  Photoacoustic tomography (PAT) is an emerging technology for biomedical
imaging that combines the superiorities of high optical contrast and acoustic
penetration. In the PAT system, more photoacoustic (PA) signals are preferred
to be detected from full field of view to reconstruct PA images with higher
fidelity. However, the requirement for more PA signals detection leads to more
time consumption for single-channel scanning based PAT system, or higher cost
of data acquisition (DAQ) module for an array-based PAT system. To address this
issue, we proposed a programmable acoustic delay line module to reduce DAQ cost
and accelerate imaging speed for PAT system. The module is based on
bidirectional conversion between acoustic signals and electrical signals,
including ultrasound transmission in between to provide sufficient time delay.
The acoustic delay line module achieves tens or hundreds of microseconds delay
for each channel, and is controlled by a programmable control unit. In this
work, it achieves to merge four inputs of PA signals into one output signal,
which can be recovered into original four PA signals in the digital domain
after DAQ. The imaging experiments of pencil leads embedded in agar phantom is
conducted by the PAT system equipped with the proposed programmable acoustic
delay-line module, which demonstrated its feasibility in biomedical imaging
system.
