Design And Development Of High-resolution Digestive Tract Ultrasound Endoscope

Endoscopic ultrasound is an important imaging approach in disease diagnosis, guiding intervention, and cancer staging of the gastrointestinal tract and nearby organs, such as the pancreas, bile ducts, and gallbladder. Gastrointestinal lesions on the surface of the wall can be observed through the electronic endoscope, and the histologic features of organs' each faults can be gotten by high frequency ultrasonic scanning. EUS expands the diagnosis range and capacity of common endoscopic, and also plays an important role in diseases diagnosis such as esophagus cancer, gastric cancer and pancreatic cancer. So far, it is the best method to diagnose the lesions of internal organs in human body. And, Endoscopic ultrasound guided fine needle aspiration can direct a needle under real-time endosonographic guidance into a target lesion or structure, the EUS-FNA needle is used as a conduit to aspirate, inject, or gain access into a structure.We have developed an integrated convex ultrasound endoscope for digestive tract imaging. For these feasibility prototypes, the whole design process was divided into two parts: the high-definition auto-focus camera module, and the high-frequency curvilinear ultrasound transducer. An auto-focusing 5 megapixel CMOS camera provided a 75-degree field of vision. A novel voice coil motor for lens focus adjustments was used to improve the image quality of the endoscope, The VCM offers a focusing position adjustment of ±200 ?m and a tilt angle adjustment of ±5 deg along both the yaw and pitch directions. This camera is capable of not only changing the focus position of the lens, but also adjusting the tilt angle of the lens to extend the depth of field. With this new technology, the imaging capability of the endoscope has been improved. A curvilinear ultrasound transducer was designed and integrated based on PZT-5H ceramic, which leaned and faced one side, provided a 180-degree scanning ultrasound view. The external diameter of the endoscope probe was 11 mm. The measured results of the ultrasonic array transducer showed that the array transducer had a center frequency of 8.09 MHz and a-6 dB fractional bandwidth of 83%, respectively. A two-way insertion loss of-40.59 dB was obtained after compensation at the center frequency. A cross-talk of less than-38 dB was achieved for the adjacent elements at the center frequency. The imaging capability of the transducer was evaluated by acquiring the B-mode images of a wire phantom. The lateral and axial resolutions were measured to be 532 ?m and 197 ?m, respectively. The results show a satisfactory performance and demonstrate that the integrated convex ultrasound endoscope is well suited for digestive tract imaging application. At last, an anthropomorphic phantom of the oesophagus suitable for use with EUS was designed and constructed. The phantom was constructed by using agar-based tissue-mimicking material of different acoustical properties to simulate various anatomical and pathologic features. Then, the EUS was used to scan the phantom. The result showed that it can clearly distinguish each layer of esophagus and surrounding vessels, aorta, lymph node and cyst.