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.

基于非线性光声的高速血流速度测量方法通常使用具有高重复频率的单脉冲激光器或双脉冲激光系统，以同时实现热标记和声激发。但是，脉冲激光的峰值功率太高，很容易超过损伤阈值，导致血液过热，这限制了该方法在活组织中的应用。在本文中，我们提出并确认了一种使用低功率连续激光辅助非线性光声检测高速血流的方法。我们首先建立了 Gruneisen 参数衰减与速度之间关系的模型。基于此，我们进一步发展了光声信号变化与血流速度之间的理论关系。然后，我们在实验中使用低功率连续激光器进行热标记，并使用低重复频率的脉冲激光器来激发光声信号。校准后，结果表明，该方法测得的速度与实际速度吻合较好，在我们的实验条件下可以测得的最高流速为 100 mm/s。