Skin disease is primarily diagnosed visually, but this subjective approach can lead to misdiagnosis, particularly for darkly-pigmented patients where increased melanin leads to more subtle disease appearance. Inflammation is characterized by shifts in tissue fluid, and the short-wave infrared (SWIR 900-1700 nm) regime, where water absorbs strongly and melanin absorbs weakly, may therefore be a pigment-insensitive modality for assessing skin inflammation. We built a multispectral SWIR imaging system and tested its ability to detect tissue fluid after intradermal saline injection in 24 healthy subjects with diverse pigmentation. Saline injection regions had 20-50 times more contrast than unaffected skin in SWIR images compared to visible photography, regardless of the degree of pigmentation. SWIR multispectral imaging may offer a new window into assessing inflammatory skin diseases in a pigmentation-independent manner.
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