Stable wavelength tunable photoacoustic imaging platform

Multi-wavelength photoacoustic imaging (PAI) has garnered significant attention due to its excellent capabilities in molecular and functional imaging. Researchers in the PAI community are consistently in need of reliable multi-wavelength imaging platforms. For clinical applications, PAI machines that are mobile, compact, and rapidly tunable are required. We have designed a stable and cost-effective PAI platform which consists of an optical parametric oscillator (OPO), a data acquisition system (DAQ), and various imaging probes. The stability of the OPO has been enhanced through the implementation of air-floating springs and mirror frame designs, alongside open-loop wavelength control. Effective monitoring of energy using built-in energy meters has improved the accuracy of PA spectral measurements. Integration with digital boards has effectively enhanced the noise resistance of DAQ and reduced its physical size. The platform can achieve a repetition rate of 10 Hz, swift wavelength tuning within the range of 680 to 950 nm (with a resolution of 1nm), and single-pulse energy greater than 80 mJ. The spectral range covers the absorption features of important chromophores such as hemoglobin, fat, and indocyanine green. The DAQ system can record PA data with 80 MHz sampling rate, 14-bit resolution, and 128/256/512 channels. The platform is equipped with linear array probes and semi-circular array probes to meet the requirements of both animal and human imaging. The semi-circular array probe utilizes a polydimethylsiloxane (PDMS) membrane with good light transmission to form a water bag for ultrasound coupling. This membrane is flexible and can conform well to different tissue shapes. Using this platform, we have conducted experiments including blood oxygen measurement, imaging of arm muscles and fat. In these experiments, we demonstrated accurate blood oxygen analyses and high-contrast muscle and fat imaging.