Viability assessment of heart muscle after a myocardial infarction is an important step for diagnosis and therapy planning. It is important to quantify the area of edema because it can differentiate between viable and death myocardial tissues. In this paper an automatic method to quantify cardiac edema is presented. The method is based on a combination of morphological operations and statistical thresholding. Using real MRI data it is demonstrated that the proposed method can delineate edema region comparable to manual segmentation with a linear correlation coefficient r=0.76 and the mean difference is around 9.95%. The quantification result is also used to generate 3D visualisation model showing normal myocardial wall and edema region, which will enhance clinician diagnosis capability with real pattern of edema distribution and quantitative description.