The difference in the capability of delineation between convex and radial arrayed echoendoscope for pancreas and biliary tract; case reports from the standpoint of both convex and radial arrayed echoendoscope.

Endoscopic ultrasound (EUS) is useful in obtaining not only high-resolution images of organs and surrounding tissue but also the tissue itself for histopathological diagnosis using fine needle aspiration. Currently, there are two types of EUS available for use: radial and convex arrayed EUS. Each type of EUS has its own advantages and disadvantages. Because radial arrayed EUS can obtain 360 degree images, it is easy to see surrounding organs and vessels. In addition, a single longitudinal image of the pancreas, gallbladder and bile duct is easy to obtain. For this reason, radial arrayed EUS is highly effective in diagnostic examinations. In contrast, while scanning range of convex arrayed EUS limited to 180 degrees, it has the advantage of being able to obtain tissue samples. Additionally while using convex arrayed EUS, the upper part of the bile duct and neck of the pancreas are easily seen beyond the portal vein. It is important to understand the characteristics of each EUS in order to select the most suitable EUS technique for diagnostic assessment.