Patent ID: 8331527

Claim:
An X-ray CT apparatus having an X-ray tube for generating X-ray with which an examinee is irradiated, and means for obtaining a tomographic image of the examinee by using a dose of transmitted X-ray collected by means for collecting X-ray transmitted through the examinee, characterized by comprising: storage means for storing relationships between an accumulated heat capacity of the X-ray tube and a focal point shift amount in a slice direction; accumulated heat capacity obtaining means for obtaining the accumulated heat capacity of the X-ray tube under heating and cooling, wherein the relationship between the accumulated heat capacity of the X-ray tube and the focal point shift amount in the slice direction obtained under heating is different than the relationship between the accumulated heat capacity of the X-ray tube and the focal point shift amount in the slice direction obtained under cooling; determining means for determining which one of heating and cooling states the X-ray tube is under; and position correcting means for correcting the position of a slice direction of X-ray beam by using a focal point shift amount of the slice direction which is determined on the basis of the accumulated heat capacity obtained by the accumulated heat capacity obtaining means, a determination result of the determining means and the relationship stored in the storage means.