Myocardial infarction remains a leading cause of morbidity and mortality worldwide. To replace damaged cells in myocardium, we created a novel approach that transdifferentiates fibroblasts into cardiomyocyte-like cells by overexpressing three core transcription factors involved in development—Gata4, Mef2C and TBX5 (GMT)—in vitro and in vivo. Notably, the degree of reprogramming was significantly higher in vivo than in vitro. Administration of these factors into an animal with myocardium infarction increased lifespan of experimental animals. Histological studies demonstrated transformation of fibroblasts into normal myocardium tissue. These promising results initiate significant research interest and several research groups conducting fibroblast reprogramming studies worldwide. In order to facilitate this research noninvasive imaging method of myocardium monitoring is needed. In the present study we compare results of in vivo imaging of cardiac anatomy and functions using two noninvasive techniques: ultrasound echocardiography and MR imaging. Taking into account very different level of complexity and price for these two techniques, the goal of the study was to evaluate which method provides sufficient amount of information about anatomy and functionality of myocardium and more preferable in the research. Left anterior descending coronary artery was permanently occluded for 12 weeks in twenty B6 black mice. Ten animals were treated with intomyocardium administration of genetically engineered lentiviruses. Viruses provided a delivery of Gata4, Mef2c and Tbx5 transcription factors into genome of cells surrounded the injection site. Another ten mice were not treated and used as control. Ultrasound imaging of myocardium were performed once a week for twelve weeks, MR imaging was performed once, twelve weeks after occlusion. Ultrasound imaging was performed on Visual Sonic Vevo 770 scanner. MR imaging was performed at 7T preclinical horizontal bore magnet interfaced to Agilent console. Spin echo MR pulse sequence was implemented with the following parameters: TR=1s, TE=10ms, in-plane image resolution 200 um and slice thickness of 1mm, acquisition time ~20min (depends on hart rate). Cardiac and breathing gating was employed. In order to evaluate the ejection fraction, nine short axis slices of the heart were acquired at diastole (zero delay after R-heart-peak) and systole (45% of the R-R interval delay from the R-peak). Ultrasound and MR images of the infarcted myocardium are shown in figure 1 (A and B respectively). Table 1 presents the results of ejection fraction (EF), left ventricle mass (LVmass) measurements obtained with ultrasound and MR methods. In addition to these two parameters, MR imaging allowed to measure scar size.Measurements of EF and LVmass with MR and ultrasound imaging provide consistent results while the evaluation of scar size with ultrasound technique is not feasible. We compared MRI measurements of the infarction size with histological staining and observed very strong correlation (). Results of our study suggest that measurements of EF and mass of left ventricle were easier and cheaper to perform with ultrasound echocardiography however evaluation of a scar tissue and re-muscularization of infarcted myocardium are only possible with MRI method.