Skin Autofluorescence Correction Algorithm for Darker Skin Types
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Solution Overview
Problem
Current methods for measuring skin autofluorescence (AF) are not reliable for individuals with darker skin colors due to skin color dependence, leading to inaccurate assessment of Advanced Glycation Endproducts (AGEs) and associated health risks.
Innovation Solution
A method and apparatus that corrects measured AF values by minimizing their dependency on UV-skin tissue reflectance, using parameters such as melanin and hemoglobin-related indices derived from reflectance and emission spectra to develop a new algorithm for calculating skin AF, applicable to various skin characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If skin AF is measured using conventional methods, then the measurement is simple and quick, but the measurement precision deteriorates for subjects with darker skin colors
Solution Approach 1:
The patent transforms the single-parameter measurement (raw AF value) into a multi-parameter analysis system that includes AF measurement, UV-reflectance measurement, and visible reflectance measurement. By measuring multiple parameters simultaneously and using their relationships, the system achieves accurate AGE assessment across all skin types without sacrificing measurement speed.
Solution Approach 2:
The patent introduces UV-reflectance and visible reflectance as intermediary parameters that mediate between the excitation light and the AF emission. These intermediaries provide information about skin optical properties (melanin content, scattering) that allow the system to correct AF measurements accurately for different skin types.
2Device complexity
If skin color compensation is performed using simple normalization methods, then the device complexity is low, but the reliability deteriorates for subjects with Fitzpatrick skin phototypes III-VI
Solution Approach 1:
The patent moves from simple normalization (dividing by single reflectance value) to a comprehensive multi-parameter model that incorporates UV-reflectance, visible reflectance, and their relationships with melanin and hemoglobin indices. This parameter expansion enables reliable compensation across all skin phototypes.
Solution Approach 2:
The patent adds spectral dimensionality by measuring reflectance across multiple wavelength ranges (UV-A, visible) and using spectral indices to characterize skin optical properties. This multi-dimensional approach provides sufficient information to distinguish between different skin types and apply appropriate corrections.
3Illumination intensity
If broad excitation range is used to maximize fluorescence signal, then the fluorescence intensity is high, but the measurement precision deteriorates due to overlapping fluorophore signals
Solution Approach 1:
The patent introduces visible reflectance measurements as intermediary data that provide information about endogenous absorbers (melanin, hemoglobin, bilirubin). These intermediaries allow the system to model and subtract their contributions from the total fluorescence signal, isolating the AGE-related fluorescence even with broad excitation.
Solution Approach 2:
The patent uses measured reflectance values to calculate skin optical property indices, which then feed back into the fluorescence analysis to correct for absorber contributions. This feedback loop enables the system to maintain high signal intensity while achieving specific AGE detection accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The new algorithm effectively corrects skin AF values, making them independent of skin color, allowing for accurate assessment of AGEs and associated health risks across different skin types, with a mean standard deviation of 14.8% of AF values, comparable to previous reliability for lighter skin colors.
Implementation Method 1
measuring the emission of light induced by the UV-A light source in a wavelength range from 420 to 600 nm
Implementation Method 2
different absorption of excitation or emission light by skin compounds
Implementation Method 3
scattering effects, especially in the epidermis
Data Source
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AI summary
A method for determining an autofluorescence value of skin tissue of a subject, comprising the steps of : - irradiating material of said skin tissue with electromagnetic excitation radiation of at least one wavelength and/or in at least one range of wavelengths; - measuring an amount of electromagnetic, fluorescent radiation emitted by said material in response to said irradiation; and - generating, based upon said measured amount of fluorescent radiation, a measured autofluorescence value for the concerning subject. The determined autofluorescence value is obtained by correcting the measured autofluorescence value for characteristics of a reflected part of an excitation spectrum and/or an emission spectrum from said material in response to such irradiation and/or for characteristics of reflectance measurements at wavelengths other than said at least one wavelength and/or other than in said at least one range of wavelengths, in such manner that the dependency of the determined autofluorescence value upon different UV-skin tissue reflectances, that different respective subjects may have, is minimized or at least diminished.