Photoacoustic imaging using narrow beam scanning

In deep tissue photoacoustic (PA) imaging, a large beam size with large pulse energy is typically used as a broad band acoustic signal excitation source. However, widely used solid state Q-switched laser systems are limited by their repetition rate for real-time applications. An emerging fiber laser with nanosecond level pulse width, hundreds of kilohertz repetition rate, and up to 1mJ pulse energy is a potential candidate for a new PA signal excitation source. However, the inherent drawbacks of narrow beam size and low pulse energy of a fiber laser make it hard to be directly applied to deep tissue imaging. To overcome this issue, a narrow beam scanning scheme is proposed in this study. However, the lower light penetration capability may still limit the depth at which this technique can be applied. The objective of this study is to compare the general quality of reconstructed images in terms of signal to noise ratio (SNR) for multiple narrow beam scanning PA excitation and conventional one shot, high pulse energy and large beam size excitation at depths appropriate for peripheral vascular applications.