In vivo measurement of the carotenoid level using portable resonance Raman spectroscopy

Carotenoid is an important antioxidant in human body, which can eliminate the free radicals and other harmful reactive oxygen species. The standard technique for measuring carotenoid is high-pressure liquid chromatography which involves using chemicals and is invasive. In this paper, we present a portable resonance Raman spectroscopy system for measuring carotenoid in vivo, which is noninvasive, highly sensitive and compact. A small diode-pumped all solid-state 473nm laser instead of a 488nm Argon ion laser is used to excite in vivo the carotenoid in the thumb, and the resonance Raman scattering light intensity is measured to assess the carotenoid level. Basically, it is difficult to detect the very weak resonance Raman scattering light because it is overlapping with the strong fluorescence. Our investigation shows that matching glycerol can help to reduce tissue scattering and increase light collecting efficiency. We demonstrate that the employment of optical matching technology for measuring carotenoid resonance Raman spectra in tissue can improve the signal-to-noise ratio by 3.9dB.