The invention relates to a
positron emission
tomography scanner and a
coincidence judging and selecting method therein. The
positron emission
tomography scanner comprises a detecting ring, wherein the detecting ring consists of a plurality of detectors. The
coincidence judging and selecting method comprises the following steps of: judging whether each
detector is correlated to opposite detectors, acquiring correlation data according to each judgment result, and judging the two detectors to be correlated to each other if a
time difference of a single event respectively detected by the two detectors stays within a
coincidence time window, wherein the opposite detectors of any
detector refer to the detectors in a sector area with a preset angle by adopting the
detector as a center; and judging whether the two detectors are exclusively correlated to each other according to the correlation data and judging the single event detected by the two exclusively-correlated detectors to be a coincidence event. The
positron emission
tomography scanner and the coincidence judging and selecting method have advantages of rapidness in coincidence judging and selection, high efficiency and wide application range.