for spatial analysis of the ADC as well as cerebral blood volume (CBV), cerebral blood flow, time to peak (TTP), and mean transit time (MTT) parameters derived from PWI. Skewness, kurtosis, area under the curve, and slope were calculated for each parameter curve and used for classification (recanalized/nonrecanalized) using a LogitBoost Alternating Decision Tree (LAD Tree). The LAD tree optimization revealed that only ADC skewness, CBV kurtosis, and MTT kurtosis are required for best possible prediction of recanalization success with a precision of 85%. Our results suggest that the propensity for macrovascular recanalization after intravenous fibrinolytic therapy depends not only on clot properties but also on distal microvascular bed perfusion. The 3D approach for characterization of perfusion parameters seems promising for further research.  相似文献   

3.
Changes in the apparent diffusion coefficient (ADC) are well established in acute ischemic stroke of arterial origin. However, ADC behaviour and its prognostic significance in cerebral venous thrombosis (CVT) are not fully understood. Diffusion-weighted imaging (DWI) findings in a 34-year old woman with deep cerebral venous thrombosis are described. Recent literature concerning DWI and cerebral venous thrombosis is also reviewed. A MRI performed within 7 hours from onset revealed hyperintensities in deep grey matter bilaterally (FLAIR/T2), without changes in ADC maps, suggesting vasogenic edema. After anticoagulation a new MRA disclosed complete recanalization of venous thrombosis. Despite her good clinical outcome the MRI showed hemorrhagic lesions suggesting venous infarct. Lesions detected in acute CVT with DWI may have normal ADC values. There is no good correlation between the acute ADC values and clinical and radiological evolution. The prognostic value of ADC in the acute phase of CVT remains unsettled.  相似文献   

4.
OBJECTIVE: To evaluate clinical, biological, and pretreatment imaging variables for predictors of tissue plasminogen activator (tPA) related intracerebral haemorrhage (ICH) in stroke patients. METHODS: 48 consecutive patients with hemispheric stroke were given intravenous tPA within seven hours of symptom onset, after computed tomography (CT) and magnetic resonance imaging (MRI) of the brain. Baseline diffusion weighted (DWI) and perfusion weighted (PWI) imaging volumes, time to peak, mean transit time, regional cerebral blood flow index, and regional cerebral blood volume were evaluated. The distribution of apparent diffusion coefficient (ADC) values was determined within each DWI lesion. RESULTS: The symptomatic ICH rate was 8.3% (four of 48); the rate for any ICH was 43.8% (21 of 48). Univariate analysis showed that age, weight, history of hyperlipidaemia, baseline NIHSS score, glucose level, red blood cell count, and lacunar state on MRI were associated with ICH. However, mean 24 hour systolic blood pressure and a hyperdense artery sign on pretreatment CT were the only independent predictors of ICH. Patients with a hyperdense artery sign had larger pretreatment PWI and DWI lesion volumes and a higher NIHSS score. Analysis of the distribution of ADC values within DWI lesions showed that a greater percentage of pixels had lower ADCs (< 400 x 10(-6) mm(2)/s) in patients who experienced ICH than in those who did not. CONCLUSION: Key clinical and biological variables, pretreatment CT signs, and MRI indices are associated with tPA related intracerebral haemorrhage.  相似文献   

5.
目的 探讨表观弥散系数(apparent diffusion coefficient,ADC)对确定急性缺血性卒中缺血半暗带的潜在价值。
方法 选择发病9 h内完成多模式磁共振成像(magnetic resonance imaging,MRI)检查的前循环急性缺血性卒中患者49例。应用自制软件进行灌注加权像(perfusion-weighted imaging,PWI)和弥散加权像(diffusion-weighted imaging,DWI)异常区域的体积测量。缺血半暗带以PWI/DWI错配表示。同时采用全自动图像分析系统,以DWI图像计算得到的ADC图作为输入数据,来判断缺血半暗带的存在(以下简称为ADC方法),然后比较这两种方法在判断缺血半暗带方面的差异。
结果 入选的49例患者中,存在PWI/DWI错配者为43例,符合ADC方法判断缺血半暗带标准者有41例。这两种方法在判断是否存在缺血半暗带的结果中有41例相符,对判断缺血半暗带的差异无统计学意义(P>0.05)。ADC方法判断缺血半暗带的敏感度为88.4%、特异度为50.0%。
结论 由于不需做PWI检查,ADC方法对确定缺血半暗带具有潜在的临床实用价值,有可能成为一种简便易行的确定缺血半暗带的方法。  相似文献   

6.
ObjectiveA role of diffusion-weighted imaging (DWI) in the diagnosis of cerebral venous thrombosis (CVT) is not wellunderstood. This study evaluates the effectiveness of DWI in the diagnosis of CVT. MethodsLiterature search was conducted in electronic databases for the identification of studies which reported the outcomes of patients subjected to DWI for CVT diagnosis. Random-effects meta-analyses were performed to achieve overall estimates of important diagnostic efficiency indices including hyperintense signal rate, the sensitivity and specificity of DWI in diagnosing CVT, and the apparent diffusion coefficient (ADC) of DWI signal areas and surrounding tissue. ResultsNineteen studies (443 patients with 856 CVTs; age 40 years [95% confidence interval (CI), 33 to 43]; 28% males [95% CI, 18 to 38]; symptom onset to DWI time 4.6 days [95% CI, 2.3 to 6.9]) were included. Hyperintense signals on DWI were detected in 40% (95% CI, 26 to 55) of the cases. The sensitivity of DWI for detecting CVT was 22% (95% CI, 11 to 34) but specificity was 98% (95% CI, 95 to 100). ADC values were quite heterogenous in DWI signal areas. However, generally the ADC values were lower in DWI signal areas than in surrounding normal areas (mean difference−0.33×10-3 mm2/s [95% CI, −0.44 to −0.23]; p<0.00001). ConclusionDWI has a low sensitivity in detecting CVT and thus has a high risk of missing many CVT cases. However, because of its high specificity, it may have supporting and exploratory roles in CVT diagnosis.  相似文献   

7.
In a model of experimental stroke, we characterize the effects of mild hypothermia, an effective neuroprotectant, on fluid shifts, cerebral perfusion and spreading depression (SD) using diffusion- (DWI) and perfusion-weighted MRI (PWI). Twenty-two rats underwent 2 h of middle cerebral artery (MCA) occlusion and were either kept normothermic or rendered mildly hypothermic shortly after MCA occlusion for 2 h. DWI images were obtained 0.5, 2 and 24 h after MCA occlusion, and maps of the apparent diffusion coefficient (ADC) were generated. SD-like transient ADC decreases were also detected using DWI in animals subjected to topical KCl application (n=4) and ischemia (n=6). Mild hypothermia significantly inhibited DWI lesion growth early after the onset of ischemia as well as 24 h later, and improved recovery of striatal ADC by 24 h. Mild hypothermia prolonged SD-like ADC transients and further decreased the ADC following KCl application and immediately after MCA occlusion. Cerebral perfusion, however, was not affected by temperature changes. We conclude that mild hypothermia is neuroprotective and suppresses infarct growth early after the onset of ischemia, with better ADC recovery. The ADC decrease during SD was greater during mild hypothermia, and suggests that the source of the ADC is more complex than previously believed.  相似文献   

8.
BACKGROUND: Diffusion-weighted (DWI) and perfusion-weighted (PI) MRI are highly sensitive techniques for early diagnosis of arterial infarction, but little data on venous cerebral ischemia are available. We describe a case in which DWI, PI, and fast T2-weighted sequences were performed in the acute phase of deep cerebral venous thrombosis (CVT). CASE DESCRIPTION: An 11-year-old girl with Crohn's disease developed deep CVT in which extensive edema was shown in the deep gray matter on T2-weighted sequence images. Isotropic echo-planar DWI demonstrated a local augmentation of the apparent diffusion coefficient (1.1 to 1.6x10(-3) mm2/s), consistent with vasogenic edema. In dynamic contrast-enhanced PI, the regional cerebral blood volume was increased and the passage time of the contrast bolus was markedly prolonged. Clinically, the patient recovered totally after intravenous full-dose heparinization. T2 abnormalities, apparent diffusion coefficient values (0.8 to 0.92x10(-3) mm2/s), and brain perfusion alterations resolved without damage to brain tissue. CONCLUSIONS: Unlike arterial infarction, DWI demonstrated vasogenic edema in a patient with deep CVT, which proved to be reversible in follow-up magnetic resonance imaging. PI showed areas with extensive venous congestion, but perfusion deficits were missing. Therefore, we believe that DWI and PI may play a role in detecting venous congestion in CVT and in prospective differentiation of vasogenic edema and venous infarction.  相似文献   

9.
BACKGROUND: Methods for determining cerebral blood flow (CBF) using bolus-tracking magnetic resonance imaging (MRI) have recently become available. Reduced apparent diffusion coefficient (ADC) values of brain tissue are associated with reductions in regional CBF in animal stroke models. OBJECTIVES: To determine the clinical and radiological features of patients with severe reductions in CBF on MRI and to analyze the relationship between reduced CBF and ADCs in acute ischemic stroke. DESIGN: Case series. SETTING: Referral center. METHODS: We studied 17 patients with nonlacunar acute ischemic stroke in whom perfusion-weighted imaging (PWI) and diffusion-weighted imaging (DWI) were performed within 7 hours of symptom onset. A PWI-DWI mismatch of more than 20% was required. We compared patients with ischemic lesions that had CBF of less than 50% relative to the contralateral hemisphere with patients with lesions that had relative CBF greater than 50%. Characteristics analyzed included age, time to MRI, baseline National Institutes of Health Stroke Scale score, mean ADC, DWI and PWI lesion volumes, and 1-month Barthel Index score. RESULTS: Patients with low CBF (n = 5) had lower ADC values (median, 430 x 10 (-6) mm(2)/s vs. 506 x 10 (-6) mm(2)/s; P =.04), larger DWI volumes (median, 41.8 cm(3) vs. 14.5 cm(3); P =.001) and larger PWI lesions as defined by the mean transit time volume (median, 194.6 cm(3) vs. 69.3 cm(3); P =.01), and more severe baseline National Institutes of Health Stroke Scale scores (median, 15 vs. 9; P =.02). CONCLUSION: Ischemic lesions with severe CBF reductions, measured using bolus-tracking MRI, are associated with lower mean ADCs, larger DWI and PWI volumes, and higher National Institutes of Health Stroke Scale scores.  相似文献   

10.
BACKGROUND: Rapid resolution of neurological deficits after severe middle cerebral artery (MCA) stroke has been coined spectacular shrinking deficit (SSD). We studied clinical and MRI patterns in patients with SSD. METHODS: Patients with acute MCA stroke <6 h were examined by stroke MRI (perfusion- and diffusion-weighted imaging (PWI, DWI), MR angiography (MRA)) at admission, day 1 and day 7. SSD was defined as a > or =8-point-reduction of neurological deficit in the National Institute of Health Stroke Scale (NIHSS) to a score of < or =4 within 24 h. PWI and DWI lesion volumes were measured on ADC (ADC < 80%) and time to peak maps (TTP > +4 s). Recanalization was assessed by MRA after 24 h. Final infarct volumes were defined on T2 weighted images at day seven. Outcome was assessed after 90 days using modified Rankin Scale (mRS) and Barthel Index (BI). RESULTS: SSD was present in 14 of 104 patients. Initial DWI and PWI lesion volumes were smaller in SSD patients - ADC < 80%: 8.9 (4.3-20.5) vs. 30 (0-266.7) ml; TTP > +4 s: 91.6 (29.7-205.8) vs. 131.5 (0-311.5) ml. Early recanalization was associated with SSD resulted in smaller final infarct volumes (11.9 (2.4-25.9) vs. 47.7 (1.2-288.5)). All SSD patients were independent at day 90 (mRS 0 (0-2); BI 100). CONCLUSION: The clinical syndrome of SSD is reflected by a typical MRI pattern with small initial DWI and PWI lesion volumes, timely recanalization and small final infarct volumes.  相似文献   

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