Hybrid multi-wavelength photoacoustic imaging

Multi-wavelength photoacoustic (PA) imaging has been studied extensively to explore the spectroscopic absorption contrast of biological tissues. To generate strong PA signals, a high-power wavelength-tunable pulsed laser source has to be employed, which is bulky and quite expensive. In this paper, we propose a hybrid multi-wavelength PA imaging (hPAI) method based on combination of single-wavelength pulsed and multi-wavelength continuous-wave (CW) laser sources. By carefully controlling laser illumination sequence (pulse-CW-pulse), and extracting the PA signals' difference before and after heating of CW lasers, the optical absorption property of multi-wavelength CW lasers could be obtained. Compared with conventional PA imaging, the proposed hPAI shows much lower system cost due to the usage of single-wavelength pulsed laser and cheap CW lasers. Theoretical analysis and analytical model are presented in this paper, followed by proof-of-concept experimental results.