High frequency focused piezoelectric ceramics transducer

Main applications of high frequency high intensity focused ultrasound at home and abroad. With the development of transducer materials and mechanical fabrication techniques, the frequency of ultrasonic transducers is now increasing. In general, higher frequency sound waves can resolve finer biological tissues, resulting in the higher imaging resolution. The relationship between the frequency and the wavelength of the ultrasonic wave, c is the propagation speed of the ultrasonic wave in the medium, depending on the mechanical properties of the medium. The limit value of its resolution is theoretically half the wavelength of the ultrasonic wave. Therefore, increasing the acoustic frequency piezoelectric ceramic element can improve the resolution of the ultrasonic transducer. In general, spatial resolution includes both axial resolution and lateral resolution. Moreover, the relationship between axial resolution, (at a 3dB) and ultrasonic frequency.

It can be seen that the spatial resolution of the ultrasound transducer includes both lateral and longitudinal resolution. among them,The vertical resolution depends on the wavelength of the ultrasound and the bandwidth of the transducer (B and width, Bw), lateral division.The resolution depends on the transducer's aperture size (aperture), depth of focus (f), and ultrasonic length. therefore,In order to improve the spatial resolution of the ultrasonic transducer, it is feasible to increase the frequency of piezoelectric sensor crystal.The higher the wavelength, the better the axial resolution. At the same time, due to the acoustic beam produced by the transducer,It is often divergent in the horizontal direction, so in order to obtain better lateral resolution, it is necessary to aggregate the ultrasonic waves.so focusing transducer can further improve the lateral resolution of the ultrasound transducer.

Piezoceramic materials piezos sensor are mostly used for extracorporeal diagnosis because they are attenuated by ultrasonic waves.center frequency of the transducer tends to be lower. For example, for abdominal diagnosis and cardiac diagnosis.The ultrasonic transducer has a frequency range of 3 MHz to 10 MHz. However, with the mechanical manufacturing technology, It is the development of piezoelectric materials and various intracavity interventional diagnostic methods. Making the frequency of the ultrasonic transducer come. The application field of high-frequency ultrasound is the interventional endoscopic imaging technique (WUS), the frequency of the transducer can reach 20MHz to 60MHZ, the resolution can reach several tens of micrometers, and the coronary artery can be checked in real time, preferably distinguishing the fine structure of the vessel wall and detecting vascular plaque is of great value and significance for the diagnosis of coronary atherosclerosis, coronary plaque and stenosis. Canada introduced an ultrasound imager with a resolution of less than 100um in small animal experiments as early as around 2002. such as the 20 MHz piezoelectric tube ultrasound for dermatological diagnosis, which was developed in 1986, and the 50 MHz high-frequency ultrasonic transducer produced by TPM in 1996 to measure the thickness of various layers and lesions. a team of professors of the University of Southern California at KK Shung in 2006 developed a 30MHz and 35MHz high-frequency focused linear array ultrasonic transducer for ophthalmologic diagnosis and the diagnosis of ophthalmic diseases such as glaucoma, ocular trauma, corneal disease, etc. .