Smith Caitlin, Shepherd Jami, Renaud Guillaume, van Wijk Kasper
Department of Physics, University of Auckland, Private Bag 92019, Auckland, 1010, New Zealand.
The Dodd-Walls Centre for Photonic and Quantum Technologies, Auckland, New Zealand.
Photoacoustics. 2024 Mar 15;38:100602. doi: 10.1016/j.pacs.2024.100602. eCollection 2024 Aug.
We present a technique called photoacoustic vector-flow (PAVF) to quantify the speed and direction of flowing optical absorbers at each pixel from acoustic-resolution PA images. By varying the receiving angle at each pixel in post-processing, we obtain multiple estimates of the phase difference between consecutive frames. These are used to solve the overdetermined photoacoustic Doppler equation with a least-squares approach to estimate a velocity vector at each pixel. This technique is tested in bench-top experiments and compared to simultaneous pulse-echo ultrasound vector-flow (USVF) on whole rat blood at speeds on the order of 1 mm/s. Unlike USVF, PAVF can detect flow without stationary clutter filtering in this experiment, although the velocity estimates are highly underestimated. When applying spatio-temporal singular value decomposition clutter filtering, the flow speed can be accurately estimated with an error of 16.8% for USVF and 8.9% for PAVF for an average flow speed of 2.5 mm/s.
我们提出了一种称为光声矢量流（PAVF）的技术，用于从声学分辨率的光声图像中量化每个像素处流动的光吸收体的速度和方向。通过在后期处理中改变每个像素的接收角度，我们获得了连续帧之间相位差的多个估计值。这些估计值用于通过最小二乘法求解超定光声多普勒方程，以估计每个像素处的速度矢量。该技术在台式实验中进行了测试，并与同时进行的脉冲回波超声矢量流（USVF）在全血大鼠上以约1毫米/秒的速度进行了比较。与USVF不同，在本实验中，PAVF无需进行静态杂波滤波就能检测到血流，尽管速度估计值被严重低估。当应用时空奇异值分解杂波滤波时，对于平均流速为2.5毫米/秒的情况，USVF的流速估计误差为16.8%，PAVF的流速估计误差为8.9%，此时流速可以被准确估计。
