title: Mapping of optical pathlength of human adult head at multi-wavelengths in near infrared spectroscopy.
abstract: Measurement of multichannel continuous-wave near-infrared spectroscopy (CW-NIRS) is dependent on the modified Beer-Lambert law, which includes optical pathlength (PL) as an essential parameter. PLs are known to differ across different head regions and different individuals, but the distribution of PLs for the whole head has not been evaluated so far. Thus, using time-resolved near-infrared spectroscopy (TR-NIRS), we measured the optical characteristics including PL, scattering coefficients (mu'(s)), and absorption coefficients (mu(a)) at three wavelengths (760, 800, 830 nm). Then, we constructed maps of these parameters on the subjects' head surface. While the PLs in nearby channels are similar, they differ depending on the regions of the head. The PLs in the region above the Sylvian fissure tended to be shorter than those in the other regions at all of the wavelengths. The difference in the distribution of PLs may be attributed to differences in tissue absorption and scattering properties. The current study suggests the importance of considering PL differences in interpreting functional data obtained by CW-NIRS.
authors.affiliation: Division of Neurological Surgery, Department of Neurological Surgery, Nihon University School of Medicine, Tokyo, Japan.
authors.forename: Akihisa
authors.initials: A
authors.lastname: Katagiri
authors.forename: Ippeita
authors.initials: I
authors.lastname: Dan
authors.forename: Daisuke
authors.initials: D
authors.lastname: Tuzuki
authors.forename: Masako
authors.initials: M
authors.lastname: Okamoto
authors.forename: Noriaki
authors.initials: N
authors.lastname: Yokose
authors.forename: Kouji
authors.initials: K
authors.lastname: Igarashi
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Hoshino
authors.forename: Tokuo
authors.initials: T
authors.lastname: Fujiwara
authors.forename: Youichi
authors.initials: Y
authors.lastname: Katayama
authors.forename: Yui
authors.initials: Y
authors.lastname: Yamaguchi
authors.forename: Kaoru
authors.initials: K
authors.lastname: Sakatani
mesh_terms: D000328:Adult; D006257:Head / Q000502:physiology*; D006801:Humans; D055620:Optical Phenomena; D019265:Spectroscopy, Near-Infrared / Q000379:methods*