Challenges remain in fluorescence reflectance imaging (FRI) in in vivo experiments, since the target fluorescence signal is often contaminated by the high level of background signal originated from autofluorescence and leakage of excitation light. In this paper, we propose an image subtraction algorithm based on two images acquired using two excitation filters with different spectral regions. One in vivo experiment with a mouse locally injected with fluorescein isothiocyanate (FITC) was conducted to calculate the subtraction coefficient used in our studies and to validate the subtraction result when the exact position of the target fluorescence signal was known. Another in vivo experiment employing a nude mouse implanted with green fluorescent protein (GFP)—expressing colon tumor was conducted to demonstrate the performance of the employed method to extract target fluorescence signal when the exact position of the target fluorescence signal was unknown. The subtraction results show that this image subtraction algorithm can effectively extract the target fluorescence signal and quantitative analysis results demonstrate that the target-to-background ratio (TBR) can be significantly improved by 33.5 times after background signal subtraction.
Dynamic fluorescence diffuse optical tomography (FDOT) is important in drug deliver research. In this letter, we first image the metabolic processes of micelles indocyanine green throughout the whole body of a nude mouse using the full-angle FDOT system with line illumination (L-FDOT). The resolution of L-FDOT is evaluated using phantom experiment. Next, in vivo dynamic tomographic images (100 frames; approximately 170 min) of mouse liver and abdomen are shown and cross-validated by planar fluorescence reflectance imaging in vitro. Results provide evidence on applicability of the tomographic image wholebody biological activities in vivo on minute timescale (approximately 1.7 min) using L-FDOT.
