Influence of extracerebral layers on estimates of optical properties with continuous wave near infrared spectroscopy: analysis based on multi-layered brain tissue architecture and Monte Carlo simulation

Figures & data

Figure 1. Multi-layered brain structure for Monte Carlo simulations.

Figure 2. Optical measurement system of NIRS. (a) Diagram, (b) Probe and measuring circuit.

Figure 3. Prepared material for making head model.

Figure 4. Tissue model of head for in vitro experiment.

Table 1. Optical parameters for five-layered head model.

No.	Scalp (3 mm) (mm^−1)	Skull (7 mm) (mm^−1)	CSF (2 mm) (mm^−1)	Gray matter (4 mm) (mm^−`1)	White matter (4 mm) (mm^−1)
1	µa = 0.022 µs^’ = 2.11	µa = 0.016 µs^’ = 1.79	µa = 0.0045 µs^’ = 0.27	µa = 0.038 µs^’ = 2.39	µa = 0.016 µs^’=9.62

Figure 5. Change of absorbance induced by absorption coefficient variation in gray matter. a) souce-detector distance of 29 mm; b) souce-detector distance of 35 mm.

Table 2. the partial optical pathlength in gray matter for different source-detector distance.

Wavelength	Source-Detector distance (mm)
	13	18	24	29	35	40
760	3.042	8.022	14.51	19.50	24.67	27.35
805	3.365	8.603	15.13	20.19	26.23	30.41
850	3.690	9.028	16.10	21.81	27.20	37.62

Table 3. Results for measurement of absorption coefficients variation of gray matter.

No.	Wavelength 760 nm (mm^−1)			Wavelength 805 nm (mm^−1)			Wavelength 850 nm (mm^−1)
	Std Value	29 mm	35 mm	Std Value	29 mm	35 mm	Std Value	29 mm	35 mm
1	0.0019	0.0021	0.0021	0.0017	0.0018	0.0019	0.0016	0.0018	0.0018
2	0.0039	0.0040	0.0041	0.0035	0.0038	0.0037	0.0033	0.0035	0.0036
3	0.0058	0.0063	0.0064	0.0053	0.0055	0.0057	0.0050	0.0053	0.0054
4	0.0078	0.0081	0.0080	0.0070	0.0076	0.0075	0.0066	0.0071	0.0070
5	0.0097	0.0096	0.0095	0.0088	0.0092	0.0089	0.0083	0.0084	0.0084