Whole body PET-CT, can detect cancer, but not 100%, can not replace other examinations such as gastrointestinal microscopy, CT, magnetic resonance and ultrasound, it is recommended to follow the doctor’s instructions for standardized examination. PET-CT its imaging can detect abnormal glucose metabolism in the early stage of tumor, can be used for early diagnosis of tumor, not only can detect the primary tumor foci, but also can check the metastasis of the tumor, in the application of tumor staging and re-staging than other imaging has the advantage of its accuracy rate can reach 90%. However, there are false positives in PET-CT, which is not very meaningful for detecting some very small masses, such as thyroid tumors. Moreover, the detection rate of PET-CT is not 100%, which will also add to the mental and economic burden of the patients, and it is recommended to combine it with gastrointestinal microscopy, CT, magnetic resonance and ultrasound and other related examinations to make a clear diagnosis. If there is any discomfort, it is recommended to consult a doctor in time for a clear diagnosis and treatment, so as to avoid delaying the condition.