1. A method for cardiac imaging, comprising: acquiring functional imaging data of a subject, the functional imaging data including at least a myocardium; determining a region of interest (ROI) encompassing at most the myocardium from the acquired functional imaging data, determining the ROI including: generating projection image representations from the functional image data, thresholding the projection image representation based on a histogram of a selected representative slice, determining a localized cardiac region within the thresholded data according to at least one of a horizontal ray casting profile and anatomical heuristics, and determining extents of the localized cardiac region according to image based and heuristics based cleaning techniques; and estimating diagnostic parameters of the myocardium based on the determined ROI.