Design And Fabrication Of 360° Electronic Radial Ultrasound Endoscope For Digestive Tract Imaging

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.We have developed an integrated radial ultrasound endoscope for digestive tract imaging.For these feasibility prototypes,the whole design process was divided into two parts: the high-definition wide-angle camera module,and the high-frequency radial ultrasound transducer.A 5 megapixel CMOS camera provided a 128.3-degree field of vision.The medical wide-angle lens was used to improve the image quality of the endoscope.The camera module can not only achieve large field of view image,but also extend the depth of field.With this new technology,the paper with 8-font size words can be distinctly imaged with both large view and 3-18 mm depth of field in lumen short-range optical imaging.A radial ultrasound transducer was designed and integrated based on PZT-5H ceramic,which provided a 360-degree scanning ultrasound view.The external diameter of the endoscope probe was 9.58 mm.The measured results of the ultrasonic array transducer showed that the array transducer had a center frequency of 8.2 MHz and a-6 dB fractional bandwidth of 83%,respectively.A two-way insertion loss of 39.62 dB was obtained after compensation at the center frequency.A cross-talk of less than-36 dB was achieved for the adjacent elements at the center frequency.Annulus phantom can be distinctly imaged with the radial array,which demonstrates the high uniformity of kerf width among elements.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 695 ?m and 133 ?m,respectively.The results show a satisfactory performance and demonstrate that the integrated radial ultrasound endoscope is well suited for digestive tract imaging application.Porcine esophagus in vitro can be distinctly imaged with the radial ultrasound endoscope.Test results demonstrate that the proposed radial endoscope is able to offer good image resolution.