DWI及FLAIR对急性脑梗塞的诊断价值

目的：回顾分析44例急性脑梗塞患者的影像学资料，评价DWI及FLAIR技术在急性脑梗塞中的临床诊断价值。方法：44例脑梗塞患者中，其中超急性期．（〈6h）31例，急性期（6—16h）13例。所有病例均在GE Signa MR 1.5 TEchospeed Plus超导MR机上进行常规T1W1，T2W1，DW1及FLAIR扫描，比较病灶显示范围、边界及对比度，检出瘸灶的数目及病灶的大小，计算病灶的ADC值，结果：DW1及FLAIR序列对病灶的显示范围、对比均优于常规T1W1、T2W1，而且DWI对病灶显示较FLAIR更清晰。所有病俐病灶的ADC均下降。结论：DWI技术对急性脑梗塞病变敏感性最高，结合FLAIR技术可以更准确地诊断急性脑梗塞。     

扩散加权成像诊断超急性和急性脑梗塞的应用价值

目的:探讨DWI和ADC图诊断超急性和急性脑梗塞的价值.材料和方法:14例脑梗塞患者(超急性期6例,急性期8例)采用1.5T MR机进行扫描,对DWI、ADC图及常规T1WI、T2WI进行对比研究分析.结果:超急性和急性脑梗塞DWI均表现为高信号,ADC图均表现为低信号,DWI对病变显示达100%.6例超急性期脑梗塞患者仅DWI可显示病变而常规T1WI、T2WI无任何相应的异常发现.全部病灶ADC值均低于其相对应的正常脑组织.结论:DWI对急性脑梗塞诊断敏感、准确,且能对脑梗塞作定量分析.     

磁共振弥散加权成像在诊断急性脑梗塞中的价值

目的探讨磁共振弥散加权成像(DWI)在急性脑梗塞诊断中的价值,及对急性与非急性脑梗塞鉴别诊断价值。方法回顾性分析25例急性脑梗塞患者。均先行CT平扫,后行常规MRI及DWI检查。结果超急性期脑梗塞4例,CT呈阴性,常规MRI序列未见明显异常,而DWI均显示不同程度高信号;急性期脑梗塞21例只有2例CT显示新病灶,9例常规MRI(T2WI)显示新病灶,而DWI明显优于常规序列。结论 DWI对超急性期、急性期脑梗塞有高度的特异性和敏感性,能准确可靠地显示病灶的部位和范围,而且可以鉴别新旧梗死灶。     

磁共振弥散加权成像对急性脑梗塞的诊断价值

目的：评价磁共振弥散加权成像对急性脑梗塞的诊断价值及对急性和非急性脑梗塞的鉴别诊断价值。方法：对临床怀疑急性脑中风35例患者，进行常规T2WI和DWI检查，并采用盲法进行对照观察。对DWI图像上出现的异常高信号的病变部位进行准确定位，并判断病变部位与临床症状与体征是否相符，对DWI图像上出现的异常高信号与FSE序列T2WI像上的表现进行对照观察。结果：35例在DWI像上均出现异常信号，其中3例是在发病后6h内进行MRI检查，而在常规T2WI像上未显示异常信号；2例是在发病后12h内进行检查，而在常规T2WI像上仅表现稍高信号；10例患者在发病后12～24h内进行检查，20例患者在发病后24-72h进行检查，在T2WI和DWI像上均出现异常高信号；其中8例在FSE T2WI像上表现为多发脑梗塞病灶，而在DWI像上显示为单一异常高信号。在DWI像上诊断急性脑梗塞的敏感性及特异性均为100％。结论：DWI图像比常规T2WI图像对诊断急性脑梗塞有较高的敏感性及特异性，能发现常规T2WI像不能发现的超早期脑梗塞，并能鉴别急性和非急性脑梗塞，故DWI图像在诊断急性脑梗塞具有十分重要的诊断价值。     

DWI及FLAIR技术在急性脑梗塞中的临床应用探讨

目的　探讨弥散加权成像 (DWI)技术及FLAIR技术在急性脑梗塞中的临床应用价值。方法　收集 60例急性脑梗塞患者 ,其中超急性期 ( <6h) 7例 ,急性期 ( 6～ 2 4h) 2 4例 ,亚急性期 ( 2 4～ 72h) 2 9例。均行常规T1WI ,T2 WI及FLAIR ,DWI扫描 ,比较病灶显示范围、边界及对比度 ,并计算病灶的ADC与rADC值。结果　①DWI及FLAIR序列对病灶的显示范围、对比均优于常规T1WI、T2 WI ,而且DWI对病灶显示较FLAIR更清晰。②DWI的b值越高 ,弥散效果越好 ,显示病灶越清晰。同时 ,弥散全方向比单方向显示病灶更清晰。③所有病例病灶的ADC与rADC值均下降。结论　DWI技术对急性脑梗塞病变敏感性最高 ,结合FLAIR技术可准确、可靠地诊断急性脑梗塞     

低场强磁共振弥散成像在脑梗死诊断中的应用价值

目的 评价低场磁共振弥散序列对各期脑梗死的诊断作用。方法 应用磁共振T1W1，T2WI和水抑制反转恢复成像(T2 FLAIR)和DWI对70例各期脑梗死病人进行86人次MRI检查，并作ADC图，测定ADC值。结果在超急性脑梗死病例中，DWI和ADC图均表现缺血，但T2及T2FLAIR成像表现正常，病灶的ADC值随梗死时间延长，呈由低向高变化的趋势。结论低场磁共振DWI对急性期及超急性期脑缺血病变高度敏感，显示率及敏感性是100％．常规T2WI敏感性37％；ADC图可进一步量化缺血程度，二者结合应用对脑梗死的早期诊断和病灶的转归评估有重要意义。     

DWI及ADC图在脑梗死不同期相中的诊断价值

目的：研究磁共振弥散加权成像（diffusion weighted imaging,DWI）及表观弥散系数（apparent diffusion coefficient,ADC）图像对不同期相脑梗死的图像特征及诊断价值。方法：对54例脑梗死患者按发病就诊时间分为超急性期（8例）、急性期（10例）、亚急性期（22例）和慢性期（14例）4组,对每例进行MRI的T1-FLAIR、FSE-T2WI、T2-FLAIR、DWI序列扫描检查及ADC图像重建,分别测量病灶中心和病灶对称点正常脑组织的信号强度,计算出两者的信号差作为本序列对病灶显示的对比度,并对在各序列图像上的信号差进行对比,对急性期患者在各序列图像上同一层面所显示面积进行比较。结果：对超急性期、急性期脑梗死病灶,DWI序列的信号差（对比度）明显高于其它序列（P＆lt;0.05）;亚急性期的病灶,T2-FLAIR的信号差低于DWI的病灶（P＆lt;0.05）,T2WI、DWI中病灶信号差类同（P＆gt;0.05）,不存在序列间的相互差别;对于慢性期的病灶,T2WI序列的病灶信号差明显高于其它序列（P＆lt;0.05）;对于急性期的相同层面,T2WI、T2-FLAIR、DWI显示的病灶面积类同,不存在序列间的相互差别（P〉O．05）。结论：DWI能对超急性期、急性期、亚急性期的脑梗死病灶做出明确诊断,并对超急性期、急性期病灶的诊断敏感性明显高于其它序列。     

低场磁共振弥散加权成像诊断急性脑梗死的可行性

目的探讨低场磁共振弥散加权成像（DWI）在急性期脑梗死诊断中的可行性。方法对临床疑诊或确诊为脑梗死的116例患者包括11例超急性期（发病后6h内），35例急性期（发病后6-24h）及70例亚急性期（发病后2～7d）进行DWI和常规MRI检查，对超急性、急性、亚急性期的MRI表现进行分析，总结病变演变规律。结果DWI较常规MRI序列显示梗死灶更有明显优势，对超急性期脑梗死灶的敏感度为100％。急性期脑梗死灶在DWI序列上为异常高信号，且信号强度随b值升高而增强，各期脑梗死灶在DWI中异常信号强度由低逐渐增高。弥散全方向比单方向DWI成像显示病变效果好。结论低场磁共振弥散加权成像技术，通过精心调整扫描技术参数，对急性期脑梗死能作出诊断，尤其对超急性期脑梗死的诊断及治疗可提供可靠依据。     

磁共振DWI、FLAIR序列和MRA在急性缺血性脑中风的临床应用

目的:探讨磁共振扩散加权成像(DWI)、FLAIR序列和磁共振血管成像(MRA)对急性缺血性脑中风的诊断价值。方法:选择97例急性脑中风患者,其中超急性期23例,急性期74例。全部患者均行脑MRI常规T1WI、T2WI序列、FLAIR序列、DWI和3D TOF MRA检查。结果:97例超急性及急性期脑中风的DWI阳性检出率为100%,FLAIR序列和3D TOFMRA的阳性检出率分别为75.3%和52.6%,常规T1WI、T2WI序列的阳性检出率分别为20.6%和34.0%。结论:对于早期脑梗死病灶,DWI比FLAIR序列敏感性高,更易于发现病灶,FLAIR序列对于脑白质变性以及脑室、脑池、脑沟周围病变观察满意,MRA在分析脑中风病因方面可提供更多的影像学信息,DWI、FLAIR序列和MRA是对常规序列的重要补充,值得临床推广应用。     

O.5T磁共振机弥散加权像诊断急性脑梗塞

目的分析0.5T磁共振机的弥散加权像(DWI)对急性脑梗塞诊断的临床价值。材料与方法计算50例健康志愿者正常脑组织各不同部位的表观弥散系数(ADC)值,并对急性脑梗塞发作后3～12小时的10名患者进行DWI及常规T1WI、T2WI、FLAIR及MRA检查。结果测得正常人额、顶、枕叶脑白质、半卵圆中心、基底节、脑干、小脑半球、脑脊液部位的ADC平均值。对于临床患者,DWI可明确显示急性期脑梗塞病灶,常规T1WI、T2WI、FLAIR均不能显示或显示不清。结论以DWI为主,结合T1WI、T2WI、FLAIR及MRA序列能非常准确、可靠的诊断急性脑梗塞。     

MR imaging of acute hemorrhagic brain infarction

Six patients with acute hemorrhagic brain infarct were imaged using spin-echo (SE) pulse sequences on a 1.5 Tesla MR scanner. Including two patients with repeated MR imaging, a total of eight examinations, all performed within 15 days after stroke, were analyzed retrospectively. Four patients revealed massive hemorrhages in the basal ganglia or cerebellum and three cases demonstrated multiple linear hemorrhages in the cerebral cortex. On T1-weighted images, hemorrhages were either mildly or definitely hyperintense relative to gray matter, while varied from mildly hypointense to hyperintense on T2-weighted images. T1-weighted images were superior to T2-weighted images in detection of hemorrhage. CT failed to detect hemorrhages in two of five cases: indicative of MR superiority to CT in the diagnosis of acute hemorrhagic infarcts.     

弥漫性轴索损伤的影像诊断比较

目的 :比较CT、常规MR和扩散加权成像 (DWI)对急性、亚急性脑弥漫性轴索损伤 (DAI)的诊断价值。方法 :5 0例患者在脑损伤后 2h～ 2 0d行CT、常规MR及MRDWI ,比较病变在CT、MR各种序列上的表现特点。结果 :5 0例中CT检查阴性者 2 4例 (占 48% ) ,阳性者 2 6例 ,发现DAI病灶 75个。 5 0例在MR各种序列显示病灶 2 40个 ,其中非出血性病灶 182个 ,有 45个病灶在DWI上能观察到而常规MRI无法显示 ,占 2 4.7% ,83个病灶在DWI上信号明显高于T2 WI的病灶 ,占 45 .6% ;出血性病灶 5 8个中 ,有 12个病灶CT显示 ,而在常规MR和DWI上显示不清。结论 :对DAI急性期及亚急性期非出血性病灶的显示 ,MR常规检查比CT敏感 ,MRDWI比常规MRT2 WI敏感 ,统计学差异均有显著性意义 (P <0 .0 1)。非出血性病灶在DWI上的信号强度明显高于常规MRT2 WI ,统计学差异有显著性意义 (P <0 .0 1)。对出血性病灶的显示 ,CT优于常规MRSE序列和MRDWI。     

急性脑梗塞磁共振弥散加权成像的演变特征

目的：研究临床急性脑梗塞病变在弥散加权（DW）MRI上的表现规律。材料和方法：用单次激发平面回波弥散加权MRI和MRI其他技术对47例脑梗塞患者和14例非脑梗塞患者进行了对比研究。分别测量梗塞灶ACD图、DWI和T2WI的信号强度，绘出时间-信号强度图。分别在DWI和T2WI上测量梗塞面积．比较两者的关系。结果：急性脑梗塞发病后局部ACD逐渐降低．至12h达到峰值．以后逐渐升高。弥散加权MRI对急性脑梗塞病变非常敏感和特异，发病3h内T2WI为阴性，DW－MRI全部显示了梗塞灶；发病24h内T2WI所显示的梗塞灶面积明显小于DWI。发病7天内梗塞灶在DWI上与正常脑信号比均＞2．0．非脑梗塞病变均＜2．0。结论：急性脑梗塞病变在DW．MRI上有特征性演变规律，DW．MRI能快速、敏感、准确地诊断急性脑梗塞     

弥散加权MRI在脑梗塞诊断中的初步应用

目的：探讨弥散加权ＭＲＩ（ＤＷＩ）对早期脑梗塞诊断的敏感性和对急性与非急性脑梗塞的鉴别诊断价值。材料和方法：３１例脑梗塞（４例超急性,７例急性,１２例亚急性,８例慢性）患者行头颅单次激发回波平面弥散加权ＭＲＩ和常规ＭＲＩ扫描。结果：超急性、急性和亚急性脑梗塞在ＤＷＩ上均表现为高信号,其中４例超急性脑梗塞常规ＭＲＩ阴性。慢性脑梗塞除１例（发病１５天）ＤＷＩ表现为高信号,其余表现为混杂信号、等信号或低信号。６例患者常规ＭＲＩ显示多发脑梗塞灶,但ＤＷＩ显示１个急性高信号病灶。结论：ＤＷＩ对急性脑梗塞,尤其是超急性脑梗塞较常规ＭＲＩ具有更高的敏感性;ＤＷＩ还可以鉴别急性和非急性脑梗塞。     

Detection of intracranial hemorrhage: comparison between gradient-echo images and b(0) images obtained from diffusion-weighted echo-planar sequences

BACKGROUND AND PURPOSE: Diffusion-weighted MR imaging (DWI) is commonly used as the initial and sole imaging examination for the detection of acute cerebral infarction, yet it remains controversial whether MR can detect hyperacute (<24 h) hemorrhage. Hemorrhage is best detected with gradient-echo (GRE) T2*-weighted sequences, because of their magnetic susceptibility effects. DWI uses a spin-echo echo-planar technique (EPI) that is more sensitive than spin-echo T2-weighted imaging to susceptibility effects. Our aim was to determine whether the b(0) image from the DWI-EPI sequence is as sensitive as GRE in detecting hemorrhagic lesions on imaging studies performed to identify acute infarction or hemorrhage. METHODS: All MR studies performed for clinically suspected or radiographically confirmed acute infarction or hemorrhage from 2/1/98 to 8/15/99 were retrospectively interpreted by one neuroradiologist in a blinded fashion. The sensitivity of hemorrhage detection, conspicuity of lesions, and diagnostic certainty were compared between the b(0) EPI and GRE sequences. RESULTS: We found 101 acute infarcts, of which 13 were hemorrhagic, as evidenced by the presence of hypointensity within the infarction on the GRE sequence. This finding served as the reference standard for detection of hemorrhage. Hemorrhage was diagnosed with confidence in only seven cases (54%) on b(0) images; 22 acute hematomas were hypointense on GRE images whereas 19 were hypointense on b(0) images (86%); 17 chronic hematomas were depicted on GRE images and 12 on b(0) scans (63%). Punctate hemorrhages and linear cortical staining were detected on 37 GRE studies but on only four b(0) studies. Hemorrhage was always more conspicuous on the GRE sequences. CONCLUSION: b(0) images from a DWI sequence failed to detect minimally hemorrhagic infarctions and small chronic hemorrhages associated with microangiopathy. GRE scans were more sensitive than b(0) images in the detection of these hemorrhages and should be included in emergency brain MR studies for acute infarction, especially when thrombolytic therapy is contemplated.     

双b值扩散加权成像在脑梗死诊断中的应用

目的:比较双b值DWI对脑梗死体积及ADC值测量的影响,探讨较高b值DWI在脑梗死诊断中的应用价值。方法:回顾性研究30例脑梗死患者,年龄44～84岁,平均67岁,发病时间3～6d,DWI取b值1000和2000s/mm2,分析脑梗死DWI及ADC图,测量兴趣区与对侧正常部位的扩散系数(ADC)并计算相对扩散系数(rADC),测量并计算梗死灶体积。结果:急性和亚急性脑梗死灶均扩散受限,DWI呈高信号、ADC图呈低信号。与b值1000s/mm2相比,b值2000s/mm2DWI示脑灰白质对比度增加,病灶显示更清晰,还能发现新病灶。不同b值下rADC比较没有统计学意义(P=0.884,P>0.05),同侧ADC有统计学意义(P=0.005,P<0.05);对侧ADC有显著统计学意义(P<0.001)。较高b值下梗死体积较低b值增加,且有统计学意义(P=0.04,P<0.05)。结论:DWI是检测脑梗死的重要技术手段,rADC不受b值影响,rADC降低可指导脑梗死诊断;较高b值DWI上脑梗死灶体积测量更准确,有利于观察病灶演变和指导临床治疗。     

Time course of lesion development in patients with acute brain stem infarction and correlation with NIHSS score

BACKGROUND AND PURPOSE: diffusion weighted magnetic resonance imaging (MRI) is highly sensitive in detecting acute supratentorial cerebral ischemia and Diffusion Weighted Imaging (DWI) lesion size has been shown to correlate strongly with the neurologic deficit in middle cerebral artery territory stroke. However, data concerning infratentorial strokes are rare. We examined the size and evolution of acute brain stem ischemic lesions and their relationship to neurological outcome. METHODS: brain stem infarctions of 11 patients were analyzed. We performed DWI in all patients and in 7/11 patients within 24 h, T2W sequences within the first 2 weeks (10/11 patients) and follow-up MRI (MR2) within 3-9 months (median 4.8 months) later (12/12 patients). Lesion volumes were compared with early and follow-up neurologic deficit as determined by National Institutes of Health Stroke Scale (NIHSS) score. RESULTS: the relative infarct volumes--with MR2 lesion size set to 100%--decreased over the time (P<0.02) with a mean shrinking factor of 3.3 between DWI (MR0) and the follow-up MRT (P<0.02), and 1.6 between early T2W (MR1) and MR2 (P<0.04). The mean DWI volume size (MR0) was larger than the early T2W (P<0.02). Although neurological outcome was good in all patients (mean NIHSS score of 1.3 at follow-up), early NIHSS and follow-up NIHSS scores were strongly correlated (r=0.9, P<0.00). NIHSS score at follow-up was highly correlated with lesion size of DWI (MR0; r=0.71, P<0.04) and T2W of MR1 (r=0.86, P<0.001). CONCLUSIONS: in this study, we saw a shrinking of the brain stem infarct volume according to clinical improvement of patients. Great extension of restricted diffusion in the acute stage does not necessarily implicate a large resulting infarction or a bad clinical outcome.     

Development of brain infarct volume as assessed by magnetic resonance imaging (MRI): follow-up of diffusion-weighted MRI lesions

PURPOSE: To investigate the development of ischemic brain lesions, as present in the acute stroke phase, by diffusion-weighted magnetic resonance imaging (DWI), and in the subacute and chronic phases until up to four months after stroke, in fluid-attenuated inversion recovery (FLAIR)- and T2-weighted (T2W) magnetic resonance (MR) images. MATERIALS AND METHODS: Twelve consecutive patients with their first middle cerebral artery (MCA) infarction were included. Lesion volumes were assessed on T2W images recorded with a turbo spin echo (TSE) and on images recorded with the FLAIR sequence on average on day 8 and after about four months. They were compared with acute lesion volumes in perfusion and DWI images taken within 24 hours of stroke onset. RESULTS: On day 8, lesion volumes in images obtained with FLAIR exceeded the acute infarct volumes in DWI. The chronic lesion volumes were almost identical in T2W and FLAIR images but significantly reduced compared with the acute DWI lesions. The lesion volumes assessed on DWI images correlated highly with the lesions in the images obtained with TSE or FLAIR, as did the lesions in the images obtained with FLAIR and TSE. The secondary lesion shrinkage was accompanied by ventricular enlargement and perilesional sulcal widening, as most clearly visible in the images obtained with FLAIR. CONCLUSION: Our results show that the acute DWI lesions are highly predictive for the infarct lesion in the chronic stage after stroke despite a dynamic lesion evolution most evident in MR images obtained with FLAIR.     

3.0T磁共振磁敏感加权成像对出血性脑梗死的诊断和鉴别诊断价值

目的探讨3.0T磁共振磁敏感加权成像(SWI)对出血性脑梗死的诊断和鉴别诊断价值。方法对430例脑梗死患者行MR的T1WI、T2WI、DWI与SWI扫描,分析T1WI、T2WI、DWI和SWI对出血性脑梗死检出率的差异和SWI对于出血性脑梗死的鉴别诊断价值。结果 SWI检出出血性脑梗死45例,T1WI检出20例,T2WI检出28例,DWI检出31例。结论 SWI较MR常规序列(T1WI和T2WI)和DWI序列可检出更多的出血性脑梗死病例;可早期发现脑梗死中的出血灶,明显优于MR常规序列(T1WI和T2WI)和DWI序列;具有一定的鉴别诊断价值;可作为出血性脑梗死检查的一线方法或常规序列。     

Diffusion-weighted imaging of cerebral infarctions: are higher B values better?

PURPOSE: The purpose of this work is to determine whether high -value ( = 3,000 s/mm ) diffusion-weighted (DW) imaging is superior to low -value ( = 1,000 s/mm ) DW imaging for the detection of cerebral infarctions older than 6 h. METHOD: Echo planar DW imaging was performed at 1.5 T in 26 consecutive patients (mean age 66 years) referred for clinical diagnosis of definite acute/subacute cerebral infarction (6 h to 14 days old). The DW imaging sequences were performed using matched parameters (TR = 10,000 ms, TE (eff)= 97 ms, FOV = 24 cm, 128 x 192 matrix, slice = 5 mm, NEX = 2) with values of 1,000 and 3,000 s/mm. Areas of infarction were compared visually by two experienced neuroradiologists. Quantitative measures of MR signal and noise levels in the infarcted areas compared with contralateral normal brain were also obtained. RESULTS: The median time after infarction was 2.5 days (range 10 h to 14 days). By visual inspection, all infarctions were reliably identified on both the = 1,000 and the = 3,000 images. The gross signal ratio (infarct/normal brain) was approximately 33% higher in the = 3,000 images, but the = 3,000 images were rated as noticeably "noisier" by both observers in every case. This visual observation was confirmed quantitatively: The signal-to-noise (SNR) and contrast-to-noise (CNR) ratios were 70% and 51% higher in the = 1,000 than the = 3,000 images (p < 0.0005 for both). CONCLUSION: For the evaluation of late acute/subacute cerebral infarctions, high -value ( = 3,000 s/mm(2) ) DW imaging offers no apparent diagnostic advantages compared with = 1,000 images and is significantly inferior in terms of SNR and CNR.