In the medical field endo scopes are used to enter the body along natural path ways. However, when there is no natural pathway, an incision is surgically created and a guiding tube called trocar or shaft is introduced. An endoscope is then inserted inside the body through the guiding tube. Incisions for receiving endoscopes are much less severe than openings required for open surgery. In the past when an endoscopic diagnostic was achieved and a surgical procedure deemed necessary, an open surgery was performed. Despite the open surgery, the endoscopic diagnostic preparing or evaluating the need of surgery was already an improvement regarding medical procedure and patient comfort.
For decades such endoscopes were used for diagnostic purposes only. These endoscopes were rigid or flexible endoscopes. Rigid endoscopes contain a lens system, and flexible endoscopes use glass fiber image bundles. The cross section of such endoscopes was divided between the illumination system and the imaging system only.
When optical performance of endoscopes improved significantly in the sixties and seventies, special endoscopes were made available to enable therapeutic procedures. These endoscopes have large rigid or flexible cylindrical tubes along the endoscope axis reserved solely for introducing instruments from the proximal side of the tubes into a patient's body through a distal end of the tube. Such instruments are large hand held mechanical instruments. Since the tubes are large, large incisions were needed. Larger incisions however result in a higher risk of infections and a longer healing process. Rarely incisions larger than for the use of 10 mm endoscopes are used. Now the cross section of an endoscope 10 mm or smaller in diameter had to be divided between the optical system containing illumination and imaging system and the instrument channel. So the introduction of such instrument channels in endoscopes reduces the cross section available for illumination fibers and imaging systems. Even with modern rod lens systems optical performance had to be compromised.
If the compromise on the optical performance for a specific application was too extreme, an endoscope without instrument channel was used and the instruments were inserted in the body through one or more additional incisions. Such additional incisions increase the risk of infection and extend the healing process. In rigid and flexible endoscopes for decades operating scopes with one or more channels for instruments or irrigation were compromises between a large channel cross section for robust instruments, strong flow of fluid or a powerful imaging system.
Since the nineties so-called video endoscopes came on the market. In video endoscopes the video chip is situated together with an objective system at the tip of the endoscope. Such combinations are used in rigid endoscopes and flexible endoscopes. Resolution of such chips has increased, signal processing improved and chips withstanding the high temperatures of the autoclave process were available.
Now more and more video endoscopes will replace rigid endoscopes with lens systems or flexible endoscopes with fiber image bundles. Such video endoscopes are having a compact unit at the tip. But along the length of the endoscope only a small portion of the cross section of the whole diameter is used for the electronic cables.