Modeling of Fluorescence Sources within Tissue using Angular Domain Imaging

Abstract

Conventional fluorescence imaging does not have a mechanism to remove the scattering effect in biological tissue. ADI is an efficient scattering filtration method and it is independent of coherence or wavelength of the light source making it a suitable addition to fluorescence imaging. We use an angular filter collimator array because of its superior performance in combining ADI and fluorescence imaging was shown in previous work. Using Monte-Carlo simulations, two fluorescence situations are emulated: series of point sources artificially inserted fluorophores, and a uniform background source simulating naturally occurred fluorophores with lines of non-emitting areas. These simulated light sources are placed beneath a 1mm to 2mm thick scattering medium with optical properties closely resembling biological tissue, followed by a collimator array with aspect ratios ranging from 5:1 to 20:1. This serves as a good approximation of collagen, a naturally occurred fluorophore, roughly 1mm underneath the epidermis. The point source simulations show that regardless of the alignment between the collimators and the light source locations, collimators with modest aspect ratios as low as 10:1 can successfully indentify their positions through a 2mm scattering medium. For the uniform source simulations, collimators with 10:1 aspect ratio can image absorbers up to 200um width at 1mm depth. The detection of the absorbers improves as the width of absorbers increases. Image quality for both scenarios can be enhanced by utilizing an additional lens in the detection system.