Research On Optical Coherence Tomography And Photoacoustic Multimode Imaging

Optical coherence tomography(OCT)and photoacoustic imaging(PAI)are two novel imaging technologies.Optical coherence tomography has been widely used from time domain OCT to frequency domain OCT since its appearance in 1991,and has been successfully transformed from structural imaging to functional imaging.Optical coherence tomography based angiography(OCTA)is an extension of frequency domain OCT technology,which uses red blood cells flowing in blood vessels as internal contrast agents to extract moving parts from static structures by measuring the differences of OCT signals caused by moving particles and finally uses specific algorithms to visualize vascular networks.Photoacoustic imaging depends on the sample’s absorption of excited light energy which causes the photoacoustic effect,and detects the generated photoacoustic signals for imaging,combining the high resolution of acoustic imaging and the high contrast of optical imaging.Due to the strong absorption effect of hemoglobin in blood vessels on the excitation light of some specific wavelengths,photoacoustic imaging technology can be used to image blood vessels.Due to the different imaging principles,these two imaging technologies carry different sample information.Combining these two imaging technologies can acquire abundant sample tissue information.Since most of the existing PAI system signal detection terminals use ultrasonic transducers for contact measurement,the ultrasonic transducers hinder the scanning mechanism of OCTA.Therefore,the PAI system built in this paper can remotely detect the tiny vibration of the surface caused by the photoacoustic effect by using the long coherence light interferometer without using the ultrasonic transducers,which makes it possible to combine with the OCTA system.This paper first introduces the basic principles of OCTA and PAI,and then introduces the OCTA system and PAI system we built,which are described from two parts:software and hardware,respectively.Next,we propose the dual-mode imaging system built in this paper which is integrated with two imaging systems including OCTA system and PAI system.We use two dichroic mirrors to make PAI excitation light,PAI detection light and OCTA samples light into one coaxial beam,sharing the same X-Y scanning galvanometer for fast two-dimensional scanning.In order to verify the stability and feasibility of the established dual-mode imaging system,we used the two sub-systems to image the simulated samples,respectively,and then we performed in-vivo imaging of the normal mouse ear’s blood vessel system,obtained high-resolution clear images of the mouse ear’s blood vessel system.To verify the performance of the system,then we artificially blocked the blood circulation of the blood vessel system,and imaged the same position using the dual-mode imaging system.The experimental results show that the system can reflect different blood flow states in the sample,and has certain application value for diagnosis,evaluation and research of related cardiovascular diseases.