Near-infrared light propagation in an adult head model. II. Effect of superficial tissue thickness on the sensitivity of the near-infrared spectroscopy signal

Eiji Okada, David T. Delpy

    Research output: Contribution to journalArticle

    270 Citations (Scopus)

    Abstract

    It is important for near-infrared spectroscopy (NIRS) and imaging to estimate the sensitivity of the detected signal to the change in hemoglobin that results from brain activation and the volume of tissue interrogated for a specific source–detector fiber spacing. In this study light propagation in adult head models is predicted by Monte Carlo simulation to investigate the effect of the superficial tissue thickness on the partial optical path length in the brain and on the spatial sensitivity profile. In the case of source–detector spacing of 30 mm, the partial optical path length depends mainly on the depth of the inner skull surface whereas the spatial sensitivity profile is significantly affected by the thickness of the cerebrospinal fluid layer. The mean optical path length that can be measured by time-resolved experiments increases when the skull thickness increases whereas the partial mean optical path length in the brain decreases when the skull thickness increases. These results indicate that it is not appropriate to use the mean optical path length as an alternative to the partial optical path length to compensate the NIRS signal for the difference in sensitivity caused by variation of the superficial tissue thickness.

    Original languageEnglish
    Pages (from-to)2915-2922
    Number of pages8
    JournalApplied Optics
    Volume42
    Issue number16
    DOIs
    Publication statusPublished - 2003 Jun 1

    ASJC Scopus subject areas

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

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