ABSTRACT
This chapter summarizes what is known about the chromophores present in biological tissues as well as techniques to measure their spectra and concentrations in the appropriate biological environment, and illustrates how this knowledge can be summarized to describe tissue spectra of normal and diseased tissue. It discusses modeling approaches to integrate the combined effects of changes in tissue chromophores and determines whether these accurately describe the measured changes in tissue fluorescence that occur with disease progression. Tissue contains three important types of chemical groups that interact with light: fluorophores, absorbers, and scatterers. Biological tissues in general are optically turbid, with probability of light scattering and absorption exceeding that of conversion to fluorescence. Endogenous fluorescence provides important tool in optical assessment of tissue metabolic status. The pyridine nucleotides and flavins have an important role in cellular energy metabolism. The aromatic amino acids tryptophan, tyrosine, and phenylalanine contribute to protein fluorescence. Significant autofluorescence has been noted in structural proteins collagen and elastin.
