| The morbidity and mortality of cardiovascular diseases reside the first in the world,which has brought a heavy burden to patients,their families as well as the entire society.A serious factor leading to cardiovascular disease is the abnormal structure of myocardial microcirculation.Therefore,the visualization of myocardial microcirculation plays a vital role in the diagnosis and treatment of cardiovascular diseases.At present,there is no clinical equipment for visualization of myocardial microcirculation structure.Ultrasound has been a research hotspot in the field of cardiovascular imaging because of its advantages of safety and noninvasive.Therefore,the development of ultrasound transducers for high-contrast and high-resolution imaging of myocardial microcirculation can help the diagnosis and treatment of cardiovascular diseases.with the problem of high contrast and high resolution imaging of myocardial microcirculation taken into consideration,this paper optimized the performance of the transducer from many aspects such as materials,structure,working frequency and process,and developed a novel focused dual-frequency(5MHz/30MHz)ultrasonic transducer,providing a new idea for the diagnosis and treatment of myocardial microvascular disease.Firstly,two kinds of focused dual-frequency ultrasonic transducers with different materials of the transmission layer were designed.Through the analysis of various factors that affect the performance of ultrasonic transducers,the optimal design of focused dual-frequency ultrasonic transducers was carried out from many aspects such as working frequency,structure,piezoelectric material,and the material of acoustic filter layers.Then,two kinds of focused dual-frequency ultrasonic transducers with different materials of the transmission layer were simulated.By establishing the acoustic transmission line model of the transmission direction and reception direction of the focused dual-frequency ultrasonic transducer,the thickness of the acoustic filter layers was optimized.By comparing the ultrasonic field and impulse response of the two transducers with and without a filter layer and a high-frequency matching layer,the performance of the transducer was further optimized.Finally,a focused dual-frequency ultrasonic transducer with PMN-PT/Epoxy1-3 of the transmission layer was experimentally studied.Unoptimized and optimized dual-frequency ultrasonic transducers were prepared for performance comparison.The electrical impedance and impulse response test results showed that the optimized transducer had better performance.Superharmonic imaging of phantom microvessels with a diameter of 110 μm in deionized water(ideal)proved that the transducer can perform superharmonic imaging of microvessels.The axial and lateral resolutions of the Superharmonic imaging of phantom microvessels with a diameter of 280 μm in agar(human-like tissue environment)were about 300 μm and 220 μm respectively.The above superharmonic experiment results showed that the focused dual-frequency ultrasonic transducer developed in this paper is expected to achieve high contrast and high resolution imaging of myocardial microcirculation,providing new ideas for the diagnosis and treatment of myocardial microtubule diseases. |
