Advanced flow dynamics mapping through volumetric photoacoustic particle velocimetry

Flow field analysis is vital for biomedical applications such as drug delivery, dosage optimization, and hemodynamic studies. Conventional optical Particle Image Velocimetry (PIV) struggles with dynamic three-dimensional analysis in turbid media. This study introduces a photoacoustic volumetric particle image velocimetry (PAV-PIV) system to address these challenges, enabling rapid three-dimensional flow field reconstruction in optically opaque environments without complex calibration. Vascular phantoms made from silicone, polyurethane, and agarose were tested, with the optimal material selected based on acoustic impedance contrast. Nickel-coated polystyrene particles served as tracers, uniformly dispersed in the fluid. Particle displacement was measured at 20 ms intervals, allowing for flow field analysis, including velocity and vorticity distributions. Reconstructed three-dimensional photoacoustic signals demonstrated superior imaging quality in turbid media, with detailed flow field characteristics derived from the best-quality images. The system's performance and measurement precision were further evaluated. Results confirm that the PAV-PIV system effectively overcomes the limitations of traditional optical methods, offering robust and dynamic flow field analysis in challenging environments. This approach shows great potential for advancing real-time biomedical applications requiring the analysis of complex flow behaviors.