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Open AccessArticle

The Optical Effective Attenuation Coefficient as an Informative Measure of Brain Health in Aging

1
Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
2
Department of Neuroscience, Imaging and Clinical Sciences, University G. D’Annunzio of Chieti-Pescara, 66100 Chieti, Italy
3
Psychology Department, University of Illinois at Urbana-Champaign, Champaign, IL 61820, USA
4
Division of Psychology, Nanyang Technological University, Singapore 639818, Singapore
5
Department of Pharmacology, National University of Singapore, Singapore 117600, Singapore
6
Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
*
Authors to whom correspondence should be addressed.
Photonics 2019, 6(3), 79; https://doi.org/10.3390/photonics6030079
Received: 24 May 2019 / Revised: 5 July 2019 / Accepted: 10 July 2019 / Published: 12 July 2019
(This article belongs to the Special Issue Neurophotonics – Optics for the Brain)
Aging is accompanied by widespread changes in brain tissue. Here, we hypothesized that head tissue opacity to near-infrared light provides information about the health status of the brain’s cortical mantle. In diffusive media such as the head, opacity is quantified through the Effective Attenuation Coefficient (EAC), which is proportional to the geometric mean of the absorption and reduced scattering coefficients. EAC is estimated by the slope of the relationship between source–detector distance and the logarithm of the amount of light reaching the detector (optical density). We obtained EAC maps across the head in 47 adults (age range 18–75 years), using a high-density dual-wavelength optical system. We correlated regional and global EAC measures with demographic, neuropsychological, structural and functional brain data. Results indicated that EAC values averaged across wavelengths were strongly associated with age-related changes in cortical thickness, as well as functional and neuropsychological measures. This is likely because the EAC largely depends on the thickness of the sub-arachnoid cerebrospinal fluid layer, which increases with cortical atrophy. In addition, differences in EAC values between wavelengths were correlated with tissue oxygenation and cardiorespiratory fitness, indicating that information about cortical health can be derived non-invasively by quantifying the EAC. View Full-Text
Keywords: diffuse optical imaging (DOI); effective attenuation coefficient (EAC); aging; cortical thinning; FreeSurfer diffuse optical imaging (DOI); effective attenuation coefficient (EAC); aging; cortical thinning; FreeSurfer
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Chiarelli, A.M.; Low, K.A.; Maclin, E.L.; Fletcher, M.A.; Kong, T.S.; Zimmerman, B.; Tan, C.H.; Sutton, B.P.; Fabiani, M.; Gratton, G. The Optical Effective Attenuation Coefficient as an Informative Measure of Brain Health in Aging. Photonics 2019, 6, 79.

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