According to one embodiment, an X-ray computed tomography imaging apparatus includes an X-ray tube, an X-ray detector, and control circuitry. The X-ray tube includes a cathode configured to generate thermoelectrons, an anode configured to generate X-rays upon receiving the thermoelectrons from the cathode, and a regulator configured to apply an electric field or a magnetic field to focus or bias the thermoelectrons from the cathode. The X-ray detector detects the X-rays generated by the anode. The control circuitry controls the regulator to switch at least one of the size and position of the focus of the thermoelectrons from the cathode on the anode between scan and warm-up.
