Low-resolution mapping of the effective attenuation coefficient of the human head: A multidistance approach applied to high-density optical recordings

Antonio M. Chiarelli, Edward L. Maclin, Kathy A. Low, Sergio Fantini, Monica Fabiani, Gabriele Gratton

Research output: Contribution to journalArticle

Abstract

Near infrared (NIR) light has been widely used for measuring changes in hemoglobin concentration in the human brain (functional NIR spectroscopy, fNIRS). fNIRS is based on the differential measurement and estimation of absorption perturbations, which, in turn, are based on correctly estimating the absolute parameters of light propagation. To do so, it is essential to accurately characterize the baseline optical properties of tissue (absorption and reduced scattering coefficients). However, because of the diffusive properties of the medium, separate determination of absorption and scattering across the head is challenging. The effective attenuation coefficient (EAC), which is proportional to the geometric mean of absorption and reduced scattering coefficients, can be estimated in a simpler fashion by multidistance light decay measurements. EAC mapping could be of interest for the scientific community because of its absolute information content, and because light propagation is governed by the EAC for source-detector distances exceeding 1 cm, which sense depths extending beyond the scalp and skull layers. Here, we report an EAC mapping procedure that can be applied to standard fNIRS recordings, yielding topographic maps with 2-to 3-cm resolution. Application to human data indicates the importance of venous sinuses in determining regional EAC variations, a factor often overlooked.

Original languageEnglish (US)
Article number021103
JournalNeurophotonics
Volume4
Issue number2
DOIs
StatePublished - 2017

Keywords

  • baseline optical properties of tissue
  • brain imaging
  • diffuse optical tomography
  • effective attenuation coefficient (EAC or μ eff)
  • functional near infrared spectroscopy

ASJC Scopus subject areas

  • Neuroscience (miscellaneous)
  • Radiological and Ultrasound Technology
  • Radiology Nuclear Medicine and imaging

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