Multispectral High-resolution Photoacoustic Microscopy Imaging Method And Experimental Research

As a combination of high optical contrast and large ultrasonic detection depth,photoacoustic imaging has achieved unprecedented rapid development.Relying on endogenous contrast agents,such as hemoglobin in red blood cells,melanin in melanoma cells,DNA/RNA in nucleus,lipid in myelin,etc.it can realize high resolution and high contrast morphologic imaging,which shows potential application value in neurology,ophthalmology,vascular biology,dermatology and so on;Meanwhile,by using exogenous contrast agents,i.e.molecular probes,such as organic dyes,nanoparticles and fluorescent proteins,highly sensitive molecular photoacoustic imaging enables visualizing specific cellular functions and molecular processes,and made up for the lack of specificity of endogenous contrast agents in diagnosing diseases or tracking biological processes,such as cancer monitoring;Multi-spectral technique can be used to quantitatively analyze the tissue components by using the spectral absorption characteristics of different components at different wavelengths,it can be used to reveal the functional information of biological tissues in addition to morphological imaging,such as the measurement of blood oxygen saturation.Traditional photoacoustic microscopy techniques rarely achieve the fusion of structural,molecular and functional imaging.Consequently,the study of multi-spectral high-resolution photoacoustic microscopy will be beneficial to the realization of morphologic imaging,multi-parameter molecular and functional imaging,and widen the application range of photoacoustic microscopy.Based on the above background,a multi-spectral high-resolution photoacoustic microscopy system is designed and built by using double excitation light source of optical parametric oscillation laser and semiconductor laser.The work includes the selection of the main components,such as optical excitation,ultrasonic detection,data acquisition and motion scanning,and in order to improve the ultrasonic detection efficiency and imaging sensitivity of the system,the key parts of the imaging probe was especially designed to optimize co-axial confocal adjustment of acoustic and optical.Meanwhile,the virtual instrument technology based on LabVIEW realized the multi-function of motion control,data acquisition,storage and image display.Finally,the reliable imaging performance of the system is verified by phantoms and in vivo experiments.Based on the multi-spectral high-resolution photoacoustic microscopy system,experimental studies on structural,molecular and functional imaging were carried out.Firstly,longitudinal unlabeled monitoring of tumor angiogenesis and vascular normalization in the process of anti-angiogenic therapy was carried out by using hemoglobin as endogenous contrast agent,besides,the vascular morphological information was quantitatively analysed by a three-dimensional hessian matrix-based vascular extraction algorithm.Secondly,using high photoacoustic sensitivity near infrared II(NIR II)conjugated polymer molecular probe as exogenous contrast agent,large imaging depth was achieved on tumors and cerebral vascular imaging in vivo.At the same time,the photoacoustic functional imaging of in vivo blood oxygen saturation measurement has been completed by using dual-wavelength laser.In a word,multi-spectral high-resolution photoacoustic microscopy has shown important value in the study of biological structural,molecular and functional imaging,and provided a new method in revealing the mechanism of diseases such as tumors in the basic research of life sciences.