Impact of skin pigmentation on photoacoustic tomography: a phantom study.

SIGNIFICANCE: 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. AIM: We aim to generate insights into the impact of skin pigmentation on the performance of 3D breast photoacoustic tomography using phantoms. APPROACH: 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. RESULTS: 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. CONCLUSIONS: 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.