In vitro hyperspectral analysis of tattoo dyes

Abstract

Background: There is no method that can guarantee effective, quick, and noninvasive removal of tattoo dyes. Laser methods are considered to be the method of choice. In this study, an attempt was made to determine the in vitro spectral characteristics of selected dyes used in permanent makeup and tattoos and to analyze the obtained parameters in terms of laser treatments optimization.

Materials and methods: Hyperspectral analysis was performed to determine the spectral characteristics of the dye on the entire surface of the slide. Seven dyes used in permanent makeup and tattoos were analyzed in vitro. The maximum reflectance and the wavelength for a given dye were determined for the maximum reflectance in the studied wavelength range: 400-1000 nm. The optical properties of the dyes were determined based on visible light imaging using camera.

Results: The maximum radiation reflectance ranges from 634 to 732 nm for the tested dyes. Visually very similar colors may differ significantly in the wavelength for which the maximum absorption of the radiation occurs. White and yellow dyes are characterized by the highest reflectance value. The black dye is characterized by the lowest reflectance coefficient. Low reflectance of black dye results in more safe and effective removal treatments.

Conclusion: The homogeneity of radiation absorption can be identified using methods of analysis and processing of images in visible light. Optimization of the wavelength of which the maximum absorption/reflectance of radiation occurs may allow us to increase the effectiveness of laser treatments for removing permanent makeup and tattoos.

Keywords: hyperspectral analysis; radiation reflectance; tattoo; tattoo dye; tattoo removal.

FIGURE 1

Summary of the dyes used in this study. For dye 7, a black envelope was used.

FIGURE 2

Schematic presentation of the idea of hyperspectral imaging. m, n, respectively, rows and lines of images, λ imaging wavelength range

FIGURE 3

Hyperspectral camera SOC 710, Surface Optics Corporation, San Diego, CA, USA

FIGURE 4

Examples of photos recorded at the following wavelengths along with fragment of gray panel (standard): 420.98 nm (A), 501.84 nm (B), 599.31 nm (C), 703.59 nm (D), 798.73 nm (E), 901.08 nm (F), and 999.30 nm (G)

FIGURE 5

Reflectance spectra of all registered dyes respectively: red (A), yellow (B), dark pink (C), black (D), light pink (E), brown (F), and white (G)

FIGURE 6

Wavelength of all tested dyes for which the maximum reflectance was identified

FIGURE 7

Maximum reflectance for all dyes tested identified in the wavelength range from 400 to 1000 nm

FIGURE 8

Normalized images of test dyes recorded in visible light. An envelope was used for dye no 7.

FIGURE 9

Gray Level Co‐occurrence Matrix (GLCM) contrast of all registered dyes determined based on photos recorded in visible light

FIGURE 10

Homogeneity of all registered dyes determined based on photos recorded in visible light