Comparison of light intensity on the brain surface due to laser exposure during optical topography and solar irradiation

Masashi Kiguchi, Noriyoshi Ichikawa, Hirokazu Atsumori, Fumio Kawaguchi, Hiroki Satou, Atsushi Maki, Hideaki Koizumi

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Optical topography (OT), which is based on the near-infrared spectroscopy, is a powerful tool for observing brain activity noninvasively. To estimate the effect of laser exposure on the brain, photon-distribution profiles in bald heads of adults and neonates during the OT were calculated using the photon-diffusion equation. These calculations showed that although the absolute values of the intensity depend on details of the head model, the relative values of OT exposure to sunlight exposure were less sensitive to the model details. As an example, the light intensities on the brain surface during OT obtained by using a commercially available system were about 2% for adults and 3% for neonates of those values obtained under midday sunlight on a sunny day in midsummer. These values were obtained under the reasonable assumptions with a large safety factor.

Original languageEnglish
Article number062108
JournalJournal of Biomedical Optics
Issue number6
Publication statusPublished - 2007 Nov 1
Externally publishedYes



  • Laser safety
  • NIRS
  • Optical topography
  • Photon-diffusion equation

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Atomic and Molecular Physics, and Optics
  • Biomedical Engineering

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