According to the latest epidemiological survey in 2018, primary liver cancer is the sixth most common cancer in the world. Among these, hepatocellular carcinoma is the most common type of liver cancer. Clinicians' diagnosis of HCC has been gradually transformed from invasive puncture diagnosis to non-invasive diagnosis based on enhanced imaging findings. In HCC tissue, the number of small blood vessels was increased and the arrangement was disordered. Compared with the surrounding normal liver tissue, there were more obvious manifestations of increased arterial blood supply. Contrast-enhanced Ultrasound (CEUS) is the most sensitive and objective tool for detecting circulatory perfusion, and can achieve a clear and dynamic display of low speed and small blood flow. Its diagnostic efficacy of HCC is similar to the diagnostic ability of Enhanced CT.~In order to better standardize the writing of liver CEUS report by sonographers, and to facilitate sonographers and clinicians to reach a consensus on the diagnosis and treatment of liver lesions, In 2017, the American Radiology College (ACR) released the CEUS-based Liver Imaging Reporting and Data System (CEUS-Li-RADS). At the same time, according to the perfusion methods in the arterial, portal and venous phases, the CEUS-Li-RADS angiographic findings were classified into main features and LR-M features by ACR Association. The former included high enhancement in arterial phase and mild clearance in portal vein phase (after 60S) or delayed phase. The latter includes annular high enhancement, early clearance and complete clearance. In the classification, CEUS Li-RADS was classified into the following categories according to the possibility of HCC diagnosis with different characteristics of CEUS: LR-1 (definitely benign), LR-2 (possibly benign),LR-3 (possibly HCC), LR-4 (highly suspected HCC), LR-5 (confirmed HCC), and LR-M (liver malignant lesion, not specifically HCC).~In January 2018, Professor Bruix, Chairman of AASLD, wrote in the journal Heaptology that a qualified LIRADS classification should meet the following requirements :(1) LIRADS classification should focus on high-risk groups for HCC; (2) In LI-RADS classification, the specificity of LR-5 in the diagnosis of HCC should be close to 100%; (3) There is a good consistency between the main evaluation criteria of LI-RADS classification, LR-M evaluation criteria and the readers of final classification.~Currently, there are few studies on the diagnostic ability of CEUS-LI-RADS in patients with non-high risk factors for liver nodules. Whether this classification is applicable to such patients remains controversial. There are relatively few studies on the diagnostic efficacy of HCC in clinical diagnosis and the consistency between map readers, and the applicable population is only focused on patients with hepatic fibrosis. Therefore, this study explored the application value of CEUS Li-RADS in liver focal lesions in patients with non-high risk factors for hepatocellular carcinoma.
Currently, there are few studies on the diagnostic ability of CEUS-LI-RADS in patients with non-high risk factors for liver nodules. Whether this classification is applicable to such patients remains controversial. There are relatively few studies on the diagnostic efficacy of HCC in clinical diagnosis and the consistency between map readers, and the applicable population is only focused on patients with hepatic fibrosis. Therefore, this study explored the application value of CEUS Li-RADS in liver focal lesions in patients with non-high risk factors for hepatocellular carcinoma.