Liver cancer is one of the highly prevalent tumors in China, and more than half of the liver cancers in the world occur in China, so early detection, early diagnosis and early treatment are very important. With the development of imaging, the diagnosis and treatment of liver cancer has been greatly changed. Imaging not only plays a crucial role in detecting, characterizing and localizing liver cancer before treatment. It also provides technical guarantee for minimally invasive treatment of hepatocellular carcinoma. The most common imaging examinations in clinical practice include ultrasound, CT and magnetic resonance imaging (MRI). Do you know what is the difference between these three? For liver cancer, when should these examinations be done? We will talk about the differences of these three today. First of all, we should know that whether it is ultrasound, CT or MRI, for liver cancer, the examination area is the abdomen. 1. Ultrasound – it is the most common examination means for liver cancer and is often used in the screening stage of liver cancer. It can significantly improve the early diagnosis rate of liver cancer through regular examination of high-risk people. The advantages of ultrasound are: it is non-invasive, non-radioactive, inexpensive and easy to repeat. disadvantages of ultrasound: there are blind areas that are difficult to detect by ultrasound, and it is largely affected by the knowledge, experience and operating skills of the operator. The clarity of the image is also the lowest among these three examinations. 2.CT–with higher resolution, it is suitable for the localization and qualitative diagnosis of liver cancer. The detection rate of small hepatocellular carcinoma of 1~3cm can reach 90%. Nowadays, it has become a routine test for liver cancer diagnosis and follow-up. Enhanced CT is commonly used for liver cancer patients, and its advantages are: it can clarify the nature of the lesion, as well as the location, number, size of the lesion and its relationship with adjacent organs and important blood vessels. For example, whether there are cancer foci in the perihepatic tissues, whether there is cancer thrombosis in the surrounding blood vessels, the degree of cirrhosis, etc. It can also clarify the treatment target and ablation range for radiofrequency ablation treatment of liver cancer. Disadvantages: Although CT provides more comprehensive information, it is difficult to display liver cancer smaller than 1cm or with density similar to normal liver parenchyma; it is also radioactive to a certain extent; there is also the problem of contrast allergy when doing enhanced CT. 3.Magnetic resonance imaging (MRI)–with high soft tissue resolution–is an important tool for diagnosis and differentiation of liver diseases. It is more accurate for spatial localization of lesions by imaging in three directions: cross-sectional, coronal and sagittal. Advantages: MRI has a greater sensitivity for small and microscopic liver cancers that are difficult to detect with CT. MRI is generally able to clearly show the intrahepatic vessels and bile ducts without enhancement, which is helpful for understanding the relationship between tumors and intrahepatic vessels and bile ducts. Disadvantages: MRI is slower than CT; the cost is relatively high, and metal has a great impact on MRI. Patients with metal in their bodies, such as pacemakers and other metal foreign bodies in their bodies, should not undergo this examination to avoid harm. Each of the three examination methods has its own advantages and disadvantages. Choosing the suitable examination method in different periods of the disease can provide a reliable diagnosis, treatment and follow-up for liver cancer.