Characterisation of Benign Focal Liver Lesions with Contrast-Enhanced Ultrasound (CEUS)

Abstract

Conventional B-mode ultrasound (US) allows for the definite diagnosis of common typical liver cysts by differences in echogenicity in comparison to the surrounding liver tissue using the following criteria: round, non-echogenic, smooth surface, sharp borders, lateral shadowing, posterior echo enhancement. Conventional B-mode US also allows for the definite diagnosis of calcifications due to their typical appearance: echo-rich with acoustic shadows [1]. Other focal liver lesions (FLL) are characterised sonographically, not only by analysis of differences in echogenicity from the surrounding liver tissue, but also by the detection of hyperor hypovascularization (colour duplex US) and by changes occurring in inflow kinetics (enhancement) of contrast media. As a result of their double blood supply via both the portal vein and the hepatic artery, focal lesions in the liver often exhibit no sustained hyperor hypoperfusion, but depending on the perfusion phase and the histology, present with a complex spatio-temporal picture of increased and reduced contrast-enhancement. Certain lesions display a characteristic vascular picture (e.g., wheel-spoke phenomenon in FNH) or a distinctive perfusion pattern (e.g., iris diaphragm phenomenon in haemangioma), allowing the lesions to be characterised. Unfortunately, contrast-enhancement does not always exhibit such typical and unique patterns. Multiple reviews and guidelines, as well as multicentre trials have been recently published using contrast-enhancing techniques [2-7]. The following chapter focuses on benign liver tumours and nodules, summarized in Table 1. II.1