Current consensus and guidelines of contrast enhanced ultrasound for the characterization of focal liver lesions

Abstract

The application of ultrasound contrast agents (UCAs) is considered essential when evaluating focal liver lesions (FLLs) using ultrasonography (US). Microbubble UCAs are easy to use and robust; their use poses no risk of nephrotoxicity and requires no ionizing radiation. The unique features of contrast enhanced US (CEUS) are not only noninvasiveness but also real-time assessing of liver perfusion throughout the vascular phases. The later feature has led to dramatic improvement in the diagnostic accuracy of US for detection and characterization of FLLs as well as the guidance to therapeutic procedures and evaluation of response to treatment. This article describes the current consensus and guidelines for the use of UCAs for the FLLs that are commonly encountered in US. After a brief description of the bases of different CEUS techniques, contrast-enhancement patterns of different types of benign and malignant FLLs and other clinical applications are described and discussed on the basis of our experience and the literature data.

Keywords: Contrast enhanced Ultrasonography (CEUS); Focal liver lesions (FLLs); Guidelines.

Figure 1

Contrast-enhanced ultrasonography (CEUS) (A) and dynamic liver computed tomography (CT) (B) findings of hemangioma according to the vascular enhancement phase. The enhancement patterns are similar in CEUS and CT, with peripheral nodular enhancement in the arterial phase and gradual filling of the entire mass with contrast agent as time passes.

Figure 2

CEUS (A) and magnetic resonance imaging (MRI) with Primovist® enhancement (B) findings for focal nodular hyperplasia (FNH) according to the vascular enhancement phase. CEUS shows that the feeding vessel presents with a spoke-wheel appearance with rapid centrifugal filling by the contrast agent as time passes. In MRI images the same lesion shows slightly low signal intensity at pre and T1, is isointense to slightly hyperintense at T2, and exhibits normal Primovist uptake in the 20-minute delayed image.

Figure 3

Typical enhancement patterns of hepatocellular carcinoma (HCC) in CEUS (A) and CT (B). Grayscale US scan showing a well-demarcated round mass with a heterogeneous hypoechoic density. CEUS scan in which the mass shows a hyperechoic density in the arterial phase. The mass shows wash out in the portal venous (PV) phase and a hypoechoic density in the late phase. The mass shows heterogeneous enhancement in the arterial phase on CT. The mass shows a slightly hypoechoic density in the PV phase and a delayed washout pattern. The arrow in each panel indicates the mass.

Figure 4

Small HCC in real-time CEUS (A) and CT (B). The mass shows an early enhancement pattern in the arterial phase on CEUS. The mass shows an early washout pattern in the PV phase and a delayed washout in the late phase. The small HCC does not show enhancement in arterial phase on CT. The mass shows an early washout pattern in PV phase and a continued washout pattern in delayed phase. The arrow in each panel indicates the mass.

Figure 5

Algorithm used to diagnose a liver mass.