Investigation Of Photoacoustic Microscopy Imaging Base On Fresnel Array Ultrasound Transducer

As a hybrid imaging method,laser ultrasound microscopy imaging has been gradually developed in the field of medical imaging in recent years.Compared with the current clinical medical imaging methods,photoacoustic imaging has the advantages of non-invasive and nonionizing properties.Therefore,photoacoustic microscopy has been attracted more and more attention.As one of the implementations of photoacoustic imaging,acoustic resolution photoacoustic microscope still has various challenges.Using a single-focus ultrasound transducers can achieve higher resolution at the focal point,but it will result in poor imaging quality outside the focus and narrow the depth of imaging;array ultrasound transducers can maintain high resolution of imaging and improve the depth of field through phase-controlled focusing,but too many elements will increase the complexity of the system.Imaging resolution and depth of field are important quantitative indicators of image reconstruction,and how to make a trade-off between the two is a key issue.Based on a 20 MHz fresnel array ultrasonic transducer,an acoustic resolution photoacoustic microscopy imaging system was built,which can observably increase the imaging depth of field while maintaining high resolution.According the structure and sound field characteristics of the fresnel array,an imaging finite element model is established.The imaging performance of fresnel array is studied by using a photoacoustic imaging system.First,a detailed description of the thermoacoustic theory that produces photoacoustic signals,a theoretical analysis of the sound field of the fresnel array ultrasonic transducer is mentioned in this article,and the possibility of expanding the imaging depth of field is studied at theory.In terms of theoretical imaging,the finite element model of the fresnel array ultrasonic transducer is established through the Field II simulation toolbox,and the numerical simulation imaging analysis is performed on it.The imaging results of the fresnel array under different parameters are compared and the optimized.The array element parameters of the ultrasonic transducer verify its imaging performance and provide a reference for subsequent array element production.Second,based on a 20 MHz six-element high-frequency fresnel array ultrasonic transducer,an acoustic resolution photoacoustic microscope imaging system was built and combined with the corresponding hardware and photoacoustic signal data acquisition software to reconstruct image.Combining with the receiving dynamic focus imaging processing,the imaging performance of the microscopy imaging system is analyzed in different imaging experiments.The carbon rod experiment verified that the system can provide high-quality photoacoustic images within a depth of about 25 mm;in the hairs imaging experiment,this system can provide a lateral resolution of about 210 μm and axial resolution of 170 μm within a depth of 16 mm.Finally,the potential of the system for biomedical imaging is revealed by the image of the lens,iris,and ciliary body in the isolated porcine eye.