Ultrasound is often used as a screening test for HCC in patients with cirrhosis, and it is usually the first type of imaging to be performed in patients suspected of having a tumour. The procedure is relatively inexpensive; moreover it is non-invasive and is not associated with exposure to ionizing radiation. However, the technique is critically dependent on the expertise of the operator and while experienced operators may detect lesions as small as 0.5 cm many ultrasonographers can identify only much larger lesions. The smallest lesions are hypoechoic but they become hyperechoic with irregular margins as they enlarge. Attempts to improve the sensitivity and specificity of ultrasound have involved
intravenous contrast agents (microbubbles). These agents are currently being evaluated but, at present, they seem able to improve the diagnostic accuracy of inexperienced operators, although they may be of less value to experienced hepatic ultrasonographers.