1. A method for optimizing an amount of radiation dose and acquisition time in cardiac Single Photon Emission Computed Tomography (SPECT) imaging, the method comprising: providing an organ; acquiring images of the organ at projected views; selecting a projected view that projects the organ as an annulus; selecting a region of interest (ROI) in the projected view, wherein the ROI is in a lateral wall of the organ; determining an average count in the ROI; and predicting an image quality of a reconstructed image based on the average count.