| Acoustic resolution photoacoustic endoscopy imaging(ARPAE)is a new imaging technique which provide rich optical contrast and ultrasonic resolution for intracavitary biological tissue.In the traditional ARPAE system,the transverse resolution of the target outside the focal area is limited due to the use of fixed-focus ultrasonic transducer.Therefore,an improved filtered back-projection algorithm for ARPAE is proposed in this paper.the reliability and stability of the algorithm are verified by numerical simulation.In addition,a set of ARPAE test system is built in this paper,and the algorithm is verified by two-dimensional photoacoustic endoscope simulation experiment.The main research contents are as follows:1、An improved back-projection reconstruction algorithm for ARPAE imaging is proposed in this paper.In this algorithm,the detection surface of the focused ultrasonic sensor is divided into finite elements,and the back-projection data of each unit signal are weighted and summed,so as to achieve the dynamic focusing of the target at different radial depths.In this paper,the stability of the algorithm is verified at first,and then the influence of the focal length,diameter and center frequency of the focused ultrasonic transducer on the transverse resolution of the image is studied emphatically.2 、 An integrated ARPAE system is designed and verified by two-dimensional photoacoustic endoscopy.By comparing the image reconstruction data of the improved photoacoustic endoscope algorithm and the traditional endoscope algorithm,the results showed that when the target is located near the focus and the numerical aperture and center frequency of the focused ultrasonic transducer are large,the transverse resolution of the improved algorithm is significantly higher than that of the traditional algorithm.In parallelly,the depth of field of the radial target is improved within a certain error range.The experimental results are consistent with the numerical simulation results. |
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