BACKGROUND: The MRJ studies of acute myocardial infarction (AMI)were more frequently focused on the changes of myocardial perfusion. OBJECTIVE: To investigate the characteristics of infarction and myocardial reperfusion in MRI, and make comparison of them with the results of their staining pathologic sections. DESIGN: Completely randomized grouping design and randomized controlled study. SETTING: Magnetic Resonance Department of Air-force General Hospital of Chinese PLA and Radiological Department of General Hospital of Chinese PLA. MATERIALS: The experiment was completed in the Medical Animal Experimental Center, General Hospital of Chinese PLA in December 2003.Fourteen miniature pigs were divided into 2 groups: infarction group and reperfusion group with 7 pigs in each group. One-month before and after the operation, MRI was performed in order to strengthen the scanning examination. One-month after operation, axial plane pathologic slices, which were corresponding to the MRI, were given TTC and SE staining. According to the TTC staining results, samples of the infarcted myocardium (corresponding to the anterior wall of the left ventricular) and normal myocardium (corresponding to the posterior wall of the left ventricular) were taken and given HE staining to observe the extent of infracted myocardium. MAIN OUTCOME MEASURES: The changes in cardiac shape and function and the changes of myocardial T1 and T2 relaxation time. RESULTS: Fourteen Chinese miniature pigs were used with 7 in each group. ①Relaxation time of T1 and T2 of infarcted myocardium in infarction group was obviously longer than that of thenormal myocardium [1 159.54±78.67, (60.15±6.31) ms, 1 056.15±70.95, (47.46±7.94) ms, t=2.63,5.38, P＜ 0.05, 0.01] and that of the infarcted myocardium in reperfusion group was also obviously longer than that of normal myocardium [1 171.14±139.98,(56.64±6.16) ms, 1 074.64±97.61, (44.57±4.25) ms, t=2.64, 6.24, P ＜ 0.05,0.01].②MRI in single infracted myocardium and reperfused infracted myocardium was both changed obviously,but without significant differences in relaxation time and stress.Dilatation of left ventricle in single infracted group was more obviously than that in the reperfusion infracted group.③Theresult of MRI was coincidence with that examinated with TTC staining CONCLUSION:①MRI is a useful imaging modality in the evaluation of AMI and the left ventricle remodeling after myocardial infarction.②It is significant for reperfusion to treat remodeling of left ventricle after acute myocardium infarction.③There is good correlation between MRI and pathological examination.

The breakdown voltage plays an important role in evaluating residual life of stator insulation in generator. In this paper, we discussed BP neural network that was used to predict the breakdown voltage of stator insulation in generator of 300 MW/18 kV. At first the neural network has been trained by the samples that include the varieties of dielectric loss factor tanδ, the partial discharge parameters and breakdown voltage. Then we tried to predict the breakdown voltage of samples and stator insulations subjected to multi-stress aging by the trained neural network. We found that it's feasible and accurate to predict the voltage. This method can be applied to predict breakdown voltage of other generators which have the same insulation structure and material.