Sensitivity of frequency-domain optical measurements to brain hemodynamics: simulations and human study of cerebral blood flow during hypercapnia

Posted on 11.01.2021 - 15:50
This study characterizes the sensitivity of noninvasive measurements of cerebral blood flow (CBF) by using frequency-domain near-infrared spectroscopy (FD-NIRS) and coherent hemodynamics spectroscopy (CHS). We consider four FD-NIRS methods: single-distance intensity (SDI), single-distance phase (SDφ), dual-slope intensity (DSI), and dual-slope phase (DSφ). Cerebrovascular reactivity (CVR) was obtained from the percent change in the measured CBF in a step hypercapnic challenge. In the first experiment on eight subjects, SDφ showed a stronger sensitivity to cerebral hemodynamics than SDI (CVR_SDI=0.32 [0.20, 0.57] %/mmHg; CVR_SDφ = 0.47 [0.33, 0.60] %/mmHg; values are in median [25%,75% quantiles]). CVR_DSI and CVR_DSφ showed no significant difference (CVR_DSI=0.6 [0.3, 0.9]%/mmHg; CVR_DSφ=0.4 [0.2, 0.5] %/mmHg). In the second experiment on four subjects, we added a 5 mm scattering layer between the optical probe and scalp tissue to increase the extracerebral layer thickness (L_ec). CVR_DSφ became significantly greater than CVR_DSI (CVR_DSI = 0.23 [0.16, 0.25] %/mmHg; CVR_DSφ = 0.35 [0.26, 0.55] %/mmHg). Theoretical simulations with two-layered media confirmed that the relative values of CVR_DSI and CVR_DSφ depend on L_ec, with the sensitivity to the brain being greater for DSI than DSφ for a thin extracerebral layer, and greater for DSφ than DSI for a thick extracerebral layer.

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Pham, Thao; Blaney, Giles; Sassaroli, Angelo; Fernandez, Cristianne; Fantini, Sergio (2021): Sensitivity of frequency-domain optical measurements to brain hemodynamics: simulations and human study of cerebral blood flow during hypercapnia. The Optical Society. Collection. https://doi.org/10.6084/m9.figshare.c.5241593.v2
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AUTHORS (5)

Thao Pham
Giles Blaney
Angelo Sassaroli
Cristianne Fernandez
Sergio Fantini

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