Diagnostic Significance of Single Center, Open and Prospective Evaluation of <Sup>18<Sup>F-FDG PET/CT Dynamic Imaging and Genomic Sequencing in Detecting Metastatic Lesions of Primary Hepatocellular Carcinoma

Hepatic malignancies have a high incidence rate and can be classified into primary liver cancer and metastatic liver cancer according to their sources. There are three main types of primary liver cancer: hepatocellular carcinoma (HCC), cholangiocellular carcinoma (CCC), and mixed hepatocellular carcinoma (both hepatocytes and cholangiolar cells). In recent years, the incidence and mortality of liver cancer have continued to rise. It has high incidence in Southeast Asia and Africa, and the number of liver cancer patients in China accounts for 55% of the world. However, the onset of liver cancer is occult; the degree of malignancy is high, and the progress rate is fast. Most patients have reached late stage or distant metastases when diagnosed. Imaging examination is an important method for the diagnosis and monitoring of liver cancer. The routine imaging examination mainly observed the morphological characteristics and blood supply changes of the liver lesions. The detection rates of CT and MRI for liver cancer can reach 81-89% and 50-80%, respectively. However, these imaging studies have limitations and are vulnerable to local anatomical locations and cannot be used to assess systemic tumor invasion and biological characteristics. Positron emission tomography (PET) is a molecular-level imaging technique that utilizes relatively specific tracers for qualitative and quantitative imaging. The good spatial and density resolutions of computed tomography (X-ray computed tomography, CT) play an important role in the localization and qualitative diagnosis of HCC. 18F-FDG PET/CT can provide functional imaging from the point of view of molecular biology. It not only can understand the tumor invasion of the whole body, but also has become an important means for qualitative diagnosis, staging, prognosis and therapeutic evaluation of tumors.

As a new imaging technology, 18F-FDG PET/CT plays an increasingly important role in the diagnosis of primary liver cancer. 18F-FDG PET/CT reflects the glycometabolism of tumor tissues. The diagnosis of benign and malignant tumors is based on the difference in glucose metabolism between tumor cells and normal tissues. 18F-FDG is an isomer of glucose and is involved in the glucose metabolism process. Since it is deoxygenated, it cannot generate diphosphate hexose, and it cannot participate in the next step of metabolism but remains in the cell. In the tumor cells, due to the high expression of glucose transporter mRNA, the glucose transporters Glut-1 and Glut-3 levels are increased; the expression of hexokinase is increased; the level of glucose-6-phosphatase is down-regulated and other common factors make the tumor cells' 18F-FDG uptake increased.

Previous researchers have found 18F-FDG PET/CT unsatisfactory in the diagnosis of HCC, especially for the diagnosis of HCC with well-differentiated tissue. The researchers also indicates that 18F-FDG PET/CT is not superior to traditional MRI and CT in the diagnosis of liver cancer. Combined with the current relevant research, it can be roughly stated that the positive rate of liver cancer using 18F-FDG PET/CT in diagnosing different grades of tissue differentiation is only about 50-70%. There appears to be a high uptake of FDG in poorly differentiated HCC. However, there is no such obvious phenomenon in HCC with medium or well-differentiated tissue. The PET/CT scans reported in all these documents are based on conventional static scans, i.e. the image data is based on a static take-up image of the tracer in tissue obtained at a fixed time point after the injection of 18F-FDG. To improve, the investigators propose to use dynamic data scanning, which captures the dynamic data of whole body tissues collected from the moment of injecting 18F-FDG to an hour. Dynamic scans can provide information on the dynamic changes in tracer metabolism and distribution in tissues over time, so they provide a richer metabolic and distributional pattern of tumor foci and metastases than static scans. However, the current domestic and international research on 18F-FDG PET/CT dynamic scan in the metastasis of hepatocellular carcinoma is very rare. Therefore, the aim of this study is to make up for this gap by performing a dynamic scan of 18F-FDG PET/CT on newly diagnosed patients with liver cancer. The lesions and/or metastases are performed for biopsy. Pathological and genomic studies are performed. The differences between tumor images and tissues are compared at the same time. 18F-FDG PET/CT dynamic imaging is explored in primary liver cancer metastases for the diagnostic value.