Interpreting diffuse reflectance for <i>in vivo</i> skin reactions in terms of chromophores

The ability to monitor changes in the concentration of hemoglobin in the blood of the skin in real time is a key component to personalized patient care. Since hemoglobin has a unique absorption spectrum in the visible light range, diffuse reflectance spectroscopy is the most common approach. Although the collection of the diffuse reflectance spectrum with an integrating sphere (IS) has several calibration challenges, this collection method is sufficiently user-friendly that it may be worth overcoming the initial difficulty. Once the spectrum is obtained, it is commonly interpreted with a log-inverse-reflectance (LIR) or “absorbance” analysis that can only accurately monitor changes in the hemoglobin concentration when there are no changes to the nonhemoglobin chromophore concentrations which is not always the case. We address the difficulties associated with collection of the diffuse reflectance spectrum with an IS and propose a model capable of retrieving relative changes in hemoglobin concentration from the visible light spectrum. The model is capable of accounting for concentration changes in the nonhemoglobin chromophores and is first characterized with theoretical spectra and liquid phantoms. The model is then used in comparison with a common LIR analysis on temporal measurements from blanched and reddened human skin.

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“…(14), with triplets outside of the diffusion theory region omitted. (14), with triplets outside of the diffusion theory region omitted.…”

Section: Empirical Determination Of the Scattering Losses Correction mentioning

confidence: 99%

Modeling changes in the hemoglobin concentration of skin with total diffuse reflectance spectroscopy

2015

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“…1,2 Those chromophores can be altered in concentration either by external insults such as chemical irritants, UV radiation or by changes of physiological environment. Colorimetry has been used as an objective measure of perceived skin color by human eye to document and score physiological responses of the skin from the various external insults.…”

Section: Introductionmentioning

confidence: 99%

Assessing human skin with diffuse reflectance spectroscopy and colorimetry

et al. 2012

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Colorimetry has been used as an objective measure of perceived skin color by human eye to document and score physiological responses of the skin from external insults. CIE color space values (L*, a* and b*) are the most commonly used parameters to correlate visually perceived color attributes such as L* for pigment, a* for erythema, and b* for sallowness of the skin. In this study, we investigated the relation of Lab color scale to the amount of major skin chromophores (oxy-, deoxyhemoglobin and melanin) calculated from diffuse reflectance spectroscopy. Thirty two healthy human subjects with ages from 20 to 70 years old, skin types I-VI, were recruited for the study. DRS and colorimetry measurements were taken from the left and right cheeks, and on the right upper inner arm. The melanin content calculated from 630-700 nm range of DRS measurements was shown to correlate with the lightness of skin (L*) for most skin types. For subjects with medium-to-light complexion, melanin measured at the blue part spectrum and hemoglobin interfered on the relation of lightness of the skin color to the melanin content. The sallowness of the skin that is quantified by the melanin contribution at the blue part spectrum of DRS was found to be related to b* scale. This study demonstrates the importance of documenting skin color by assessing individual skin chromophores with diffuse reflectance spectroscopy, in comparison to colorimetry assessment.

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“…The optics of skin chromophores have been described in detail by Anderson and Parish. 7 The use of spectrophotometry of skin by many authors has shown good results in assessing melanin and hemoglobin, Masuda et al, 8 Stamatas et al, 9,10 Kollias et al, [11][12][13] Andersen et al, 14,15 Hegyi et al, 16 Verkruysse et al, 17 Hamzavi et al, 18 Taylor et al, 19 Bjerring et al 20 and Nielsen et al 21 The stimulus for this paper was to find a method to assess the efficacies of various vitiligo treatment modalities, by early signs of re-pigmentation.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic observations on human pigmentation

Sadiq¹,

Kollias

Baqer

2019

Photoderm Photoimm Photomed

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Background:The main chromophores of human skin are melanins and hemoglobins along with carotenoids, bilirubin, and other compounds. In an effort to study the spectral signatures of skin melanin, we measured absorption spectra in a variety of situations, including a method to show early signs of re-pigmentation in vitiligo. Methods:To measure skin in vivo, the essential component was a "Bifurcated OpticalFiber" with one end connected to the light source and the second end connected to the spectrometer while the common end was placed on the skin. Results:In a typical in situ "melanin in skin" spectrum, the absorbance values first rise gradually, from 750 to 600 nm, then rise moderately from 600 to 450 nm, and rise sharply from 450 nm to a broad peak at 335 nm, below which it gradually rolls down to much lower values. Conclusion:We successfully studied melanin spectroscopically in subjects with vitiligo lesions, obtaining the differential spectra. Higher melanin levels can be shown by steeper negative slopes of a straight line fitted between 620 and 720 nm. Also, absorption peak at 335 nm showed the presence of melanin. K E Y W O R D Smelanin spectra, skin chromophores, spectrophotometry, vitiligo

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Interpreting diffuse reflectance for in vivo skin reactions in terms of chromophores

Cited by 27 publications

References 38 publications

Modeling changes in the hemoglobin concentration of skin with total diffuse reflectance spectroscopy

Modeling changes in the hemoglobin concentration of skin with total diffuse reflectance spectroscopy

Assessing human skin with diffuse reflectance spectroscopy and colorimetry

Spectroscopic observations on human pigmentation

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