The device used in medicine to directly observe the internal cavities of human organs is called an endoscope, or endoscope for short.
The English word "endoscopy" is "endoscopy", which originates from the Greek word. It is a combination of the letter "endo" (meaning inside) and the verb "skopein" (meaning to observe). Its original meaning is to peer into the deep cavities of the human body. a way. Since Bozzini in Germany pioneered the use of candlelight as a light source and a thin iron tube to peer into the urinary tract in 1805, medical endoscopy has developed rapidly, and the process can be roughly divided into four periods.
Early rigid endoscope (1805-1932)
As early as 1805, Bozzini of Germany first proposed the idea of endoscopy, using candlelight to see the inner lumen of the rectum and urinary tract through the endoscope. In 1826, Segales in France produced the cystoscope and esophagoscope. In 1853, Desormeaux in France used a kerosene lamp fueled by a mixture of alcohol and turpentine as a light source to observe the urethra, bladder, rectum, uterus and other organs. In 1868, Kussmaul of Germany made the first straight endoscope inspired by his performance of sword swallowing. It is made of a metal tube with a soft stopper at the tip, 1.3cm thick and 47cm long, and is illuminated by a Desormeaux lamp. Because the hard part is too long and the lighting is insufficient, the gastric cavity cannot be clearly seen. After Edison invented the electric light in 1880, electric lamps or small electric beads were used as the light source for endoscopes. In 1881, Mikulicz made a 65cm long, 14mm diameter rigid tube gastroscope with a 30-degree bend in the lower 1/3 of the gastroscope. A small bulb was installed at the tip and there was an air channel for gas injection. This idea makes endoscopy initially of practical value. However, this kind of rigid endoscope is not only very difficult to operate when examining the upper gastrointestinal tract with its curvature and changeable lumen, but also brings great pain and damage to the patient. In addition, the illumination of the external reflected light source of small electric beads or tungsten filaments is very low, so there are many blind spots in peeping.
Semi-flexible gastroscope (1932-1957)
In 1923, Wolf-Schindler developed the semiflexible lens gastroscope, which consists of a proximal rigid part and a distal flexible part, and is composed of 26 prism segments. Since most of the mirror body is bendable, the visible area of the gastric mucosa is greatly increased. Later, Henning and Eder-Hufford further made the rigid part of the Wolf-Schindler gastroscope thinner and increased the eyepiece magnification to facilitate observation. In 1941, Taylor installed a bending device on the operating part of the gastroscope, which allowed the end to be bent in both "upward" and "downward" directions, greatly reducing the blind area for observation. In 1948, Benedict installed the biopsy tube on the endoscope, further improving the performance of the gastroscope.
Regarding endoscopic imaging technology, as far back as 1939, Henning et al. successfully took color photos of the stomach for the first time. In 1950, Japan produced the first generation gastrocamera, which partially made up for the shortcomings of Schindler's semi-flexible gastroscope.
Fiberscope (after 1957)
1. Development history of fiber endoscopy
In 1957, Hirschowitz of the United States made the first fiberoptic gastroduodenal endoscope, which brought endoscopy into the development stage of fiber optic endoscopy.
Japan began to produce fiberoptic gastroscopes in 1963. A fiber beam was installed on the original intragastric camera to create an intragastric camera with a fiberscope. In addition, a biopsy tube was added to the fiber gastroscope, a curved structure at the end of the fiber gastroscope was added, and cold light technology with a light guide beam connected to an external strong light source was adopted, finally bringing the fiber gastroscope into a more practical stage. After the 1960s, Japanese and American scientists made various improvements to the initial fiberoptic gastroscopy, such as increasing the brightness of the field of view, expanding the field of view angle, increasing the multi-directional bending control capability of the distal end of the gastroscope, adding biopsy and treatment channels, etc.; at the same time, Forward-looking and strabismus-type endoscopes have been developed from the measuring gastroscope, allowing the esophagus, stomach, and duodenum to be seen in one endoscopic examination. In 1963, Overhoet first developed the fiberoptic colonoscope and applied it clinically. In 1968, Mccune was the first to successfully intubate the duodenal papilla through a fiberscope and perform retrograde cholangiopancreatography (ERCP). In recent years, the application of gastrointestinal endoscopy has evolved from a simple diagnostic function into the field of non-surgical treatment. Endoscopic high-frequency electrical resection of polyps, foreign body removal, esophageal variceal sclerotherapy, endoscopic duodenal papilla incision and stone removal, endoscopic bile duct internal and external drainage, esophageal stricture dilation, catheterization, and domestic Nd-YAG laser and microwave are used to treat digestive tract tumors, stop bleeding, and perform laparoscopic gallbladder resection. Not only abroad, but also gradually developed and applied in various parts of our country. In short, the application field of endoscopy, especially digestive endoscopy, has a broad world.
2. Optical principles of fiberscope
Total internal reflection: The fiber bundle that conducts the image forms the core part of the fiber endoscope, which is composed of tens of thousands of extremely fine glass fibers. Each fiber must be able to effectively transmit light from one end to the other without losing too much brightness, without changing its color, and without leaking light into adjacent fibers. These are the requirements for making fiberscope guide bundles. Foundation. In order to meet the above requirements, according to the "total reflection principle" of optics, the outside of all glass fibers (core fibers) used to make the fiber inner diameter must be covered with a layer of extremely thin glass fibers (coated fibers) with a lower refractive index. It is guaranteed that all light transmitted along the core fiber can undergo total internal emission.
In fact, there is a loss in light transmission within the fiber, which is mainly manifested in:
Fiber self-absorption: The longer the fiber, the longer the distance the light travels within the fiber, and the greater the light loss.
In fact, total reflection is not 100%. There is also a very small amount of refraction in each reflection. Light needs to be reflected tens of thousands of times when passing through a 1m-long fiber, so the very small amount of refraction in each reflection becomes considerable when it reaches the end of the fiber.
Loss at both ends of the fiber:
Optical fiber bundle: The transmission of a single fiber can only produce a light point. If you want to see an image, a large number of fibers must be bundled. In order to transmit an image to the other end to form the same image, each fiber needs to be in the same position at both ends. Fiber bundles made in this form are called "end-to-end" bundles. Only such "end-to-end" bundles can produce images, also called guide bundles. The thinner the imaging fiber, the thinner the coating, the greater the number of fibers in the imaging bundle, and the higher the resolution of the image formed (that is, the clearer the image). However, the thinner the fiber, the worse the light conductivity. The coating layer cannot be thinner than 1.5 μm due to limitations of craftsmanship and optical principles, and the number of fibers cannot be excessive due to limitations of the thickness of the lens body. The length and number of imaging tract fibers vary greatly depending on the endoscope model, size, and manufacturer. Generally, the number of fibers in the imaging tract is between 5000-4000. The diameter of the imaging beam is between 0.5-3mm, and the diameter of a single fiber is generally between 8-12 μm. The fiber bundle that transmits light is called a light guide. Since there is no need to transmit an image, the fibers do not need to be aligned end to end and can be arranged randomly. Since its resolution is not considered, the diameter of each fiber can be thicker to increase light conductivity. The general diameter of the light guide fiber bundle is 30μm.
3. Composition of fiberscope
Front end: On the cross section of the front end, you can see: ① the suction port and biopsy; ② the light guide mirror; ③ the objective lens surface; ④ the air/water ejection hole. Some fiber endoscopes have air and water ejection holes. divided. There is also a forceps lifter at the front of the side-viewing or strabismus-type fiberscope.
Mirror body: The mirror is a flexible tube, and its degree of bending varies with the purpose of the fiberscope. Generally, the gastroscope body is harder, and the front end of the colonoscope body is harder than the back end. The mirror body is made of steel mesh tubes and snake-shaped steel tubes. It contains guide beams, guide beams, biopsy and suction channels, air/water injection pipes and angle-controlling wires. It is wrapped with a polyurethane plastic tube, which has sealing and anti-corrosion functions to prevent the entry of water and gastric juice and acid corrosion.
Operation part: including eyepiece, focusing ring, suction valve, air/water injection valve, angle control knob, biopsy hole, etc.
Light guide connection part: The light guide connection part connects the light source and air pump of the fiber endoscope, and also connects the water bottle and suction pump.
4.Main accessories of fiberscope
Light source: There are many types of cold light sources for fiberoptic endoscopes, ranging from simple, low-energy halogen light sources to complex, high-current intensity xenon light sources. Large, more advanced light sources generally have automatic flash, which can automatically adjust the light in photography, television video and movie shooting.
Teaching scope: can be attached to the eyepiece for viewing by a second person. Due to the re-conduction of the guide beam, the brightness is greatly weakened, and the brightness that can be observed by both is only 20% of the original brightness.
Camera system:
Ordinary camera: It is connected to the eyepiece in the fiber, and can automatically expose and take pictures through the light source of the fiber endoscope. When the camera shutter is pressed, the following series of things happen automatically. The light shutter of the light source is closed, cutting off the light from the light source. The camera shutter is opened, the light shutter of the light source is opened, and the flash is triggered. At this time, it is located in the camera. The photocell starts to measure the light intensity of the mirror and feeds it back to the automatic exposure circuit in the light source. When the circuit determines that the exposure brightness of the photo is sufficient, it will stop flashing. After a short interval, the photo will be taken. The shutter of the camera is closed, the whole process takes 0.25 seconds, and then the light source returns to the normal light intensity during observation.
The instant imaging camera prints endoscopic photos in 90 seconds.
Movie camera: can provide high-quality materials for teaching.
Endoscopic television systems allow many people to watch simultaneously, and the images can also be transmitted on tape.
