A computer-aided image acquisition and diagnosis system, which generates and files images for facilitating the reading and diagnosis based on the acquired images. The X-ray CT apparatus for obtaining diagnosis image from the projection data of imaging of a subject, includes a selector means for selecting the detection object to be anticipated, a scanner means for scanning the subject placed in position, an image processing means for reconstructing the subject image from the projection data obtained from the scanner means, an extractor means for extracting the detection object selected in the selector means from within the reconstructed image, and a display means for displaying the detection object extracted by the extractor means.