Endoscopic ultrasound places a micro-ultrasound probe at the top of the endoscope. When the endoscope is inserted into the digestive tract, the pathological changes on the mucosal surface can be directly observed through the endoscope. Ultrasound scanning can be performed to obtain the tissues at each level of the digestive tract closure. Blood characteristics and ultrasound images of surrounding important organs have expanded the diagnostic function and scope of endoscopy and improved the diagnostic ability of endoscopy. In addition, ultrasound scanning in the digestive tract can significantly shorten the distance between the ultrasound probe and the target organ, and avoid the influence and interference of abdominal wall fat, intestinal gas and skeletal system on ultrasound. Compared with the general extracorporeal "B" ultrasound, it can use a higher frequency ultrasound probe, which significantly improves the resolution, so that the lesions at the end of the common bile duct and the head of the pancreas located deep in the abdominal cavity can also be clearly displayed. Therefore, endoscopic ultrasound not only has the dual functions of endoscopy and ultrasound, but also makes up for the shortcomings of both and improves the diagnostic level of endoscopic and ultrasound.
1. Development of endoscopic ultrasound
Intracorporeal ultrasound examination was first used in rectal, gynecological and urological diseases. In 1957, Wild and Reid et al. rubbed a 10-15MHz ultrasound probe into the rectal cavity for ultrasound examination of rectal cancer. In 1968, Watanabe et al. carried out ultrasound examination of the prostate. In 1976, Franzin inserted a probe into the esophageal cavity to perform M-mode ultrasound examination of the heart. However, all of the above were attempts to insert ultrasound probes into shallower body cavities under indirect vision. It was not until 1980 that Dimagno and Green achieved success in animal testing for the first time using an electronic linear ultrasonic gastroscope that combined endoscopy and ultrasound. Since then, endoscopic ultrasound has been continuously improved. According to the relationship between the ultrasound scanning direction and the axis of the ultrasound endoscope, the ultrasound endoscope can basically be divided into two categories:
Line scanning endoscopic ultrasound perpendicular to the axis of the endoscope: It uses a set of transducers arranged perpendicular to the long axis of the endoscope to electronically trigger linear scanning.
Sector-type scanning ultrasonic endoscope with the axis of the endoscope perpendicular to the axis of the endoscope: it uses a DC television to drive and rotate the ultrasonic transducer or acoustic mirror located at the top of the mirror to obtain an ultrasonic scanning image perpendicular to the axis of the endoscope. Currently, The most widely used is sector scanning endoscopic ultrasound.
2. Basic functions of ultrasonic gastroscopy
The most widely used sector-type scanning ultrasonic gastroscope uses a DC motor located under the operating part to rotate and drive the reflector at the top of the endoscope at a speed of 10 times/second, so that the ultrasonic pulses are emitted perpendicularly to the mirror body, delivered to the target organ in the body, and reflected back The ultrasonic waves reach the ultrasonic transducer through the rotating reflector, and then are transmitted to the display device. The size of the ultrasonic frequency is inversely proportional to the penetration depth and directly proportional to the resolution. That is, the greater the ultrasonic frequency, the shallower the penetration depth, and the higher the resolution. After the ultrasonic gastroscope is placed into the digestive tract, the distance between the ultrasound probe and the target organ is shortened, and the requirements for the depth of ultrasound penetration are reduced. Therefore, it is possible to use higher frequencies than general extracorporeal ultrasound to obtain high-resolution images. Therefore, ultrasonic gastroscopy can objectively determine the depth of esophageal and gastric cancer infiltration into the wall and whether there are surrounding lymph nodes; it can also determine the origin of submucosal tumors and the nature of the lesions in the head of the pancreas and the end of the common bile duct. The accuracy of endoscopic ultrasonography in preoperative judgment of the depth of invasion of esophageal cancer is 58% - 85%, that of gastric cancer is 80% - 85%, that of gastric submucosal tumors is 96%, and that of pancreatic cancer and cholangiocarcinoma is 100% each.
In addition to endoscopic ultrasonography, ultrasonic colonoscopy and ultrasonic duodenoscopy have also been used clinically. However, the current endoscopic ultrasound still has the following shortcomings that need to be improved: ① Compared with general fiber endoscopes, the field of view is narrow and observation is laborious; ② The mirror body is thick, with an outer diameter of 13 mm, and a front rigid part of 4.2 cm. When the patient is examined, there is It must be painful; ③ The examination must be carried out along the direction of the digestive tract, which limits the range of activities of the ultrasound probe, and it cannot scan in two mutually perpendicular sections. Therefore, endoscopic ultrasound cannot completely replace general fiber endoscopy and in vitro "B" ultrasound examination.
Endoscopes can be divided into two types: rigid endoscopes and flexible endoscopes, also known as rigid endoscopes and flexible endoscopes.
Rigid endoscopes include three parts: image transmission, lighting, and stoma. The image transmission part is divided into objective lens, relay system and eyepiece to form the transmission image. The lighting part adopts the method of penetrating the cold light source into the interior with optical fiber. The function of the stomata is to supply air, water, and pass the biopsy forceps. Rigid endoscope products include hysteroscope, proctoscope, hysteroscope, thoracoscope, etc. Among them, they are widely used in laparoscopy. WOLF is the best in the rigid endoscope market. There are also many domestic rigid endoscopes, and the competition is fierce.
Endoscopes that use fiber beams to transmit images and guide light or use CCDs to transmit images become flexible endoscopes. Because of its good softness and convenient operation performance, it has been widely used in medicine. The current products include gastroscopy, duodenoscopy, colonoscopy, choledochoscopy, enteroscopy, bronchoscopy, nasopharyngoscope, ureteroscopy, etc.
The characteristics of flexible endoscopes are:
It is relatively soft and can easily enter the complex internal organs of the human body, which not only reduces the patient's pain, but also can reach places that rigid scopes cannot reach. Coupled with the head bending mechanism, blind spots can be eliminated. Samples and treatments can be taken through the biopsy hole.
Flexible endoscopes can be divided into fiber endoscopes and electronic endoscopes:
How to hold a flexible endoscope: Wear gloves and hold it with both hands. Hold the handle with one hand and the lens body with the other. Do not let the tip hang down and hold it steadily.
Fiber endoscope structure: tip part, bending part, insertion part, operating part, light guide hose, light guide connection part, eyepiece.
The tip is a small rigid section, and there are direct-viewing (front-viewing), side-viewing, and squinting types. Gastroscopy and colonoscopy use direct viewing, while duodenoesophagoscopy uses side viewing.
There are: objective lens hole (image guide beam), optical hole (light guide beam), air and water hole (nozzle), and biopsy hole on the tip.
The bending part uses four steel wire traction methods. The head has four steel wires connected to the control part. By twisting the up, down, left and right handwheels of the control part, the steel wires in different directions can be pulled respectively, making the bending head swing in the corresponding direction. There are guide beams, guide image beams, various pipes, traction devices, bending tubes, and bending rubber in the bending part.
The hose part includes a bending part and an insertion part, also called a snake tube. It is equipped with a guide beam, an image guide beam, a water and gas pipe, a biopsy pipe (also a suction pipe), a traction wire, and is wrapped with a stainless steel belt hose and a metal mesh tube. The outermost layer is a smooth plastic casing.
The fiber bundle that transmits the image forms the core part of the fiber endoscope. It is composed of tens of thousands of extremely fine glass fibers. According to the principle of total optical reflection, all glass fibers must be covered with a film with a lower refractive index. Ensure that all light transmitted by the inner core fiber can undergo total reflection. The transmission of a single fiber can only produce a point of light. If you want to see an image, you must bundle a large number of fibers. If you want to transmit the image to the other end to form the same image, you must make each fiber in its direction. The two ends are arranged in the same position and are called guide beams. If one guide beam is disconnected, there will be one more black spot in the image. The light guides do not need to be arranged in the same position. If many of them are disconnected, the brightness will be significantly reduced.
The complete set of fiber optics includes: cold light source, fiber optics, and TV system monitor (optional).
Electronic endoscopes use CCDs instead of guide beams to conduct image signals, which are then processed and converted into video signals by an image processing center. The CCD solid-state imaging device is called a CCD image sensor. Its structure is to arrange many photodiodes (pixels) on a silicon substrate, convert the imaging light on them into electrical signals, and then transmit them out to obtain image signals.
The structure of electronic endoscopes is basically the same as that of fiber endoscopes. It can be simply understood that CCD is used to replace the guide beam. Many functions are beyond the reach of fiber endoscopes.
The complete set of electronic endoscopy includes: cold light source, image processing center, monitor, electronic gastrointestinal endoscope, and cart.
The image of the electronic microscope is clear and easy to observe, and is suitable for endoscopy rooms in large and medium-sized hospitals. Fiber gastrointestinal endoscopy equipped with a TV system can also be observed through a monitor. The image quality is much worse than that of an electronic endoscope. It is mainly used by small and medium-sized hospitals.
The above is a comprehensive interpretation of endoscopy. If you have more information about endoscopy, you are welcome to contact us to communicate and discuss.
