The present disclosure is related to a system. The system may include a gantry, a detector assembly including a plurality of detector modules arranged on the gantry, and/or a cooling assembly configured to cool the detector assemble. Each of the plurality of detector modules may include a crystal array configured to detect radiation rays, and a shielding component configured to shield the crystal array from an electromagnetic interference. The cooling assembly may include a plurality of cooling components. Each of the plurality of cooling components may be embedded in a corresponding detector module of the plurality of detector modules.