Wavelength dependence of effective pathlength factor in noninvasive optical measurements of human brain functions

Hiroki Sato, Masashi Kiguchi, Atsushi Maki

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In the noninvasive optical measurements of human brain functions, the dependence of pathlength factor in an activation area (effective pathlength factor: EPF) on wavelength was examined by simultaneously recording five wavelengths of 678, 692, 750, 782, and 830 nm, with three different source/detector distances of 20, 30, and 40 mm. We obtained an activation signal in the visual cortex using four wavelength pairs, where 830 nm was fixed as one wavelength. The dependence of EPF on the source/detector distance showed similar tendencies when the wavelengths of 692, 750, and 782 nm were considered. This suggests that it is feasible to use these wavelengths paired with an 830 nm wavelength to investigate the same region.

Original languageEnglish
Pages (from-to)L361-L363
JournalJapanese Journal of Applied Physics, Part 2: Letters
Issue number12-16
Publication statusPublished - 2006 May 17



  • Brain function
  • Effective pathlength factor (EPF)
  • Near-infrared spectroscopy (NIRS)
  • Noninvasive measurement
  • Optical measurement
  • Spatial sensitivity
  • Wavelength dependence

ASJC Scopus subject areas

  • Engineering(all)
  • Physics and Astronomy (miscellaneous)
  • Physics and Astronomy(all)

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