The effect of irradiance and integration time in in vivo normal skin Raman measurements assessed by multivariate statistical analysis

BACKGROUND: The successful discrimination of the subtle spectral characteristics of human skin in Raman spectra requires optimal acquisition parameters. We explore the translational momentum of Raman spectroscopy towards clinical practice by fine-tuning two basic experimental parameters (irradiance and integration time) of a portable Raman system used in skin measurements. OBJECTIVE: The aim of this study is to construct a generic protocol for recording the optimal Raman signal for in vivo skin measurements. METHODS: In vivo spectra were collected from two individuals of normal Fitzpatrick type III skin type. We assessed two different irradiation setups with three different integration times each by separating the raw signal from the noise using multivariate analysis. RESULTS: Our results showed that under a time threshold no optimal measurement conditions can be achieved. On the other hand, increased laser power and acquisition time do not offer a significant advantage over the selected lower values. Baseline correction is the most critical component for analysing normalized skin Raman spectra. CONCLUSIONS: A simple working protocol based on multivariate statistics offers the relative adjustment of irradiance and signal integration time among other experimental parameters that must be examined for optimal Raman measurements of skin.