【作者】 龚良庚；

【导师】 夏黎明；

【作者基本信息】 华中科技大学 ， 影像医学与核医学， 2011， 博士

【摘要】 第一部分MRI评估兔心脏术后粘连程度的实验研究目的：探讨MRI对兔心肌梗死模型术后心脏与周围组织粘连程度的评估价值。方法：25只日本长耳白兔,开胸结扎冠状动脉制备心肌梗死模型,随机分成两组,其中常规手术组11只,改性壳聚糖防粘连膜放置组14只。术后2～3个月分别行在体MRI检查和二次开胸手术,分别评估粘连程度,结果分析采用Wilcoxon秩和检验。结果：MRI评估常规手术组无粘连、轻度粘连、重度粘连的动物数量分别为3只、3只、5只；防粘连膜放置组分别为4只、9只、1只。二次开胸手术评估常规手术组和防粘连膜放置组相应粘连程度的动物数量分别为2只、4只、5只和5只、7只、2只。常规手术组和防粘连膜放置组心脏与周围组织的粘连程度有统计学差异(MRI与开胸手术评估的P值分别为0.021和0.025)。MRI和开胸手术评估不同粘连程度相互吻合的动物数量分别为5只、9只、6只,两种评估方法的一致性检验Kappa值为0.69,P值<0.001。结论：MRI与开胸手术评估心脏术后粘连程度具有较好的一致性。MRI可以取代开胸手术评估心脏术后的与周围组织的粘连程度。第二部分兔心脏术后粘连对心功能影响的MRI研究目的：探讨兔心肌梗死模型术后心脏与周围组织的不同粘连程度对心功能的影响。方法：30只日本长耳白兔,开胸结扎冠状动脉制备心肌梗死模型,剔除死亡或术后严重感染的5只动物后,共有25只动物被纳入本研究。术后8周分别行在体MRI测定左室各项心功能参数,包括：EDV、ESV、SV和EF。二次开胸直视观察分为无粘连、轻度粘连、中度粘连和重度粘连共4组,观察各心功能参数随粘连程度的变化,对结果进行单因素方差分析,取P<0.05有统计学差异。结果：开胸手术观察心脏与周围组织粘连程度,无粘连、轻度粘连、中度粘连和重度粘连的动物数量分别为7只、5只、6只和7只。各组间EDV均值无统计学差异(P=0.33)。重度粘连组的ESV均值与其它3个粘连组之间存在显著性差异(P值均小于0.001)。各组间SV和EF均值有统计学差异(P值分别等于或小于0.001),与粘连程度之间存在线性关系。结论：在兔心肌梗死模型制备过程中,术后心脏与周围组织的重度粘连会明显影响心功能,尤其以收缩功能最为明显,这种动物模型在心功能的相关研究中应予剔除。第三部分兔心肌梗死后心室重塑的MRI研究目的：观察兔急性心肌梗死后心功能的变化随时间的演变规律,探讨MRI影像特征及心功能指标的变化与心室重塑的关系。方法：日本长耳白兔45只,采用开胸结扎法制备心肌梗死模型。分别于术前(0周)和术后1周、2周、4周、6周、8周共六个时间点分别行在体MRI检查测定各项心功能指标,包括：左室舒张末期容积(EDV)、每博输出量(SV)、射血分数(EF)、射血率峰值(PER)、充盈率峰值(PFR)。比较心肌梗死后心功能参数随时间变化规律。在每个时间点随机取5只动物的心脏离体标本,行MRI扩散张量成像(DTI)。测量表观扩散系数(ADC)值、各向异性分数(FA)值,同时重建心肌纤维走行的三维结构彩色方向图(colored orientationmap)及局部心肌走行方向的主要特征向量图(main eigenvector map)。结果：梗死相应部位室壁变薄,以梗死后期室壁变薄明显。左室舒张期和收缩期的曲线斜率减低。以第2周和第4周之间变化最为明显。随着梗死时间的延长,EDV呈现增加趋势(F=1.71,P=0.148),EF则明显下降(F=12.713,P<0.001)。EF随着EDV增加呈现下降趋势,线性回归分析得出一次方程：y=-5.58x+57.7,(F=8.855,R=1.30,P=0.0049)。随梗死时间的延长,PER呈进行性下降,以前4周变化明显,而PFR下降以第4至8周变化明显。心肌首过灌注曲线的上升斜率随时间呈下降趋势,但各时间点无显著性差异(P=0.305)。梗死区FA值随着梗死时间的延长而下降,而ADC值则随着梗死时间的延长呈上升趋势。FA值、ADC值在梗死中心区与边缘区比较时都有统计学差异(P=0.024),而边缘区和外围区的FA值、ADC值无统计学差异(P>0.327)。结论：MRI测量的心功能参数变化及心肌纤维束排列秩序的演变规律与心室重塑的病理变化基础是吻合的,MRI可以作为心肌梗死后心室重塑的预测手段。第四部分心肌梗死后心室重塑的MRI临床研究目的：观察陈旧性心肌梗死后的心功能变化,探讨MRI心功能指标对心室重塑的预测价值。方法：收集陈旧性心肌梗死患者33例,其中男性27例,女6例,年龄45-79岁,平均(60.2±9.5)岁。健康志愿者12例作为对照组,年龄40-62岁,平均(52.2±5.8)岁。所有患者及健康对照组均接受MRI检查。MRI测量参数包括：DIR、TIR、EDV、ESV、EF、PER、PFR,同时测量梗死心肌面积所占的百分比,以24%为分界值,分为无重塑组(≦24%)和重塑组(>24%),分析各组间的心功能参数的差异。进行ROC分析筛选能独立预测心室重塑的心功能指标。所有资料统计利用SPSS 17.0进行分析,P<0.05有显著性差异。结果：梗死部位室壁变薄,平均5.64 mm±1.21mm。心室轮廓不规则,局部呈膨隆状改变,其中3例见室壁瘤形成。与正常心肌信号相比,12例在DIR上呈低信号,6例在TIR上呈略高信号,15例在FIESTA可见有相对高信号。延迟增强扫描见梗死部位心肌呈明显强化。与正常对照组比较,陈旧性心肌梗死的EDV、ESV、SV均较前者增加,EF、PER和PFR等则不同程度下降。ESV与EDV的增加有线性关系(P<0.001); PER、PFR及EF均随EDV的增加呈线性下降趋势；而SV与各参数间的变化关系均无显著性差异。ROC分析各参数对心室重塑预测的结果显示：PFR、EDV.ESV的ROC曲线下面积分别为0.725、0.741、0.764,分界值分别为2.27 EDV/sec、140.23ml和79.12ml,P值分别为0.036、0.021和0.032。SV、PER和EF对心室重塑预测能力的分析结果显示P值均大于0.05。结论：MRI可以准确评估心肌梗死的形态学变化,可以从收缩和舒张功能全面地评估心功能变化。MRI心功能参数对预测心室重塑有重要作用。PFR、EDV、ESV可以作为独立因子预测心室重塑。更多还原

【Abstract】 Part 1 MRI evaluation of postoperative pericardial adhesions in rabbit models of myocardial infarctionObjective:The aim of the present study was to investigate the role of MRI in evaluating postoperative pericardial adhesions in rabbit models of myocardial infarction.Methods:Twenty-five Japanese white rabbits were randomly divided into conventional operation group (n=11) and anti-adhesion membrane placed group (n=14), both underwent chest-opening coronary artery ligation surgery. After 8 weeks, in vivo MRI and exploratory thoracotomy were performed respectively to observe the degree of adhesions according to respective criteria. Data were analyzed by Wilcoxon’s rank test. The consistence between MRI and exploratory thoracotomy were detected using consistency check.Results:The number of none adhesion, mild adhesions and severe adhesions observed by MRI were 3,3,5 cases respectively in conventional operation group and 4,9,1 cases respectively in anti-adhesion membrane placed group; the number observed by exploratory thoracotomy were 2,4,5 cases in conventional operation group and 5,7,2 cases in anti-adhesion membrane placed group. The difference between the two groups was statistically significant. (P=0.021 from MRI, and P=0.025 from reoperation). The cases of none adhesions, mild adhesions and severe adhesions from MRI consistent with exploratory thoracotomy were 5,9,6 cases. MRI results were consistent with exploratory thoracotomy results (Kappa=0.69, p<0.001).Conclusions:Magnetic resonance imaging assessment of pericardial adhesions is in good agreement with exploratory thoracotomy, MRI would be a good means of adhesions evaluation after cardiac surgery. Part 2 Effect of postoperative pericardial adhesions on cardiac function in rabbit models by using MRIObjective:To elucidate the effect of the degree of postoperative pericardial adhesions on cardiac function in rabbit models of myocardial infarction.Methods:Thirty Japanese white rabbits underwent chest-opening coronary artery ligation surgery to obtain rabbit models of myocardial infarction. Rule out 5 animals with serious infection or death, and the remaining 25 rabbits were enrolled in this study. After 8 weeks, in vivo MRI was performed to calculate the left ventricular function; the parameters are EDV, ESV, SV and EF values. Then, exploratory thoracotomy was performed to observe the degree of adhesions according to clinical criteria:no adhesion, mild adhesions, moderate adhesions and severe adhesions. Measured data of four groups were compared with One-way ANOVA analysis.Results:The number of no adhesion, mild adhesions, moderate adhesions and severe adhesions observed by exploratory thoracotomy were 7,5,6,7 cases. EDV and ESV values from MRI showed no significant difference between four groups (P=0.33 and 0.95, respectively). But the value of ESV in severe adhesions showed significantly statistical differences from the other 3 groups (P<0.001, respectively). SV and EF values from MRI showed significantly statistical differences between four groups (P=0.001 and<0.001, respectively), and in a linear relation with the adherent degree. Conclusions:In the preparation of myocardial infarction model, Severe postoperative pericardial adhesions affect cardiac function significantly, particularly in the systolic function. Such models should be rejected in the studies of cardiac function. Part 3 Ventricular remodeling after myocardial infarction in MRI studyPurpose:To observe the change of cardiac function after acute myocardial infarction in rabbit models, and to study MRI imaging characteristics of ventricular remodeling.Methods:Forty-five Japanese white rabbits underwent chest-opening coronary artery ligation surgery to obtain rabbit models of myocardial infarction. The animals were performed in vivo MRI at totla six time-point with before surgery,1 week,2 weeks,4 weeks,6 weeks,8 weeks. Cardiac function parameters were measured, including:left ventricular end diastolic volume (EDV), stroke volume (SV), ejection fraction (EF), peak ejection rate (PER) and peak filling rate (PFR). Comparison of heart function is variation with time after myocardial infarction. At each time point,5 animals randomly selected and were performed re-thoracotomy for gaining specimens of the heart. Each heart speciment was examined by MRI with the sequence of diffusion tensor imaging (DTI). The value of apparent diffusion coefficient (ADC) and fractional anisotropy (FA) were collected; meanwhile, three-dimensional reconstruction of cardiac fiber structure of colored orientationmap and the regional main eigenvector map were performed.Results:Left ventricular diastolic and systolic slope of the curve reduced, the change was in the most obvious between the first 2 weeks and 4 weeks. Left ventricular EDV increase in progress according to the time extending, EF was significantly decreased (F=12.713, P <0.001), and EDV showed an increasing trend (F=1.71, P=0.148). EF show a downward trend with the increase of EDV, linear regression analysis, an equation was set up with y=-5.58x+57.7, (F=8.855, R=1.30, P=0.0049). On the other hand, PER decreased progressively before 4-weeks post-infarction (P=0.034). PFR also decreased, but with no significant difference (P=0.065). Myocardial first pass perfusion rising slope of the curve decreased with time in each group showed no significant difference (P> 0.05). FA value decreased, but ADC value showed upward trend according to the post-infarction time. FA value and ADC value were significantly different between the infarct region and adjacent region (P<0.05), but there was no significantly different between adjacent region and remote region (P> 0.05).Conclusions:MRI measurement of parameters of cardiac function and arranged orderly of myocardial fiber bundles are consistent with the evolution of pathological changes. MRI can be used to predict ventricular remodeling after myocardial infarction.Part 4 The role of function parameters on prediction of ventricular remodeling postinfarction by using MRIPurpose:To observe the change of cardiac function of old myocardial infarction (OMI) and to investigate the role of cardiac function parameters in prediction of ventricular remodelingMethods:Collection of 33 patients with old myocardial infarction, including 28 males and 6 females,60.2 years±9.5(from 45 to 79 years old). Healthy volunteers as the control group with 12 patients, aged from 40 to 62 years old, mean age wae (52.2±5.8) years. All patients and healthy controls underwent MRI examination. MRI measurement of heart function parameters including:DIR, TIR, EDV, ESV, EF, PER, PFR, and measure the percentage of the area ratio of myocardial infarction. As a dividing line of 24%, patients were divided into two groups with no remodeling group and remodeling group. Parameters were nalysised of the groups of heart function. The ROC analysis was used to evaluate the preidiction of cardiac funtion patameters for ventricular remodeling. All statistics using SPSS 17.0, and P<0.05 was significant difference. Results:Thinning wall were observed after infarction, with an average 5.64 mm±1.21mm. The ventricual morphology after infarction was irregular, and bulging like on local wall.3 of them were accompanied with vntricular aneurysm. Compared with normal myocardium signal,12 cases showed low signal on the sequence of DIR, and 6 cases showed slightly higher signal on the sequence of TIR.15 cases showed relatively hyerintensity on the sequence FIESTA. On delayed enhancement, the regions of myocardial infarction were showed obviously hyperintensity. The ventricular function parameters EDV and ESV of old myocardial infarction were increase than control group, otherwise, the values of EF, PER and PFR were decreased. The increase of ESV has a linear relationship with EDV, but the change of PER, PFR and EF showed a negative linear relationship with EDV. The change of SV was no significantly with other paprameters. PFR, EDV, ESV can be used as independent factors for predicting ventricular remodeling, with the areas under the curve (AUC) were 0.725,0.741 and 0.764, respectivly, using ROC analysis. The cut-off values were 2.27 EDV/sec,140.23ml and 79.12ml, respectivly.Conclusion:MRI can evaluate the morphological changes of myocardial infarction. Systolic and diastolic function can be used to assessment of cardiac function parameters, and these parameters act important roles on predicting ventricular remodeling,更多还原