Acute Stroke Imaging Research Roadmap

Department of Radiology, University of California, San Francisco, CA 94143-0628, USA.
American Journal of Neuroradiology (Impact Factor: 3.59). 06/2008; 29(5):e23-30. DOI: 10.1161/STROKEAHA.107.512319
Source: PubMed


The recent "Advanced Neuroimaging for Acute Stroke Treatment" meeting on September 7 and 8, 2007 in Washington DC, brought together stroke neurologists, neuroradiologists, emergency physicians, neuroimaging research scientists, members of the National Institute of Neurological Disorders and Stroke (NINDS), the National Institute of Biomedical Imaging and Bioengineering (NIBIB), industry representatives, and members of the US Food and Drug Administration (FDA) to discuss the role of advanced neuroimaging in acute stroke treatment. The goals of the meeting were to assess state-of-the-art practice in terms of acute stroke imaging research and to propose specific recommendations regarding: (1) the standardization of perfusion and penumbral imaging techniques, (2) the validation of the accuracy and clinical utility of imaging markers of the ischemic penumbra, (3) the validation of imaging biomarkers relevant to clinical outcomes, and (4) the creation of a central repository to achieve these goals. The present article summarizes these recommendations and examines practical steps to achieve them.

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    • "However, recent data including a meta-analysis of the mismatch trials have raised questions regarding the effectiveness of the mismatch approach [2,16]. In parallel, there has been increasing concern over the reliability of perfusion imaging data [17]. Quantification of cerebral hemodynamics is affected by numerous factors which have not been standardized, including image acquisition, post-processing and choice of perfusion parameter [4-6]. "
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    ABSTRACT: Background We tested the hypothesis that in patients with occlusion of the terminal internal carotid artery and/or the proximal middle cerebral artery, a diffusion abnormality of 70 ml or less is accompanied by a diffusion/perfusion mismatch of at least 100%. Methods Sixty-eight consecutive patients with terminal ICA and/or proximal MCA occlusions and who underwent diffusion/perfusion MRI within 24 hours of stroke onset were retrospectively identified. DWI and mean transit time (MTT) volumes were measured. Prospectively, 48 consecutive patients were identified with the same inclusion criteria. DWI and time to peak (TTP) lesion volumes were measured. A large mismatch volume was defined as an MTT or TTP abnormality at least twice the DWI lesion volume. Results In the retrospective study, 49 of 68 patients had a DWI lesion volume ≤ 70 ml (mean 20.2 ml; SEM 2.9 ml). A DWI/MTT mismatch of > 100% was observed in all 49 patients (P < .0001). In the prospective study, there were 35/48 patients with DWI volumes ≤ 70 ml (mean 18.7 ml; SEM 3.0 ml). A mismatch > 100% was present in all 35 (P < .0001). Conclusions Acute stroke patients with major anterior circulation artery occlusion are exceedingly likely to have a major diffusion/perfusion mismatch if the diffusion lesion volume is 70 ml or less. This suggests that physiology-based patient assessments may be made using only vessel imaging and diffusion MRI as a simple alternative to perfusion imaging.
    BMC Neurology 11/2012; 12(1):132. DOI:10.1186/1471-2377-12-132 · 2.04 Impact Factor
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    • "The benefit of extending the period of eligibility for thrombolysis to 9 h following an acute stroke is being evaluated by the ongoing extending the time for thrombolysis in emergency neurological deficit (EXTEND)1 clinical trial, using modern imaging techniques (diffusion, perfusion MRI, perfusion CT; Wintermark et al., 2008). "
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    ABSTRACT: According to the guidelines of the European Stroke Organization (ESO) and the American Stroke Association (ASA), acute stroke patients should be managed at stroke units that include well organized pre- and in-hospital care. In ischemic stroke the restoration of blood flow has to occur within a limited time window that is accomplished by fibrinolytic therapy. Newer generation thrombolytic agents (alteplase, pro-urokinase, reteplase, tenecteplase, desmoteplase) have shorter half-life and are more fibrin specific. Only alteplase has FDA approval for the treatment of acute stroke (1996). The NINDS trial proved that alteplase was effective in all subtypes of ischemic strokes within the first 3 hours. In the ECASS-III trial, intravenous alteplase therapy was found to be safe and effective (with some restrictions) if applied within the first 3-4.5 hours. In middle cerebral artery (MCA) occlusion additional transcranial Doppler insonication may improve the breakdown of the blood clot. According to the ESO and ASA guidelines, intra-arterial thrombolysis is an option for recanalisation within 6 hours of MCA occlusion. Further trials on the intra-arterial (IA) therapy are needed, as previous studies have involved relatively small number of patients (compared to IV. trials) and the optimal intra-arterial dose of alteplase has not been determined (20-30 mg is used most commonly in 2 hours). Patients undergoing combined (IV+IA) thrombolysis had significantly better outcome than the placebo group or the IV therapy alone in the NINDS Trial (IMS Trials). If thrombolysis fails or it is contraindicated, mechanical devices (e.g. MERCI- FDA approved in 2004) might be used to remove the occluding clot. Stenting can also be an option in case of acute internal carotid artery occlusion in the future. An intra-aortic balloon was used to increase the collateral blood flow in the SENTIS trial (results are under evaluation). Currently, there is no approved effective neuroprotective drug.
    Frontiers in Neurology 05/2011; 2:32. DOI:10.3389/fneur.2011.00032
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    • "An important focus of imaging research in the ischemic stroke is the differentiation of the ischemic penumbra from the infarct core and the normal tissue. Especially in patients presenting beyond the established time window of 4.5 hours after the stroke, in candidates for endovascular treatment, and in patients older than 80 years, a precise characterization of brain ischemia is required (Wintermark et al, 2008). The mismatch between ischemic areas measured by diffusion-weighted imaging (DWI) and perfusion imaging (PI) has been considered to be a good approximation of the ischemic penumbra, yet it tends to overestimate it by containing regions of benign oligemia (Heiss et al, 2004; Sobesky et al, 2005). "
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    ABSTRACT: The aim of this study was to test the feasibility of vessel size imaging with precise evaluation of apparent diffusion coefficient and cerebral blood volume and to apply this novel technique in acute stroke patients within a pilot group to observe the microvascular responses in acute ischemic tissue. Microvessel density-related quantity Q and mean vessel size index (VSI) were assessed in 9 healthy volunteers and 13 acute stroke patients with vessel occlusion within 6 hours after symptom onset. Our results in healthy volunteers matched with general anatomical observations. Given the limitation of a small patient cohort, the median VSI in the ischemic area was higher than that in the mirrored region in the contralateral hemisphere (P<0.05). Decreased Q was observed in the ischemic region in 2 patients, whereas no obvious changes of Q were found in the remaining 11 patients. In a patient without recanalization, the VSI hyperintensity in the subcortical area matched well with the final infarct. These data reveal that different observations of microvascular response in the acute ischemic tissue seem to emerge and vessel size imaging may provide useful information for the definition of ischemic penumbra and have an impact on future therapeutic approaches.
    Journal of cerebral blood flow and metabolism: official journal of the International Society of Cerebral Blood Flow and Metabolism 04/2011; 31(8):1687-95. DOI:10.1038/jcbfm.2011.38 · 5.41 Impact Factor
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