Illumination is provided by an external source: - ANSeither by a xenon arc, or a halogen-filled
tungsten filament lamp.
Flexible scopes are designed to view - ANSthe lumen either in a front or side viewing manner.
The front viewing scope is most commonly used - ANSin endoscopic procedures.
The side viewing scope allows for - ANSoptimal evaluation of and access to certain lesions in
the stomach and the duodenum.
The side viewing scope is most commonly utilized - ANSwhen performing biliary and pancreatic
ductal imaging through the ampulla of Vater.
Fiber optic endoscopes are based on fiber optic light transmission technology. Light is conveyed
through - ANStwo bundles of fine glass fibers, each smaller than a human hair (8 to 10 µm in
diameter), packed tightly together in the shaft of the scope. One bundle of fibers carries light
into the examined organ, and a second bundle transmits the image from the organ to the
viewing optic. The latter bundle must have all the fibers arranged in a coherent bundle. This
method of bundling produces the image on the monitor in its correct orientation.
Each fiber is clad in a wrapping of higher optical density, creating a reflective layer that causes
light to bounce back and forth within the fiber. This configuration allows for minimal light loss.
Although the cladding does not transmit light, it does appear - ANSas a dark rim around the
portion of the image transmitted by the fiber, giving images seen through a fiber optic
endoscope a newsprint-like quality.
Fiber optic endoscopes are generally - ANSdirect-viewing, meaning the endoscopist looks
directly into an eyepiece. An optical beam splitter allows a second observer to view the image
through a separate eyepiece.
Fiber optic endoscopes are most often used - ANSwhen a small diameter is required such as in
bronchoscopy or choledochoscopy. They are no longer commonly used in standard GI
endoscopy.
Video endoscopy applies video technology to the endoscope. The video endoscope has
replaced many of the flexible fiber optic endoscopes - ANSbecause it brings significant
improvements in image quality and endoscope durability.
In a modern video system, light is transmitted to the tip of the endoscope through - ANSa fiber
optic bundle, similar to the direct-viewing fiber optic system described earlier. However, the
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