Tissue-like phantoms for near-infrared fluorescence imaging system assessment and the training of surgeons

Living tissue has relatively low photon absorption in the near-IR (NIR) range of the electromagnetic spectrum (700 to $1000\mathrm{nm}$ ). Endogenous fluorophores are strong contributors to autofluorescence in the UV and visible regions of the spectrum, but are significantly weaker in the NIR. Hence, from an absorbance and autofluorescence standpoint, NIR light has distinct advantages. Scatter is significant at all wavelengths, and is a complex function of tissue composition (discussed in Ref. 1). However, for many tissues, the absolute value of scatter tends to be lower in the NIR.