Research On Ultrasound/photoacoustic Dual-modality Imaging Based On An Acoustic Scanning Galvanometer

Currently,the most clinically used medical imaging is ultrasound imaging,but due to the shortcomings of the imaging technology itself,it still cannot meet the imaging requirements for certain functional information,so other medical imaging is needed as a supplement.Photoacoustic imaging,a new medical imaging technology,is attracting attention for its non-destructive and high contrast advantages,and has been rapidly developed and gradually applied to clinical applications in recent decades.Ultrasound and photoacoustic dual-modality techniques can combine the advantages of both imaging types and have great potential for clinical applications.In this thesis,we analyze the current photoacoustic scanning mechanism and find that large-scale tomographic imaging mainly uses an array ultrasound detector structure to acquire photoacoustic signals,while microscopy imaging often uses a two-dimensional stepper motor,which affects the imaging speed;or uses a high-precision MEMS scanner to acquire photoacoustic signals with a small imaging range,and the two modalities are not friendly to be directly applied to dual-modality imaging.Therefore,this thesis proposes a new scanning mechanism based on acoustic scanning oscilloscope,and builds an ultrasound/optoacoustic dualmode miniaturized imaging system based on this scanning galvanometer,which can provide a large imaging range and fast imaging speed,The main research contents and conclusions of this thesis are as follows.First,the current research status of ultrasound,photoacoustics and their dual modality is briefly introduced,and the theory of photoacoustic imaging based on photoacoustic effect and photoacoustic fluctuation equation is introduced,and the structure of current commonly used photoacoustic imaging systems is analyzed.The principle of dual-modality imaging and the imaging system were further explored.Next,a complete ultrasound/optoacoustic dual-modality imaging system is designed and built independently,using scanning galvanometer to achieve reflection of ultrasound and photoacoustic signals and miniaturization of the system.The hardware selection,parameter configuration,software control and imaging algorithm of the system are further described.The hardware part includes: scanning galvanometer,integrated mold design,pulsed laser,point-focus ultrasound transducer,data acquisition card,etc.The software part includes: Labview program writing,maximum projection image algorithm writing.Finally,a test experiment was conducted to verify the imaging performance of the system,test results: spatial resolution of 152μm for system ultrasound imaging and 350μm for photoacoustic imaging;the temporal resolutions of ultrasound and photoacoustic imaging were 1B-scan/s and 0.1 B-scan/s,respectively（the speed of photoacoustic imaging was mainly limited by the repetition frequency of the pulsed laser）,the maximum imaging range of the system is 21.1 mm;The imaging system was followed by fast ultrasound experiments,dual-modality mimic experiments,and dual-modality in vivo experiments,which gradually verified the imaging capability of the system and proved that the dualmodality system based on scanning galvanometer has certain application potential;finally,the possibility of applying scanning galvanometer to tri-modality imaging of ultrasound,photoacoustic and microwave thermoacoustic was explored.In conclusion,the proposed dual-modality imaging technique uses a scanning galvanometer to achieve fast scanning of acoustic waves,and uses mold integration to achieve miniaturization and low-cost requirements,which helps to promote the clinical and popularization of ultrasound/photoacoustic dual-modality imaging technology.