CT imaging systems and methods thereof are disclosed. A common CT scanning is performed (S41) on an object to obtain a common CT imaging. An area of interest is determined (S43) from the image. A CT scanning is performed (S44) on the area of interest under a plurality of energy windows by a photon counter detector. A high resolution image of the area of interest is reconstructed (S46). The discrimination of energy spectrum is higher and the result so obtained is more stable by using a photon counter detector to collect photon count projection data of a plurality of energy windows and thus it may be decomposed into a plurality of basis functions.
