PET-CT refers to positron emission computed tomography imaging. After some patients have PET-CT, if they are found to be patients with early stage tumors, they must have biopsy before receiving treatment, which is used to diagnose the benignity and malignancy of the tumor, its stage, whether it is metastatic or not, and to guide the treatment. PET-CT has various outstanding advantages, such as very fine and accurate examination of lung cancer and brain cancer, but its examination of tumors of cavity organs, such as stomach cancer, liver cancer and bladder cancer, is relatively weak. However, it is relatively weak for tumors of cavity organs, such as stomach, liver and bladder cancer. In addition, PET-CT is not sensitive to lesions less than 5 mm in diameter, which can easily lead to false negative results. Biopsy is the examination of biopsies, by which isolated tissues and cells are produced, observed, and diagnosed. Biopsy is a common clinical examination involving various tissues and organs, such as gastroscopy and colonoscopy, puncture of parenchymal organs such as lung tissue and liver, and extraction of pleural fluid and ascites for cytological examination, and therefore has a high degree of accuracy.