High-speed blood flow measurement based on a continuous laser-assisted nonlinear photoacoustic

Nonlinear photoacoustic-based methods for measuring high-speed blood flow velocity typically use a single-pulse laser or a dual-pulse laser system with high repetition rate to achieve thermal tagging and acoustic excitation at the same time. However, the peak power of the pulsed laser is too high and can easily exceed the damage threshold, causing the blood to be overheated, which limits the application of this method in living tissue. In this paper, we propose and confirm a method of detecting high-speed blood flow with a low-power continuous laser-assisted nonlinear photoacoustic. We first establish a model of the relationship between the attenuation of Gruneisen parameters and velocity. Based on this, we further develop a theoretical relationship between the change of photoacoustic signal and the blood velocity. Then we used a low-power continuous laser for thermal tagging and a low repetition rate of pulsed laser to excite photoacoustic signals in the experiment. After calibration, the results show that the velocity measured by this method is in good agreement with the actual velocity and the highest flow velocity can be measured was 100 mm/s under our experimental conditions.