A CT scan of the liver reveals “occupying lesions”, which are mostly small, slightly enlarged nodules. To determine the nature of the small nodules, enhanced CT is required, which is an injection of contrast to distinguish nodular lesions. Carcinoma nodules can either be aggregated from primitive hepatocytes or develop gradually from sclerotic nodules. In the malignant change of liver cells, at the same time the blood vessels in the nodules are transformed. Non-cancerous liver tissue is supplied with blood by the portal vein and accompanying small arteries. In nodal carcinoma, the normal portal vein and small arteries gradually decrease until these vessels disappear completely; at the same time, newly formed small arteries that travel alone replace the entire blood supply to perfuse the tumor. The identification of hepatocellular carcinoma by imaging is mainly based on the vascular architecture of the nodule. The newly occurring vessels in the carcinoma nodule are all small arteries, which are not only increased in number but also abnormal in morphology. The contrast agents injected into the vessels are all in the arteries first, and enhanced CT has already illuminated many sheets in the arterial phase to the venous phase within a short period of time when the patient holds his breath. If a nodule is enhanced in the arterial phase due to contrast, but not in the venous phase due to the absence of contrast, the diagnosis of liver cancer is confirmed by the so-called “fast in and fast out”. Magnetic resonance imaging (MRI) can be multi-directional and can be more accurate in showing intrahepatic vascular structures and liver lobe segmentation. Blood vessels and bile ducts can be visualized without contrast. It is more sensitive and specific for tumor detection and identification than enhanced CT. Enhanced MRI is mainly used for the differential diagnosis of atypical nodules.