Challenges in Sub-Surface Fluorescence Diffuse Optical Imaging

A fully non-contact CCD-based approach to sub-surface fluorescence diffuse optical imaging is presented. An overview of CCD-noise sources are described and a possible solution for obtaining an adequate SNR in CCD-based diffuse optical imaging is implemented. To examine the impact of excitation and remission light attenuation in this geometry, the linearity of response in recovering object position was examined in simulations, with respect to changes in target size, target-to-background contrast, and depth. To provide insight regarding the technological complications of sub-surface imaging, liquid phantom experiments were performed for targets of size 4mm, 8mm and 14mm having 10:1 target-to-background contrast. Overall, the results indicate that steps must be taken to eliminate blooming artifacts, perhaps by physically blocking the active source as it is projected onto the CCD chip. In general, response linearity in the recovered target centroid position, size, and fluorophore concentration as well as complications arising due to partial volume sampling effects are expected to improve if prior structural images obtained from another modality are incorporated into the DOT reconstruction algorithm.