多模态磁共振成像评估急性缺血性卒中缺血半暗带的研究进展

急性缺血性卒中（acute ischemic stroke,AIS）的缺血半暗带（ischemic penumbra,IP）一直是 急性血管内介入治疗中影像评估关注的重点和热点问题。由于多模态MRI可以提供丰富的病理生理学 参数,在IP临床评估中具有良好前景。本文对各类MRI成像策略对于IP评估的特点与局限进行介绍,重 点介绍了新型技术酰胺质子转移成像（amide proton transfer,APT）。APT通过对脑缺血区域细胞内pH 值的精确判断,能够准确评估IP。虽然目前APT临床应用尚少,但随着其成像技术的不断改进,有望成 为辅助决策AIS患者治疗的重要影像学检查手段。     

磁敏感加权成像与弥散成像不匹配在预测急性缺血性脑卒中缺血半暗带的价值

目的：探讨SWI-DWI不匹配对预测缺血半暗带的价值。方法对26例经临床及影像确诊的急性脑缺血患者行常规MRI（含DWI）、DSC和高分辨SWI检查,分别对DWI、SWI和DSC进行阿尔伯特早期CT评分（ASPECTS）,将SWI-DWI不匹配与DSC-DWI不匹配区域对照,并进行统计学分析。结果 SWI-DWI和DSC-DWI上不匹配区域相同,两种技术在显示缺血半暗带上差异无统计学意义（P＝0·148）。结论 SWI和DWI联合可无创性地显示缺血半暗带,为评价缺血脑组织的血流灌注状态提供一种简单易行的方法。     

磁共振血管成像-弥散成像不匹配在尿激酶静脉溶栓治疗急性脑梗死中的应用

目的 研究磁共振血管成像-弥散成像(MRA-DWI)不匹配在尿激酶静脉溶栓治疗急性脑梗死中的临床应用价值.方法 符合溶栓标准且溶栓前行1.5 T超导磁共振(MRI)检查的36例急性脑梗死病人,根据MRI检查结果分为MRA-DWI不匹配组及MRA-DWI匹配组,给予尿激酶静脉溶栓治疗,比较2组间治疗前后神经功能缺损评分变化及不良反应的发生率.结果 溶栓治疗后第1天及第14天2组神经功能缺损评分比较差异有统计学意义(P＜0.01),溶栓治疗后第14天MRA-DWI不匹配组基本治愈率50.00%,总有效率94.44%, MRA-DWI匹配组基本治愈率5.55%,总有效率66.66%,2组比较差异有统计学意义(P＜0.05);2组溶栓后48h内不良反应的发生率(11.11%、55.56%)比较差异有统计学意义(P＜0.05). 结论磁共振血管成像-弥散成像不匹配能准确预测缺血半暗带,指导尿激酶静脉溶栓治疗急性脑梗死.     

急性脑梗死缺血半暗带演变的磁共振成像研究

目的：探讨应用磁共振弥散／灌注成像技术判断急性脑梗死后缺血半暗带IP存在的范围和时间规律。方法：对72例发病时间在1～24h的急性脑梗死患者行常规MRI、磁共振弥散加权成像（DWI）和磁共振灌注加权成像（PWI）确定IP的范围，计算梗死中心区、IP区及对侧镜像区的ADC值和rADC值并加以比较。结果：26例发病时间〈6h的患者PWI显示存在低灌注区者，其中PWI〉DWI者21例，30例发病时间在6～24h的患者PWI显示存在低灌注区者，其中PWI〉DWI者2例；PWI〉DWI者病灶中心ADC值与IP区及对侧镜像区ADC值差异有统计学意义，其IP区ADC值与其对侧镜像区差异无统计学意义。结论：DWI和PWI结合能灵敏的判断IP的存在，IP存在的时间窗有一定的个体差异。     

卒中缺血性半暗带功能磁共振成像评估的研究进展

急性缺血性卒中是导致急性脑组织损伤的重要原因,是中老年人致残、死亡的主要因素,可挽救缺血组织的早期发现是临床及时干预治疗的关键。随着功能磁共振成像技术的发展,临床可从水分子扩散、血流动力学、氧合水平、pH值、代谢及侧支循环等方面全方位评价脑组织的病理改变,为疾病进展及预后评估提供更全面的信息。本文综述急性缺血性卒中缺血性半暗带功能磁共振成像的研究进展,以期为卒中患者的评估和治疗计划提供影像学支撑与指导。     

灌注及弥散磁共振成像在急性缺血性脑卒中的应用

目的　评估磁共振 (MRI)弥散加权成像 (DWI)及灌注加权成像 (PWI)在急性缺血性卒中指导溶栓治疗的应用价值。方法　对 44例急性 (≤ 6h)缺血性卒中患者行DWI、PWI扫描 ,DWI及PWI的不匹配区为缺血半暗带 ,根据半暗带是否存在确定患者是否适合溶栓治疗。结果　脑梗死患者 33例 ,其中 2 3例 (52 3 % )有明显半暗带存在 (PWI >DWI) ;1 0例 (2 2 7% )无明显半暗带 (PWI=DWI)。临床表现为短暂性缺血发作 (TIA)者 1 1例 (2 5 0 % )。结论　PWI及DWI对照研究有助于发现超早期脑梗死半暗带 ,指导溶栓治疗 ;临床表现结合DWI有助于除外TIA     

关于急性缺血性卒中发病时间与缺血半暗带相关关系模式的思考

急性缺血性脑血管病溶栓治疗是一个多因素、多环节作用的复杂临床干预过程。在溶栓治疗的实践过程中,“时间窗”是一个普遍沿用的概念,但单纯的依赖“时间窗”,往往不足以提供足够的信息以保证溶栓治疗的安全性和有效性。目的:探讨急性缺血性脑血管病发病时间与缺血半暗带之间的相关关系,以指导临床溶栓干预的决策。方法:本研究采用例证的方法,通过代表不同发病时间及相应缺血半暗带存在情况的4例典型病例,探讨关于急性缺血性脑血管病发病时间与缺血半暗带之间相关关系的模式。结果:根据基础血管病变、血流储备、侧支循环、缺血耐受等因素的不同,急性缺血性脑血管病发病时间与缺血半暗带存在情况分为三种模式,即骤变型、渐变型和缓冲型。结论:急性缺血性脑血管病发生时间与缺血半暗带之间对应关系存在个体差异。临床进行急性缺血性脑血管病溶栓干预时,要树立个体化的“时间窗”评价理念。     

早期脑梗死的临床与磁共振弥散加权成像

目的 从临床角度探讨磁共振弥散加权成像（diffusion weighted imagine,DWI)对早期脑梗死的诊断价值和确定DWI在区分常规MRI上所示的多发梗死灶中急性梗死方面的能力。方法 60例脑梗死均进行MRI常规程序及DWI（程度检查,并由4位经验丰富的医师在不了解患者临床体征的情况下进行阅片、记录出病变所在的详细的神经解剖部位,对同一层面所有的磁共振像进行比较,重点分析信号强度的病灶大小。数据经统计学分析。结果 DWI对超急性合肥市急性期脑梗死可显示T2加权像不能显示的病灶,并随时间延长显影范围逐渐增大,在T2加权像上可显示的病灶中,DWI可更清楚、更全面地显示病灶,大于T2病灶。在急性后期,常规MRI及DWI均有较清晰的影像学改变,恢复期及慢性期,DWI影像学逐渐改变变成等信号、杂信号,部分为囊性信号,且不易显示病灶。结论 DWI能非常可靠地显示超急性及急性脑梗死,而在急性后期及慢性期不如T2WI。其具有区分急性和非急性脑梗死的能力。     

核磁共振脑灌注成像及DWI联合应用在诊断早期脑梗死缺血半暗带中的临床价值

目的 探讨核磁共振脑部灌注加权成像(PWI)及脑部弥散加权成像(DWI)联合应用在诊断早期脑梗死缺血半暗带中的临床价值。方法 本研究中的受试对象均来自2016年1月-2017年4月来本院就诊的脑梗死患者,选出符合纳入标准的100例作为研究对象,并根据脑梗死发生时间分成超急性期、急性期、亚急性期和慢性期,分别观察PWI和DWI表现,以表观弥散系数(ADC)为DWI的检测评价指标,以局部脑血容量(rCBV)、局部脑血流量(rCBF)、平均通过时间(MTT)和达峰时间(TTP)为PWI的检测评价指标,并比较不同时期脑梗死的PWI和DWI表现。结果 随着脑梗死患者发病时间的延长,T₂WI显示信号随之增高,DWI信号随之降低,ADC信号随之增高。随着梗死时间延长,梗死区ADC值随之增加,健侧对应区随着梗死时间的变化,ADC值无明显变化; 在每个不同分期中健侧对应区的ADC值均高于梗死区(P均<0.05); 超急性期rCBV和rCBF值均为降低信号,MTT和TTP均为升高信号; 急性期rCBV、rCBF、MTT和TTP值在三种信号上均有表现,但rCBV和rCBF值均以降低信号为主,MTT和TTP均以升高信号为主; 亚急性期中rCBV和rCBF为正常和降低信号,其中以正常信号为主,MTT和TTP均为降低和升高信号,并以升高信号为主; 慢性期rCBV和rCBF均表现为降低信号,MTT和TTP均为降低和升高信号,并以降低信号为主; 超急性期DWIPWI均有表现,并以DWIPWI均有表现,并以DWIPWI为主; 亚急性期DWI=PWI和DWI>PWI均有表现,并以DWI=PWI为主; 慢性期均为DWI=PWI。结论 PWI联合DWI对脑梗死早期的诊断价值较高,PWI对缺血半暗带有较好的诊断,其与DWI相结合可更准确地判定缺血半暗带。     

缺血半暗带的影像学判定

脑梗死是指因脑部血液循环障碍,缺血、缺氧所致的局限性脑组织的缺血性坏死或软化。梗死组织周边存在半暗带是缺血性卒中现代治疗的基础。脑梗死早期,病变中心部位已经是不可逆性损害,但是及时恢复血流和改善组织代谢就能抢救梗死周围仅有功能改变的半暗带组织,避免形成坏死。那么临床迫切需要有一种方法在脑梗死发生后能尽早准确地判定缺血区域的脑血流量,以指导临床治疗和评估预后。1缺血半暗带的概念及意义脑缺血半暗带(ischemic penumbra,IP)的概念最初于1977年由Abtrup[1]等通过对狒狒大脑中动脉闭塞的电生理、血流灌注、细胞外K 和p…     

Proton magnetic resonance spectroscopy in patients with ischemic stroke

Proton magnetic resonance spectroscopy (¹H-MRS) is a non-invasive technique which has proved to be useful for monitoring various brain metabolites (N-acetyl-aspartate, choline, creatine-phosphocreatine, lactate). A total of 18 patients underwent a combined magnetic resonance imaging (MRI)/¹H-MRS protocol in order to evaluate the distribution of the metabolites in the various stages of cerebral ischemia. Our results show a marked decrease of N-acetyl-aspartate and a large content of Lactate during the early phases, and a decrease in N-acetylaspartate, choline and creatine-phosphocreatine (Cr-PCr) during the chronic phase.

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Sommario La risonanza magnetica protonica spettroscopica (¹H-RMS) è una tecnica non invasiva che si è dimostrata essere utile per il monitoraggio di alcuni metaboliti (N-Acetil-aspartato, Colina, Creatina-Fosfocreatina, Lattato) del tessuto cerebrale. Un totale di 18 pazienti è stato sottoposto ad un protocollo combinato di risonanza magnetica imaging e¹H-RMS per valutare la distribuzione dei metaboliti in differenti stati dell'ischemia cerebrale. I nostri risultati nelle fasi precoci mostrano un marcato decremento dell'N-Acetil-aspartato ed un notevole contenuto di lattato, mentre nella fase cronica un decremento dell'N-Acetil-aspartato, della Colina e Creatina-Fosfocreatina.

     

Validation of hyperintense middle cerebral artery sign in acute ischemic stroke Comparison between magnetic resonance imaging and angiography

We performed a retrospective analysis of non-contrast computed tomography (CT) scans, immediately subsequent magnetic resonance imaging (MRI), and cerebral angiography data from 30 consecutive patients with acute ischemic stroke within 6 hours after symptom onset. Results showed that eleven patients developed subsequent hemorrhagic transformation at follow-up. A hyperintense middle cerebral artery sign on MRI was found in six hemorrhagic patients, all of who had acute thrombosis formation on magnetic resonance angiography and digital subtraction angiography. No patients in the non-hemorrhagic group had hyperintense middle cerebral artery sign on MRI. The sensitivity, specificity, and positive predictive values of the hyperintense middle cerebral artery sign on MRI T1-weighted image for subsequent hemorrhagic transformation were 54.5%, 100%, and 100% respectively. Hyperdense middle cerebral artery sign on non-contrast CT was observed in nine patients, five of who developed hemorrhagic transformation. These data suggest that hyperintense middle cerebral artery sign on MRI T1-weighted image is a highly specific and moderately sensitive indicator of subsequent hemorrhagic transformation in patients after acute ischemic stroke, and its specificity is superior to CT.     

Refining the mismatch concept in acute stroke: lessons learned from PET and MRI

In ischemic stroke, positron-emission tomography (PET) established the imaging-based concept of penumbra. It defines hypoperfused, but functionally impaired, tissue with preserved viability that can be rescued by timely reperfusion. Diffusion-weighted and perfusion-weighted (PW) magnetic resonance imaging (MRI) translated the concept of penumbra to the concept of mismatch. However, the use of mismatch-based patient stratification for reperfusion therapy remains a matter of debate. The equivalence of mismatch and penumbra, as well as the validity of the classical mismatch concept is questioned for several reasons. First, methodological differences between PET and MRI lead to different definitions of the tissue at risk. Second, the mismatch concept is still poorly standardized among imaging facilities causing relevant variability in stroke research. Third, relevant conceptual issues (e.g., the choice of the adequate perfusion measure, the best quantitative approach to perfusion maps, and the required size of the mismatch) need further refinement. Fourth, the use of single thresholds does not account for the physiological heterogeneity of the penumbra and probabilistic approaches may be more promising. The implementation of this current knowledge into an optimized state-of-the-art mismatch model and its validation in clinical stroke studies remains a major challenge for future stroke research.     

Diffusion-weighted magnetic resonance imaging in two patients with polycythemia rubra vera and early ischemic stroke

Polycythemia rubra vera (PRV) is a rare myeloproliferative disorder with a high risk of ischemic stroke. Although thrombosis of large cerebral arteries is the most frequently presumed pathomechanism, various infarct patterns have been described in patients with PRV and ischemic stroke. We report two patients with mild acute ischemic strokes and known PRV, in whom a scattered lesion pattern was detected by diffusion-weighted magnetic resonance imaging (DWI), but was not visible on computed tomography (CT) and conventional magnetic resonance imaging (MRI). Further diagnostic work-up including extra- and transcranial Doppler sonography (ECD, TCD), transesophageal echocardiography (TEE), magnetic resonance angiography and Holter monitoring revealed no obvious sources of cerebral embolism in both cases. However, TEE in one patient demonstrated spontaneous echo contrast (SEC) in the left atrium. In both patients the symptomatology resolved completely. The detection of a scattered infarct pattern by DWI in patients with PRV and acute ischemic stroke has not been reported previously. DWI findings together with the SEC in one patient emphasize the assumption that a prothrombotic state with subsequent arterial embolism rather than local arterial thrombosis may be the underlying pathomechanism of stroke in some patients with PRV. Adding DWI to the diagnostic work-up may help to clarify etiology in patients with PRV and acute ischemic stroke.     

急性缺血性脑卒中伴发抑郁障碍的静息态脑功能磁共振成像研究

目的利用静息态脑功能磁共振成像(rsfMRI)技术探讨急性缺血性脑卒中伴发抑郁障碍患者的脑功能情况。方法对13例急性缺血性脑卒中伴发抑郁障碍患者(病例组)及13名性别、年龄、优势手与之相匹配的健康对照(对照组),进行常规MRI、rsfMRI扫描并采集图像,包括矢状位T1WI和轴位T1WI、T2WI、FLAIR、DWI像,以及rsfMRI图像,分析比较两组的局部一致性(regional homogeneity,ReHo)。结果病例组与对照组相比,双额上回内侧、左颞下回、左顶下小叶、右角回、右扣带回中部及右小脑的ReHo降低(P<0.01);右枕叶中部、双楔叶及距状沟的ReHo增高(P<0.01)。结论急性缺血性脑卒中伴发抑郁障碍患者在静息状态下存在多个脑区功能异常。     

Mechanical thrombectomy for acute ischemic stroke in pregnancy using the penumbra system

Even though intravenous thrombolysis with tissue plasminogen activator (IV tPA) is the standard of care in acute ischemic stroke, its use in pregnancy is not clearly defined. Mechanical thrombectomy devices can be an option; however, literature on the use of such mechanical devices in stroke in pregnancy is lacking. Here we describe two cases that developed acute embolic stroke during pregnancy who were successfully treated by mechanical clot retrieval using the Penumbra system 28 (Penumbra Inc., Alameda, California, USA). To the best of our knowledge, these are the only case reports on the use of the Penumbra device in pregnant patients with acute ischemic stroke.     

Assessment of leptomeningeal collaterals using dynamic CT angiography in patients with acute ischemic stroke

Whole-brain dynamic time-resolved computed tomography angiography (CTA) is a technique developed on the new 320-detector row CT scanner capable of generating time-resolved cerebral angiograms from skull base to vertex. Unlike a conventional cerebral angiogram, this technique visualizes pial arterial filling in all vascular territories, thereby providing additional hemodynamic information. Ours was a retrospective study of consecutive patients with ischemic stroke and M1 middle cerebral artery +/−intracranial internal carotid artery occlusions presenting to our center from June 2010 and undergoing dynamic time-resolved CTA and perfusion CT within 6 hours of symptom onset. Leptomeningeal collateral status was assessed by determining relative prominence of pial arteries in the ischemic region, rate and extent of retrograde flow, and various topographical patterns of pial arterial filling. Twenty-five patients were included in the study. We demonstrate the existence of the following novel properties of leptomeningeal collaterals in humans: (a) posterior (posterior cerebral artery (PCA)–MCA) dominant collateralization, (b) intra-territorial ‘within MCA region'' leptomeningeal collaterals, and (c) significant variability in size, extent, and retrograde filling time in pial arteries. We also describe a simple and reliable collateral grading template that, for the first time on dynamic CTA, incorporates back-filling time as well as size and extent of collateral filling.