Development Of A Convex Array Ultrasonic Transducer For Endoscopic Imaging

In recent years,malignant tumors have become one of the main health problems that threaten the health of the population in China,and the incidence and mortality rate of patients with malignant tumors have been rising.Among the incidence and mortality rates of the six major cancer patients in China,gastrointestinal tumors account for half of them,which is higher than the world average.The site of gastrointestinal tumors is relatively insidious and not easily detected,resulting in a low early diagnosis rate and a low survival rate within five years.Gastrointestinal tumor detection methods mainly include abdominal ultrasound（US）,computed tomography（CT）,pancreatic tube（POPS）and magnetic resonance imaging（MRI）,etc.Compared with these detection methods,ultrasound endoscopy（EUS）has the advantages of radiation-free,simple operation and high image resolution,and is widely used in the early detection of gastrointestinal tumors.At present,threedimensional real-time dynamic imaging is one of the key development directions of ultrasound technology,and the development of ultrasonic transducers for highperformance real-time three-dimensional imaging can provide strong help for the early diagnosis of gastrointestinal tumors.In this paper,a novel high-performance endoscopic convex surface array ultrasonic transducer is developed to provide a new method for the early diagnosis of gastrointestinal tumors.By analyzing the factors affecting the performance of ultrasonic transducers,a kind of ultrasonic transducers based on 1-3 piezoelectric composite materials is designed from the design structure,material selection,operating frequency and the size of array elements.The working frequency of the transducers is 8.5 MHz,and the array element size is 0.3 mm×0.3 mm.The number of elements is 484（22×22）.By establishing an equivalent model of the acoustic transmission line of the endoscopic convex surface array ultrasonic transducer,the thickness of the piezoelectric layer and the matching layer material is 0.17 mm and 0.047 mm,respectively.Using Piezo CAD and PZFlex software,the electrical and acoustic properties of ultrasonic transducers were simulated and designed,and the center frequency of the convex surface array ultrasonic transducer was 8.5 MHz,the-6 d B bandwidth was 76.3%,the impedance was 47.307 Ω,and the phase was-67.35°.The thickness and size of each layer of material are designed by establishing the equivalent model of acoustic transmission line for the ultrasonic transducer with convex array.Piezo CAD and PZFlex software were used to simulate the electrical and acoustic performance of ultrasonic transducer.The center frequency of the simulated ultrasonic transducer was 8.5 MHz,the bandwidth of-6 d B was 76.3%,the electrical impedance was 47.307 Ω,and the phase was-67.35°.The precision impedance analyzer and pulse transmitter were used to measure the electrical impedance characteristics and acoustic pulse return characteristics of the transducer,and the test results showed that the center frequency of the endoscopic convex surface array ultrasonic transducer was 8.3 MHz,the-6 d B bandwidth was 54.2%,the pulse echo amplitude was 70 m V,the resistive impedance value was 45 Ω,the resistive phase was-67°,and the impedance test and pulse echo reached the ultrasonic transducer design index.Ultrasound imaging of the body in a deionized water（ideal）environment works well.The results show that the endoscopic convex surface array ultrasonic transducer developed in this paper can achieve three-dimensional real-time ultrasound image acquisition with high sensitivity,high resolution and large imaging field of view for gastrointestinal tumors,which can provide strong help for the early diagnosis of gastrointestinal tumors.