Quantitative analyses of biological tissue using phase modulation spectroscopy

摘要

A spectroscopic system for quantifying in vivo concentration of an absorptive pigment in biological tissue includes an oscillator for generating a first carrier waveform of a first frequency on the order of 10⁸ Hz, a light source for generating light of a selected wavelengths modulated by the carrier waveform, and a detector for detecting radiation that has migrated over photon migration paths in the tissue from an input port to a detection port spaced several centimeters apart. The wavelength is sensitive to concentration of an absorptive pigment present in the tissue. A phase detector compares the detected radiation with the introduced radiation and determines therefrom the phase shift of the detected radiation. A processor quantifies the concentration of the absorptive pigment by calculating a value of the absorption coefficient.