title: Practical and adequate approach to modeling light propagation in an adult head with low-scattering regions by use of diffusion theory.
abstract: A practical and adequate approach to modeling light propagation in an adult head with a low-scattering cerebrospinal fluid (CSF) region by use of diffusion theory was investigated. The diffusion approximation does not hold in a nonscattering or low-scattering regions. The hybrid radiosity-diffusion method was adopted to model the light propagation in the head with a nonscattering region. In the hybrid method the geometry of the nonscattering region is acquired as a priori information. In reality, low-level scattering occurs in the CSF region and may reduce the error caused by the diffusion approximation. The partial optical path length and the spatial sensitivity profile calculated by the finite-element method agree well with those calculated by the Monte Carlo method in the case in which the transport scattering coefficient of the CSF layer is greater than 0.3 mm(-1). Because it is feasible to assume that the transport scattering coefficient of a CSF layer is 0.3 mm(-1), it is practical to adopt diffusion theory to the modeling of light propagation in an adult head as an alternative to the hybrid method.
authors.affiliation: Department of Electronics and Electrical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan. koyama@okd.elec.keio.ac.jp
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Koyama
authors.forename: Atsushi
authors.initials: A
authors.lastname: Iwasaki
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Ogoshi
authors.forename: Eiji
authors.initials: E
authors.lastname: Okada
mesh_terms: D016880:Anisotropy; D001931:Brain Mapping / Q000379:methods; D002555:Cerebrospinal Fluid / Q000166:cytology* / Q000502:physiology*; D003198:Computer Simulation; D006257:Head / Q000033:anatomy & histology* / Q000502:physiology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008027:Light; D008954:Models, Biological; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D041622:Tomography, Optical / Q000379:methods*