犬心肌梗塞的MRI与病理对照研究

目的：研究心肌梗塞演变过程中不同时期的ＭＲＩ影像特征及其病理基础。探讨ＭＲＩ在心肌梗塞方面的应用价值。材料与方法：２５只杂种犬结扎冠状动脉左前降支后,于心肌梗塞演变过程的不同时期行ＭＲＩ平扫、电影磁共振成像和Ｇｄ－ＤＴＰＡ增强扫描。取心脏标本进行病理检查。结果：ＭＲＩ平扫不能区别梗塞心肌和非梗塞心肌。Ｃｉｎｅ－ＭＲＩ能真实反映梗塞心肌的部位、厚度及运动功能状态。心肌梗塞演变的不同时期,由于其病理基     

急性、亚急性、慢性心肌梗塞在Gd－DTPA增强MRI上的信号表现

通过对Ｇｄ－ＤＴＰＡ增强前后ＭＲＩ上急性、亚急性和慢性心肌梗塞区的心肌信号变化规律的总结，期望对心肌梗塞作出定性定量的诊断。材料和方法：３２例不同时期心肌梗塞及１２例正常心脏做了Ｇｄ－ＤＴＰＡ增强前后ＭＲＩ扫描，增强后为动态观察。结果：１０例急性心肌梗塞和１０例亚急性心肌梗塞均见到心肌的异常强化信号：１２例慢性心肌梗塞中仅４例（３３％）见到异常强化信号。正常心肌为均匀一致的轻度信号增强。不同时期的心肌梗塞异常信号范围不同，信号率的动态变化规律也不同。结论：Ｇｄ－ＤＴＰＡ增强ＭＲＩ及动态观察可以显示心肌梗塞的部位、范围及为心肌梗塞的分期提供依据。     

亚急性和慢性心肌梗塞的MRI诊断和评价

目的：确定自旋回波（ＳＥ）和电影动态ＭＲＩ（ｃｉｎｅＭＲＩ）评价亚急性和慢性心肌梗塞信号变化、室壁节段运动和其他合并症的价值。材料和方法：对心肌梗塞亚急性期５例和慢性期１３例进行ＭＲ横断面、左室长／短轴Ｔ１ＷＩ，其中１３例还经Ｔ２ＷＩ，５例经Ｇｄ－ＤＴＰＡ增强。结果：前壁（包括前间壁）受累６例，下壁、侧壁和后壁受累各２例，前壁和下壁均受累６例。Ｔ１ＷＩ显示４例梗塞室壁信号略低，４例亚急性期注射Ｇｄ－ＤＴＰＡ后强化，慢性期１１例室壁厚度变薄；ｃｉｎｅＭＲＩ显示１５例室壁节段运动减低；发现合并二尖瓣返流６例、主动脉瓣返流４例、心包积液４例。结论：ＳＥ和ｃｉｎｅＭＲＩ能较好地显示心肌梗塞的部位、范围和室壁厚度，ｃｉｎｅＭＲＩ评价室壁节段运动和瓣膜返流更具优势     

Gd—DTPA增强MRI诊断心肌梗塞

15例心脏作Gd-DTPA增强前后MRI检查,增强后为连续动态观察。其中7例为正常对照;7例为心肌梗塞(包括5例亚急性和2例慢性心肌梗塞);1例为陈旧性心肌梗塞。结果显示:增强前正常心肌信号率与梗塞心肌信号率无差别。增强后梗塞心肌信号率既高于增强前也明显高于其周围的正常心肌。无论肉眼观察还是信号测量均发现Gd-DTPA增强MRI能诊断心肌梗塞,改善心肌梗塞的显示。作者对增强后心肌信号率的系列变化作了描述。     

心内膜心肌纤维化症的MRI诊断

目的评价ＭＲＩ对心内膜心肌纤维化症（ＥＭＦ）的诊断价值和限度。材料与方法对９例经影像学（包括超声心动图、心导管、Ｘ线心血管造影以及放射性核素显像）诊断、或（和）病理证实（５例）的ＥＭＦ患者，行心电图门控心脏自旋回波和梯度回波电影ＭＲＩ扫描。结果ＥＭＦ分为右室型（ＲＶＥＭＦ）、左室型（ＬＶＥＭＦ）和双室型（ＢＶＥＭＦ）三个亚型，ＭＲＩ所见为：（１）右室型（６例）：右室心内膜显著增厚呈较高信号，右室腔缩小变形，流入道短缩，心尖闭塞而流出道扩张，室壁运动减弱，电影ＭＲＩ（３例）显示有中至大量三尖瓣返流。右心房高度扩大，腔静脉亦显著扩张。（２）左室型（１例）：左室心尖圆钝，心内膜凸凹不平、显著增厚，呈“异常肌束”改变，电影ＭＲＩ可见中等量以上的二尖瓣返流，左室壁运动减弱。左心房显著扩大，肺静脉和主肺动脉扩张。（３）双室型（２例）：兼有二心室受累的改变，但以一侧受累为主。其中１例合并右室心尖附壁血栓，表现为Ｔ１ＷＩ球形高信号，Ｔ２ＷＩ为中等度略高信号。结论ＥＭＦ的ＭＲＩ所见具有相当的特征性，ＭＲＩ可以作为确定ＥＭＦ诊断的手段     

磁共振电影成像估价心肌功能

采用磁共振电影成像（Ｃｉｎｅ－ＭＲＩ）估价９例正常人和１３例左心室陈旧心肌梗塞患者的左心室功能状况。其方法是应用小角度翻转角、短ＴＲ和信号聚焦的梯度场成像序列，通过观察左心室各段肌壁运动状态和测量肌壁厚度的变化以判断各段肌壁的运动功能。结果提示，Ｃｉｎｅ－ＭＲＩ无论对心肌壁运动状态的定性还是运动功能的定量均有一定的价值。     

增强超高速MRI在犬慢性心肌梗塞的初步应用

目的：应用超高速磁共振成像（ＭＲＩ）观察犬慢性心肌梗塞的心肌灌注。材料与方法：采用聚氯乙烯狭窄器闭胸制备犬慢性心肌梗塞模型。心肌灌注成像的参数包括预备反转脉冲１８０°；ＴＥ２毫秒；ＴＲ４．９毫秒；翻转角８°及采集矩阵６４×６４。静脉注射钆－二乙烯三胺五乙酸（Ｇｄ－ＤＴＰＡ）的同时，在３２秒内获得连续图像。结果：左旋支（ＬＣＸ）或左前降支（ＬＡＤ）致窄术５～１０个月后呈９５％狭窄或闭塞。４条犬左心室壁运动减弱，３条犬为运动消失。在光、电镜下见心肌发生纤维化。注射Ｇｄ－ＤＴＰＡ后，右室、左室及心肌信号逐渐明显增强，正常心肌信号远高于梗塞区心肌（Ｐ＜０．０１）。结论：本研究结果显示Ｇｄ－ＤＴＰＡ增强超高速ＭＲＩ能非创伤地评价心肌缺血     

造影增强MRI对急性心肌梗塞的评价

ＭＲＩ技术的发展及及ＭＲＩ造影剂的应用，能有效地评价急性心肌梗塞：①可以直接显示梗塞灶，表现为Ｔ２加权上病灶信号高于正常心肌，增强后病灶信号增强大于正常心肌。②可以区别梗塞心肌是否获得再灌注，表现为Ｔ２加权象上再灌注梗塞心肌信号高于非再灌注心肌，增强再灌注后梗塞心肌信号强化更明显，倾向于均匀强化；非再灌注心肌磁化相对较弱，倾向于不均匀强化；但两信号改变有交叉重叠。③可以测定梗塞大小及其动态变化。     

正常心脏Gd－DTPA动态增强MRI的表现

目的：探讨正常心脏心肌在Ｇｄ－ＤＴＰＡ动态ＭＲＩ上的信号表现及动态变化规律。材料和方法：１２例正常心脏于０．３５～０．３８ＴＭＲＩ机上作Ｇｄ－ＤＴＰＡ增强前后ＭＲＩ检查，增强后为动态观察。结果：左心室前壁、侧壁、下壁以及室间隔的信号强度在增强前其差别无统计意义（Ｐ＞０．０５）；增强后及其动态观察中，各时间段内各部心肌信号率差别无统计意义（Ｐ＞０．０５）。正常心肌增强后呈均匀一致强化，最大强化是在增强后５分钟内，随增强时间延长而递减。结论：正常心肌在Ｇｄ－ＤＴＰＡＭＲＩ增强前后的信号均匀一致，局部心肌信号增高或减低应视为病理改变。     

脾脏疾病的CT,MRI诊断

脾脏的大体及断面解剖。２ ．脾脏的先天变异（ 位置、形态及数目） 。３ ．脾感染性疾病：脾脓肿,脾结核及脾包虫病。ＣＴ、ＭＲＩ 均表现病灶中心为低密度液化坏死区,边缘可见环行强化。病灶多发及钙化有助于脾结核的诊断。４ ．脾脏的囊性病变：主要包括脾囊肿、脾内假性胰腺囊肿及脾包虫病。ＣＴ、ＭＲＩ 像呈液性密度或信号,边缘光整。鉴别诊断需结合临床病史及包虫皮试。５ ．脾良性肿瘤：主要包括脾血管瘤,脾错构瘤和淋巴管瘤。以脾血管瘤最多见,较特征性的影像学表现为ＣＴ 增强扫描病灶明显强化,ＭＲＩ Ｔ１ Ｗ 像呈低信号或等信号,Ｔ２ Ｗ 像呈高信号。６ ．脾脏恶性肿瘤：常见有恶性淋巴瘤和转移瘤。恶性淋巴瘤ＣＴ 表现为脾肿大,脾内多发或单发低密度灶,边缘不规整。脾转移瘤表现多种多样,病灶可单发或多发,实性或囊性。ＭＲＩ呈稍长Ｔ１ 、Ｔ２ 信号。７ ．脾梗塞：常见于脾血管血栓、癌栓栓塞及肿瘤组织的包埋。典型梗塞形状为尖端指向脾门、内小外大的锥形。ＣＴ 增强扫描为低密度灶。ＭＲＩ 呈稍长Ｔ１、长Ｔ２ 信号。８ ．脾外伤包括三种：ａ 完全性破裂;ｂ 脾中心破裂;ｃ 包膜下破裂。ＣＴ、ＭＲＩ 可显示脾损伤裂口,还可区分新鲜、陈旧出血及腹腔积液等。     

急性心肌梗塞的MRI特征及其超微病理基础

目的　探讨急性心肌梗塞后不同心肌损伤区的MRI特征及其超微病理学基础。方法　结扎兔冠状动脉左前降支 2 4h制作AMI模型 10只 ,行常规MRI、对比剂动态增强MRI、电影MRI及多巴酚丁胺负荷试验。放射微球测定心肌血流量 ,伊文氏蓝和TTC染色确定缺血和梗塞心肌 ,并制作电镜标本观察肌原纤维和线粒体的改变 ,测定病变值和对损伤程度分级。结果　AMI后T1信号无明显改变 ,T2 信号增高 ,40 %可见病变局部心肌壁变薄 ,60 %可见病变邻近左室腔内异常血流高信号 ;正常、缺血和梗塞心肌动态增强时间 -信号强度曲线表现不同 ;cine -MRI表现为局部室壁变薄、运动减弱 ,多巴酚丁胺负荷表现为室壁变厚、运动增强。病变心肌较正常肌含水量显著增高而血流显著减少。正常、缺血及梗塞心肌线粒体体密度、数密度存在显著差异。结论　AMI的MRI表现与心肌超微结构损伤程度及残余血流量有关     

Expanded indication of percutaneous transluminal coronary angioplasty to the infarcted zone--using thallium-201 exercise scintigram after rehabilitation

In some cases of old myocardial infarction (OMI), left ventricular wall motion was improved after revascularization, though viability of the infarcted myocardium was not detected by left ventriculography (LVG) and exercise thallium-201 myocardial scintigraphy (EX-Tl). So to obtain more correct information of the viability, EX-Tl was performed again after ergometer rehabilitation for an OMI patient whose myocardial viability of the infarcted zone could not detected by LVG and EX-Tl. Incomplete fill in was showed in the EX-Tl after rehabilitation. So percutaneous transluminal coronary angioplasty (PTCA) was performed. Left ventricular wall motion was improved after three months. EX-Tl after rehabilitation is useful to evaluate the viability that could not detected by LVG and EX-Tl.     

Real-time dynamics of an extravascular magnetic resonance contrast medium in acutely infarcted myocardium using inversion recovery and gradient-recalled echo-planar imaging.

RATIONALE AND OBJECTIVES. The purposes of this study are to evaluate the first-pass profile of gadolinium-BOPTA/Dimeg (Gd-BOPTA/Dimeg) during its transit through hearts subjected to acute myocardial infarction, and to delineate these infarcted regions by the use of ultrafast magnetic resonance imaging (MRI). METHODS. Regional ischemia was induced in anesthetized rats by occluding the left coronary artery. Imaging parameters for single shot EPI included TE, 10 mseconds; AT, 33 mseconds; and 64 x 64-pixel matrix. Consecutive images were obtained every 1 to 2 seconds over a 30-second period. After approximately two images, Gd-BOPTA/Dimeg was injected intravenously (0.05 and 0.25 mmol/kg). RESULTS. Gd-BOPTA/Dimeg (0.05 mmol/kg), with inversion recovery EPI, produced a substantial increase in signal intensity of right and then left ventricular blood. Normally perfused myocardium also was enhanced, but not the acutely infarcted region. Clear delineation of the infarcted region as negatively enhanced "cold spots" persisted for at least 20 seconds. Gd-BOPTA/Dimeg (0.25 mmol/kg) with standard gradient-recalled EPI produced a different profile of signal intensity changes. Signal intensities of ventricular blood and normal myocardium were greatly reduced, leaving the infarcted zone as a positively enhanced "hot spot." Delineation of the infarcted region persisted for 6 to 8 seconds. The infarcted zone detected with MRI corresponded to that observed at autopsy. CONCLUSIONS. Regions of acute myocardial infarction can be detected as negatively enhanced "cold spots" or positively enhanced "hot spots" by studying the first-pass dynamics of Gd-BOPTA/Dimeg through hearts with regional ischemia by use of single shot EPI.     

心脏节段性室壁厚度变化在冠心病MRI诊断中的价值

探讨节段室壁厚度变化在冠心病诊断中的价值。材料与方法：分析３１例冠心病和１１例正常对照组的ＭＲ电影,判断ＭＲ电影对冠心病的检测率。结果：正常对照组心肌各室壁厚度变化一致,缺血和梗塞心肌节段室 壁壁厚度变化明显小于正常心肌。     

Integrated MRI assessment of regional function and perfusion in canine myocardial infarction

A single integrated examination using regional measurements of perfusion from contrast-enhanced MRI and three-dimensional (3D) strain from tissue-tagged MRI was developed to differentiate infarcted myocardium from adjacent tissue with functional abnormalities. Ten dogs were studied at baseline and 10 days after a 2-hour occlusion of the left anterior descending coronary artery (LAD). Strain was determined using a 3D finite element model. Two-dimensional measurements of hypoenhancing regions were highly correlated with myocardial viability (r = 0.96). Signal intensity versus time curves obtained from contrast-enhanced MRI were used for quantitative perfusion analysis. The remote and adjacent noninfarcted tissue of the dogs with LAD occlusion, as well as the infarcted tissue, exhibited abnormal deformation patterns as compared to normal dogs positive predictive value (PPV) of strain determination of infarction = (66%). Integration of contrast-enhanced MRI results with 3D strain analysis enabled the delineation of the myocardial infarction (PPV = 100%) from functionally compromised myocardium. This integrated cardiac examination shows promise for noninvasive serial assessment of potentially jeopardized noninfarcted myocardium to study the process of infarct remodeling and expansion.     

Magnetic resonance imaging of ischemic heart disease

Magnetic resonance imaging (MRI) has several attributes important for evaluating ischemic heart disease. Internal cardiac anatomy is well delineated owing to inherent contrast between the blood pool and the cardiac walls. Using relaxation times and signal intensity differences, it is possible to discriminate between infarcted (acute and chronic) and normal myocardium. Gated MRI can also be used to quantitate regional myocardial infarction.     

Magnetic resonance imaging of chronic myocardial infarcts in man

To evaluate the magnetic resonance imaging (MRI) features of chronic myocardial infarction (MI), 22 patients and several normal volunteers were studied with a 0.35-T cryogenic imaging system. The MIs were 9 months to 16 years old. The patients also had either left ventriculography (17 patients) or two-dimensional echocardiography (17 patients). At least one abnormality indicative of prior infarction was demonstrated on MRI in 20 of the 22 patients. Wall thinning was seen in 20 patients; in six of these, the thinning resulted in aneurysm formation. The other 14 patients had sufficient residual wall thickness to permit measurement of T2 relaxation times and MR signal intensity in the infarcted region. Ten of these 14 patients demonstrated low intensity and shortened T2 of the thinned segments (mean T2 = 28.7 msec) compared to adjacent normal myocardium (mean T2 = 45.4 msec) and to the myocardium of volunteers (mean T2 = 41.3 msec). The percentage of difference in intensity between thinned and normal myocardium was greater on 56-msec-TE images (98.2%) than on 28-msec-TE images (46.1%). In the other four patients, no difference in intensity of the myocardium was perceptible in the thinned region of the myocardial wall. Thus MRI shows regional wall thinning at the site of prior MI. In some patients, the chronic infarct is characterized as decreased spin-echo signal intensity and shortened T2 consistent with replacement of myocardium by fibrous scar.     

Quantitative analysis of regional left ventricular function after myocardial infarction in the pig assessed with cine magnetic resonance imaging

To assess the accuracy of quantitative analysis of global and regional wall motion and wall thickening of the left ventricle with cine magnetic resonance (MR), images obtained in eight pigs before and after myocardial infarction were compared with those obtained using gadolinium diethylenetriaminepen-taacetic acid (Gd-DTPA)-enhanced multislice spin-echo MR imaging and determination of pathology. The region with abnormal wall motion and wall thickening, as determined with cine MR imaging, identified the same region of infarction as indicated by Gd-DTPA-enhanced spin-echo MR imaging and pathology. Within the infarcted region wall motion and wall thickening analyzed with the centerline method were significantly reduced. We conclude that the use of quantitative analysis of cine MR images accurately determines localization and extent of regional left ventricular dysfunction in the infarcted heart in vivo. This analysis using dedicated software including the centerline method allows sequential assessment of regional left ventricular function in normal and infarcted hearts.     

Computed tomography of the normal and infarcted myocardium.

After intravenous administration of contrast agent, in vitro cardiac scanning showed a significant difference between the attenuation coefficients of the intracavitary blood pool and the myocardial wall, permitting clear delineation of the ventricular cavity. A substantial alteration in hematocrit permitted similar visualization of the intracavitary blood pool-myocardial wall interface. The attenuation coefficient of infarcted myocardium differed sufficiently from that of normal myocardium to render computed tomographic distinction feasible. In three hour old infarctions, the differences between normal and ischemic or infarcted tissue were enhanced by prior administration of contrast agent. These differences in attenuation coefficient indicate that a properly gated CT scanner could be utilized as a noninvasive approach to evaluating suspected or known myocardial infarction and other aspects of cardiac structure and function both in man and in experimental animals.     

心肌淀粉样变性的MRI与超声心动图诊断价值

目的 探讨心肌淀粉样变性的MRI与超声心动图诊断价值.方法 回顾性分析11例经病理活检证实的心肌淀粉样变性患者的MR和超声心动图检查结果.结果 MRI和超声心动图示心肌淀粉样变性患者中,11例均存在不同程度的左心室、室间隔轻度增厚,5例房间隔轻度增厚,7例左心室心肌质量增加,7例左心房增大,6例左心室射血分数减低,10例舒张功能减低,多伴随心包积液、胸腔积液.8例MRI延迟增强显示特征性的弥漫性、广泛性心内膜下至透壁性延迟强化.6例超声心动图显示心肌回声增强,呈磨玻璃样改变,并可见散在颗粒样斑点状强回声.结论 超声心动图具有较好的初步诊断价值,延迟增强MRI能为心肌淀粉样变性诊断及鉴别诊断提供更为全面、丰富的信息.