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.