Speaker
Description
Photoacoustic imaging (PAI) is a promising non-invasive technique for clinical diagnostics, combining optical contrast with ultrasound resolution to visualise functional tissue properties. However, melanin absorption in the epidermis introduces significant effects in photoacoustic measurements, leading to spectral distortion and image artefacts. These effects impair the accuracy of key biomarkers, such as blood oxygen saturation, and may compromise diagnostic reliability across diverse skin tones. To quantify the impact of skin pigmentation, we conducted a human imaging study with 42 healthy volunteers across all six Fitzpatrick skin types [Else, 2025]. Multispectral PAI were acquired at multiple anatomical sites alongside colorimetry-based skin-tone quantification. Previous analysis shows a strong dependency of photoacoustic intensity on melanin concentration, demonstrating melanin as a major confounding factor in PAI. To correct these effects, we developed a two-stage pipeline combining orthogonal projection-based acoustic clutter removal with data-driven optical spectral decoloring. The projection method identifies and removes melanin-like superficial signal components that spatially overlap with vascular signals. For spectral decoloring, large-scale optical and acoustic simulations inspired by the clinical study were used to train a digital-twin-based regression model to estimate skin mask, melanin concentration, and wavelength-dependent fluence correction factors.Clinical validation demonstrated improved consistency of arterial sO₂ estimates across participants after correction. In representative arterial measurements, mean sO₂ increased from approximately 0.57 in raw data to 0.80 after acoustic clutter removal and spectral decoloring, approaching physiologically expected arterial oxygenation. These findings show that skin pigmentation effects in clinical PAI arise from coupled optical and acoustic mechanisms, and support clinically validated correction strategies for more reliable imaging across diverse skin tones.