A method for cardiac imaging for determining a myocardial region of interest (ROI) is disclosed. The method includes acquiring functional imaging data of a subject, where the functional imaging data includes at least the myocardium. A ROI encompassing at most the myocardium from the acquired functional imaging data, and diagnostic parameters relating to the myocardium are estimated and quantified based on the determined ROI. In one embodiment, the ROI is determined from a projection image representation utilizing histogram based thresholding and ray casting based localization to determine the extents of the ROI. In another embodiment, the ROI is determined from a volumetric image representation utilizing clustering Manhattan distance based cleaning to determine cardiac angles used for reorienting the left ventricle.