Design And Research Of High Resolution Photoacoustic Microscope Based On High Frequency Annular Array

Photoacoustic imaging,as a new imaging technology,has attracted more and more attention in biomedical imaging due to its unique laber-free,high-resolution and high-contrast multi-scale imaging capabilities.As one of the important branches of photoacoustic imaging,there are still many challenges in the development of acoustic resolution photoacoustic microscopy.In this paper,the following research is carried out in order to make it more applicable in biomedical imaging applications:1.In this paper,the six circular Fresnel ultrasonic transducer array is used instead of the traditional single element ultrasonic transducer to deal with the problem of the mutual restriction between the imaging resolution and the imaging depth of field.By applying time delay and weight factors to the photoacoustic signals detected by each element in the array,a narrow-band and long focal area is formed in the imaging acousitc field,so as to expand the imaging depth of field,and finally achieve the purpose of maintaining a higher imaging resolution in a large imaging depth of field.The feasibility of the proposed method is verified by numerical simulation and experiment.2.In the current annular array photoacoustic imaging system,the medium / low frequency ultrasonic transducer array is usually used as the receiving end of the signal.However,the imaging resolution of this medium / low frequency system is still difficult to meet the requirements for the detection of Ophthalmology and other diseases.Therefore,the center frequency of the array is further increased to 20 MHz,which greatly improves the imaging resolution of the system and verifies the imaging ability of the system for the biological eyeball.It is expected to be applied to the diagnosis of ophthalmic diseases in the future.3.In the design of the photoacoustic microscopy imaging system,the improvement of the imaging depth of the system,the future miniaturization of the system and the development trend of portability are taken into account.The whole imaging system is designed as a reflective structure,and the transmission optical path and the ultrasonic transducer array are designed on the same side of the fabric tobe tested,so as to ensure that the acoustic transmission distance and the optical transmission distance in the tissue are equal,making the acoustic attenuation and scattering of the tissue can be controlled in a small range,and the imaging depth of tissue is larger than that of the traditional transmission structure acoustic resolution photoacoustic microscope.