Contrast-Enhanced Ultrasound (CEUS) of the Liver: Technique, Vascular Phases, Wash-out, and CEUS LI-RADS Algorithm
Clinical Significance of the Method
CEUS allows for the visualization of dynamic vascular events in real-time and serves as a problem-solving tool, especially in cases with conflicting or ambiguous data from cross-sectional imaging methods, as well as in patients for whom MRI or CT with contrast is contraindicated. Due to its ability to display hemodynamics in real-time, CEUS may surpass CT or MRI in assessing hepatic vascular processes.
Methodological Basics and Phases
The diagnosis of focal liver lesions with CEUS is based on determining the enhancement characteristics of the lesion in the arterial phase and wash-out kinetics relative to the surrounding liver parenchyma. The combination of these parameters is used to classify malignancy risk. Technical and lexicon recommendations for performing liver CEUS are outlined by the ACR CEUS LI-RADS working group (Lyshchik A. et al., Abdom Radiol, 2018).
When using a contrast agent specific to the reticuloendothelial system (RES), visualization of the delayed enhancement phase is possible, reflecting accumulation in stationary microbubbles phagocytized by the RES.
CEUS LI-RADS Algorithm
Diagnostic criteria for characterizing focal liver lesions on CEUS in patients with cirrhosis are incorporated into the Liver Imaging Reporting & Data System (LI-RADS) of the American College of Radiology (ACR). Standardization requires determining the enhancement of the lesion in the arterial phase and wash-out kinetics relative to the surrounding parenchyma to classify malignancy risk (Kim TK et al.; Lyshchik A et al.).
Regulatory Framework
The clinical practice of liver CEUS is regulated by the recommendations of WFUMB-EFSUMB (Claudon M. et al., 2013; Dietrich CF. et al., 2020), AIUM practice parameters (2024), and the ACR-AIUM-SPR-SRU practice parameter for abdominal ultrasound (2023). Specific numerical thresholds for arterial phase timing and wash-out in source fragments are not provided [clarify].
Frequently asked questions
What are the two key parameters determined in liver CEUS?
The enhancement characteristics of the lesion in the arterial phase and the wash-out kinetics relative to the surrounding liver parenchyma.
For which category of patients are the CEUS LI-RADS criteria developed?
Diagnostic criteria are incorporated into the ACR LI-RADS system for characterizing focal liver lesions in patients with cirrhosis.
When is CEUS particularly useful as a problem-solver?
In cases with conflicting or ambiguous data from cross-sectional methods, as well as when MRI or CT with contrast is contraindicated.
What does the use of an RES-specific contrast agent provide?
It allows for the visualization of the delayed enhancement phase from stationary microbubbles phagocytized by the reticuloendothelial system.
What are the exact time intervals for phases and wash-out thresholds?
Specific numerical values are not provided in the given fragments [clarify]; reference to the full texts of WFUMB-EFSUMB and ACR CEUS LI-RADS recommendations is necessary.