In order to provide an X-ray CT apparatus which reduces a waiting time period until irradiation with X-rays is permitted with a simple configuration without detecting a rotation speed of an anode, a controller (23) selects a rating anode rotation speed among a plurality of types thereof depending on an X-ray irradiation condition, and supplies driving power for realizing the selected rating anode rotation speed to a stator coil (81) from a starter circuit (10). The controller (23) obtains time required to reach an irradiation possible rotation speed which is lower than the rating anode rotation speed and is required to apply X-rays in an X-ray irradiation condition. If arrival time has elapsed, irradiation with X-rays is permitted. Consequently, it is possible to reduce a waiting time period in which an operator waits for an anode rotation speed to rise.

In order to provide an X-ray CT apparatus which reduces a waiting time period until irradiation with X-rays is permitted with a simple configuration without detecting a rotation speed of an anode, a controller (23) selects a rating anode rotation speed among a plurality of types thereof depending on an X-ray irradiation condition, and supplies driving power for realizing the selected rating anode rotation speed to a stator coil (81) from a starter circuit (10). The controller (23) obtains time required to reach an irradiation possible rotation speed which is lower than the rating anode rotation speed and is required to apply X-rays in an X-ray irradiation condition. If arrival time has elapsed, irradiation with X-rays is permitted. Consequently, it is possible to reduce a waiting time period in which an operator waits for an anode rotation speed to rise.

Systems and methods for improving x-ray sources with switchable electron emitters. Improved systems may use the functionality of the switchable electron emitters in various configurations to provide power regulation, multidimensional analysis, and electron beam forming so as to increase the durability and the reliability of the system. Cooling mechanisms may be used to further protect the anode from deterioration over time.