X-ray computed tomography apparatus

The present invention provides an X-ray CT apparatus capable of improving image quality of a dual energy image. The X-ray CT apparatus comprises an X-ray tube for applying X rays having a first energy spectrum and X rays having a second energy spectrum different from the first energy spectrum to a subject, an X-ray data acquisition unit for acquiring X-ray projection data of the first energy spectrum projected onto the subject and X-ray projection data of the second energy spectrum projected thereonto, dual energy image reconstructing unit for image-reconstructing tomographic images indicative of X-ray tube voltage-dependent information at X-ray absorption coefficients related to a distribution of atoms, based on the X-ray projection data of the first energy spectrum and the X-ray projection data of the second energy spectrum, and adjusting unit for adjusting conditions for the image reconstruction in order to optimize the tomographic images indicative of the X-ray tube voltage-dependent information.