The disclosure relates to PET imaging systems and methods. The systems may execute the methods to obtain an anatomical image and PET data of a subject, and gate the PET data into a plurality of bins. The systems may execute the methods to reconstruct a plurality of gated PET images based on the gated PET data. The systems may execute the methods to determine a motion vector field corresponding to a target respiratory phase with respect to a reference respiratory phase relating to the anatomical image. The systems may execute the methods to obtain a respiratory phase-matched anatomical image for the target respiratory phase by transforming a VOI in the anatomical image based on the motion vector field corresponding to the target respiratory phase with respect to the reference respiratory phase, and reconstructing an attenuation corrected PET image corresponding to the target respiratory phase.
