Rapid NIR Raman spectroscopy for in vivo skin tissue characterization and evaluation

摘要

Raman spectroscopy is a noninvasive, nondestructive analytical method capable of determining the biochemical constituents based on molecular vibrations. It does not require sample preparation or pretreatment. However, the use of Raman spectroscopy for in vivo applications will depend on the feasibility of measuring Raman spectra in a relatively short time period (a few seconds). In this work, a rapid dispersive-type near-infrared (NIR) Raman spectroscopy system and a skin Raman probe were developed to facilitate real-time, noninvasive, in vivo human skin measurements. Spectrograph image aberration was corrected by a parabolic-line fiber array, permitting complete CCD vertical binning, thereby yielding a 3.3 -16-fold improvement in signal-to-noise ratio. Good quality in vivo skin NIR Raman spectra free of interference from fiber fluorescence and silica Raman scattering can be acquired in less than 5 seconds, which greatly facilitates practical noninvasive tissue characterization and clinical diagnosis. With the rapid Raman system, we have conducted Raman spectroscopy measurements on 50 normal volunteers. A total of 25 body sites were measured for each subject. The spectral measurements were performed from 800 cm~(-1) to 1800 cm~(-1) with a 785 nm diode laser as the excitation source. Raman signatures of proteins, lipids, and nucleic acids are clearly identifiable from the measured spectra. We found that within the same subject, skin Raman signals are significantly different for different body sites, which presumably reflects differences in tissue chemical composition according to body sites, while the inter-subject differences of skin Raman signals for a given body site are relatively small. We have also demonstrated that Raman spectral signature changes from normal to malignant skin diseases. Systematic measurements of various skin diseases are in progress.