OPTICALLY DILUTE, ABSORBING, AND TURBID PHANTOMS FOR FLUORESCENCE SPECTROSCOPY OF HOMOGENEOUS AND INHOMOGENEOUS SAMPLES

This paper presents a phantom which simulates the optical properties o f tissue. The phantom absorption coefficient, scattering coefficient, anisotropy factor, and fluorescence quantum yield can be independently varied to investigate the effects of these parameters on fluorescence excitation and emission spectra from 300 to 650 nm. Phantom fluoropho res include Flavin Adenine Dinucleotide (FAD) and Rhodamine B. Absorpt ion is controlled by adjusting phantom hemoglobin concentration. On th e basis of their smoothly varying scattering coefficient and the relat ively low amount of fluorescence contributed to the mixture in compari son to other available scatterers, 1.05-mum-diameter polystyrene micro spheres were selected as a scatterer. Sample inhomogeneities are simul ated by preparing the phantom in a gelatin substrate. The optical prop erties of turbid phantoms determined with the use of indirect techniqu es agree well with known values as long as mu(s)(1-g) > mu(s). Data ar e presented from dilute, absorbing, and turbid phantoms and inhomogene ous phantoms to qualitatively illustrate the effects of optical proper ties and sample geometry on fluorescence spectra. The phantom provides the framework for detailed quantitative investigations of the effects of optical properties, sample size, shape, and structure, boundary co nditions, and collection geometry on fluorescence spectra.