The most widely used and reliable endosonography instruments are the Olympus GF-EUM imaging units. The scope is 130cm in length and can be passed into the last part of the duodenum. This instrument is dedicated solely to EUS and cannot be interfaced with other conventional ultrasound consoles. Because the GF-EUM echoendoscope has a rigid tip 4.2 cm in length, expertise and experience is necessary to pass the echoendoscope safely. Endoscopic maneuverability is more difficult than with standard endoscopes. The oblique viewing optics make endoscopy with the echoendoscope similar to that with a side viewing endoscope.

The large, 12.6mm diameter of the echoendoscope shaft restricts passage through a significant number of strictures, narrowed areas. While a prototype endoscopic echoprobe, which can pass through many strictured areas, can be inserted through the 3.5mm biopsy channel of a standard therapeutic endoscope, the very small acoustic field of view and limited penetration of their 20MHz or even 12MHz sound wave frequency limits the accuracy and utility of this probe compared with the standard echoendoscopes. Balloons are being developed to improve the images, but their reliability is still being tested.

Biopsies of abnormal areas that are seen with EUS, but not with any other imaging methods, can now be performed with the state-of-the-art GF-UMC/30 AI Olympus system.

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