Contemporarily, significant progress has been made in the development and application of image fusion technology in the field of diagnostic imaging. Image fusion is a fully automated image alignment and interpretation system that not only allows images with different characteristics to be displayed, interpreted, compared, and analyzed on the same platform, but also provides a fast and seamless pathway to clinical diagnosis and treatment. The purpose of this study was to explore the imaging theory, clinical advantages and limitations of CT. At the beginning of the study, the definition and development history of CT will be explained. Subsequently, in addition to imaging theory and key parameters, one can also understand the individual advantages and clinical application of CT. Afterwards, the limitations of CT will be mentioned, and the new technology of PET/CT will be introduced. As the most advanced medical imaging technology, PET/CT has improved the way of single PET and CT scanning, making them more widely used, making it the best combination of medical imaging and diagnostic technology. Overall, these results shed light on guiding further exploration of CT.