Ultrasound and CT are both localization methods for liver cancer diagnosis, and each has its own advantages and disadvantages in terms of sensitivity and specificity of liver cancer diagnosis. Since the sensitivity of B-ultrasound and CT is not much different, but the cost of B-ultrasound is significantly lower than that of CT, B-ultrasound should be chosen for the initial examination of liver cancer, and CT can be further examined if the condition requires. 1.When the benignity and malignancy of liver occupying lesions are difficult to be determined by B-ultrasound, enhanced CT can be done to further determine its nature. 2.When preparing for surgical resection treatment, CT can be done to understand whether there is metastasis in the liver. 3.After surgery, follow-up is only done by B-ultrasound combined with methemoglobin examination, but CT examination can be done if B-ultrasound reveals recurrence or suspected recurrence. 4.After hepatic artery embolization chemotherapy for hepatocellular carcinoma, CT examination should be done to understand the filling of iodized oil in hepatocellular carcinoma, so as to guide the next treatment. 5.Sometimes, as a diagnostic method, CT examination is done 2-3 weeks after injecting a small amount of iodized oil via hepatic artery. This CT scan is called iodized oil CT, which can detect hepatocellular carcinoma with the diameter of 0.5cm.