What is endoscopic ultrasound

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. Working principle of endoscopic ultrasound
Endoscopic ultrasound is a medical device that combines endoscopic and ultrasound imaging technology. Its working principle is to introduce ultrasonic waves into the human body cavity by building an ultrasonic probe at the end of the endoscope, and form an image of the tissue structure through the reflection and echo of the ultrasonic waves. Compared with traditional ultrasound imaging, endoscopic ultrasound can directly place the probe on the surface of the organ or tissue of interest to achieve more precise and intuitive imaging results.

2. Application fields of endoscopic ultrasound
Endoscopic ultrasound is mainly used for endoscopic examination in many fields such as the digestive system, respiratory system and urinary system. In the digestive system, endoscopic ultrasound can be used for diagnosis and treatment monitoring of gastrointestinal diseases, such as gastrointestinal tumors, ulcers, and inflammation. In the respiratory system, endoscopic ultrasound can be used to examine bronchial and pulmonary lesions, such as bronchial cancer and pulmonary nodules. In the urinary system, endoscopic ultrasound can be used for the diagnosis and treatment of bladder and prostate diseases, such as bladder cancer and prostatic hyperplasia.

3. 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.

4. 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 and delivered to the target tube in the body. The reflected ultrasonic wave reaches the ultrasonic transducer through the rotating reflector, and then is 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 rate of endoscopic ultrasonography in determining the depth of invasion of esophageal cancer before surgery is 58% - 85%, and that of gastric cancer is 80% - 85%. The accuracy rate of diagnosis 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, currently endoscopic ultrasound still has the following shortcomings that need to be improved:

① Compared with ordinary fiber endoscopes, the field of view is narrow and observation is laborious;
②The mirror body is thick, with an outer diameter of 13mm and a hard front end of 4.2cm. The patient will experience some pain during the examination;
③The inspection must be carried out along the direction of the digestive tract, which limits the range of activities of the ultrasound probe, and cannot scan in two mutually perpendicular sections. Therefore, endoscopic ultrasound cannot completely replace general fiber endoscopy and in vitro "B" ultrasound examination.

5. Advantages of endoscopic ultrasound
High-resolution imaging: Endoscopic ultrasound uses high-frequency ultrasound to achieve high-resolution imaging, showing clear tissue structure and lesion characteristics.

Real-time imaging: Endoscopic ultrasound has the characteristics of real-time imaging. Doctors can observe the intracavity conditions in real time during the examination, improving the accuracy and efficiency of diagnosis.

Non-invasive: Endoscopic ultrasound is a non-invasive examination method that does not require surgery or puncture, minimizing patient discomfort and risk of complications.

6. Future development trends
With the continuous advancement of ultrasound technology and the increasing demand for medical imaging diagnosis, endoscopic ultrasound will play an increasingly important role in future development. In the future, with the further maturity of ultrasound technology and the continuous updating of equipment, endoscopic ultrasound will achieve more accurate, faster and comprehensive imaging diagnosis, provide doctors with better diagnostic tools, and provide patients with better medical services.

In general, endoscopic ultrasound, as a cutting-edge tool in the field of medical imaging diagnosis, has the advantages of high-resolution imaging, real-time imaging, and non-invasiveness, and is widely used in endoscopic examinations in many fields such as the digestive system, respiratory system, and urinary system. examine. With the continuous advancement of technology and the continuous expansion of application scope, endoscopic ultrasound will play an increasingly important role in the field of medical imaging diagnosis and make greater contributions to the development and progress of medical imaging diagnosis.