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Comprehensive interpretation of endoscopy (Part 2)

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Update time : 2023-09-28 11:29:00
Electronic endoscopy was first created and used clinically in 1983 by the American Welch Allyn Company. The characteristic of the electronic endoscope is that it does not transmit images through prisms or optical fibers. Instead, it converts light energy into electrical energy through a CCD called a "mini camera" installed on the top of the endoscope, and then processes the image to displayed on the TV monitor. Therefore, the mechanism of electronic endoscopes transmitting images is completely different from that of traditional endoscopes. Through video processing, images can be processed in a series of ways and images can be stored and reproduced in various ways. Foreign scholars regard electronic endoscopes as It is the third milestone in the history of digestive system development.
1. Basic principles of electronic endoscopy
The basic concept of coupled solid device (couple charge device CCD). The basic structure of CCD is a light-sensitive silicon wafer. This silicon wafer is separated into mountain-like potential wells by insulators. When light signals of different intensities are irradiated to the CCD, Photon stimulation of the silicon chip can generate charges with corresponding energy and accumulate them in the potential well, and convert the optical signal into an electrical signal in a charge-coupled manner, and transmit it to the video processor to complete the transmission and regeneration of the image. Therefore, the angle of the conductive image can also be regarded as the pixel unit. The smaller the potential well, that is, the more pixels, the more accurate the image conduction will be.
The method of electronic endoscope color imaging: CCD can only sense the light and dark intensity of the light signal, and can only obtain black and white images. In order to obtain color images, color filters must be placed in the optical path. There are generally two ways:
Surface sequential method: Place a circular plate with 3 color filters attached between the light source and the light guide fiber. When the circular plate rotates, the three colors of red, green and blue light will illuminate the object sequentially. object. The three color signals of red, green, and blue generated by the CCD camera are also transmitted sequentially (with time differences) and stored in the video processor. The first and third generation products of Welch Aiiyn, Fujitsu and Olympus all adopt this colorization method.
Simultaneous method: Install an inlaid primary color or complementary color filter on the light-receiving surface of the CCD. When the signal emitted by the object illuminated by the white light source acts on the CCD, it is immediately converted into a color signal due to the action of the inlaid filter, and is transmitted and stored in memory. Entering the video processor, red, green, and blue color signals are transmitted simultaneously with no difference in time. The second-generation products of Toshiba and Olympus all use this colorization method. The characteristic of the surface sequential method is that the number of pixels of each of the three primary colors of red, green, and blue is equal to the number of pixels of the CCD. For example, it is generally 30,000, and the pixels of the three primary colors of red, yellow, and blue are also 30,000. At the same time, the number of pixels of the three primary colors or complementary colors of the method is also 30,000 decibels respectively. The number of pixels of the three primary colors or complementary colors in the simultaneous mode is related to the number of corresponding color filters of the mosaic color filter. The resolution of electronic endoscopes is related to the number of pixels. The more pixels, the better the image quality. Therefore, if the number of CCD pixels is the same, the resolution of the surface sequential method is better than that of the simultaneous method. However, the disadvantage of the surface sequential method is that there is a time difference in the transmission of the three color signals of red, yellow, and blue, which may cause image blur.
Video processor: Mainly has the following two functions: ① Provide split color light source for red, yellow, and blue surface sequential electronic endoscope; ② Convert the analog signal provided by the CCD of the electronic endoscope into a binary code signal. Once converted, Images can be stored on video tapes, computer hard drives, laser disks, or copied, printed, etc. When necessary, the image can be regenerated and compared with images from the past or future. In addition, the video processor can be equipped with a printer, which can print and store data related to the patient and condition.
Electronic endoscope: Except for the fact that it does not have an eyepiece for observation, the other mechanical structures of the electronic endoscope - air and water supply system, live picking channel, angle button, etc. are exactly the same as the optical endoscope. The replacement part of the eyepiece varies from factory to factory. Welch Allyn's product replaces it with a biopsy hole, and Olympus's product replaces it with a control knob for agglutination images, or photographic images.
2. Performance comparison between electronic endoscopes and optical endoscopes
  Observation method: The operating part of the optical endoscope is equipped with an eyepiece. The operator must observe the image through the eyepiece. Although a TV camera can be connected to the eyepiece part and the image is displayed on the fluorescent screen through the TV system, the image is far less clear than that of the electronic endoscope. . Electronic endoscopy uses a high-performance TV monitor to display clear and undistorted color images, which can be viewed by multiple people at the same time, which is conducive to teaching and consultation. It is conducive to the communication between assistants and operators during various endoscopic treatments. work close with. In addition, because the surgeon uses both eyes to view the clear images on the high-performance monitor, it can avoid the visual fatigue caused by the monocular observation eyepiece and the adverse effects on the eyes caused by long-term strong light stimulation.
Insertion performance: The quality of insertion performance is related to factors such as the shape, thickness, softness of the endoscope, and the length of the hard part at the top of the endoscope. The top device of the electronic endoscope has a size of 3, which occupies a certain volume. The size of the 3 must be reduced, otherwise the length of the hard part at the top of the endoscope will be increased and the insertion performance of the electronic endoscope will be reduced. In the early products, the hard part at the top of the endoscope was too long, and the insertion performance was not as good as similar models of optical endoscopes. However, new products in recent years have overcome the above shortcomings, and their insertion performance is exactly the same as that of similar models of optical endoscopes.
Optical properties
Viewing angle: In early products, the viewing angle was relatively small, ranging from 75° to 105°. In recent products, the viewing angle has been expanded to 120°, and the depth of field range is 3-100mm, which has exactly the same optical performance as similar optical gastroscopes.
Reproducibility of color tone: The factors that affect the pigment of the fiber endoscope image are the objective lens, optical fiber and eyepiece. Among them, the hanging optical fiber has the greatest influence. An optical fiber with a length of more than 1m may absorb light of a certain wavelength and affect the internal image. tone. The factors that affect electronic endoscopes are the characteristics of CCD, video processor and monitor. Compared with optical endoscopes, the factors that affect electronic endoscopes are more and complex. Kenzo Mitsuzane once used a TV color analyzer and various color standards to measure the color tone reproducibility of the Olympus GIF-Q100 electronic endoscope and the GIF-Q10 optical endoscope. The measurement results showed that the color tone reproducibility of the electronic endoscope was excellent. in optical endoscopy.
Diagnostic ability for microscopic lesions: Tatsuo Katsube conducted optical endoscopy and electronic endoscopy on 45 patients with various gastric diseases before surgery, and compared the examination results with surgical pathology. He concluded that electronic gastroscopy can detect microscopic lesions. The diagnostic ability of lesions is better than that of optical endoscopy. It is easier for him to identify the exposed blood vessels of gastric ulcer bleeding and the characteristics of the surrounding regenerated epithelium, and it is easier to make a differential diagnosis between flat and raised atypical epithelium and type IIa early gastric cancer. In addition, because the image of electronic endoscopy is clear and has a certain magnification effect, it can display subtle color changes and other character changes on the mucosal surface, thus improving the detection of micro-type II b and II c early gastric cancer to a certain extent. Rate. Satake Yiji believes that electronic colonoscopy has improved the detection rate of small colon polyps (diameter <0.5cm>).
Performance of saving images: Optical endoscopes can only record and save the images transmitted by optical fibers through photography. The method is monotonous and the images are not clear enough. Because electronic endoscopes use CCDs to convert optical signals into electrical signals, images can be recorded and saved in a variety of ways after being processed by a video processor. ①Use a tape video recorder to record the clear image of the electronic endoscope and save the dynamic image; ②After "freezing" the electronically constructed image, use a 35mm camera to record the still image; ③Use the laser disc to record both dynamic images and It can record incoming images, and the maximum recording capacity of still images is 24,000 frames; ④ It can record 50 frames of still images using soft plastic disks. The electronic endoscope can also be connected to an electronic computer, and the patient's name, gender, age, main symptoms, diagnosis results and other clinical data and various recorded images can be input into the computer. When it is necessary to follow up the patient or conduct statistics on a large number of cases, When researching, you can search for various information at any time.
Durability: Fiberoptic endoscopes have tens of thousands of fine glass fibers that transmit images. As the number of uses increases, the glass fiber will gradually break, and the black electricity in the field of vision will gradually increase, making it dim and unclear. Electronic endoscopes are guided by CCDs and do not have the defects of glass fiber ends and being easily damaged by X-rays. Therefore, the durability of electronic endoscopes is due to optical fiber endoscopes.
3. The future of electronic endoscopy
Electronic endoscopy uses CCD to convert light signals into electrical signals. Therefore, it is possible to perform image processing through an electronic computer to selectively enhance or weaken the structural information of color information, making it easier for the observer to diagnose the presence of human lesions. and qualitative diagnosis. The image processing methods currently under research and development are as follows:
Differential processing and other methods enhance the morphological contour of the image: the image is composed of components of various frequencies - high-frequency components that represent the sharp changes and fine parts of the image, low-frequency components that represent the slow changes and rough parts of the image, and the average value of the entire picture. DC component. High-frequency components are enhanced through differential processing to make the contours of the image more prominent.
Enhance or weaken a certain tone in RGB to make the lesion more prominent and easier to spot.
Enhanced grayscale contrast of RGB signals can make the boundaries, mucosal spots, redness, and submucosal veins of type IIb early gastric cancer lesions more clearly visible.
Electronic computers quantitatively measure image structure (convexo-concave) information and color information, which is helpful to provide objective basis for diagnosis and changes of lesions.
In addition, electronic endoscopy to measure the temperature and blood flow of the digestive tract mucosa is also being developed and studied.
Although electronic endoscopes have the above advantages compared with ordinary optical endoscopes, and there is still considerable room for development in image processing, they are currently quite expensive. General medical units are still equipped with optical fiber endoscopes for diagnosis and treatment. Economical use.
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