1. A diagnostic imaging system for imaging a subject and for obtaining a diagnostic image from projection data of the subject, said diagnostic imaging system comprising: a setting device configured to: set a detection object within an imaging region of the subject prior to performing a scan of said imaging region; and set a first imaging condition and a second imaging condition prior to performing the scan of said imaging region, said first imaging condition configured to generate a tomographic image of said imaging region after the scan is performed and said second imaging condition configured to generate an enlarged image with respect to said tomographic image after the scan is performed, said enlarged image including an image of said detection object and having a magnification larger than a magnification of said tomographic image; a scanner configured to perform the scan of said imaging region to obtain a set of projection data of said imaging region; a first image processing device configured to generate said tomographic image of said imaging region using said first imaging condition and the set of projection data obtained by said scanner during the scan; an extractor device configured to extract said detection object selected in said setting device from said tomographic image based on a character of said detection object, said character comprising a shape of said detection object; a second image processing device configured to generate said enlarged image using said second imaging condition and one of tomographic image data of the extracted detection object and a subset of projection data of the extracted detection object, the tomographic image data and the subset of projection data derived from the set of projection data obtained during the scan; and a display device configured to independently display said tomographic image generated by said first image processing device and said enlarged image generated by said second image processing device.