X-ray CT apparatus

An X-ray CT apparatus comprising:

• an X-ray source that emits an X-ray to a subject;
• an X-ray detector that detects the X-ray transmitted through the subject;
• a rotating plate that causes the X-ray source and the X-ray detector to rotate around the subject;
• an image generation section that generates a tomographic image of the subject based on a detection signal of the X-ray detector;
• and
• a controller that controls each unit,
• wherein the controller has a modulation pattern setting section that sets a modulation pattern used for modulation of an emission dose, which is an X-ray dose emitted from the X-ray source while the rotating plate rotates, such that the emission dose to a site having high radiation sensitivity of the subject is reduced more than the emission dose to other sites, and a modulation pattern adjustment section that adjusts the modulation pattern based on an upper limit speed, which is an upper limit of a modulation speed of the emission dose.