The aim of this study was to improve quantitative assessment of rat myocardial infarct size using attenuation corrected PET polar map with gated CT image and MRI polarmap. The PET/CT images obtained with a small animal PET/CT scanner. Gating was realized with the help of an external trigger device. Contrast enhanced FLASH sequence MRI image was acquired with a 3-T clinical MRI using ECG triggering. The SUV PET image pixel size was percent variation was calculated anterior wall (ANT), septal wall (SEP), inferior wall (INF) and lateral wall (LAT) in polar map. Homogeneity was calculated no corrected PET (NC), attenuation corrected PET with CT image (AC-CT) and AC gated PET with gated CT image (gAC-gCT). TTC staining measures tissue viability used to evaluate real infarct size. The reference infarct size was defined by infarction area percentage of the total left myocardium. The infarct size for optimal size was repeated varying threshold values. The NC and AC-CT image percent variation of ANT, SEP, INF and LAT was 0.42%, 1.61%, 0.41% and 0.86% respectively. The gAC-gCT image percent variation of ANT, SEP, INF and LAT was 3.74% 1.21% 3.28% and 4.29% respectively. The gated CT AC gated PET polar map homogeneity was improved myocardial activity in anterior, inferior and lateral region. MRI based polar map with FLASH sequence at threshold lower 60% provide good result of infarct size measurement. Integrated myocardial analysis technology of high sensitive PET and high resolution MRI images may potentially facilitate the improvement of volume and attenuation correction information in cardiology.