Positron Emission Computed Tomography (PET-CT) is a functional molecular imaging system that integrates PET and CT into one, which can reflect the biochemical and metabolic information of liver occupying tissues by PET functional imaging and precise anatomical localization of lesions by CT morphological imaging, and the whole body scan can understand the overall situation and assess the metastasis to achieve the purpose of early detection of lesions. It can also understand the size and metabolic changes before and after tumor treatment. The most widely used metabolite and marker is fluorodeoxyglucose (18F-FDG), which is taken up by tissue cells and phosphorylated by the action of hexokinase. In contrast, the high expression of glucose transporter on the tumor cell membrane and the enhanced expression and activity of intracellular hexokinase showed the high concentration of 18F-FDG in the tumor tissue, and the standard uptake value was significantly increased by PET examination. However, according to domestic and foreign literature, the PET-CT positivity rate is 50-60% for primary liver cancer, which is not too high because the uptake of 18F-FDG is not too high in a part of well-differentiated hepatocellular carcinoma, because the tumor cells contain a certain level of glucose-6-phosphatase, which can hydrolyze the 6-phospho-18F-FDG that has been catalyzed by glucokinase into the tumor cells. The tumor cells contain a certain level of glucose-6-phosphatase, which can hydrolyze the 6-phosphate-18F-FDG that enters the tumor cells and is catalyzed by glucokinase to generate 18F-FDG, and 18F-FDG can be cleared by the tumor cells through the cell membrane, which is close to normal hepatocytes, and there is no accumulation of 18F-FDG in PET-CT imaging, resulting in false-negative results. 18F-FDG PET-CT has a higher uptake of FDG and shows a hypermetabolic lesion. 18F-FDG PET-CT has a higher detection rate for cholangiocellular hepatocellular carcinoma than hepatocellular hepatocellular carcinoma. For benign intrahepatic occupying lesions, the specificity of PET-CT can be as high as 90%. Although individual liver abscesses may show 18F-FDG uptake and cause false positives, the vast majority of benign intrahepatic lesions (e.g., hemangiomas, hepatic adenomas, hepatitis, hepatic fatty infiltrates, focal nodular hyperplasia, and the vast majority of hepatitis pseudotumors) generally do not show high uptake of 18F-FDG. PET-CT is effective for the diagnosis of metastatic liver cancer or metastases from primary liver cancer. In metastatic liver cancer, there is often high uptake of 18-FDG, and according to the literature, the positive imaging rate of PET-CT for metastatic liver cancer is over 90%. In conclusion, enhanced CT or MRI is superior to PET-CT for the diagnosis of primary liver cancer, but PET-CT can be considered in the following cases: 1) when benign and malignant differentiation cannot be made by conventional examinations alone; 2) when the staging and grading of liver cancer need to be determined, to clarify the systemic metastasis, to guide the formulation of the best treatment plan, and whether there are indications for radical resection or liver transplantation; 3) for efficacy assessment. determine whether there are residual lesions and activity, and determine further treatment plan; 4. When tumor indexes are progressively elevated and lesions cannot be detected by conventional examination.
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