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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Magnetic resonance diffusion-weighted imaging (MR-DWI) is sensitive to the diffusibility of water and may offer characterization and anatomical localization of stroke leading to early tailored therapeutic intervention. We compared DWI, the apparent diffusion constant (ADC), and autoradiographic cerebral blood flow (CBF) in a model of focal cerebral ischemia in the rat. Sprague-Dawley rats were embolized with a single silicone cylinder injected into the internal carotid artery. Both common carotids were permanently ligated. The animals were anesthetized (isoflurane in O2), and paralyzed (gallamine). MR-DWI were obtained with a GE 4.7 T magnet (TE = 3 s, TR = 80 msec, b = 2393.10(-3) mm2/s, slice thickness 3 mm). DWI and CBF autoradiograms were compared visually. ADC was assessed in various regions, including ischemic cortex and a region homologous to ischemic cortex. Imaging times from stroke onset were 50 +/- 6 min (mean +/- SEM) for DWI, 185 +/- 17 min for a second DWI. CBF was determined at 258 +/- 15 min. The specificity was 100% at both 50 min and 185 min, indicating that there were no false positives; in 3 animals ischemia was not present. However, the sensitivity analysis indicated that early DWI yields some false negatives; at 50 min the sensitivity was 60%. We attribute our result of low early sensitivity to small infarcts in relation to the slice thickness. Later, at 185 min, sensitivity was 100%. The first ADCs were higher than the second ADC values in ischemic cortex. For infarcts larger than the slice thickness, early MR-DWI is highly sensitive for imaging evolving ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Magnetic resonance diffusion-weighted imaging: sensitivity and apparent diffusion constant in stroke. 797 48

Thrombolysis of embolic stroke in the rat was measured using diffusion (DWI)-, T2 (T2WI)-, and perfusion (PWI)-weighted magnetic resonance imaging (MRI). An embolus was placed at the origin of the middle cerebral artery (MCA) by injection of an autologous single blood clot via an intraluminal catheter placed in the intracranial segment of internal carotid artery. Rats were treated with a recombinant tissue plasminogen activator (rt-PA) 1 hour after embolization (n = 9) or were not treated (n = 15). Diffusion-weighted imaging, T2WI, and PWI were performed before, during, and after embolization from 1 hour to 7 days. After embolization in both rt-PA-treated and control animals, the apparent diffusion coefficient of water (ADCw) and cerebral blood flow (CBF) in the ischemic region significantly declined from the preischemic control values (P < 0.001). However, mean CBF and ADCw in the rt-PA-treated group was elevated early after administration of rt-PA compared with the untreated control group, and significant differences between the two groups were detected in CBF (24 hours after embolization, P < 0.05) and ADCw (3, 4, and 24 hours after embolization, P < 0.05). T2 values maximized at 24 (control group, P < 0.001) or 48 hours (treated group, P < 0.01) after embolization. The increase in T2 in the control group was significantly higher at 24 hours and 168 hours than in the rt-PA-treated group (P < 0.05). Significant correlations (r > or = 0.80, P < 0.05) were found between lesion volume measured 1 week after embolization and CBF and ADCw obtained 1 hour after injection of rt-PA. Within a coronal section of brain, MRI cluster analysis, which combines ADCw and T2 data maps, indicated a significant reduction (P < 0.05) in the lesion 24 hours after thrombolysis compared with nontreated animals. These data demonstrate that the values for CBF and ADCw obtained 1 hour after injection of rt-PA correlate with histologic outcome in the tissue, and that the beneficial effect of thrombolysis of an intracranial embolus by means of rt-PA is reflected in an increase of CBF and ADCw, a reduction in the increase of T2, and a reduction of the ischemic lesion size measured using MRI cluster analysis.
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PMID:Diffusion-, T2-, and perfusion-weighted nuclear magnetic resonance imaging of middle cerebral artery embolic stroke and recombinant tissue plasminogen activator intervention in the rat. 966 6

Combined NMR imaging and spectroscopy have been applied to mouse brain during focal cerebral ischemia. The present study evaluated the feasibility of NMR measurements on mice in order to fine-tune the sequences and experimental setup for systematic investigations on stroke including future studies on transgenic animals. The acquisition of high quality diffusion-weighted, perfusion-weighted, and T2-weighted images (DWI, PWI, T2-WI, respectively) is demonstrated and complemented by measurements of 1H volume-selective spectroscopy and spectroscopic imaging (SI). Despite the small volume of the mouse brain, a satisfactory signal-to-noise ratio can be achieved with reasonably short measurement times. C57black/6J mice with an average body weight of 25 g were studied using state-of-the-art NMR sequences at 4.7 T. After induction of focal cerebral ischemia, the lesion was found clearly distinguishable in all imaging techniques. The apparent diffusion coefficient (ADC) was reduced in the ischemic region, and an expansion of the affected volume was observed with ongoing ischemia time. In the H spectra of ischemic animals a distinct change in the concentrations of NAA and lactate was visible. This is the first report on both SI data and perfusion-weighted imaging on mouse brain. It is demonstrated that the perfusion deficit during ischemia can be well demarcated. The spatial resolution of changes in metabolite concentrations allows the clear differentiation of elevated lactate levels in ischemic brain tissue.
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PMID:High resolution MRI and MRS: a feasibility study for the investigation of focal cerebral ischemia in mice. 1022 85

A prospective longitudinal diffusion-weighted and perfusion-weighted magnetic resonance imaging (DWI/PWI) study of stroke patients (n = 21) at five distinct time points was performed to evaluate lesion evolution and to assess whether DWI and PWI can accurately and objectively demonstrate the degree of ischemia-induced deficits within hours after stroke onset. Patients were scanned first within 7 hours of symptom onset and then subsequently at 3 to 6 hours, 24 to 36 hours, 5 to 7 days, and 30 days after the initial scan. Lesion evolution was dynamic during the first month after stroke. Most patients (18 of 19, 95%) showed increased lesion volume over the first week and then decreased at 1 month relative to 1 week (12 of 14, 86%). Overall, lesion growth appeared to depend on the degree of mismatch between diffusion and perfusion at the initial scan. Abnormal volumes on the acute DWI and PWI (<7 hours) correlated well with initial National Institutes of Health (NIH) stroke scale scores, outcome NIH stroke scale scores, and final lesion volume. DWI and PWI can provide an early measure of metabolic and hemodynamic insufficiency, and thus can improve our understanding of the evolution and outcome after acute ischemic stroke.
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PMID:Longitudinal magnetic resonance imaging study of perfusion and diffusion in stroke: evolution of lesion volume and correlation with clinical outcome. 1051 90

This study presents histological validation of an objective (unsupervised) computer segmentation algorithm, the iterative self-organizing data analysis technique (ISODATA), for analysis of multiparameter magnetic resonance imaging (MRI) data in experimental focal cerebral ischemia. T2-, T1-, and diffusion (DWI) weighted coronal images were acquired from 4 to 168 hours after stroke on separate groups of animals. Animals were killed immediately after MRI for histological analysis. MR images were coregistered/warped to histology. MRI lesion areas were defined using DWI, apparent diffusion coefficient (ADC) maps, T2-weighted images, and ISODATA. The last techniques clearly discriminated between ischemia-altered and morphologically intact tissue. ISODATA areas were congruent and significantly correlated (r = 0.99, P < 0.05) with histologically defined lesions. In contrast, DWI, ADC, and T2 lesion areas showed no significant correlation with histologically evaluated lesions until subacute time points. These data indicate that multiparameter ISODATA methodology can accurately detect and identify ischemic cell damage early and late after ischemia, with ISODATA outperforming ADC, DWI, and T2-weighted images in identification of ischemic lesions from 4 to 168 hours after stroke.
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PMID:Unsupervised segmentation of multiparameter MRI in experimental cerebral ischemia with comparison to T2, diffusion, and ADC MRI parameters and histopathological validation. 1076 72

The preliminary results of MR echoplanar diffusion-weighted imaging (EPI DWI) in patients with stroke are presented. Twelve patients (5 females, 7 males) aged 36-78 years (mean 63.8) were examined by 2T system. No focal lesions were found in the acute phase of stroke on T1-weighted images. Narrowing of sulci in the region of stroke was the only abnormal finding. Focal hyperintense lesions were shown on PD and T2-weighted images in 50% of patients in the acute phase, 7 hours after the onset of clinical symptoms. On EPI diffusion-weighted images focal decrease of apparent diffusion coefficient (ADC) was observed in all cases of the acute phase of stroke after 3 hours. EPI DWI allows for earliest detection of ischaemic lesions in brain tissue. The method is especially useful in characterisation of the acute phase of stroke and shows its evolution thanks to the use of ADC.
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PMID:[The usefulness of the method of planar diffusion echo imaging (EPI DWI) in the diagnosis of cerebral ischemia]. 1096 19

The aim of this study was to evaluate the differences in cerebral perfusion seen on mean transit time (MTT) and cerebral blood volume (CBV) maps and to assess the subsequent prognostic value of the MTT-DWI (diffusion-weighted MRI) and CBV-DWI mismatch in the first three days of stroke on lesion enlargement and clinical outcome. In 38 patients, imaged 1-46 h after onset of symptoms, lesion volumes on proton-density (PD)-weighted MRI, DWI and PWI (both MTT and CBV maps) were compared with lesion volumes on follow-up PD-weighted scans, and to clinical outcome (National Institutes of Health Stroke Scale, Barthel index, and Rankin scale). The MTT-CBV, MTT-DWI and CBV-DWI mismatches were compared with change in lesion volume between initial and follow-up PD-weighted scans. Lesion volume on both DWI and PWI correlated significantly with clinical outcome parameters (p < 0.001) with strongest correlation for lesion volume on CBV. Perfusion-diffusion mismatches were found for both CBV and MTT and correlated significantly with lesion enlargement on PDweighted imaging with strongest correlation for the CBV-DWI mismatch. The CBV-DWI mismatch has the highest accuracy in predicting lesion size on follow-up imaging and in predicting clinical outcome. Lesion volume measurements on CBV maps have a higher specificity than on PD-weighted, MTT or DWI images in predicting clinical follow-up imaging and in predicting clinical outcome.
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PMID:Prognostic value of perfusion- and diffusion-weighted MR imaging in first 3 days of stroke. 1099 32

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.
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PMID:Diffusion- and perfusion-weighted magnetic resonance imaging of focal cerebral ischemia and cortical spreading depression under conditions of mild hypothermia. 1110 75

The progress in the technical procedures of stenting in the ICA and the growing expertise in this field need primary multidisciplinary efforts for improving both, indication and periinvasive management of stroke patients. From a neurological point of view in the acute stroke there is an indication on the single case basis, only, e.g. in crescendo-TIA and given TEA-indication but without operability given in the patient. Later on, the stenting should be taken into account only after complex neurovascular workup, incl. CMRT with DWI and PWI, interdisciplinary definitive indication and qualified periinvasive management, i.e., apparative monitoring and neurological examination, e.g., on a stroke unit. Some indications emerge from the present expertise: re-stenosis after TEA, radiogenic stenosis, given indication for TEA, but no operability for technical reasons, e.g. distal ICA-stenosis, or class III or IV risk patients. The contraindications remain to be clarified.
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PMID:[Carotid stenting--stratification of the acute phase, indications in secondary prevention from the neurological viewpoint]]. 1114 93

The recent reports confirm the idea that the selection of cerebral stroke patients for thrombolysis should be performed by MRI. These studies suggested that DWI/PWI/MRA may be able to identify patients who are most likely to benefit from thrombolytics, and that the PWI>DWI pattern in particular is associated with an improved outcome from thrombolytic therapy. However, many questions remain unanswered and a lot of work is necessary before MRI guided thrombolysis in acute cerebral stroke becomes a part of the standard care.
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PMID:Actual trends in diagnosis/thrombolytic therapy of acute cerebral stroke. 1128 62


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