The Study Of Myocardial Hypertrophy Rats By Using 7.0T Magnetic Resonance Imaging With Multiple Parameters

Part 1 The Study of Myocardial Hypertrophy rats in vivo by Using 7.0T Magnetic Resonance imagingObjective To assess the structures and function of myocardial hypertrophy rats in vivo by using 7.0T MRI system.Material and Methods A total of 32 SD rats were randomly assigned to sham group( n=8) and TAC(transverse aortic constriction) group( n=24).After TAC surgical procedure, TAC group were divided into 4 week group( n=8),8 week group( n=8)and 12 week group( n=8).Sham group also underwent surgery except constriction. MRI scanning were performed with all rats at 4 week,8 week and 12 week after surgery. Using BRUKER PARAVISION 5.0 software to measure the parameters of left ventricular as follow : LVEDV,LVESV,SV,LVEF%,LVEDD,LVESD,LVFS%,LVM. Pathological changes of all groups were observed after HE stain and Masson’s trichrome stain. Statistics were analyzed by using one-way ANOVA.Results There were significant differences in LVEDV、LVESV、SV、LVEDD、LVM between TAC group and sham group(P< 0.01). There were no significant differences in LVEF%, LVFS% and LVESD between TAC group and sham group. An increasing trend of LVEDV,LVESV,SV,LVEDD,LVM were showed within 4 week group,8 week group and 12 week group( P< 0.05).There were no significant differences in LVEF%, LVFS% and LVESD within three groups as well。Myocardial HE stained and Masson’s trichrome stained sections showed that cellular hypertrophy, increasingly extracellular space and interstitial fibrosis had been recognized in TAC group compared with sham group.Conclusion The variation of myocardial structures and function in myocardial hypertrophy rats had been assessed dynamically by using 7.0T MRI system for the first time to our knowledge. Our research demonstrate that MRI is promising technology to quantitatively evaluate myocardial structures and function and lay the foundation for further study of heart failure.Part 2 The Study of Characteristic of Hypertrophy Myocardial Fibers in Rat by Using 7.0T Diffusion Tensor Magnetic Resonance ImagingObjective To quantitatively evaluate the characteristic of myocardial fibers in myocardial hypertrophy rats from the viewpoint of water molecular diffusion, microstructure and mechanical unit by using 7.0T diffusion tensor magnetic resonance imaging(DT-MRI).Materials and Methods A total of 16 fixed rat hearts(sham group n=8, transverse aortic constriction [TAC]) group n=8) underwent DT-MRI and the myocardial structures were quantitatively measured by Diffusion Toolkit, Trackvis and Matlab. The characteristic of global 3D tractography of myocardium, tractography of myocardium and tensor in papillary muscle plane and HE stained section were discussed between the two groups. Mean ADC value, FA value and helix angle of left ventricular between the two groups were analyzed by using Independent-Sample T Test.Results Sham group and TAC group showed that myocardial fibers arranged orderly and densely from epicardium to endocardium at global 3D tractography of myocardium. Regular direction and arrangement were presented at tractography of myocardium and tensor in papillary muscle plane. Left ventricular wall thickness in TAC group was thicker than sham group. The number of tensor had been increasingly recognized in TAC group compared with sham group. There were significant differences in ADC value(P< 0.01) and FA value(P< 0.05) between TAC group and sham group. Left ventricular mean helix angle from epicardium to endocardium in TAC group were larger than sham group(P< 0.01).Conclusion DT-MRI and imaging post-processing technique can quantitatively measure the variation of myocardial fibers in myocardial hypertrophy and visualize the character of myocardial fibers in multiple parameters. This promising approach also lay the foundation for further study of myocardial fibers in vivo.