A source switching apparatus comprises a plurality of collimators, a switch carrier, a source carrier. The switch carrier is assembled with a plurality of shielding elements regularly distributed thereon. The source carrier is assembled with a plurality of radiation sources regularly distributed thereon. The collimator, the switch carrier, and the source carrier are connected to one another via respective driver, to rotate with common angular velocity or in a differential movement, and wherein in the case when the differential movement is holding, a angle difference is formed between the switch carrier and the source carrier.
