Assessment Of Acute Reperfused Myocardial Infarction With MSCT: A Study Of Porcine Model

PartⅠAssessment of Acute Myocardial Infarction with Low-dose DE-MSCT:A Feasibility Study in Porcine ModelObjective:The purpose was to assess the influence of radiation dose on the visualization of acute myocardial infarction with MSCT,and study feasibility of MSCT low-dose protocols.Materials and Methods:Acute myocardial infarction was induced in 11 Chinese mini pigs by 90-minute balloon occlusion of the left anterior descending artery,and then reperfusion was created by withdrawing the balloon.All successful models accepted MSCT and MRI examinations after 72 hours. MSCT scan was performed 4 times with different radiation dose:120kV/250mA, 80kV/250mA,120kV/120mA,80kV/120mA.DE-MRI was applied with prospective ECG-gated 2D myocardial delayed enhancement(2D MDE)sequence and 5～10min delayed time.The hearts were excised and stained with TTC.The CT attenuations (normal myocardium,infarct myocardium,and left ventricular cavity)and the areas (epicardial,endocardial,and infarct myocardium)were measured on workstation.The attenuation difference%,contrast-to-noise ratio(CNR),and volume percent of myocardial infarction were calculated.The statistics methods included analysis of variance(ANOVA),Pearson correlation analysis,Bland-Altman plots,and paired t test.A significance level of 5%was assumed.Results:8 pigs were induced with acute reperfusion myocardial infarction(72.73%).The infarct myocardium volume measured with DE-MRI and TTC were 21.6±6.1%and 21.1±6.2%,respectively.The volumes of DE-MSCT with 4 settings were 22.9±6.9%,18.4±5.8%,22.5±6.6%, and 17.4±4.8%,respectively.The results of 120kV/250mA and 80kV/250mA showed no significant difference(P＞0.05)and significant positive correlation (P=0.001,P=0.000)with TTC,while results of 120kV/120mA and 80kV/120mA showed significant difference(P＜0.05)with TTC.The decrease of tube voltage and tube current could increase the image noise.However,decrease of tube voltage could improve difference%and CNR(P＜0.05).The difference%and CNR with 80kV/250mA were optimizing with limited increase of image noise.Conclusion: Low tube voltage technique appears to be feasible and more advantageous for assessing myocardial infarction.PartⅡAssessment of Acute Myocardial Infarction and No-reflow Phenomenon with MSCT:Ability of Visualization and Characteristic FindingsObjective:The purpose was to assess the ability of MSCT to detect acute myocardial infarction and no-reflow phenomenon,and study the MSCT characterize of myocardial infarction and no-reflow phenomenon.Materials and Methods:All the successful models accepted MSCT and MRI examinations after 72 hours.MSCT scan was performed at 3min,5min,10min,15min,20min,25min,and 30min following the injection of contrast medium.The hearts were excised and stained with TTC.The CT attenuations and the volume percent were measured on workstation. The attenuation difference%,CNR,and infarct myocardial volumes were calculated. The statistics methods included analysis of variance(ANOVA),Pearson correlation analysis,and linear regression.Results:Infarct myocardium volume measured with DE-MRI and TTC were 21.6±6.1%and 21.1±6.2%,respectively.The infarct myocardium volumes of DE-MS CT with 3min～30min were 21.5±6.4%,22.0±6.6%, 22.0±6.9%,22.1±6.4%,22.3±6.2%,21.7±6.0%,and 21.8±6.4%,respectively. There was no significant difference among them.The CT attenuations of left ventricle cavity(P=0.001),normal myocardium(P=0.000),and infarct myocardium(P=0.000) were decreased with time,and difference%(P=0.019)and CNR(P=0.000)were also decreased.The no-reflow volumes of DE-MSCT with 3min～30min were 21.9±6.7%, 17.7±5.7%,16.7±5.1%,13.8±4.8%,12.1±4.6%,10.9±4.5%,and 10.1±4.6%. The volume decreased with time(P=0.000),and results at 5min and 10min approached DE-MRI(17.6±5.5%).The CT attenuation of no-reflow area showed no significant difference with time(P=0.745).Conclusion:DE-MSCT could visualize the border,extent,and size of myocardial infarction and no-reflow phenomenon accurately,and correlated well with DE-MRI and TTC. PartⅢAssessment of Acute Myocardial Infarction and No-reflow Phenomenon with DE-MSCT and DE-MRI:Findings of Time Course in Acute StageObjective:The purpose was to analyze the size and time course of acute myocardial infarction and no-reflow phenomenon in 72 hours after acute reperfusion myocardial infarction.Materials and Methods:All the successful models accepted MSCT and MRI examinations after 1,24,48,and 72 hour.DE-MSCT parameters including:80kV,250mA,16×0.625mm,420ms/rot,0.23:1,5min delayed time,and retrospective ECG-gate.DE-MRI examination was applied with prospective ECG-gated 2D MDE sequence and 5～10min delayed time.The hearts were excised and stained with TTC.The CT attenuations and areas were measured on workstation. The attenuation difference%of infarct myocardium and normal myocardium,CNR, and area of acute myocardial infarction were calculated.The statistics methods included repeated measurements ANOVA and Bland-Altman plots.A significance level of 5%was assumed.Results:The measurements of infarct myocardium volume (P=0.331)and no-reflow volumes(P=0.515)with DE-MSCT and DE-MRI showed no significant difference,and there was good agreement between the two methods. The infarct myocardium volume increased from lh to 48h,and decreased slightly from 48h to 72h.The no-reflow volumes increased from lh to 72h.Conclusion:In the first 72 hours after acute reperfusion myocardial infarction,the volume of infarct myocardial increased significant in 48h and decreased from 48h to 72h,while no-reflow area increased significantly all the time.