When a command to start imaging is issued, the heart beat of a subject is detected to measure his/her heart beat period. A static period is determined from a cardiac waveform. The duration of one rotation of a rotary table is determined. In accordance with the determined duration of time, the rotary table starts rotating. When a predetermined rotation angle of the rotary table and the predetermined number of views are achieved, emission of X-rays is halted and the rotary table is stopped. Data acquired from the static period are rearranged. An image is reconstructed using the rearranged data. The first reconstructed image may include artifacts and should be evaluated. When artifacts are observed, a command to redetermine the static period is issued to modify the static period.