What is the first phase of hepatic contrast enhancement?

The first phase of hepatic contrast enhancement is the arterial phase. This phase occurs shortly after the administration of contrast material when the contrast begins to enhance the hepatic arteries. During the arterial phase, the contrast fills the arteries and the hypervascular areas of the liver become well-visualized, making this phase critical for evaluating liver lesions that are supplied by arterial blood flow.

In this phase, the timing is crucial as the enhancement helps differentiate between various types of liver lesions, such as hepatocellular carcinoma, which typically show rapid enhancement due to their arterial supply. Understanding the dynamics of blood flow in the liver and how contrast agents behave during these phases is fundamental for accurate imaging interpretation and diagnosis.

Other phases like the portal phase and delayed phase come after the arterial phase and are used to evaluate different aspects of liver pathology, but they do not represent the initial contrast enhancement of liver structures. Therefore, recognizing the significance of the arterial phase is essential for effective CT evaluation of the liver.