Functional near infrared spectroscopy using spatially resolved data to account for tissue scattering: A numerical study and arm‐cuff experiment

• Published in: Journal of biophotonics Vol. 12; no. 10; pp. e201900064 - n/a
• Main Authors: Veesa, Joshua D., Dehghani, Hamid
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY‐VCH Verlag GmbH & Co. KGaA 01.10.2019; Wiley Subscription Services, Inc
• Subjects: Algorithms; Brain - metabolism; Chromophores; Computer simulation; Continuous radiation; Diffusion; Distance measurement; Full; Hemodynamics; Humans; Infrared spectroscopy; Light intensity; Luminous intensity; Models, Biological; Near infrared radiation; near‐infrared spectroscopy; Optical Phenomena; Oxygen - metabolism; Oxygenation; Parameters; Scattering; Spectroscopy, Near-Infrared; Spectrum analysis; tissue optics; tissue scattering; Tissues; Wave attenuation; Wavelengths; tissue optics; near-infrared spectroscopy; tissue scattering
• ISSN: 1864-063X; 1864-0648; 1864-0648
• DOI: 10.1002/jbio.201900064

Functional Near‐Infrared Spectroscopy (fNIRS) aims to recover changes in tissue optical parameters relating to tissue hemodynamics, to infer functional information in biological tissue. A widely‐used application of fNIRS relies on continuous wave (CW) methodology that utilizes multiple distance measurements on human head for study of brain health. The typical method used is spatially resolved spectroscopy (SRS), which is shown to recover tissue oxygenation index (TOI) based on gradient of light intensity measured between two detectors. However, this methodology does not account for tissue scattering which is often assumed. A new parameter recovery algorithm is developed, which directly recovers both the scattering parameter and scaled chromophore concentrations and hence TOI from the measured gradient of light‐attenuation at multiple wavelengths. It is shown through simulations that in comparison to conventional SRS which estimates cerebral TOI values with an error of ±12.3%, the proposed method provides more accurate estimate of TOI exhibiting an error of ±5.7% without any prior assumptions of tissue scatter, and can be easily implemented within CW fNIRS systems. Using an arm‐cuff experiment, the obtained TOI using the proposed method is shown to provide a higher and more realistic value as compared to utilizing any prior assumptions of tissue scatter. The gradient of attenuation of multi‐spectral Near Infrared light as measured at two or more detectors placed on forehead can provide cerebral tissue oxygenation index by accounting for the subject dependent scattering properties of the underlying tissue.