In vivo local determination of tissue optical properties: applications to human brain

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Abstract
Local and superficial near-infrared (NIR) optical-property characterization of turbid biological tissues can be achieved by measurement of spatially resolved diffuse reflectance at small source–detector separations (-1, ±0.05 mm-1, and ±0.2, respectively. In vivo measurements performed intraoperatively on a human skull and brain are reported for four NIR wavelengths (674, 811, 849, 956 nm) when the spatially resolved probe and FDPM are used. The spatially resolved probe shows optimum measurement sensitivity in the measurement volume immediately beneath the probe (typically 1 mm3 in tissues), whereas FDPM typically samples larger regions of tissues. Optical-property values for human skull, white matter, scar tissue, optic nerve, and tumors are reported that show distinct absorption and scattering differences between structures and a dependence on the phase-function parameter γ.