Low-Cost Photoacoustic Tomography System Enabled by Frequency-Division Multiplexing

Abstract

Photoacoustic tomography (PAT) is a newcomer in the biomedical imaging community. The image is constructed through photoacoustic waves emitted from the sample after absorbing light energy. The ultrasound signals are converted into electrical signals by ultrasound transducers and sent to a multi-channel data acquisition (DAQ) system for transmission to the personal computer. Traditionally, one ultrasound signal would occupy one channel of the DAQ. However, high-performance DAQ is awfully expensive. Nowadays, to improve PAT's imaging result, imaging systems with multi-detector is usually required, which means multi-channel DAQ is exceedingly desired. Therefore, in this paper, a 4-to-1 circuit module is proposed to reduce the PAT system's cost by fusing four channels of signals into one signal employing frequency- division multiplexing (FDM). Specifically, the original four PA signals are multiplied with high-frequency sine waves with different frequencies and then summed into one channel so that the signals are carried separately in a bandwidth that does not overlap in the frequency domain. After the modulated signal's acquisition, the original signal can be recovered through bandpass filters and an associated demodulation algorithm. We have performed imaging experiments and proved the feasibility of this module in the PAT system.