1. A method implemented on at least one machine each of which has at least one processor and storage, the method comprising: acquiring list mode data relating to a subject; dividing the list mode data based on time information and/or spatial information; establishing a relationship between data-space and reconstruction space; obtaining, based on the divided list mode data and the relationship, expectation information of rigid motion of subject without performing image reconstruction; and determining, based on the expectation information, translation information and rotational information to detect the rigid motion of the subject.