Contrast-enhanced ultrasound of focal liver masses

Abstract

Non-invasive imaging is the current method of choice for the characterization of frequently discovered focal liver disease. Although historically, contrast-enhanced computed tomography (CT) and magnetic resonance (MR) scans have been selected for this purpose, contrast-enhanced ultrasound (CEUS) now offers a less expensive and safer method to acquire the same information. Performed with the intravenous injection of a microbubble contrast agent, CEUS provides some unique advantages that make it a valuable addition to an imaging toolbox. CEUS is performed in dynamic real-time, providing superior temporal resolution compared to other modalities and allowing detection of enhancement regardless of its timing or duration. CEUS is performed with a purely intravascular contrast agent, providing accurate depiction of the presence of microbubbles in the circulation in all phases of imaging. This compares with CT and MR contrast agents, which have a well-recognized interstitial phase. Resulting discordant imaging may occur especially in the portal venous phase, when CT and MR may show pseudoenhancement from interstitial contrast, while CEUS will accurately show washout in malignant tumors. Lastly, the contrast specific software used to perform CEUS has an excellent subtraction technique, which produces a contrast only image with high sensitivity to enhancement in thin septations and small nodules. CEUS makes a positive contribution to liver mass characterization in any situation.