Cooling device and PET system

The invention discloses a cooling device and a PET system, the PET system comprises a plurality of detector units and a mounting back plate, the plurality of detector units are arranged on the mounting back plate, each detector unit is internally provided with a liquid path coil pipe, the cooling device comprises at least one total flow guide cavity channel, and the total flow guide cavity channel is communicated with the liquid path coil pipe. The main flow guide cavity channel is communicated with the liquid path coil pipe in each detector unit according to a bus type structure, and the main flow guide cavity channel is communicated with an external cooling-water machine to form a circulating cooling flow path; wherein the main flow guide cavity channel is formed in the mounting back plate. Interference between the diversion pipeline and a communication line can be avoided, damage to a pipeline joint is avoided, and the leakage risk is reduced. Meanwhile, the integration level is further improved, and assem