Impact of skin pigmentation on photoacoustic tomography: a phantom study

Skin pigmentation is a known source of bias in optical and photoacoustic imaging. Although these effects are well investigated for two-dimensional photoacoustic imaging systems, their impact on three-dimensional (3D) photoacoustic tomography remains largely unexplored.

We aim to generate insights into the impact of skin pigmentation on the performance of 3D breast photoacoustic tomography using phantoms.

We developed hemispherical breast phantoms compatible with a multi-wavelength photoacoustic-ultrasound tomography system. The phantoms incorporate a thin skin-mimicking layer over an adipose-mimicking bulk material. Four phantoms with identical geometry and increasing pigmentation levels were fabricated. Embedded wall-less channels filled with sulfate solutions of varying concentrations enabled depth- and spectral-dependent analysis.

Increasing pigmentation led to stronger skin photoacoustic signals, reduced signal-to-background ratios at depth, and increased reflection-related background artifacts. Spectral measurements revealed pigmentation-dependent attenuation and reduced chromophore contrast in the wavelength range relevant for oxygen saturation estimation.

Three-dimensional photoacoustic tomography is susceptible to pigmentation-induced bias affecting imaging depth and spectral analysis. The presented phantom provides a validated platform for developing strategies to improve the reliability and inclusivity of photoacoustic tomography imaging across skin tones.