The Study Of Design Method And Manufacture Of High Frequency IVUS Transducer

With the gradual improvement of people’s living standards,coronary heart disease has gradually become one of the main reasons threatening human health.In recent decades,X-ray coronary angiography has always been the gold standard for the evaluation of coronary artery disease,but because it only reflects the size of the lumen and not the nature of atheromatous plaque disease itself,it has great limitations in reasonably defining the treatment plan according to the shape and histological characteristics of atheromatous plaque.IVUS is a new diagnostic method combining non-invasive ultrasound imaging technology and invasive cardiac catheterization technology.Compared with traditional X-ray coronary angiography,IVUS can not only accurately measure the geometric size of the lumen and atheromatous plaque,but also more importantly,it can provide the general histological characteristics of atheromatous plaque.It is important in making a reasonable treatment plan,selecting the size of instrument correctly,evaluating the therapeutic effect and predicting the occurrence of restenosis.In order to improve the image quality of IVUS imaging system,it is necessary to improve the performance of IVUS transducer.Similar to the traditional ultrasonic transducer,IVUS ultrasonic transducer consists of piezoelectric material,matching layer and backing layer.The difference is that in order to adapt to the size of IVUS catheter,the size of IVUS ultrasonic transducer needs to be very small.This leads to the low amplitude of IVUS ultrasonic transducer.In order to improve the signal amplitude,new high-performance piezoelectric materials can be used to improve the electromechanical conversion efficiency.In addition,the amplitude of the signal can be increased by making the matching layer and the backing layer material matched with the acoustic impedance of piezoelectric materials to improve the transmission efficiency of ultrasonic energy.In order to achieve the above purpose,the traditional piezoelectric ceramic PZT-5H and high-performance piezoelectric single crystal PMN-PT are selected as the piezoelectric materials of IVUS transducer,a kind of epoxy mixed with silver powder is used as the matching layer,and its density and sound velocity are measured by Archimedes drainage method and pulse echo method respectively,and then its acoustic impedance is calculated to be about 5.7 Mrayl,which basically meets the requirements of matching layer acoustic impedance.The conventional E-solder 3022 is selected as the backing layer of IVUS transducer.PiezoCAD simulation software based on KLM equivalent circuit is used to obtain the piezoelectric material,matching layer and backing layer thickness of IVUS transducer with center frequency of 40 MHz.Then the PZFlex simulation software based on the finite element is used to simulate the sound field of the transducer.Finally,according to the simulation results,IVUS transducers with different piezoelectric materials,matching layer and backing layer are fabricated.IVUS transducers with center frequency of 40 MHz and bandwidth of more than 50%are successfully fabricated.