Method and apparatus for performing single gating in positron emission tomograpy sytems

An apparatus for processing list-mode data obtained by a positron emission tomography (PET) system scanning an imaging object, the apparatus comprising:

• processing circuitry configured to
• divide the list-mode data into a plurality of sets of data;
• generate a first plurality of vectors corresponding to a different one of the plurality of sets of data;
• generate a reference vector corresponding to a target respiration phase included in a cycle of a respiration of the imaging object based on a second plurality of vectors included in the first plurality of vectors, each of the second plurality of vectors corresponding to the target respiration phase;
• select, from the plurality of sets of data, a set of data to be used to reconstruct an image, based on respective differences between the generated reference vector and the first plurality of vectors;
• and
• generate the image based on the selected set of data.