Study of skin spectrum for quantitative determination of skin pigmentation

Quantitative assessment of pigments’ aggregation in skin lesions helps accurate diagnosis. This is also instrumental in monitoring the process of treatment especially when lasers are used to treat skin lesions. Spectroscopy has provided necessary instrumentations for quantitative evaluation of skin pigmentation. Having a broad wavelength range, ease of use and quickness are some advantages of spectroscopy. On the other hand, due to the overlapping of pigments’ absorption spectra, separation of pigments’ intensities is not a straightforward issue and requires scientific methods. In this study, the spectrum of human skin has been achieved for 5 different parts of 10 volunteers’ skin. The volunteers were 24-28 years old from both genders. The achieved spectrum was fitted according to absorption Gaussian peaks of pigments using Qtiplot software package and the intensity of each sub-peak was calculated. Two comparisons were performed in order to assess accuracy of the experiment. In the first comparison which shows accuracy of the experimental method, the redness and the blood concentration of different parts of skin were evaluated. In the second comparison, the accuracy of fitting process was tested. To do so, the ratio of di-oxi homoglobin to oxy hemoglobin in volunteers’ lips was compared. This ratio represents how bright the person’ lips might be. In this paper, we have presented a method for quantifing the amount of pigments in absorption spectrum of human skin. This was done by fitting the spectrum according to absorption peaks of pigments. The excellent correlation coefficient between the experimental spectrum and fitted curve shows a good precision. Two comparisions were performed in order to test the accuracy and precision of this method. Both comparisons confirmed the viability of the method. With this method, the changes in skin pigmentation caused by disease can be expressed quantitively.