Graphical user interfaces and methods for displaying ECG, slice images and a reconstruction projection image of the slices. In exemplary embodiments, the graphical user interfaces and methods facilitate the selection of slice images that are taken during a quiet part of the patient's heart cycle in which the heart is relatively motionless so as to reduce blurring and the introduction of artifacts into the resultant reconstructed projection image of the heart. In exemplary embodiments, the resultant projection image can be used for coronary calcium detection and scoring or 3-D rendering.