Last Updated on May 10, 2023 by You Ling
The field of medical diagnostic ultrasound has experienced tremendous growth in recent years, thanks to the rapid development of innovative materials and technologies. Among these advancements, piezoelectric composite materials have emerged as a game-changer, offering significant improvements in the performance and efficiency of ultrasound transducers. These materials have shown the potential to revolutionize medical diagnostic ultrasound, enhancing diagnostic accuracy and patient care.
In this article, we will delve into the applications of piezoelectric composite materials in medical diagnostic ultrasound, exploring their impact on transducer performance, acoustic impedance matching, and energy transmission. We will also discuss the research and development of these materials and their future prospects in the ever-evolving world of medical imaging. By understanding the role piezoelectric composite materials play in medical diagnostic ultrasound, we can appreciate the strides made in this field and the potential for continued improvement in the years to come.
1、Introduction to Medical Diagnostic Ultrasound
Medical diagnostic ultrasound is a non-invasive, painless, convenient, and intuitive diagnostic method that uses ultrasonic detection technology to measure and analyze physiological and tissue data in the human body. This helps detect diseases and provide diagnostic information. Ultrasound diagnosis, especially B-mode ultrasound, is widely used and has a significant impact, alongside X-rays, CT scans, and magnetic resonance imaging (MRI), as one of the top four medical imaging technologies.
2、Working Principle of Medical Diagnostic Ultrasound
An ultrasound system is composed of a transducer, transmitter circuit, receiver circuit, backend digital processing circuit, control circuit, and display module. The digital processing module typically includes a field-programmable gate array (FPGA), which generates a transmit beamformer and corresponding waveform patterns based on the system configuration and control parameters. The transmitter circuit’s driver and high-voltage circuitry generate high-voltage signals to excite the ultrasound transducer, typically made of PZT ceramic. The transducer converts voltage signals into ultrasonic waves that enter the human body while receiving echoes generated by human tissues. The echoes are converted back into low-voltage signals and transmitted to the transmit/receive (T/R) switch. The T/R switch’s primary purpose is to prevent high-voltage transmit signals from damaging the low-voltage receive analog front-end. The analog voltage signals are then transmitted to the AFE’s integrated ADC, where they are converted into digital data. The digital data is sent via a JESD204B or LVDS interface to the FPGA for receive beamforming, and then to the backend digital part for further processing, ultimately creating the ultrasound image.
3、Application of Piezoelectric Composite Materials in Medical Ultrasound
High-intensity focused ultrasound (HIFU) transducers are the core components of high-intensity focused ultrasound tumor treatment systems. Traditional transducers suffer from narrow bandwidth, low electro-acoustic conversion efficiency, and poor energy output stability. The transducer’s performance directly determines HIFU’s therapeutic effect. Therefore, research on transducer performance optimization is crucial. Transducers mainly consist of piezoelectric vibrators, matching layers, backing layers, electrode wires, and casings. As the acoustic components of the ultrasound wave, the comprehensive performance of 1-3 piezoelectric composite materials directly determines the various performance indicators of the transducer. High-performance 1-3 piezoelectric composite materials allow transducers to have stable output performance and high electro-acoustic conversion efficiency. With a fixed piezoelectric material, a well-designed matching layer can achieve acoustic matching between the transducer and the working medium, significantly improving the transmission efficiency of acoustic energy between human tissue and the transducer, and widening the transducer’s bandwidth. The matching layer also protects the transducer surface and piezoelectric ceramic from contamination or damage during operation. Transducers made from 1-3 piezoelectric composite materials without matching layers have been tested, showing a significant improvement in electro-acoustic conversion efficiency, increasing from 59% to 83% within the resonance frequency range, while maintaining good electro-acoustic performance output stability. Studies on the matching layer of the transducer found that as the acoustic impedance of the matching layer increased, the -3dB bandwidth of the transducer significantly widened, and the electro-acoustic conversion efficiency increased. When the acoustic impedance value reached 3.5 Mrayl, the -3dB bandwidth reached 295 kHz, and the maximum electro-acoustic conversion efficiency reached 90%.
The application of piezoelectric composite materials in medical diagnostic ultrasound significantly improves the performance and efficiency of ultrasound transducers. The use of 1-3 piezoelectric composite materials not only enhances electro-acoustic conversion efficiency but also contributes to the stability of the transducer output. The matching layer plays a critical role in improving the acoustic impedance match between the transducer and the human body, resulting in better energy transmission and broader bandwidth.
In summary, piezoelectric composite materials have great potential in advancing the field of medical diagnostic ultrasound. The continued research and development of these materials will further optimize transducer performance, leading to improved diagnostic accuracy and more effective medical treatment for patients. As technology advances, the integration of piezoelectric composite materials in ultrasound devices will play an increasingly important role in the medical imaging field, contributing to the betterment of healthcare for individuals around the world.