Application Of Fluorescence Diffuse And Photoacoustic Imaging In Small Animal Abdomen

The important role of biomedical imaging techniques serving for the medical care and clinical treatment is to detect and identify diseases and monitor the effectiveness of treatment.Besides,the imaging technique also plays an important role in exploring the pathological mechanism of diseases.As the image acquisition and laser technology have advanced rapidly,many new optical imaging methods have emerged,driving the development of medical imaging and diagnosis.Animal testing should verify emerging imaging techniques and treatment methods first.The development of human diseases is very complicated,such as tumors,intestinal ischemia,and cardiovascular diseases.Much clinical experiment is limited in morality and methods,and it is too slow to study the mechanism of disease occurrence through clinical observes.It is easier and faster to understand the mechanism of human disease with the use of experimental animal disease model.The key step in the drug development process is pre-clinical development,which requires the safety,metabolism and pharmacokinetics testing of drugs.These practical needs have promoted the rapid development of small animal imaging techniques.The small animal in vivo imaging has developed into an important part of preclinical and translational biomedical research.Fluorescence diffuse optical imaging(FDOT)and photoacoustic tomography(PAT)are two emerging optical imaging methods.FDOT reconstructs the fluorescence yield distribution inside the tissue by collecting the diffuse light emitted from the tissue.Most of the detectors of the existing commercial fluorescence imaging systems use a CCD with a compact structure and a higher cost performance.In order to monitor the metabolic rate of ICG fluorescent dyes in the liver of mice,photomultiplier tubes(PMT)with higher sensitivity and strong temperature stability were used as the detectors,and the FDOT system was built based on the single-photon counting principle.The main research content includes:1.Build the FDOT system.Based on the FPGA development board,the Verilog HDL was used to achieve these functions,including multi-channel single-photon counting,UART communication,and command of LD sources.Based on continuous wave modality,these instruments including an optical switch,four filter wheels and four PMTs were used to assemble the 4×4 parallel acquisition system.Using the LabVIEW software achieves commands for each instrument and automatic data acquisition.2.The parameters of the built fluorescent system were tested.The fluorescent dye used was ICG.The measured spatial resolution was 7mm and the sensitivity was 50 nM.The metabolic rate of ICG in mouse liver was monitored by the system.PAT is essentially a hybrid imaging modality,which absorbs the advantages of high optical contrast and high acoustic resolution.Hemoglobin has a high absorption coefficient in near-infrared wavelength,and PAT can generate images of the vascular system.Functional information such as oxygen saturation can be calculated by multispectral analysis.Intestinal ischemia-reperfusion(IRI)injury is a life-threatening condition in surgery.The mechanisms of IRI,which involve energy attenuation,oxygen free radical injury and endothelial cell injury are complex and poorly understood.Most pathological studies focus on biochemical methods such as biopsy,cytology,and animal experiments,and there are few imaging studies on intestinal ischemia-reperfusion injury.In PAT of the intestine,there is no convenient and rapid method that can be applied to the study of IRI injury.Therefore,this paper develops a method suitable for rapid PA imaging of mesenteric blood vessels in small animals according to the laboratory conditions.The main content includes:1.Tring the different PAT methods including single-channel scanning,in vivo and in vitro imaging,and different coupling methods to image rat intestines,we finally found a technique that can clearly image the rat mesenteric blood vessels—Photoacoustic imaging using phantom cavity coupling in vitro intestine.2.This method was applied to the study of dynamic monitoring of intestinal ischemia-reperfusion injury in rats.The results showed that PAT was a potential tool used for the study of small animal IRI injury.