Brain perfusion-CT in acute stroke patients

The role of neuro-imaging in the evaluation of acute stroke has changed dramatically in the past decade. Previously, neuro-imaging was used in this setting to provide anatomic imaging that indicated the presence or absence of acute cerebral ischemia and excluded lesions that produce symptoms or signs mimicking those of stroke, such as hemorrhage and neoplasms. More recently, the introduction of thrombolysis has changed the goals of neuro-imaging from providing solely anatomic information to providing physiologic information that could help to determine which patients might benefit from therapy. In particular, significant emphasis has been placed on the delineation of the ischemic penumbra, also called tissue at risk. Modern CT survey, consisting of three indissociable elements: noncontrast CT (NCT) of course, perfusion-CT (PCT) and CT-angiography (CTA), fulfill all the requirements for hyperacute stroke imaging. CTA can define the occlusion site, depict arterial dissection, grade collateral blood flow, and characterize atherosclerotic disease, whereas PCT accurately delineates the infarct core and the ischemic penumbra. CT offers a number of practical advantages over other cerebral perfusion imaging methods, including its wide availability. Using PCT and CTA to define new individualized strategies for acute reperfusion will allow more acute stroke patients to benefit from thrombolytic therapy.     

The anterior cerebral artery is an appropriate arterial input function for perfusion-CT processing in patients with acute stroke

Introduction Dynamic perfusion-CT (PCT) with deconvolution requires an arterial input function (AIF) for postprocessing. In clinical settings, the anterior cerebral artery (ACA) is often chosen for simplicity. The goals of this study were to determine how the AIF selection influences PCT results in acute stroke patients and whether the ACA is an appropriate default AIF. Methods We retrospectively identified consecutive patients suspected of hemispheric stroke of less than 48 h duration who were evaluated on admission by PCT. PCT datasets were postprocessed using multiple AIF, and cerebral blood volume (CBV) and flow (CBF), and mean transit time (MTT) values were measured in the corresponding territories. Results from corresponding territories in the same patients were compared using paired t-tests. The volumes of infarct core and tissue at risk obtained with different AIFs were compared to the final infarct volume. Results Of 113 patients who met the inclusion criteria, 55 with stroke were considered for analysis. The MTT values obtained with an “ischemic” AIF tended to be shorter (P=0.055) and the CBF values higher (P=0.108) than those obtained using a “nonischemic” AIF. CBV values were not influenced by the selection of the AIF. No statistically significant difference was observed between the size of the PCT infarct core (P=0.121) and tissue at risk (P=0.178), regardless of AIF selection. Conclusion In acute stroke patients, the selection of the AIF has no statistically significant impact of the PCT results; standardization of the PCT postprocessing using the ACA as the default AIF is adequate.     

Brain perfusion CT in acute stroke: current status

Dynamic perfusion CT has become a widely accepted imaging modality for the diagnostic workup of acute stroke patients. Although compared with standard spiral CT the use of multislice CT has broadened the range from which perfusion data may be derived in a single scan run. The advent of multidetector row technology has not really overcome the limited 3D capability of this technique. Multidetector CT angiography (CTA) of the cerebral arteries may in part compensate for this by providing additional information about the cerebrovascular status. This article describes the basics of cerebral contrast bolus scanning with a special focus on optimization of contrast/noise in order to ensure high quality perfusion maps. Dedicated scan protocols including low tube voltage (80 kV) as well as the use of highly concentrated contrast media are amongst the requirements to achieve optimum contrast signal from the short bolus passage through the brain. Advanced pre and postprocessing algorithms may help reduce the noise level, which may become critical in unconscious stroke victims. Two theoretical concepts have been described for the calculation of tissue perfusion from contrast bolus studies, both of which can be equally employed for brain perfusion imaging. For each perfusion model there are some profound limitations regarding the validity of perfusion values derived from ischemic brain areas. This makes the use of absolute quantitative cerebral blood flow (CBF) values for the discrimination of the infarct core from periinfarct ischemia questionable. Multiparameter imaging using maps of CBF, cerebral blood volume (CBV), and a time parameter of the local bolus transit enables analyzing of the cerebral perfusion status in detail. Perfusion CT exceeds plain CT in depicting cerebral hypoperfusion at its earliest stage yielding a sensitivity of about 90% for the detection of embolic and hemodynamic lesions within cerebral hemispheres. Qualitative assessment of brain perfusion can be further enhanced by adding relative perfusion indices from regions of interest. Multislice CTA using a collimation of 4 x 1 mm and high pitch factors allows for isotropic scanning of the brain supplying arteries from the aortic arch to the vertex in a single run. Various image processing modalities such as multiplanar reformations, curved planar reconstructions, maximum intensity projections, and volume rendering techniques are available to deal with the extensive data and to bring out those vascular lesions, which are of relevance for individual stroke. With the advent of multidetector CT advanced stroke protocols combining plain CT, perfusion CT and CTA can routinely be accomplished within a very short timespan thus ensuring the role of CT in the diagnostic workup of acute stroke.     

Brain ischemia: CT and MRI techniques in acute ischemic stroke

Imaging plays a central role for intravenous and intra-arterial arterial ischemic stroke treatment patient selection.Computed tomography (CT) / CT angiography or magnetic resonance (MR) / MR angiography imaging are used to exclude stroke mimics and haemorrhage, to determine the cause and mechanism of stroke, to define the extension of brain infarct and to identify the arterial occlusion. Imaging may identify the patients that will be benefit more from revascularization therapies independently of the conventional therapeutic time window allowing individualized treatment decisions and improving individual patient outcome. Multiparametric CT/MR imaging may be used to identify the extension of potential viable brain tissue (penumbra) and of irreversible brain lesion (core) using CT perfusion and/or diffusion weighed and perfusion weighted MR imaging. The status of the arterial collateral circulation and the type and extension of the clot may be assessed by imaging.The accuracy and the clinical significance for treatment and patient clinical outcome of different imaging techniques are reviewed.     

Automated versus manual post-processing of perfusion-CT data in patients with acute cerebral ischemia: influence on interobserver variability

Introduction  The purpose of this study is to compare the variability of PCT results obtained by automatic selection of the arterial input function (AIF), venous output function (VOF) and symmetry axis versus manual selection. Methods  Imaging data from 30 PCT studies obtained as part of standard clinical stroke care at our institution in patients with suspected acute hemispheric ischemic stroke were retrospectively reviewed. Two observers performed the post-processing of 30 CTP datasets. Each observer processed the data twice, the first time employing manual selection of AIF, VOF and symmetry axis, and a second time using automated selection of these same parameters, with the user being allowed to adjust them whenever deemed appropriate. The volumes of infarct core and of total perfusion defect were recorded. The cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT) and blood–brain barrier permeability (BBBP) values in standardized regions of interest were recorded. Interobserver variability was quantified using the Bland and Altman's approach. Results  Automated post-processing yielded lower coefficients of variation for the volume of the infarct core and the volume of the total perfusion defect (15.7% and 5.8%, respectively) compared to manual post-processing (31.0% and 12.2%, respectively). Automated post-processing yielded lower coefficients of variation for PCT values (11.3% for CBV, 9.7% for CBF, and 9.5% for MTT) compared to manual post-processing (23.7% for CBV, 32.8% for CBF, and 16.7% for MTT). Conclusion  Automated post-processing of PCT data improves interobserver agreement in measurements of CBV, CBF and MTT, as well as volume of infarct core and penumbra.     

卒中单元联合高压氧治疗急性脑卒中的疗效观察

目的观察卒中单元联合高压氧治疗急性脑卒中的疗效。方法将研究对象分为对照组、卒中单元组、卒中单元+高压氧组,均采用常规的药物治疗,卒中单元组早期制定标准化操作程序,给予规范的综合康复治疗,卒中单元+高压氧组在卒中单元的基础上加上高压氧治疗。在治疗前后均采用欧洲卒中量表(ESS)和Barthel指数(BI)评分,并与对照组比较。结果治疗后卒中单元组、卒中单元+高压氧组ESS评分及BI评分显著高于对照组(P<0.01),卒中单元+高压氧组ESS评分及BI评分显著高于卒中单元组(P<0.05)。结论卒中单元联合高压氧治疗能明显改善急性脑卒中患者的运动功能及日常生活活动能力,改善生活质量。     

Echoplanar MRI in patients with an acute stroke syndrome

An increasing number of patients with an acute stroke syndrome are being admitted to hospitals with on-site echoplanar MRI scanners. In this pictorial review, we describe our experience of an MRI protocol in the first 150 such patients scanned in our hospital. We illustrate some of the advantages of using echoplanar MRI. Diffusion and susceptibility weighted acquisitions may supplement conventional MR sequences by providing useful additional information about the age and location of the lesion, together with a high sensitivity to the presence of blood breakdown products.     

Imaging preventable infarction in patients with acute ischemic stroke

One of the goals of neuroimaging in acute ischemic stroke is to identify those patients whose outcome will be improved by therapeutic intervention. This article will discuss the design, analysis, and interpretation of clinical research studies carried out to establish the accuracy and clinical value of neuroimaging to select such patients.     

Dual-energy perfusion-CT of pancreatic adenocarcinoma

Purpose

To evaluate the feasibility of dual-energy CT (DECT)-perfusion of pancreatic carcinomas for assessing the differences in perfusion, permeability and blood volume of healthy pancreatic tissue and histopathologically confirmed solid pancreatic carcinoma.

Materials and methods

24 patients with histologically proven pancreatic carcinoma were examined prospectively with a 64-slice dual source CT using a dynamic sequence of 34 dual-energy (DE) acquisitions every 1.5 s (80 ml of iodinated contrast material, 370 mg/ml, flow rate 5 ml/s). 80 kV_p, 140 kV_p, and weighted average (linearly blended M0.3) 120 kV_p-equivalent dual-energy perfusion image data sets were evaluated with a body-perfusion CT tool (Body-PCT, Siemens Medical Solutions, Erlangen, Germany) for estimating perfusion, permeability, and blood volume values. Color-coded parameter maps were generated.

Results

In all 24 patients dual-energy CT-perfusion was. All carcinomas could be identified in the color-coded perfusion maps. Calculated perfusion, permeability and blood volume values were significantly lower in pancreatic carcinomas compared to healthy pancreatic tissue. Weighted average 120 kV_p-equivalent perfusion-, permeability- and blood volume-values determined from DE image data were 0.27 ± 0.04 min⁻¹ vs. 0.91 ± 0.04 min⁻¹ (p < 0.0001), 0.5 ± 0.07 *0.5 min⁻¹ vs. 0.67 ± 0.05 *0.5 min⁻¹ (p = 0.06) and 0.49 ± 0.07 min⁻¹ vs. 1.28 ± 0.11 min⁻¹ (p < 0.0001). Compared with 80 and 140 kV_p the standard deviations of the kV_p120 kV_p-equivalent values were manifestly smaller.

Conclusion

Dual-energy CT-perfusion of the pancreas is feasible. The use of DECT improves the accuracy of CT-perfusion of the pancreas by fully exploiting the advantages of enhanced iodine contrast at 80 kV_p in combination with the noise reduction at 140 kV_p. Therefore using dual-energy perfusion data could improve the delineation of pancreatic carcinomas.     

急性脑卒中患者合并吞咽困难的临床分析与康复治疗

目的观察急性脑卒中合并吞咽困难患者康复治疗的疗效评定及吸入性肺炎的发生率。方法将168例急性脑卒中合并吞咽困难的患者随机分为康复组和对照组,康复组在对照组应用药物治疗的同时给予综合康复训练治疗。治疗时间为1个月．以治疗前后患者吞咽功能恢复情况及吸入性肺炎的发生率作为观察指标。结果康复组患者吞咽功能恢复情况显著优于对照组,而其吸入性肺炎的发生率显著低于对照组。结论对于急性脑卒中合并吞咽困难的患者早期给予及时、系统的综合康复训练能够有效改善患者的吞咽功能,并显著减少此类患者吸入性肺炎的发生率。     

Mechanical thrombectomy with snare in patients with acute ischemic stroke

Introduction We evaluated the efficacy and safety of thrombus extraction using a microsnare in patients with acute ischemic stroke (AIS). Methods This was a prospective, observational, cohort study in which consecutive patients with AIS (<6 hours of ischemia for anterior circulation and <24 hours for posterior circulation) who had been previously excluded from intravenous tissue plasminogen activator (tPA) thrombolysis were included and followed-up for 3 months. Mechanical embolectomy with a microsnare of 2–4 mm was undertaken as the first treatment. Low-dose intraarterial thrombolysis or angioplasty was used if needed. TIMI grade and modified Rankin stroke scale (mRSS) score were used to evaluate vessel recanalization and clinical efficacy, respectively. Results Nine patients (mean age 55 years, range 17–69 years) were included. Their basal mean NIHSS score was 16 (range 12–24). In seven out of the nine patients (77.8%) the clot was removed, giving a TIMI grade of 3 in four patients and TIMI grade 2 in three patients. Occlusion sites were: middle cerebral artery (four), basilar artery (two) and anterior cerebral artery plus middle cerebral artery (one). The mean time for recanalization from the start of the procedure was 50 min (range 50–75 min). At 3 months, the mRSS score was 0 in two patients and 3–4 in three patients (two patients died). Conclusion According to our results, the microsnare is a safe procedure for mechanical thrombectomy with a good recanalization rate. Further studies are required to determine the role of the microsnare in the treatment of AIS.     

Carotid stenting in acute ischemic stroke patients with intraluminal thrombus

Introduction  

Carotid stenosis with intraluminal thrombus is associated with a high risk of early recurrent stroke. We evaluated the feasibility and outcome of carotid stenting in acute ischemic stroke patients with carotid stenosis and intraluminal thrombus.     

Snare retrieval of intracranial thrombus in patients with acute stroke

Intravenous or intraarterial thrombolysis of intracranial emboli is becoming an accepted clinical treatment modality for acute ischemic stroke, but not all emboli respond to the lytic drug regimens available today. If drug therapy fails, mechanical retrieval seems warranted. Four patients whose condition was resistant to intravenous and intraarterial thrombolytic drug treatment underwent at least partial clot removal with use of a snare, and almost immediate clinical improvement was noted. A fifth patient's clot was removed before lytic drugs were administered. All five patients, who presented with a sudden onset of stroke, were evaluated by arterial angiography; then, after a failed trial of intraarterial fibrinolytic drugs, they were treated by passing a 2- or 4-mm snare through a microcatheter. The snare wire was guided around the thrombus, gently brought back toward the microcatheter-but not into it-and the entire microcatheter and snare assembly was then removed. In four of the five cases, follow-up angiography performed immediately after the retrieval showed wider distal branches than normal. Follow-up computed tomography results were abnormal in all cases, showing hyperdense material in the territory that was previously ischemic. This hyperdensity subsided within 48 hours in all but one patient who developed small parenchymal hemorrhages; however, he remained asymptomatic. The snare device offers an additional or alternative therapy until completely effective thrombolytic agents become available. Although use of a snare is not ideal, device improvements should make the retrieval less technically challenging and more effective. There is a need for improved mechanical extraction devices, especially in light of the patient improvement that occurred. This experience also suggests that immediate removal of a mature clot could reduce the total time of brain ischemia more quickly than administration of thrombolytic drugs.     

脑卒中合并吞咽困难的早期评估及治疗

 目的 观察脑卒中合并吞咽困难的发病率、早期标准吞咽功能评估方法 及治疗效果.方法 对132例急性脑卒中患者进行早期标准吞咽功能评估,选择其中56例合并吞咽困难患者随机分成治疗组和对照组.治疗组根据评估情况选择综合治疗措施,对照组按照常规治疗,治疗时间为4周,以治疗前后吞咽功能恢复情况及吸入性肺炎发生率作为观察指标.结果 急性脑卒中后吞咽困难发生率为52%,治疗组吞咽功能恢复率显著高于对照组,治疗组吸入性肺炎发生率明显低于对照组.结论 吞咽困难是脑卒中急性期最常见的问题,对这类患者进行早期标准吞咽功能评估,并及时干预能有效促进吞咽功能恢复,降低吸入性肺炎的发生率.     

Imaging in acute stroke

Stroke is a syndrome characterized by a sudden neurological deficit caused by intracranial hemorrhage or ischemia. Computed tomography (CT) maintains a primary role in the evaluation of patients with acute stroke. The optimal magnetic resonance imaging (MRI) protocol in acute stroke includes diffusion-weighted imaging (DWI) to show acute ischemic lesion and MR perfusion study to estimate brain perfusion. Careful selection of patients for a thrombolytic therapy is crucial to improve safety and efficacy.     

Emergency carotid artery stent placement in patients with acute ischemic stroke

BACKGROUND AND PURPOSE: An effective intervention has not yet been established for patients with acute ischemic stroke who present with serious neurologic symptoms due to occlusion or a high-grade stenosis of the internal carotid artery (ICA). The aim of our retrospective study was to investigate the feasibility, safety, and efficacy of emergency carotid artery stent placement to improve neurologic symptoms and clinical outcome. METHODS: Of 896 consecutive patients with acute ischemic stroke who were admitted to our institution within 7 days of onset from July 2000 to June 2003, 17 patients (1.9%) with occlusion or a high-grade stenosis of the ICA underwent emergency carotid artery stent placement. We reviewed their records for neurologic outcome, per the National Institutes of Health Stroke Scale (NIHSS) score, before and at 7 days after stent placement; clinical outcome, per the modified Rankin Scale score (mRS), at 90 days; frequency of procedure-related complications within 30 days; and recurrence rate of ipsilateral ischemic stroke within 90 days. RESULTS: Carotid lesions were dilated completely in all patients. Median NIHSS scores before emergency stent placement and at 7 days were 12 and 5, respectively, showing significant improvement (P < .01, Wilcoxon rank sum test). Ten patients (59%) had favorable outcomes (mRS score 0-1) at 90 days. Irreversible complications occurred in two patients (12%): distal embolism in one and intracerebral hemorrhage in the other. No ipsilateral ischemic stroke recurred. CONCLUSION: Emergency carotid artery stent placement can improve the 7-day neurologic outcome and may improve the 90-day clinical outcome in selected patients with ischemic stroke.     

Social factors influencing hospital arrival time in acute ischemic stroke patients

Introduction  

This is a multi-center, hospital-based study aiming to estimate social factors influencing pre-hospital times of arrival in acute ischemic stroke, with a perspective of finding ways to reduce arrival time and to augment the number of patients eligible for intra-arterial thrombolysis.