Comparison of simplified Monte Carlo simulation and diffusion approximation for the fluorescence signal from phantoms with typical mouse tissue optical properties.

A simplified approach is proposed to simulate the fluorescence signal from a fluorophore submerged inside a turbid medium using the Monte Carlo method. Based on the reversibility of photon propagation, the fluorescence signal can be obtained from a single Monte Carlo simulation of the excitation light. This is computationally less expensive and also allows for the direct use of well-validated nonfluorescence photon migration Monte Carlo codes. Fluorescence signals from a mouse tissuelike phantom were computed using both the simplified Monte Carlo simulation and the diffusion approximation. The relative difference of signal intensity was found to be at most 30% for a fluorophore placed in the medium at various depths and horizontally midway between a source-detector pair separated by 3 mm. The difference in time characteristics of the signal is also examined.