定量磁敏感加权成像在急性缺血性脑卒中的应用进展

磁敏感加权成像(SWI)对显示静脉、血液成分、钙化、铁沉积等非常敏感,已广泛应用于脑血管病的诊断。近年来,定量SWI对急性缺血性脑卒中进行早期诊断及评估成为热点。SWI优势在于显示急性缺血性脑卒中血栓、不对称显著皮质静脉征、不对称深髓质静脉以及对急性缺血性脑卒中后血氧饱和度变化的判断,进而指导临床治疗及提示预后。主要综述定量磁敏感加权成像在急性缺血性脑卒中的应用。     

Leptomeningeal collateralization in acute ischemic stroke: Impact on prominent cortical veins in susceptibility-weighted imaging

Background

The extent of hypoperfusion is an important prognostic factor in acute ischemic stroke. Previous studies have postulated that the extent of prominent cortical veins (PCV) on susceptibility-weighted imaging (SWI) reflects the extent of hypoperfusion. Our aim was to investigate, whether there is an association between PCV and the grade of leptomeningeal arterial collateralization in acute ischemic stroke. In addition, we analyzed the correlation between SWI and perfusion-MRI findings.

Methods

33 patients with acute ischemic stroke due to a thromboembolic M1-segment occlusion underwent MRI followed by digital subtraction angiography (DSA) and were subdivided into two groups with very good to good and moderate to no leptomeningeal collaterals according to the DSA. The extent of PCV on SWI, diffusion restriction (DR) on diffusion-weighted imaging (DWI) and prolonged mean transit time (MTT) on perfusion-imaging were graded according to the Alberta Stroke Program Early CT Score (ASPECTS). The National Institutes of Health Stroke Scale (NIHSS) scores at admission and the time between symptom onset and MRI were documented.

Results

20 patients showed very good to good and 13 patients poor to no collateralization. PCV-ASPECTS was significantly higher for cases with good leptomeningeal collaterals versus those with poor leptomeningeal collaterals (mean 4.1 versus 2.69; p = 0.039). MTT-ASPECTS was significantly lower than PCV-ASPECTS in all 33 patients (mean 1.0 versus 3.5; p < 0.00).

Conclusions

In our small study the grade of leptomeningeal collateralization correlates with the extent of PCV in SWI in acute ischemic stroke, due to the deoxyhemoglobin to oxyhemoglobin ratio. Consequently, extensive PCV correlate with poor leptomeningeal collateralization while less pronounced PCV correlate with good leptomeningeal collateralization. Further SWI is a very helpful tool in detecting tissue at risk but cannot replace PWI since MTT detects significantly more ill-perfused areas than SWI, especially in good collateralized subjects.     

预测脑卒中的进展:MR磁敏感加权成像与MR灌注成像的比较研究

摘要目的与MR灌注加权成像(PWI)比较,探讨磁敏感加权成像(SWI)在预测脑卒中进展方面的作用。方法对一组(15例)发病24h内的非腔隙性缺血性脑卒中病人的回顾性分析中,我们使用Alberta卒中项目早期CT评分标准(Alberta Stroke Program Early CT Score,ASPECTS)比较了发病初期和发病至少5d后扩散加权成像(DWI)、SWI、PWI上病变的变化。     

Predicting stroke evolution: comparison of susceptibility-weighted MR imaging with MR perfusion

Objectives

To investigate the ability of susceptibility-weighted imaging (SWI) to predict stroke evolution in comparison with perfusion-weighted imaging (PWI).

Methods

In a retrospective analysis of 15 patients with non-lacunar ischaemic stroke studied no later than 24?h after symptom onset, we used the Alberta Stroke Program Early CT Score (ASPECTS) to compare lesions on initial diffusion-weighted images (DWI), SWI, PWI and follow-up studies obtained at least 5?days after symptom onset. The National Institutes of Health Stroke Scale scores at entry and stroke risk factors were documented. The clinical–DWI, SWI–DWI and PWI–DWI mismatches were calculated.

Results

SWI–DWI and mean transit time (MTT)–DWI mismatches were significantly associated with higher incidence of infarct growth (P?=?0.007 and 0.028) and had similar ability to predict stroke evolution (P?=?1.0). ASPECTS values on initial DWI, SWI and PWI were significantly correlated with those on follow-up studies (P?≤?0.026) but not associated with infarct growth. The SWI ASPECTS values were best correlated with MTT ones (ρ?=?0.8, P?Conclusions SWI is an alternative to PWI to assess penumbra and predict stroke evolution. Further prospective studies are needed to evaluate the role of SWI in guiding thrombolytic therapy. Key Points ? SWI can provide perfusion information comparable to MTT ? SWI–DWI mismatch can indicate ischaemic penumbra ? SWI–DWI mismatch can be a predictor for stroke evolution     

MRI patient selection for endovascular thrombectomy in acute ischemic stroke: correlation between pretreatment diffusion weighted imaging and outcome scores

Introduction

Eligibility for endovascular treatment (EVT) in patients with acute ischemic stroke (AIS) depends, amongst other factors, on CT- or MR-based scores. The aim of this study was to investigate the role of Alberta Stroke Program Early CT score based on diffusion weighted imaging (MR-ASPECT) in the assessment of brain damage pre-EVT, patient selection for EVT and outcome.

Materials and methods

We included in this study patients with National Institute of Health stroke score (NIHSS) at admission?≥?8, MR-ASPECT?≥?5 and anterior AIS, who were treated with EVT in our hospital. All patients were clinically evaluated at admission, post-EVT, discharge and at 3-month follow-up. We used MR-ASPECT to establish infarct core extension at admission. We evaluated ASPECT score at admission (CT-ASPECT-IN), 24 h after EVT and at discharge, NIHSS, modified Ranking Scale (mRS), Thrombolysis in Cerebral Infarction scale (TICI), onset-to-intervention-delay (OTID) and Collateral Circulation Score (CCS).

Results

68 patients (mean age 78?±?11.9 years) were included in this study. 54.4 and 64.7% of patients had strong clinical improvement after 24 h from EVT and at discharge, respectively. NIHSS evaluated 24 h after EVT correlated with CCS, TICI and OTID. We observed a favourable outcome (mRS 0–2) in 52.9% of patients at 3-month follow-up. MR-ASPECT score correlated with post-EVT outcome better than CT-ASPECT-IN scores.

Conclusion

MR-ASPECT score based on diffusion weighted imaging is useful for the selection of patients with AIS that can have a favourable outcome from EVT. A prompt EVT has huge impact on patient outcome.

     

急性缺血性脑卒中血管腔内治疗后对比剂外渗影像学研究现状北大核心CSCD

对比剂外渗(CE)和出血性转化(HT)是急性缺血性脑卒中血管腔内治疗(EVT)后的常见并发症,两者有相似的影像学表现,不同的临床治疗方法和转归。早期鉴别诊断CE和HT,对临床治疗和预后至关重要。本文就临床CE影响因素,常规CT、双能CT(DECT)及MRI诊断EVT后CE研究现状作一综述,为预防CE和早期鉴别诊断提供帮助。     

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.     

Diffusion-weighted MR imaging of acute stroke: correlation with T2-weighted and magnetic susceptibility-enhanced MR imaging in cats

We evaluated the temporal and anatomic relationships between changes in diffusion-weighted MR image signal intensity, induced by unilateral occlusion of the middle cerebral artery in cats, and tissue perfusion deficits observed in the same animals on T2-weighted MR images after administration of a nonionic intravascular T2 shortening agent. Diffusion-weighted images obtained with strong diffusion-sensitizing gradient strengths (5.6 gauss/cm, corresponding to gradient attenuation factor, b, values of 1413 sec/mm2) displayed increased signal intensity in the ischemic middle cerebral artery territory less than 1 hr after occlusion, whereas T2-weighted images without contrast usually failed to detect injury for 2-3 hr after stroke. After contrast administration (0.5-1.0 mmol/kg by Dy-DTPA-BMA, IV), however, T2-weighted images revealed perfusion deficits (relative hyperintensity) within 1 hr after middle cerebral artery occlusion that corresponded closely to the anatomic regions of ischemic injury shown on diffusion-weighted MR images. Close correlations were also found between early increases in diffusion-weighted MR image signal intensity and disrupted phosphorus-31 and proton metabolite levels evaluated with surface coil MR spectroscopy, as well as with postmortem histopathology. These data indicate that diffusion-weighted MR images more accurately reflect early-onset pathophysiologic changes induced by acute cerebral ischemia than do T2-weighted spin-echo images.     

替罗非班在急性颅内大血管闭塞血管内治疗中应用的安全性分析

目的探讨颅内大血管闭塞性缺血性脑卒中行血管内再通治疗术中合并使用替罗非班对颅内出血的影响。 方法回顾性分析本中心接受血管内再通治疗的急性颅内大血管闭塞性缺血性卒中患者的临床资料,比较术中使用替罗非班与未使用替罗非班两组患者的一般临床特点、治疗方式以及颅内出血并发症等差异。 结果共计纳入173例患者接受血管内再通治疗,其中替罗非班组87例,非替罗非班组86例,替罗非班组中后循环（39.08% vs 25.58%,P=0.034）、糖尿病（24.14% vs 10.47%,P=0.026）比例显著高于非替罗非班组,非替罗非班组中房颤患者比例显著高于替罗非班组（P<0.001）,两组患者手术再通率及随访90 d预后良好比例相当,围手术期颅内出血并发症未见差异。 结论血管内再通治疗合并使用替罗非班是相对安全的,并未增加出血风险。     

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.     

Thrombus imaging in acute ischaemic stroke using thin-slice unenhanced CT: comparison of conventional sequential CT and helical CT

Objectives

Thin-slice helical unenhanced CT can be used for thrombus imaging but increases radiation exposure. Conventional sequential images obtained by multidetector CT can be reconstructed into thin-slice images. The purpose of this study was to evaluate if conventional sequential unenhanced CT images can replace helical unenhanced CT for thrombus imaging.

Methods

Fifty consecutive patients with acute ischaemic stroke underwent both 5-mm conventional sequential unenhanced CT and helical unenhanced CT. Each of the sequential and helical unenhanced CT images was subsequently reconstructed into four 1.25-mm images. Thrombus volumes and HU were measured semi-automatically using both types of unenhanced CT. Thrombus HU ratio (rHU) was calculated using the HU of the contralateral segment. The intraclass correlation coefficient (ICC) and Bland–Altman plots were used to assess measurement agreement.

Results

The mean rHUs were 1.47?±?0.17 for sequential unenhanced CT and 1.47?±?0.18 helical unenhanced CT (P?=?0.542). The mean thrombus volumes were 124.25?±?125.65?mm³ and 117.84?±?124.32?mm³ on sequential and helical unenhanced CT images, respectively (P?=?0.063). Measurement agreement between thrombus volumes from the two unenhanced CT images was high (ICC?=?0.981).

Conclusions

Thin-slice unenhanced CT images reconstructed from 5-mm sequential images can replace helical unenhanced CT for thrombus imaging in acute ischaemic stroke.

Key Points

? Unenhanced CT is used to evaluate intra-arterial thrombus. ? Thrombus HU and volume measurements using sequential or helical CT are comparable. ? Conventional sequential images can replace helical CT for thrombus imaging. ? Radiation dose for thrombus imaging can be reduced using sequential CT.     

急性缺血性脑卒中血栓的薄层平扫CT成像:常规层面CT与螺旋CT的比较

目的薄层螺旋CT平扫可用于血栓的检查,但是增加了辐射剂量。多层CT采集的常规层面影像可重建为薄层影像。本研究的目的是评价常规层面平扫CT影像是否可代替螺旋CT平扫用于血栓的检查。方法 50例急性缺血性脑卒中病人,进行5mm常规层面CT和螺旋CT平扫检查。两种检查方法所得影像均重建为4幅1.25mm层厚的薄层影像。对两种平扫CT影像分别采用半自动软件计算血栓体积和CT值。以对侧相同节段的CT值为参照计算血栓的相对密度比率(rHU)。采用组内相关系数(ICC)和Bland-Altman曲线评价测量的一致性。结果层面CT和螺旋CT的平均rHU分别为1.47±0.17和1.47±0.18(P=0.542)。层面CT和螺旋CT的平均血栓体积分别为(124.25±125.65)mm3和(117.84±124.32)mm3(P=0.063)。两种方法测量血栓体积的一致性很高(ICC=0.981)。结论对于急性缺血性脑卒中的血栓检查,采用由5mm层面扫描重建获得的薄层平扫CT影像可替代螺旋CT影像。     

Clinical applications of neuroimaging with susceptibility-weighted imaging

Susceptibility-weighted imaging (SWI) consists of using both magnitude and phase images from a high-resolution, three-dimensional, fully velocity compensated gradient-echo sequence. Postprocessing is applied to the magnitude image by means of a phase mask to increase the conspicuity of the veins and other sources of susceptibility effects. This article gives a background of the SWI technique and describes its role in clinical neuroimaging. SWI is currently being tested in a number of centers worldwide as an emerging technique to improve the diagnosis of neurological trauma, brain neoplasms, and neurovascular diseases because of its ability to reveal vascular abnormalities and microbleeds.     

The prominent hypointense vessel sign on susceptibility-weighted imaging (SWI) as a potential imaging biomarker for poor clinical outcome in acute ischemic stroke (AIS)

Susceptibility-weighted imaging (SWI) is a relatively new magnetic resonance imaging (MRI) technique used in the workup and diagnosis of brain pathologies. In the context of acute ischemic stroke (AIS), it is increasingly becoming useful in the diagnosis, treatment, and further management of these patients. An elderly man with metabolic syndrome presented to us with an acute onset of right sided body weakness and aphasia. Urgent imaging via MRI noted a left middle cerebral artery (MCA) occlusion. Diffusion-weighted imaging (DWI)/fluid attenuated inversion recovery (FLAIR) mismatch was noted with an acute infarct involving the left MCA territory; hence, treatment with intravenous (IV) thrombolysis was administered. On SWI, the prominent hypointense vessel sign was noted. Recanalization of the occluded left MCA was seen on diagnostic cerebral angiography post IV thrombolysis, however, the patient was noted to have early neurological deterioration (END) and poor early stage clinical outcome, despite repeat MRI showing recanalization of the left MCA occlusion and reversal of the prominent hypointense vessel sign on SWI. Presence of the prominent hypointense vessel sign on SWI in AIS patients is associated with poor clinical outcome, unsuccessful recanalization rates, END, poor early stage clinical outcome, and infarct core progression. Some studies have shown an association between this imaging sign and poor collateral circulation status. Therefore, this imaging sign could potentially prove to be a useful imaging biomarker. However, more studies are needed to validate this theory.     

Defining reperfusion post endovascular therapy in ischemic stroke using MR-dynamic contrast enhanced perfusion

ObjectivesCerebral blood flow (CBF) measurements after endovascular therapy (EVT) for acute ischemic stroke are important to distinguish early secondary injury related to persisting ischemia from that related to reperfusion when considering clinical response and infarct growth.MethodsWe compare reperfusion quantified by the modified Thrombolysis in Cerebral Infarction Score (mTICI) with perfusion measured by MRI dynamic contrast-enhanced perfusion within 5 h of EVT anterior circulation stroke. MR perfusion (rCBF, rCBV, rTmax, rT0) and mTICI scores were included in a predictive model for change in NIHSS at 24 h and diffusion-weighted imaging (DWI) lesion growth (acute to 24 h MRI) using a machine learning RRELIEFF feature selection coupled with a support vector regression.ResultsFor all perfusion parameters, mean values within the acute infarct for the TICI-2b group (considered clinically good reperfusion) were not significantly different from those in the mTICI <2b (clinically poor reperfusion). However, there was a statistically significant difference in perfusion values within the acute infarct region of interest between the mTICI-3 group versus both mTICI-2b and <2b (p = 0.02). The features that made up the best predictive model for change in NIHSS and absolute DWI lesion volume change was rT0 within acute infarct ROI and admission CTA collaterals respectively. No other variables, including mTICI scores, were selected for these best models. The correlation coefficients (Root mean squared error) for the cross-validation were 0.47 (13.7) and 0.51 (5.7) for change in NIHSS and absolute DWI lesion volume change.ConclusionMR perfusion following EVT provides accurate physiological approach to understanding the relationship of CBF, clinical outcome, and DWI growth.Advances in knowledgeMR perfusion CBF acquired is a robust, objective reperfusion measurement providing following recanalization of the target occlusion which is critical to distinguish potential therapeutic harm from the failed technical success of EVT as well as improve the responsiveness of clinical trial outcomes to disease modification.     

CT imaging selection in acute stroke

Acute stroke has become an increasingly treatable cause of acute neurological deficits. Indeed, over the last two decades, the introduction of first thrombolysis, and now thrombectomy has improved patient outcomes and extended the therapeutic window. Computed tomography has been established as the most simple and readily available technique for the diagnosis and management of patients with acute stroke. Indeed, CT allows easy confirmation or exclusion of acute hemorrhage on the one hand, and on the other hand the early signs are quite reliable in the detection of ischemia. In the early phase the clot can be seen as well as exchanges related to early changes in water concentration in ischemia and the surrounding penumbra. Additional techniques such as angio-CT show the location of the clot and perfusion techniques reveal local hemodynamics as well as potential tissue viability. Newer techniques such as double energy CT and late phase CT should provide information on collateral flow as well as on the presence of early hemorrhagic transformation. All these techniques should thus make available new information on tissue viability,that is indispensable in the choice of revascularization technique. Thus CT techniques allow a quick and reliable triage as well as a finer characterization of the ischemic process. The use of all these CT techniques in an optimal way should help improve patient triage and selection of the most adequate treatment with further improvements in clinical outcomes as a result.