Contrast-enhanced harmonic ultrasonography with Sonazoid in pancreatic diseases

Background Contrast-enhanced ultrasonography by means of Levovist, a galactose-based ultrasound contrast agent that is infused intravenously has allowed the observation of the vasculature of the abdominal organs. Particularly, contrast harmonic imaging, which is the specific imaging mode for Levovist, can depict signals from microbubbles in very slow flow without Doppler-related artifacts and is used to characterize tumor vascularity in liver, pancreas, gallbladder, and gastrointestinal tract during transabdominal ultrasonography . The diagnosis of pancreatic diseases has sometimes been difficult even when combination of various imaging modalities such as ultrasonography, magnetic resonance imaging, endoscopic retrograde cholangiopancreatography (ERCP), endosonography (EUS) and contrast-enhanced computed tomography (CT) were employed. Among those imaging technologies, EUS has been widely used to diagnose pancreatic diseases, because it is superior to any other modality with respect to spatial resolution . Until recently, there was no contrast harmonic imaging technique available for EUS examination, because the transducer for current echoendoscopes is of a limited band frequency and too small to produce enough acoustic power for contrast harmonic imaging using Levovist. Second generation ultrasound contrast agents like Sonazoid produce harmonic signals at a low acoustic power, and are therefore suitable for EUS of low acoustic power. We have recently developed an echoendoscope with a wide-band transducer and a specific imaging mode for contrast-enhanced harmonic EUS. The echoendoscope has a wide-band transducer that can produce and detect harmonic signals from second generation contrast agents. In this lecture, usefulness of contrast-enhanced harmonic EUS (CEH-EUS) for depiction and differentiation of the pancreatic diseases are discussed.