A CT system including a multi-array detector that includes a plurality of detector cell, a data acquisition system that acquires data items representing doses of radiation incident on the detector according to output signals of the detector cells, and a data processing unit that identifies a distribution of doses of radiation incident on the detector, which is used to construct tomographic images acquired by the data acquisition system. The data acquisition system includes a smaller number of amplifiers, which amplify signals produced by the detector cells and transmit the resultant signals, than the number of detector elements, and a switching unit that changes the continuities between the detector cells and amplifiers so that detector cells whose signals are amplified by each of the amplifiers will be changed into others juxtaposed in the direction of slices during the scanning of a subject.