A system and method of imaging a patient are provided. The system may include an acquisition configured to obtain a PET dataset relating to a target organ of a patient. The system may also include a processing module configured to determine a reference point of the target organ, divide the PET dataset into a plurality of data frames, and determine a motion signal of the target organ based on a plurality of first statistical parameters and a plurality of second statistical parameters. The processing module may further sort the PET dataset into a plurality of bins based on the motion signal.
