PET is positron emission tomography/X-ray computed tomography, which is an organic combination of PET and CT equipment, using the same examining bed and the same image processing workstation. CT is a computerized body scan that allows for clear anatomical tomographic images of body structures. The fusion of PET images with CT images can reflect the pathophysiological changes and morphological structure of the lesion at the same time, clearly, lucidly and accurately reflecting the lesions of all organs of the human body. PET-CT technology is the most perfect and highest grade medical imaging equipment at present, as well as a unique medical diagnosis technology, which is called “the crown of modern medical high technology”.