ABSTRACT
This chapter discusses the use of diffusion theory, a mathematical model for light propagation, to describe the influence of tissue on fluorescence measurements. The application of fluorescence techniques to assay ex vivo tissue samples or for in vivo measurements is confounded by the interactions with tissue of the excitation and fluorescence emission light. The nature of the source term for the emission energy fluence rate makes it extremely difficult to find analytical solutions for the coupled differential equations. The point source solution can be used to approximate a solution to the spatially resolved steady-state fluorescence emitted from tissue when irradiated using a pencil beam of excitation light. The chapter utilizes Fourier transforms to derive a more general solution for the pencil beam excitation problem. An alternate solution of the diffusion equation is provided by the Green’s function approach. The chapter describes the technique only for steady-state conditions but it is readily extended to time-dependent problems as well.
