PET-CT is relatively accurate in detecting cancer, with an accuracy rate of more than 90%. However, it cannot be used as a standard to diagnose cancer. Diagnosis of cancer requires pathology or other imaging tests. PET-CT examination can scan the whole body to find lesions. It usually has a high accuracy rate of more than 90%, and can be used as an effective test for checking cancer in the whole body. However, it is not possible to use one test as a standard for determining cancer. When a suspicious lesion is found, additional imaging, pathology, and blood tests are needed to determine whether it is cancer. For example, after a suspicious lesion is found in the stomach and intestines through PET-CT examination, a biopsy can be taken for pathological examination through gastroscopy. Or malignant tumor of the bladder, which requires another puncture test to confirm the diagnosis.