Extraction of absorption coefficients from two-layer phantoms based on crossover point in diffuse reflectance

Abstract

We performed a Monte Carlo simulation to detect the tattoo ink location in the dermis layer of the human skin. Tattoo ink (thickness of 0.2mm) was located between the upper dermis layer (thickness of 2mm) and the lower dermis layer (thickness of 8mm). An appreciable difference in the spatially resolved diffuse reflectance (DR) intensity was found between the skin without tattoo and the tattooed skin. The point at which the skin without tattoo and the tattooed skin DR intensity profile intersect is called the crossover point (Cp). The slopes were extracted from the DR intensity profile before and after the Cp for a wavelength range from 400-1,000nm. The slopes are extracted from each wavelength, and we plotted the calculated square slopes versus wavelength. In the shorter wavelengths region (400-500nm), two-layer (2L) behavior was observed, and in the longer wavelengths region (600-1,000nm), a single layer behavior was observed. This confirms the tattoo ink was located at the dermis layer, and the longer wavelengths penetrate the deeper tissue. This Cp can be used to assess ink depth in order to remove the tattoo ink completely without damage to the surrounding skin.