Design And Realization Of The Acoustic Resolution Photoacoustic Microscopy System

Because it's advantage in high optical absorption contrast and large ultrasonic imaging depth,photoacoustic imaging technology get rapid development since the end of the 20 th century.Acoustic resolution photoacoustic microscope is one of the application of the photoacoustic imaging technology.This article first to the mainstream of biomedical imaging methods: X-ray,nuclear magnetic resonance,two-photon,optical coherence tomography,ultrasonic,such as a brief narrative,illuminates the pure optical imaging barrier is the scattering property of the tissue,and other imaging methods are also has its drawbacks.Spectrum specificity absorption curve of different absorber of the biological tissue,combined with photoacoustic effect,produced optical absorption and acoustic emission imaging mode,opened up a new direction for biomedical imaging.Then,this paper illustrates the principle of photoacoustic imaging,the generation of photoacoustic signal and SNR formula was deduced.This thesis introduces that,both the short pulse excitation and the continuous laser excitation with intensity modulated can generate photoacoustic signals,the former is characterized by a high signal-to-noise ratio,system cost.However,the latter has low signal-to-noise ratio,compact system,and low cost.Then,this thesis introduces the present situation of the research in acoustic resolution photoacoustic microscope.Starting from the existing acoustic resolution photoacoustic microscope,it shows that there are several drawbacks regarding to the mainstream illumination design of current acoustic resolution photoacoustic microscopy systems.Switch between bright filed illumination and dark field illumination is not available,and the utilization efficiency of laser energy is very low,and therefore the application of the system is limited.In this study,two novel optical illumination design has been proposed to overcome these limitations.A convex lens is applied to focus the diverging ring shape light before it is reflected by the optical condenser,and as a result,the ultimate laser spot on the surface of the sample can be decreased.The Monte Carlo simulation results showed that laser fluence within the volume of effective ultrasound detection has been improved by as much as 6 times,and therefore the intensity of photoacoustic signals can be linearly increased as well.Acoustic resolution photoacoustic microscopy is capable of imaging at centimeter depth.Considering the cost and difficulty in installation,select the one which cost low and install less difficult.All the hardware composition and control software are briefly introduced.Finally,resolution of 180 um was tested by a tungsten filament with 10 um diameter.8mm imaging depth can get in a scatteing phantom.Clear vascular net and the phenomenon of nano-particals flow into sentinel node was detected by Mouse experiments.These prove that the design of the feasibility of this acoustic resolution photoacoustic microscope.