Gastrointestinal endoscopes are highly evolved and sophisticated flexible instruments with a broad range of diagnostic and therapeutic applications. The development of modern flexible gastrointestinal endoscopes followed the development of fiber optics and subsequently the charge-coupled device (CCD). At present, fiber-optic image guides have largely been replaced by CCD that transmits digital information, from the endoscope tip to a video processor for display. This signal is converted to a color image by one of two systems.
- Color CCD has a multicolor mosaic filter affixed to the surface of the CCD with illumination by a steady white light.
- RGB sequential imaging has a rotating multicolor wheel filter (red-green-blue) located between the light source and the light guide.
The standard magnification is 7* with a 20-inch monitor. Magnifyed endoscopes offer image magnification capabilities (70*-150*).The last several years we have seen major improvements in digestive endoscopes. This is mainly because of the enhanced quality of the charge-coupled device (CCD). Thanks to technological advances, CCDs, like in digital cameras, become progressively smaller while the number of pixels in the image increases. Applied to digestive endoscopy this has meant that:
- Small scopes specifically for nasal gastroscopy could be produced, with full endoscopic features and a 5-mm external diameter.
- Routine endoscopes have a higher resolution, and the advantages of high definition television (HDTV) can be exploited, which means higher resolution imaging and the full benefit of digital zoom.
A variety of endoscope models from several manufacturers are commercially available. While there are variations among endoscope manufacturers, there is general uniformity to endoscope design. Flexible endoscopes are composed of three sections: the control section, the insertion tube, and the connector section. Variables include insertion tube length, diameter, and stiffness; instrument channel size and number; and configuration of the distal end of the insertion tube. Instrument models are designed with forward-, side-, or oblique-viewing optics with different angle and focus of view. Insertion tube lengths range from 63 to 2800cm, with diameters ranging from 2.8 to 13.7 mm. Instrument channel diameters vary from 0.75 to 4.8mm. The endoscope tip contains an opening(s) to the accessories/suction channel; an air/water nozzle for air insufflation, positioned to wash the lens; light guide illumination system; objective lens system. Some models include a separate lavage port. Procedure-specific endoscopes are designed to enhance endoscopic diagnosis and therapy. Dedicated ERCP and EUS scopes have use-specific modifications at the distal tip. Specialty components may include such things as variable stiffness and video magnification controls. Efforts are underway to develop optical biopsy techniques that would allow accurate and reliable tissue discrimination without the need for tissue sampling. Examples include light immunofluoresence spectroscopy, optical coherence tomography, and narrow-band imaging. The use of optical filters is important for mucosal analysis and for detection of the superficial vascular network. Numerous papers have been published on the benefits of NBI, which has been developed by Olympus. Fujinon is also developing a new method of digital signal analysis and treatment called FICE (Fuji Intelligent Chromo Endoscopy). There are two techniques with potential for optical biopsy: confocal microscopy, developed by Pentax and endocystoscopy, based on optical methods, developed by Olympus.
However, digestive endoscopy is still the major tool for all image analysis of the digestive tract in spite of new technologies such as virtual colonoscopy.
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