Free-space Fluorescence Diffuse Optical Tomography For In-vivo Small Animal Imaging

Fluorescence diffuse optical tomography(FDOT) is a technology combining fluorescence probe with diffuse optical tomography(DOT) to realize in-vivo tracking and measurement for the specific biomacromolecule. FDOT becomes a hotspot in the research of optical imaging with the advantage of high specificity and sensitivity, and has a great practical application value in the fields of small animal molecular imaging. In-vivo imaging of small animals can explore origin and laws of development of the living pathology, and provide important basis for the early diagnosis and treatment of human disease. The free-space FDOT system based on CCD-camera-based detection can provide a large dataset and avoid the errors caused by the fiber coupling, which has a obvious advantage in in- vivo imaging of small animals.In this paper, a continues wave free-space FDOT system based EMCCD was set up for in-vivo imaging of small animals. Firstly, for the cylindrical model usually adopted in the in-vivo FDOT imaging of small animals, a novel Data-Extraction-Extension-Method(DEEM) was investigated to avoid the complex focus correction calculation for the optical lens and alleviate the ill-posedness of inverse problem. In this method only the middle range of the EMCCD image was used as detection information. A lot of FDOT experiments were carried on the solid phantoms. It proved that the best reconstruction results can be achieved when the Data-Extraction-area is half of the whole projection of the cylinder phantom on the EMCCD and is decomposed into three sub-areas.To further validate the spatial resolution, sensitivity and imaging depth of the FDOT imaging method, a lot of FDOT experiments were carried on the liquid phantoms imitating mice optical model. With the preferably reconstruction parameters, the experiments using Cy5.5 fluorescence probe show that the minimum detection concentration and maximum imaging depth that the FDOT imaging method can achieve respectively is 240 nm and 6.5mm. And two fluorescence targets with a CCS of 4.5mm can be distinguished by the FDOT imaging method.Finally, in this paper, an implantable fluorescence target imitating the tumor model was applied to validate the feasibility of the FDOT imaging method for in-vivo imaging of small animal. According to the preferably experimental scheme, the FDOT experiment for in-vivo imaging of mice was carried on. Contrasted with X-CT imaging result, the FDOT results show that the FDOT imaging method can reconstruct the original location of the fluorescence target effectively and complete the relative quantified reconstruction for two targets with different concentration. Precision of detection target localization and accuracy of relative yield reconstruction can be achieved by the FDOT imaging method. The FDOT imaging method can be applied to the early diagnosis for small animal tumor.