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

ATP, 2-deoxy ATP (dATP), CTP, and UTP support isometric force and unloaded shortening velocity (Vu) to various extents (Regnier et al., Biophys. J. 74:3044-3058). Vu correlated with the rate of cross-bridge dissociation after the power stroke and the steady-state hydrolysis rate in solution, whereas force was modulated by NTP binding and cleavage. Here we studied the influence of posthydrolytic cross-bridge steps on force and fiber shortening by measuring isometric force and stiffness, the rate of tension decline (kPi) after Pi photogeneration from caged Pi, and the rate of tension redevelopment (ktr) after a sudden release and restretch of fibers. The slope of the force versus [Pi] relationship was the same for ATP, dATP, and CTP, but for UTP it was threefold less. ktr and kPi increased with increasing [Pi] with a similar slope for ATP, dATP, and CTP, but had an increasing magnitude of the relationship ATP < dATP < CTP. UTP reduced ktr but increased kPi. The results suggest that the rate constant for the force-generating isomerization increases with the order ATP < dATP < CTP < UTP. Simulations using a six-state model suggest that increasing the force-generating rate accounts for the faster kPi in dATP, CTP, and UTP. In contrast, ktr appears to be strongly affected by the rates of NTP binding and cleavage and the rate of the force-generating isomerization.
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PMID:The effect of ATP analogs on posthydrolytic and force development steps in skinned skeletal muscle fibers. 963 60

The roles of noncontrast computed tomography (NCCT) and CT angiographic/CT perfusion (CTA/CTP) imaging in the rapid triage of clinically suspected hyperacute stroke patients to appropriate therapy is reviewed. Contraindications to thrombolysis include NCCT hemorrhage (absolute) and significant parenchymal hypodensity (relative). The sensitivity of NCCT for early (<6 h) stroke detection, higher than that of conventional magnetic resonance imaging, is improved further by using nonstandard window and level review settings. CTA/CTP is fast and convenient, adding approximately 10 min to the NCCT examination. CTA/CTP's accuracy in diagnosing ischemia and localizing thrombus to proximal or distal intracranial vessels far exceeds that of clinical examination (including National Institutes of Health stroke scale use), facilitating triage of appropriate candidates to intra-arterial thrombolysis. The size of the ischemic CTP hypodensity (proportional to reduced cerebral blood volume) predicts final infarct volume and clinical outcome; its location can guide the decision to perform intra-arterial thrombolysis, intravenous thrombolysis, or other treatment.
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PMID:Computed tomographic angiography and computed tomographic perfusion imaging of hyperacute stroke. 1114 26

The Alberta Stroke Program Early Computed Tomography Score (ASPECTS) has not been previously applied to perfusion CT (CTP). Five raters assigned ASPECTS to baseline noncontrast CT (NCCT), CT angiography source images (CTA-SI), CTP source images (CTP-SI), and CTP maps of cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT) from 37 consecutive patients with less than 6-hour anterior circulation ischemic stroke. Major reperfusion was identified on follow-up imaging. Mean baseline ASPECTS was compared with follow-up imaging ASPECTS. Rates of favorable outcome were compared for dichotomized baseline ASPECTS. In patients with major reperfusion, mean CBV and CTP-SI ASPECTS closely predicted final infarct ASPECTS. In patients without major reperfusion, mean CBF and MTT ASPECTS best predicted final infarct ASPECTS. There were significant increases in rates of favorable outcome for CTP-SI and CBV ASPECTS of greater than 6, versus less than or equal to 6, but not for other baseline CT modalities. ASPECTS applied to CTP is more accurate at identifying the extent of reversible and irreversible ischemia and at predicting final clinical outcome than NCCTor CTA-SI.
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PMID:Perfusion computed tomography: prediction of final infarct extent and stroke outcome. 1643 64

The ability to rapidly and accurately evaluate the location and extent of hyperacute brain ischemia is of major clinical importance. Herein, we aimed to develop imaging criteria to classify the ischemic lesion by computed tomography (CT) perfusion (CTP) and CT angiography (CTA) in hyperacute ischemic stroke patient. Non-contrast-enhanced CT, CTP and CTA were performed in patients with symptoms of hyperacute stroke lasting <8 hours. According to the volume of infarct core, ischemic penumbra and vessel status, three ischemic lesion types were defined. Twenty-six patients were included in our study. Among them, ten patients were classified into severe group, 15 patients were classified into mild group and one patient was classified into reversible group. In acute stroke patients, the ischemic lesion typing may assist in individualizing therapeutic decisions for patients by possibly extending the window for giving thrombolytics beyond the current 3 hour limit.
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PMID:Ischemic lesion typing on computed tomography perfusion and computed tomography angiography in hyperacute ischemic stroke: a preliminary study. 1854 47

Combining perfusion CT (CTP) with CT angiography (CTA) and noncontrast CT (NCCT) provides much more information about acute stroke pathophysiology than NCCT alone. This multimodal CT approach adds only a few minutes to the standard NCCT and is more accessible and rapidly available in most centres than MRI. CTP can distinguish between infarct core and penumbra, which is not possible with NCCT alone. A small infarct core and large penumbra, plus the presence of vessel occlusion on CTA may be an ideal imaging 'target' for thrombolysis. To date, multimodal CT has predominantly been assessed in hemispheric stroke due to its limited spatial coverage. This will become less of an issue as slice coverage continues to improve with new generation CT scanners. Apart from the concepts above, more specific CTP and CTA criteria that increase (or decrease) probability of response to thrombolytic treatment are yet to be determined. Nonetheless, CTP thus has the potential to improve patient selection for thrombolysis.
Int J Stroke 2008 Feb
PMID:Perfusion CT: is it clinically useful? 1870 14

CTP has a growing role in evaluating stroke. It can be performed immediately following NCCT and has advantages of accessibility and speed. Differentiation of salvageable ischemic penumbra from unsalvageable core infarct may help identify patients most likely to benefit from thrombectomy or thrombolysis. Still, CTP interpretation can be complex. We review normal and ischemic perfusion patterns followed by an illustrative series of technical/diagnostic challenges of CTP interpretation in the setting of acute stroke syndromes.
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PMID:Evaluation of CT perfusion in the setting of cerebral ischemia: patterns and pitfalls. 2019 Feb 8

The routine diagnostic tool of acute ischemic stroke is noncontrast computed tomography (CT). Modern multi-slice CT scanners permit also functional imaging with brain perfusion and CT angiography. Wider adoption of thrombolytic therapy in acute stroke have advanced their application. CTP is fast and widely available. It allows verification of cerebral ischemia, and may potentially assist in determining the extent of the ischemic tissue that still is salvageable with thrombolytic therapy. Major cerebral arteries can also be visualized to detect occlusions or stenosis, which also assists in clinical decision making. Noncontrast CT still remains the mainstay of acute stroke imaging.
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PMID:[Computed tomography perfusion (CTP) imaging in diagnostics of cerebral ischemia]. 2040 7

We investigated the utility of computed tomographic (CT) perfusion (CTP) with 64-row multi-detector row CT (MDCT) to diagnose acute infarction and ischemic penumbra. We reviewed 58 clinical cases with acute ischemic stroke with CTP, compared the size of the area with long mean transit time (MTT) to that with abnormal intensity in magnetic resonance (MR) diffusion-weighted imaging (DWI) to diagnose penumbra, and compared the size of the area with reduced cerebral blood volume (CBV) in CTP to that in MR DWI to evaluate sensitivity for infarction. The total sensitivity of MTT to acute ischemic lesions was 81% (47/58). Sensitivity of MTT to segmental lesions was 100% (42/42) and for spot and focal lesions, 31% (5/16). In 13 patients, penumbra was diagnosed as lesions mismatched between MTT in CTP and MR DWI. When we regarded a lesion with decreased CBV as infarction, the sensitivity of CBV to segmental lesions was 85% (11/13), and the sensitivity to small infarction was 14% (4/28). Use of 64-row MDCT improves coverage and radiation exposure in head CTP. The combination of plain CT, CT angiography, and CTP with MDCT can demonstrate all segmental ischemic lesions and most large segmental infarctions, and their combined application is useful in considering indication and contraindication for thrombolysis. The problem of low sensitivity for small lesions remains, and MR DWI may be required to assess small infarctions when findings from combined plain CT, CT angiography, and CTP are negative in patients with suspected acute brain stroke.
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PMID:Utility of CT perfusion with 64-row multi-detector CT for acute ischemic brain stroke. 2084 2

Flat detector CT perfusion (FD-CTP) is a novel technique using C-arm angiography systems for interventional dynamic tissue perfusion measurement with high potential benefits for catheter-guided treatment of stroke. However, FD-CTP is challenging since C-arms rotate slower than conventional CT systems. Furthermore, noise and artefacts affect the measurement of contrast agent flow in tissue. Recent robotic C-arms are able to use high speed protocols (HSP), which allow sampling of the contrast agent flow with improved temporal resolution. However, low angular sampling of projection images leads to streak artefacts, which are translated to the perfusion maps. We recently introduced the FDK-JBF denoising technique based on Feldkamp (FDK) reconstruction followed by joint bilateral filtering (JBF). As this edge-preserving noise reduction preserves streak artefacts, an empirical streak reduction (SR) technique is presented in this work. The SR method exploits spatial and temporal information in the form of total variation and time-curve analysis to detect and remove streaks. The novel approach is evaluated in a numerical brain phantom and a patient study. An improved noise and artefact reduction compared to existing post-processing methods and faster computation speed compared to an algebraic reconstruction method are achieved.
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PMID:Denoising and artefact reduction in dynamic flat detector CT perfusion imaging using high speed acquisition: first experimental and clinical results. 2506 1

The authors reported a case with acute right, middle cerebral artery infarct in which the early infarct area was detected by CTP recovery later after the treatment. The patient had hypoxia and tachypnea from pulmonary edema during acute ischemic stroke, which may have accentuated the ischemic change in cerebral hemodynamic. With treatment, the causes of hypoxia were corrected and the patient got better and some parts ofthe brain, previously identified as infarct, turned out to be normal.
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PMID:Misidentification of infarct core by computed tomography perfusion (CTP) in a patient with acute ischemic stroke with hypoxia. 2551 15


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