Vascular phases in imaging and their role in focal liver lesions assessment

Abstract

The incidental finding of a liver lesion with basic ultrasound is one of the most common clinical issues. Some of the liver lesions which present typical morphological B-mode features (e.g. cysts, typically localized focal fatty sparing/accumulations, hyperechoic hemangiomas) can be easily diagnosed by conventional ultrasound without the need of further diagnostic procedures. Others frequently necessitate further investigation with contrast-enhanced imaging techniques or biopsy in order to differentiate benign from malignant lesions and obtain a final diagnosis. This paper will discuss differences between vascular phases of different cross-sectional contrast-enhanced methods, as well as their subsequent benefits for focal liver lesions (FLLs) assessment, adding also a particular emphasis on small FLLs detection and characterization.

Guidelines and Good Clinical Practice Recommendations for Contrast Enhanced Ultrasound (CEUS) in the Liver – Update 2020 – WFUMB in Cooperation with EFSUMB, AFSUMB, AIUM, and FLAUS

“…Atypical appearances, in particular LP hypoenhancement (UCA washout) or lack of centripetal fill-in, have been described and may be explained by the destruction of microbubbles that are not adequately replenished due to very long bubble transit times within the lesion [95]. Hemangiomas with arteriovenous shunts (also called high flow or shunt hemangiomas) show rapid homogeneous hyperenhancement in the AP and therefore can be confused with focal nodular hyperplasia (FNH), or even with hepatocellular adenomas (HCA) or HCCs [76].…”

Advantages and Limitations of Focal Liver Lesion Assessment with Ultrasound Contrast Agents: Comments on the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) Guidelines

“…UCAs perform as blood pool tracers and enhance the visualization of the parenchymal microvasculature with the best temporal resolution [ 6 ]. Even though technological advancements have led to time resolution values of 83 ms for dual-source CT [ 7 ] and of about 35 ms for MRI [ 8 , 9 ], the advantages of CEUS are due to the practically real-time examination and real-time assessment [ 10 ], allowing for a better visualization of enhancement patterns during all phases, without the need of specifically planned time acquisitions. The size of the microbubbles is fairly uniform between 1 and 4 μm.…”

“…The most commonly observed patterns of enhancement for benign and malignant FLLs are shown in table 1 as previously published [ 2 , 3 ]. Issues such as enhancement during the arterial phase, including onset, peripheral or central initial enhancement, homogeneity/heterogeneity of FLL enhancement, as well as presence or absence of portal-venous or late-phase washout should all be assessed, as these parameters are important for the differentiation between malignant and benign FLLs and for a further differential diagnosis [ 10 ]. Some examples are shown in figures 1 , 2 , 3 .…”

“…It is a reticuloendothelial system-specific agent which improves the detection of hepatic lesions with negligible reticuloendothelial cells such as liver metastases [ 30 , 31 ]. Recently, the use of gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA; Primovist® in Europe and Eovist® in the USA) further improved the detection and characterization of FLLs by CEMRI due to its progressive distribution within the hepatocytes during the so-called hepatobiliary phase [ 10 , 32 , 33 ].…”

Kontrastmittelsonografie zur Charakterisierung von Lebertumoren: Praktische Aspekte

“…Ultraschall und CEUS sind ubiquitär verfügbare schnittbildgebende Verfahren, portabel bettseitig einsetzbar und zeitlich deutlich höher auflösend als CT und MRT. Ein Vergleich der Methoden wurde kürzlich beschrieben [95,96]. Für eine gute Darstellung im CEUS gelten die gleichen Voraussetzungen wie für den normalen Ultraschall (Luft und Knochen sowie Adipositas sind ein Untersuchungshindernis; ein qualifizierter Untersucher ist für ein gutes Ergebnis erforderlich).…”