Theoretical and experimental investigation of near-infrared light propagation in a model of the adult head

Eiji Okada, Michael Firbank, Martin Schweiger, Simon R. Arridge, Mark Cope, David T. Delpy

Research output: Contribution to journalArticlepeer-review

457 Citations (Scopus)


Near-infrared light propagation in various models of the adult head is analyzed by both time-of-flight measurements and mathematical prediction. The models consist of three- or four-layered slabs, the latter incorporating a clear cerebrospinal fluid (CSF) layer. The most sophisticated model also incorporates slots that imitate sulci on the brain surface. For each model, the experimentally measured mean optical path length as a function of source-detector spacing agrees well with predictions from either a Monte Carlo model or a finite-element method based on diffusion theory or a hybrid radiosity-diffusion theory. Light propagation in the adult head is shown to be highly affected by the presence of the clear CSF layer, and both the optical path length and the spatial sensitivity profile of the models with a CSF layer are quite different from those without the CSF layer. However, the geometry of the sulci and the boundary between the gray and the white matter have little effect on the detected light distribution.

Original languageEnglish
Pages (from-to)21-31
Number of pages11
JournalApplied Optics
Issue number1
Publication statusPublished - 1997 Jan 1


  • Near-infrared spectroscopy
  • Optical path length
  • Oxygenation monitoring
  • Spatial sensitivity profile

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Engineering (miscellaneous)
  • Electrical and Electronic Engineering


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