Olivia Pucci, Vladislav Toronov, and Keith St. Lawrence, "Measurement of the optical properties of a two-layer model of the human head using broadband near-infrared spectroscopy," Appl. Opt. 49, 6324-6332 (2010)
We present the development of a continuous-wave method of quantifying the optical properties of a two-layered model of the human head using a broadband spectral approach. Absolute absorption and scattering properties of the upper and lower layers of phantoms with known optical properties were reconstructed from steady-state multi-distance measurements by performing differential fit analysis of the near-infrared reflectance spectrum between 700 and . From spectra acquired at 10, 20, and , the concentration of a chromophore in the bottom layer was determined within an error of 10% in the presence of a thick top layer. These results demonstrate that our method was able to determine the optical properties of the lower layer, which represents brain, with acceptable error at specific source–detector distances.
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Errors are shown relative to the known values for the given type of the medium. Homogeneous Type I had higher absorption and reduced scattering coefficients than the Homogeneous Type II phantom.
The values separated by slashes in this column are top/bottom layer carbon black concentrations. In these cases, the error in [Carbon Black] refers to the lower layer.
The two rows labeled “bulk” refer to values obtained by fitting the homogeneous model solution to the two-layered phantoms. Errors for “bulk” were relative to the known optical properties of the top layer. These values were used as the optical properties of the top layer when retrieving the optical properties of the bottom layer, shown by cells with bold content.
The thickness of the top layer was 14 mm. “Exact values” were those known for homogeneous phantoms as discussed in Subsection 2C. In particular, for Type I homogeneous phantom and for Type II homogeneous phantom (.
Table 2
Values of the Carbon Black Concentration and Errors in Recovered Optical Properties of the Bottom Layers of the Two-Layer Phantoms Assuming a Wrong Thickness of the Top Layer (11 mm Instead of 14 mm)a
The top layer optical properties were obtained using the 10/20 SD distance combination. Errors are shown relative to the known values for the given type of the medium.
The values in diagonally divided cells are top/bottom layer carbon black concentrations.
Tables (2)
Table 1
Values of the Carbon Black Concentration and the Associated Error in the Recovered Optical Properties of the Homogeneous and Two-Layered Phantomsa
Errors are shown relative to the known values for the given type of the medium. Homogeneous Type I had higher absorption and reduced scattering coefficients than the Homogeneous Type II phantom.
The values separated by slashes in this column are top/bottom layer carbon black concentrations. In these cases, the error in [Carbon Black] refers to the lower layer.
The two rows labeled “bulk” refer to values obtained by fitting the homogeneous model solution to the two-layered phantoms. Errors for “bulk” were relative to the known optical properties of the top layer. These values were used as the optical properties of the top layer when retrieving the optical properties of the bottom layer, shown by cells with bold content.
The thickness of the top layer was 14 mm. “Exact values” were those known for homogeneous phantoms as discussed in Subsection 2C. In particular, for Type I homogeneous phantom and for Type II homogeneous phantom (.
Table 2
Values of the Carbon Black Concentration and Errors in Recovered Optical Properties of the Bottom Layers of the Two-Layer Phantoms Assuming a Wrong Thickness of the Top Layer (11 mm Instead of 14 mm)a
The top layer optical properties were obtained using the 10/20 SD distance combination. Errors are shown relative to the known values for the given type of the medium.
The values in diagonally divided cells are top/bottom layer carbon black concentrations.