FIGURE 2.

Absolute absorption coefficients (μ_a: top panels) and reduced scattering coefficients (${\mu }_s^{\prime }$: middle panels) measured with multi-distance FD-NIRS at 690 nm (left panels) and 830 nm (right panels) on the forehead of 16 elderly subjects (85 ± 6 years old) using diffusion theory for a homogeneous semi-infinite medium. From the absorption coefficients at two wavelengths, absolute values of concentration of hemoglobin ([HbT]) and tissue saturation (StO₂) were obtained (bottom panels). The blocks represent the mean ± standard error (vertical dimension) of the measurements performed at the range of distances corresponding to the horizontal range. The black and gray blocks correspond to two measurement sessions performed on the same group of 16 subjects 5 months apart. Reprinted with permission from Hallacoglu et al. (2012).