Abstract
Motivated by the fact that dark and indistinct endoscopic ultrasonoraphy (EUS) images are usually observed even if the region of interest (ROI) is situated on focal distances, we studied the influence of the angle between the center axis of the EUS and the surface of ROI (angle φ) upon the observed images. In order to investigate the influence of the angle φ, the phantom simulation and the experiment on the resected specimen were performed. In these simulations, the darkness and the indistinctness of EUS images were found to be caused by the angle φ. The results of experiments showed that the optimal angle, which yields distinct images, was within 15 degrees. We consider that the angle φ plays an important role in observing distinct EUS images. Proper adjustments are, therefore, necessary in the observation of tissue by using EUS.
