When the contrast agent flows into the arterial system of the body, the period of time when the contrast agent is circulating in the arterial system is called the arterial phase. Its clinical significance is to detect lesions that are mainly arterial blood supply, for example, hepatocellular liver cancer will show significant enhancement in the arterial phase, which is characterized as a blood-rich tumor with arterial blood supply as the main feature, and it will be very effective for the diagnosis and differential diagnosis of such diseases. In addition, the arterial phase often shows the best arterial vasculature in the human body and is the best for arterial vascular imaging. The arterial phase can make a good assessment of whether there are lesions in the arterial vessels, and the degree and extent of lesions, which is of great significance for clinical guidance.