Design considerations and performance of a variable gain, variable bandwidth signal processing circuit for acoustoelectric imaging

Acoustoelectric (AE) imaging is a new technique for mapping current densities in the heart and brain at a high resolution determined by the size of the ultrasound (US) focus. Because the amplitude of the AE interaction signal in biological tissue is weak (on order of 1 μV), detection of small currents is challenging with poor signal-to-noise ratio (SNR). Because optimal detection depends on minimizing background noise, the design and performance of the recording system, especially amplifiers and filters, is crucial for efficient and sensitive AE imaging. The amplitude and bandwidth of the AE signal depends on a variety of factors, including the US bandwidth and beam pattern, distribution of current densities, properties of the recording electrodes, and amount of averaging/sampling. The primary goal of this work was to optimize the design and performance of the acoustoelectric differential amplifier, including signal processing circuits, to minimize noise and maximize sensitivity for detection of the AE signal. Variable gain, band-pass filter (BPF) cutoffs, and bandwidth are critical design parameters for optimizing the AE imaging platform for mapping weak electric currents in tissue.