W56 AJR:205, July 2015 Doppler ultrasound [3–9]. Moreover, it is im- possible to characterize a focal liver lesion in the presence of underlining oncologic history of the patient or chronic liver disease and cir- rhosis because the aspect of a malignant lesion may be similar to a benign lesion. CEUS has improved the detection and characterization of focal liver lesions [10–16]. Technique and Protocol Before CEUS, a thorough conventional ul- trasound examination of the entire liver must be performed. The baseline study includes the assessment of the lesions on B-mode im- aging and by means of color Doppler ultra- sound together with the use of tissue har- monic imaging [17]. The currently used contrast agents (sec- ond-generation) are gas-filled (sulfur hexa- fluoride) microbubbles stabilized by a shell made by albumin, surfactants, or phospho- lipids. They are designed to be smaller than 7 μm (mean diameter, 2.5 μm) to circulate freely in the capillary beds, showing both macrovasculature and microvasculature, with no interstitial phase because they are exclusively intravascular. In CEUS, 2.4 mL (a much lower dose than with CT and MRI) of microbubble contrast agent is rapidly injected via an antecubital vein followed by a 5-mL saline flush. A suf- ficiently large needle (20-gauge minimum diameter) should be used to avoid causing bubble rupture. Contrast-Enhanced Ultrasound of Focal Liver Lesions Mirko D’Onofrio 1 Stefano Crosara Riccardo De Robertis Stefano Canestrini Roberto Pozzi Mucelli D’Onofrio M, Crosara S, De Robertis R, Canestrini S, Pozzi Mucelli R 1 All authors: Department of Radiology, G. B. Rossi Hospital, University of Verona, Piazzale L.A. Scuro 10, 37134 Verona, Italy. Address correspondence to M. D’Onofrio (mirko.donofrio@univr.it). Gastrointestinal Imaging • Review WEB This is a web exclusive article. AJR 2015; 205:W56–W66 0361–803X/15/2051–W56 © American Roentgen Ray Society C ontrast-enhanced ultrasound (CEUS) is an imaging method that has been used in European and Asian countries for more than 10 years. The use of ultrasound con- trast agents has been approved in several countries, but the Food and Drug Adminis- tration (FDA) in the United States has not yet approved their application for a noncar- diac use. The injection of microbubble con- trast agents improves the accuracy of ultra- sound study. The main liver application of CEUS is for focal liver lesions. Focal liver lesions are usually detected in- cidentally during an abdominal ultrasound ex- amination, during first evaluation or follow-up for a primary neoplasm, or during surveillance in chronic liver diseases and cirrhosis. In cases of incidental findings, focal liver lesions can be characterized by conventional B-mode and color Doppler ultrasound when a typical pat- tern is identified, as in the case of homoge- neously hyperechoic hemangiomas [1] or fo- cal nodular hyperplasia with a spoke-wheel shaped central vascular pattern on color Dop- pler ultrasound [2], but the accuracy of the fi- nal definitive diagnosis can be limited. In fact, even though color Doppler imaging during an ultrasound study of the liver can improve di- agnostic confidence in the characterization of focal liver lesions, it has important limita- tions because of limited sensitivity and spec- ificity because benign and malignant lesions may show similar appearance on B-mode and Keywords: contrast-enhanced ultrasound (CEUS), focal liver lesions, HCC, metastasis, microbubbles DOI:10.2214/AJR.14.14203 Received November 29, 2014; accepted after revision January 10, 2015. FOCUS ON: OBJECTIVE. The purpose of this article is to discuss the use of contrast-enhanced ultra- sound (CEUS) in focal liver lesions. CONCLUSION. Focal liver lesions are usually detected incidentally during abdominal ultrasound. The injection of microbubble ultrasound contrast agents improves the character- ization of focal liver lesions that are indeterminate on conventional ultrasound. The use of CEUS is recommended in official guidelines and suggested as a second diagnostic step after ultrasound detection of indeterminate focal liver lesions to immediately establish the diagno- sis, especially for benign liver lesions, such as hemangiomas, avoiding further and more ex- pensive examinations. D’Onofrio et al. CEUS of Focal Liver Lesions Gastrointestinal Imaging Review Downloaded from www.ajronline.org by Az. Osp. Univ. Integrata Verona on 08/24/15 from IP address 157.27.7.156. Copyright ARRS. For personal use only; all rights reserved