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。     

Gd-DTPA动态增强MRI评价心肌微血管损伤

目的：探讨Gd-DTPA动态增强MRI评价心肌微血管损伤的可行性。方法：制作急性犬心肌梗死动物模型，在活体上用放射微球^99Tc—MAA测量心肌血流量，0．5％伊文蓝染色区分缺血心肌；心脏离体后用3％TTC染色区分梗死心肌，SP免疫组化染色观察心肌微血管并计算微血管体积分数。犬离体心脏左冠状动脉插管后作MRI平扫及Gd—DTPA动态增强扫描，测量正常、缺血和梗死心肌的信号强度，绘制时间-信号强度曲线。结果：在T1WI上，心肌信号强度无明显差异；在T2WI上，病变心肌信号强度较正常增高；Gd-DTPA灌注动态增强扫描，正常心肌时间-信号强度曲线呈下降形，危险心肌呈上升形，梗死心肌呈平直形，灌注晚期病变区呈明显环状强化。正常、危险和梗死心肌血流量、微血管体密度差异显著。结论：急性心肌梗死后心肌间质水肿、心肌含水量增加致T2WI信号增高。Gd-DTPA动态增强时间-信号强度曲线上升的斜率及峰值可以反映心肌微血管损伤及组织水肿的程度。     

急性、亚急性、慢性心肌梗塞在Gd—DTPA增强MRI上的信号表现

目的：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侧(38%)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．     

Gd-DTPA增强MRI诊断肺内结节

目的：研究Gd－DTPA增强MRI在孤立性肺结节鉴别诊断中的作用。材料和方法：对26例≤3cm的孤立肺内结节（肺癌16例，结核10例）进行了常规和动态Gd－DTPA增强MRI检查，测量病灶的增强程度，分析MRI表现并与病理对照。结果：16例肺癌在静脉注入Gd－DTPA后均有强化，表现为实体均匀（9例）和不均匀（7例）增强，而多数（8／10）结核球表现为环形增强。肺癌平均增强71％，与结核球（23％）有显著差异。肺癌结节的动态增强曲线也与结核球不同。结论：肺癌与结核球的MRI增强形态和增强程度不同，对鉴别诊断很有帮助。     

Gd-BOPTA增强MRI对小肝癌的诊断价值

目的　比较Gd BOPTA增强MRI与MRI平扫、Gd DTPA动态增强MRI在诊断小肝癌 (SHCC)方面的差异 ,进一步提高小肝癌检出率和诊断准确性并观察其不良反应。资料与方法　手术或穿刺病理证实为SHCC患者 2 5例。采用GESigna 1.5T磁共振扫描仪。行SE序列T1WI、FSE序列T2 WI及Gd DTPA快速动态增强多期扫描。Gd BOPTA增强扫描亦采用静脉团注快速动态增强扫描 (同Gd DTPA) ,并在团注后 15min、6 0min行SE序列T1WI和FMPSPGR序列T1WI扫描各 1次。观察MRI平扫、Gd DTPA快速动态增强和Gd BOPTA增强扫描及延迟扫描对病灶的检出率、包膜显示情况以及病灶的强化特征并行统计学分析。观察其不良反应。结果　 2 5例患者共发现病灶4 2个。对SHCC病灶的检出率 ,MRI平扫为 6 9.0 5 % ,Gd DTPA增强为 85 .71% ,Gd BOPTA增强 (动态 延迟 )为95 .2 4 % ,和Gd DTPA增强之间无统计学差异 ,和MRI平扫有统计学意义。病理检查发现 30个病灶有包膜。Gd BOPTA增强对SHCC包膜的显示 ...     

颅咽管瘤的MRI诊断

目的：探讨MRI在诊断颅咽管瘤中的作用。材料和方法：取70例(男37，女33，平均年龄33．2岁，平均病程2年半)经手术和病理证实的颅咽管瘤患者术前MRI检查资料，其中25例加作Gd—DTPA增强MRI扫描，分析MRI表现特征及找出诊断与鉴别诊断要点。结果：本组术前MRI诊断定位正确率为：100％，定性正确率为80%，误诊率为20％，其MRI特征性表现为：(1)肿瘤形态以结节状．分叶状为主(本组为67％)，边界清楚．(2)肿囊信号多不均匀(本组为65％)，表现复杂．(3)Gd—DTPA增强多数肿瘤呈不均匀强化(本组56%)。结论：：MRI的多轴位成像及Gd—DTPA应用有助于颅咽管瘤的诊断与鉴别诊断．     

磁共振心肌灌注成像急性心肌梗死的实验研究

目的 研究猪急性心肌梗死的首过灌注和延迟时相MRI特点.方法 猪心肌梗死模型12只,均进行快速梯度回波序列(FGREET)首过灌注扫描及反转恢复梯度回波序列(MDE)延迟时相扫描.扫描后处死,分析心肌首过灌注和延迟时相特点,并与病理检查对照.结果 9例(75%)首过灌注时梗死心肌表现为灌注减低,其信号强度显著低于周围心肌,10例(83.33%)延迟期梗死心肌表现为延迟强化,而正常心肌信号强度下降,低于梗死心肌.结论 MR心肌灌注成像可有效检测急性心肌梗死的梗死心肌以及其程度和范围.     

坏死亲和性对比剂MRI显示梗死心肌及病理对照研究

目的：通过冠状动脉注射坏死组织亲和性非卟啉类顺磁性对比剂（ECⅢ-60）后MR延时影像与病理对照的方法明确其强化区与梗死心肌的关系，并与静脉注射非特异性对比剂钆喷替酸葡甲胺（Gd－DTPA）比较，以期为MRI准确评价心肌活性提供可靠的病理依据。方法：经导管采用闭胸法成功建立8只猪的急性心肌梗死再灌注模型。经静脉以0．2mmol／kg快速团注Gd-DTPA后行心电激发的心脏MR短轴面T1WI，延时扫描至局部Gd-DTPA完全消失。然后再以0．0025mmol／kg经冠状动脉导管缓慢注入ECⅢ-60后短轴面T1WI，延时成像至5h。比较分析ECⅢ-60增强MRI延时强化区和金标准病理所示梗死区的关系；并和Gd－DTPA增强MRI的对比增强效果（CR）与范围（RIS）进行比较。结果：ECⅢ-60增强MRI可见梗死区的信号较正常对照区明显升高（CR〉3．0）并持续超过5h，其强化区相对面积[占同层面左室面积的百分率为（11．84±3．63）％]与TTC染色心肌梗死面积[（11．78±3．64）％]一致（t=2．251，P〉0．05），两者呈正相关，其决定系数为r=0．999。Gd-DTPA也能产生CR〉3．0的强化效果，但对梗死区的对比度在2h内逐步消失。结论：坏死亲和性对比剂增强MRI能持续准确地反映心肌梗死，能成为冠状动脉介入术后心肌活力评估的有潜在价值的方法。     

脑实质内海绵状血管瘤MRI表现

目的分析脑实质内海绵状血管瘤的MRI表现，提高本病的诊断水平。方法回顾分析18例经临床及手术病理证实脑实质内海绵状血管瘤的MRI影像表现。结果18例共26个病灶，表现为T1WI等信号、高信号、混杂信号或环状高信号，T2WI低信号、均匀高信号或环状高信号，周围可见低信号环；大部分病灶无占位效应及周围水肿，所有病灶在梯度回波（GRE）序列上均可见到病灶边缘低信号环；Gd—DTPA增强扫描部分病灶强化。结论海绵状血管瘤MRI表现较为特异，MRI检查是诊断脑实质内海绵状血管瘤最为敏感的方法。     

急性缺血再灌注心肌磁共振成像实验研究

目的：通过MR灌注成保评价急性梗死心肌组织血流灌注特点。方法：采用结扎左前降支90min存灌注的方法建立为存灌注梗死心肌组，对6只犬行MRI灌注成保及延迟扫描，观察犬心肌缺血存灌注模型梗死心肌MRI特点。结果：犬心肌缺血存灌注梗死心肌MR灌注成保表现为灌注缺损区，延迟扫描表现为高信号。结论：MR灌注成保有助于评价心肌血流，诊断心肌缺血存灌注梗死心肌。     

Occlusive and reperfused myocardial infarcts: MR imaging differentiation with nonionic Gd-DTPA-BMA

To increase the time during which effective contrast exists between normal and infarcted myocardium, a high dose (0.6 mmol/kg) of the nonionic contrast medium gadolinium diethylenetriaminepentaacetic acid bismethylamide (Gd-DTPA-BMA) was used to distinguish between occlusive and reperfused myocardial infarctions in rats. After administration of Gd-DTPA-BMA, there was clear and persistent demarcation of both occlusive and reperfused infarcts on T1-weighted MR images. In occlusive infarcts, normal, infarcted, and periinfarcted myocardium could be identified. High signal intensity was evident for 60 minutes in a band straddling the border between infarcted and normal myocardium, namely, the periinfarction zone. In the reperfused infarct, normal and infarcted myocardium could be identified. The reperfused zone was immediately enhanced after injection of Gd-DTPA-BMA. A differential pattern of enhancement between occlusive and reperfused myocardial infarcts was evident for 1 hour. Thus, Gd-DTPA-BMA has the potential to allow (a) depiction of occlusive and reperfused acute myocardial infarcts, (b) documentation of reperfusion of myocardial infarction, and (c) distinction between occlusive and reperfused infarction.     

急性心肌梗塞面积与心功能的关系

目的定量分析急性心肌梗死面积与心功能的关系。材料和方法初发急性穿壁心肌梗死患者,再通组15例,平均年龄57.7岁,未通组19例,平均年龄61.7,在发病早期和发病3周行SPECT显像,并于发病3周行核素左心室造影测量心肌缺血范围和LVEF。结果再通组第2次心肌显像心肌缺损范围显著小于第1次显像,未通组两次心肌显像,心肌缺损范围无显著差别,两组病例第2次心肌显像,再通组心肌缺损范围显著小于未通组,而LVEF显著高于未通组第2次心肌显像,心肌缺损范围与LVEF呈负相关性。结论早期血管再通可缩小心肌梗死面积,心肌梗死面积与左室射血分数有负相关性。     

MRI evaluation of microvascular obstruction in experimental reperfused acute myocardial infarction using a T1 and T2 preparation pulse sequence

PURPOSE: To investigate a T1 and T2 preparation pulse sequence to evaluate microvascular obstruction (MO) in a porcine model of reperfused acute myocardial infarction (AMI). MATERIALS AND METHODS: A total of 14 pigs with reperfused AMI underwent MRI examinations at baseline and three to four hours after reperfusion. MRI scans included a left ventricular functional study, T1 and T2 measurement on a 1.5T MRI system. At reperfusion, first-pass myocardial perfusion (FPMP) images were obtained after bolus injection of gadopentetate dimeglumine followed by an intravenous drip. Delayed contrast-enhanced MRI (DE-MRI) and T1 measurements were performed 30 and 45 minutes, respectively, after the bolus, during a constant infusion of gadopentetate dimeglumine. RESULTS: In 11 pigs MO was hypoenhanced in FPMP and DE-MRI. In later T1 preparation difference images postcontrast, MO was hyperenhanced while delayed hyperenhanced (DHE) regions appeared dark. MO areas on DE-MRI and T1 images were comparable. T1 reduction (%) postcontrast in MO was small compared to measurements from DHE regions (P < 0.0001) and similar to those from control segments (P = 0.66). Precontrast T1 and T2 values at reperfusion from MO and DHE regions were larger than in control regions. CONCLUSION: Using T1 preparation under a constant gadopentetate dimeglumine (Gd-DTPA) infusion, delayed imaging at 30 to 45 minutes demonstrates MO as a positive contrast with larger T1 values. Elevated T1 and T2 values in MO precontrast may also help to differentiate them from both control and DHE regions.     

Occlusive and reperfused myocardial infarcts: differentiation with Mn- DPDP--enhanced MR imaging

To assess whether the administration of manganese N,N'-bis(pyridoxal-5-phosphate)ethylenediamine-N,N'-diacetic acid (DPDP) permits differentiation between occlusive and reperfused infarcts, the authors subjected rats to either 6 hours of left coronary artery occlusion (n = 13) or 2 hours of occlusion followed by 4 hours of reperfusion (n = 10) before magnetic resonance (MR) imaging. Electrocardiographic-gated T1-weighted images were obtained before and for 1 hour after injection of 400 mumol/kg of Mn-DPDP. On T1-weighted images obtained before injection of Mn-DPDP. no significant differences in signal intensity were observed between normal and infarcted regions. Use of Mn-DPDP permitted delineation of the area of infarction. The pattern of enhancement in the injured zone was different for occlusive and reperfused myocardial infarcts. In rats with occlusive infarcts, In rats with occlusive infarcts, three well-defined zones were seen. Epicardium and endocardium were enhanced, while the midmyocardial zone was hypointense. The midmyocardial signal intensity gradually increased during the 60 minutes after injection. In rats with reperfused infarcts, the injured area was uniformly and intensely enhanced. Histologic examination confirmed the presence and location of myocardial infarct. Mn-DPDP may improve the detection and delineation of acute myocardial infarcts, demonstrate perfusion of the infarct, and permit discrimination between reperfused and occlusive infarcts.     

Paradoxical uptake of F-18 fluorodeoxyglucose by successfully reperfused myocardium during the sub-acute phase in patients with acute myocardial infarction

The myocardial uptake of F-18 fluorodeoxyglucose (FDG) has been shown to indicate ischemia. To elucidate whether this is applicable to reperfused myocardium in patients with acute myocardial infarction (AMI), Tl-201 SPECT and F-18 FDG PET were performed in 10 patients with successfully recanalized AMI (male : female = 8 : 2; mean age = 62 ± 9 years old). Regional myocardial perfusion of the infarct-related area was classified, on the basis of Tl-201 images, into 2 groups (normal and defect) during the sub-acute phase, and into 3 grades (normal, redistribution (RD), and persistent defect) during the chronic phase (1 and 3 months after onset). Regional FDG uptake was calculated as FDG uptake in the region of interest normalized relative to that in a normal area. During the chronic phase, FDG accumulated only in the region of RD, indicating ischemia, but during the sub-acute phase, FDG accumulated mainly in the peri-infarct area. To elucidate whether the reperfused myocardium itself shows signs of accelerated glucose uptake, an experimental study was performed in rats. Glucose uptake in the isolated heart was measured by deoxyglucose and^3IP-NMR spectroscopy, and was significantly increased after reperfusion compared with the pre-ischemic level. In conclusion, the enhancement of FDG uptake during the sub-acute phase was observed in successfully reperfused myocardium of patients with acute myocardial infarction. Such augmentation disappeared during the chronic phase. An experimental study in rats indicated that ischemia and reperfusion themselves augment glucose uptake. This mechanism may be responsible for the increase in FDG uptake of reperfused myocardium observed clinically.     

Reperfusion and irreversible myocardial injury: identification with a nonionic MR imaging contrast medium.

The potential of a new nonionic gadolinium complex--gadodiamide injection--to (a) allow distinction between reperfused and occlusive infarction and (b) enable differentiation between reperfused reversible and irreversible myocardial injury was investigated. Three groups of rats were used: 10 with reversibly reperfused myocardial injury, 10 with irreversibly reperfused injury, and 10 with occlusive infarction. Before administration of contrast material, there was no significant difference in signal intensity between normal and injured regions on T1-weighted images. After administration of gadodiamide injection (0.2 mmol/kg), the reversibly injured myocardium was indistinguishable from normal myocardium, while the reperfused irreversibly injured zone showed prominent and homogeneous enhancement. Occlusive infarcts showed three zones of differential enhancement consisting of normal, periinfarction, and infarction regions. Gadodiamide injection provides differential enhancement in reversibly reperfused, irreversibly reperfused, and occlusive infarcts. Thus, it may be useful as a marker of reperfusion and extent of infarction after thrombolytic therapy.     

结节样周围型胆管细胞癌的CT和MRI表现

目的:分析结节样周围型胆管细胞癌(PCC)的CT和MRI表现及其病理基础.方法:15例经病理证实的结节样PCC患者,11例行多层螺旋CT平扫及动态增强扫描,6例行MRI平扫和动态增强扫描.结合病理结果分析其CT和MRI表现.结果:15例共检出病灶19个,直径(2.8±1.4)cm,于肝左、右叶均见分布.CT共检出15个病灶,增强扫描示14个病灶动脉期呈周边强化,门脉期显示8个病灶内对比剂向中央扩散强化,6个病灶未见上述强化方式;1个病灶CT动态增强扫描呈"快进快出"改变.4个病灶见邻近肝包膜凹陷,2个病灶伴随胆管轻度扩张.6例MRI共检出6个病灶,T2WI示5个病灶呈不规则低信号,动态增强扫描示相应区域均见强化;另1例病灶增强扫描动脉期有异常强化,门脉期及延迟期呈等信号.结论:结节样周围型胆管细胞癌的CT和MRI表现多样,与病灶内各种成分的比例和分布相关,其动态增强表现有一定特征性.     

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。     

Blood pool contrast agent CMD-A2-Gd-DOTA-enhanced MR imaging of infarcted myocardium in pigs.

The purpose of this study was to assess the ability of the new blood pool contrast agent meglumine-carboxymethyldextran-ethylenediamino-gadoterate (CMD-A2-Gd-DOTA) to depict acute occlusive myocardial infarction (AMI). First-pass gradient-echo and delayed spin-echo magnetic resonance imaging (MRI) was performed 5 days after induction of AMI in a pig model. MRI was correlated with pathology. First-pass imaging with CMD-A2-Gd-DOTA allowed detection of infarcted myocardium in all pigs (n = 7). The infarction was recognized as a black spot on MRI as well as on a parametric image. The signal intensity (SI) amplitudes of normal versus infarcted myocardium were 80.55 +/- 18.61 versus 8.48 +/- 15.50 on MRI and 81.62 +/- 18.50 versus 1.61 +/- 3.73 on the parametric image (both P values < 0.001. The contrast ratio between normal and infarcted myocardium was not significantly improved on spin-echo MRI, suggesting largely intact vascular integrity outside the occluded area. CMD-A2-Gd-DOTA is useful for depicting occlusive myocardial infarction by first-pass MRI. Spin-echo imaging is promising in assessing vascular integrity. J. Magn. Reson. Imaging 1999;10:170-177.