An imaging system is provided that includes at least one detector unit and at least one processor. The at least one detector unit is configured to acquire nuclear medicine (NM) imaging information. The at least one processor operably coupled to the at least one detector unit, and is configured to acquire initial imaging information over an initial time range corresponding to administration of a radiopharmaceutical； acquire cardiac cycle information over the initial time range； determine targeted portions of the initial imaging information based on the cardiac cycle information to provide targeted initial imaging information； generate an activity curve using the targeted portions of the initial imaging information； and reconstruct an image using the activity curve.
