X-ray computed tomography apparatus and contrast medium inflow amount detection method

An X-ray computed tomography apparatus that executes a monitoring scan for detecting an inflow amount of a contrast medium administered to an object and an actual scan under a scan condition different from that of the monitoring scan, comprising:

• reconstruction circuitry configured to, at the time of the monitoring scan, based on an output of an X-ray detector for detecting X-rays having passed through the object, reconstruct a first image concerning the object at the time of administration of the contrast medium and a second image concerning the object after a predetermined period elapses since administration of the contrast medium;
• and
• control circuitry configured to shift from the monitoring scan to the actual scan based on a change amount of a CT value obtained when the entire reconstructed first image is compared with the entire reconstructed second image.