基于动态聚焦的声聚焦光声内窥成像算法研究

目的 声聚焦光声内窥成像具有成像深度大的优点，是一种非常有前景的功能成像技术，该技术被广泛应用于直肠、食道等内窥成像中。声聚焦光声内窥成像通常采用基于单个聚焦超声传感器的侧向扫描方式，同时采用传统的B扫描方法进行重建，会大大降低图像质量。为了获得高质量的图像，本文提出了几种动态聚焦的声聚焦光声内窥成像算法。方法 本文使用几种动态聚焦算法进行了数值仿真，并搭建系统进行了仿体实验验证，从横向分辨率和信噪比等多方面比较了各算法在动态聚焦中的成像效果。结果 相比B扫描方法，动态聚焦后的图像在离焦区域的横向分辨率与信噪比方面都有提升，仿真模拟中最高可将离焦区域的成像目标分辨率提升约26倍，其信噪比经动态聚焦后最高可提高2.3倍左右，实验中的远距离点目标经动态聚焦重建后分辨率提升3～6倍。结论 整体而言，基于时空响应的算法和合成孔径聚焦重建算法是在实验条件下更为适用的算法。本工作对后续的声聚焦光声内窥成像的设计具有指导意义。

Research on Acoustic Resolution-based Photoacoustic Endoscopy Imaging Algorithm Based on Dynamic Focusing

Objective Acoustic resolution-based photoacoustic endoscopy is a promising functional imaging technique with its large focusing depth. It is widely used in endoscopic imaging of the rectum and esophagus. Acoustic resolution-based photoacoustic endoscopy imaging usually adopts the lateral scanning method based on a single focused ultrasonic sensor, while using the traditional B-mode method for reconstruction, which will greatly reduce the image quality. In order to obtain high-quality images, several dynamic focusing photoacoustic endoscopic imaging algorithms are proposed in this paper.Methods Numerical simulations were performed using these algorithms. In addition, photoacoustic endoscopic imaging experiments were conducted on the phantom to verify the results of the simulation experiments. In the simulation experiments, photoacoustic endoscopic imaging experiments with a focused transducer were simulated. We chose nine points including the focal point as the targets for reconstruction in the imaging area. The characteristics of each algorithm were compared in terms of imaging effect, resolution and signal-to-noise ratio. We made a phantom to verify the imaging effects of several algorithms using a photoacoustic endoscopic imaging system. Several metal wires were inserted in it to simulate targets at different distances and shapes. We compare the advantages of these algorithms over the B-mode method in reconstructing the above objectives.Results The results show that the transverse resolution and signal-to-noise ratio of defocused region are improved compared with which of the B scan method. In the simulation, the resolution of the defocus area can be improved by about 26 times, and the signal-to-noise ratio can be improved by about 2.3 times after dynamic focusing. In the experiment, the resolution of remote point targets is improved 3-6 times after dynamic focusing reconstruction.Conclusion On the whole, we think that the algorithm based on spatial-temporal response and synthetic aperture focusing technology algorithm are more suitable for experimental conditions. This work has guiding significance for the design of acoustic focusing photoacoustic endoscopy imaging.