Challenging the skin pigmentation bias in tissue oximetry via time-domain near-infrared spectroscopy

Recently, skin pigmentation has been shown to affect the performance of pulse oximeters and other light-based techniques like photo-acoustic imaging, tissue oximetry, and continuous wave near-infrared spectroscopy. Evaluating the robustness to changes in skin pigmentation is therefore essential for the proper use of optical technologies in the clinical scenario. We conducted systematic time-domain near-infrared spectroscopy measurements on calibrated tissue phantoms and in vivo on volunteers during static and dynamic (i.e., arterial occlusion) measurements. To simulate varying melanosome volume fractions in the skin, we inserted, between the target sample and the measurement probe, thin tissue phantoms made of silicone and nigrosine (skin phantoms). Additionally, we conducted an extensive measurement campaign on a large cohort of pediatric subjects, covering the full spectrum of skin pigmentation. Our findings consistently demonstrate that skin pigmentation has a negligible effect on time-domain near-infrared spectroscopy results, underscoring the reliability and potential of this emerging technology in diverse clinical settings.