Computed tomography apparatus

A computed tomography apparatus comprising:

• a radiation source that emits radiation having a pyramid shape to a subject positioned in either a standing posture or a sitting posture and that includes a radiation tube having a cold cathode;
• a radiation detector in which a plurality of pixels detecting the radiation transmitted through the subject are two-dimensionally arranged and which outputs a projection image of the subject;
• a rotation mechanism that rotates the radiation source and the radiation detector around a body axis of the subject;
• a plurality of imaging units each of which is composed of a set of the radiation source and the radiation detector and which have different phases in a rotation direction;
• a displacement mechanism that changes an interval between the plurality of imaging units in a rotation axis direction;
• and
• a processor that controls operations of the radiation source, the radiation detector, and the rotation mechanism,
• wherein the processor directs the radiation source to intermittently and alternately emit first radiation having a first energy distribution and second radiation having a second energy distribution different from the first energy distribution whenever the rotation mechanism rotates the radiation source and the radiation detector by a preset angle, directs the radiation detector to output a first projection image based on the first radiation and a second projection image based on the second radiation which are obtained by the intermittent emission of the first radiation and the second radiation, and generates a tomographic image on the basis of the first projection image and the second projection image.