Photoacoustic coded excitation using periodically perfect sequences

Photoacoustic imaging is based on the generation of ultrasound using laser irradiation. Nd:YAG laser systems are commonly employed for this purpose, but cheap and handy pulsed laser diodes can be an attractive alternative. They emit significantly lower pulse energies, but fast averaging is feasible due to high repetition rates. Averaging is limited by the time-of-flight of the acoustic signal, but coded excitation can be used to overcome this limit. Here, we examine the performance of difference set based sequences with perfect correlation properties (periodically perfect sequences, PPS). PPS can be used for continuous, artifact free acquisition, the acquisition scheme is simpler than for all previously reported coding strategies. The coding gain reached for periodic imaging is higher than for Golay codes and Legendre sequences.