Acoustoelectric signal measurement system based on FPGA

Abstract

Although conductivity of biological tissues is highly sensitive to their physiological and pathological status, traditional electrical impedance tomography (EIT) has low spatial resolution. Acoustoelectric tomography (AET) is a hybrid imaging technique that aims to overcome the ill-posedness of EIT, which is expected to have high spatial resolution. AET utilizes the acoustoelectric effect, which refers to the localized variation in conductivity produced by a focused ultrasonic wave. Acoustoelectric effect has also been applied in ultrasound current source density imaging (UCSDI) for mapping the cardiac activation. This paper develops and designs an acoustoelectric signal measurement system based on FPGA to generate and measure acoustoelectric coupling signals. The system mainly includes: FPGA and its configuration circuit, electrical excitation, ultrasonic excitation, signal acquisition and processing, data communication and power management modules. Among them, the electrical excitation module can realize single-frequency or multi-frequency current output with adjustable frequency and adjustable amplitude. Also, it has high output impedance and wide frequency band. The ultrasonic excitation module can realize arbitrary waveform high-voltage ultrasound generation, and the peak-to-peak excitation signal can reach ± 100V. The ultrasonic excitation and the electrical excitation are matched in timing to realize the collaboration of ultrasound modal and electrical modal in the system. Besides, the performance of the hardware system is tested. Finally, the ultrasonic modulated electrical signal is obtained through experiments. The effects of sound pressure and time interval of triggering ultrasonic pulse on acoustoelectric signal are investigated.