Contrast-Enhanced EUS

Abstract

Endoscopic ultrasonography (EUS) is more accurate than other imaging methods in terms of detecting and staging pancreatic masses. However, for characterizing undetermined pancreatic masses, contrast-enhanced EUS that employs Doppler mode or contrast harmonic mode is better than conventional EUS. Three typical contrast-enhanced EUS enhancement patterns associate with specific types of pancreatic lesions: Ductal carcinomas, inflammatory pseudotumors, and neuroendocrine tumors in the pancreas characteristically exhibit hypoenhancement, iso-enhancement, and hyperenhancement, respectively. Contrast-enhanced EUS differentiates ductal carcinomas from other diseases with a sensitivity and specificity of 94 % and 89 %, respectively. Contrast-enhanced EUS is also useful for T- and N-staging of pancreatic carcinomas. Recently, contrast-enhanced harmonic EUS was developed as a result of the production of second-generation ultrasound contrast agents and the specific mode for contrast harmonic imaging. Unlike contrast-enhanced Doppler EUS, contrast-enhanced harmonic EUS depicts signals from microbubbles in very slow flow without Doppler-related artifacts. Thus, it can depict the microcirculation and parenchymal perfusion in the pancreas. Quantitative analyses with a time–intensity curve in contrast-enhanced EUS also aid the characterization of pancreatic masses. Contrast-enhanced harmonic EUS is as accurate as contrast-enhanced computed tomography (CT) and EUS-guided fine-needle aspiration (EUS-FNA) for diagnosing ductal carcinomas. In particular, contrast-enhanced harmonic EUS is useful for characterizing small lesions that cannot be identified by contrast-enhanced CT. It also complements EUS-FNA by identifying lesions with EUS-FNA false-negative findings and by depicting the target of EUS-FNA. In the future, contrast-enhanced EUS technology is likely to be used to evaluate treatment response, to perform molecular imaging, and to provide local therapy.