PET is relatively a leading and new imaging technology. It is a very useful reference for the diagnosis and differential diagnosis of many diseases. It is relatively more sensitive than CT, and in many diagnostic aspects it is superior to MRI, and can obtain significant stereoscopic imaging. This test is very valuable for early diagnosis of tumors and is superior to other devices. It is relatively capable of detecting very small lesions, usually those larger than 5 mm in diameter, which can be completely detected. It is also unique for tumors, as well as brain and cardiovascular examinations. It usually takes only a few minutes to scan the neck, chest, abdomen and pelvis, and it is possible to obtain cross-sectional, sagittal and coronal images of the whole body to clarify the lesions of the internal organs.