Table 2. Intensity and path length of detected light for the head models with different types of FS.

Type of frontal sinus	Detected intensity	Total path length (mm)	Partial optical path length (mm)
			Scalp	Skull	FS	CSF	Gray matter	White matter
(a) Whole FS	3.4 × 10−8	166	88.4	67.7	37.6	7.81	2.06	0.253
(b) Without FS	7.5 × 10−9	230	115	101	0	11.3	2.71	0.397
(c) Shallow FS	2.7 × 10−8	179	91.6	80.7	29.0	5.23	1.35	0.163
(d) Deep FS	1.3 × 10−8	210	100	94.7	16.6	12.4	3.01	0.404