Abstract

The feasibility of employing fluorescent contrast agents to perform optical imaging in tissues and other scattering media has been examined through computational studies. Fluorescence lifetime and yield can give crucial information about local metabolite concentration or environmental conditions within tissues. This information can be employed towards disease detection, diagnosis, and treatment if non- invasively quantitated from re-emitted optical signals. However, the problem of inverse image reconstruction of fluorescence yield and lifetime is complicated due to the highly scattering nature of the tissue. In this work, a light propagation model employing the diffusion equation is used to account for the scattering of both the excitation and fluorescent light. Simulated measurements of frequency-domain parameters of fluorescent modulated AC intensity and phase-lag are used as inputs to an inverse image reconstruction algorithm which employs the diffusion model to relate frequency-domain measurements resulting from a modulated input at the phantom periphery. In the inverse image reconstruction algorithm, we employ a Newton-Raphson technique combined with Marquardt algorithm to converge upon the fluorescent properties within the medium. The successful reconstruction of both the fluorescence yield and lifetime in the case of heterogeneous fluorophore distribution within a scattering medium has been demonstrated without a priori information or without the necessity of obtaining "absence" images.

© 1996 Optical Society of America