Patent ID: 7269242

Claim:
An X-ray CT apparatus comprising: X-ray generating means for generating X-rays; X-ray detecting means arranged opposite to the X-ray generating means for two-dimensionally detecting a dose of X-rays passing through an object to be examined; means for holding the X-ray generating means and the X-ray detecting means so that the object is located therebetween; means for adjusting a distance between the X-ray generating means and the X-ray detectinci means on the holdinci means; rotation driving means for driving the holding means to rotate around the object; image processing means for producing a tomogram of the object based on the X-ray dose detected by the X-ray detecting means; display means for displaying the tomogram; and means for changing an FOV size of the X-ray detecting means so as to reduce the FOV size of the X-ray detecting means to less than a maximum FOV size of the X-ray detecting means in accordance with a detected portion of the object displayed by the display means; wherein the FOV size changing means includes X-ray converting means for converting the X-rays into visible light; light receiving means for converting the visible light converted by the X-ray converting means into electrical signals; and means for changing a portion of the visible light converted by the X-ray converting means necessary for creating the tomogram.