Noninvasive estimation of superficial layer thickness using multi-channel diffuse correlation spectroscopy.

Diffuse correlation spectroscopy (DCS) is a promising, noninvasive, light-based method for continuous bedside monitoring of cerebral blood flow. However, its sensitivity to brain tissue is affected by extracerebral layers. Although layered-model analysis improves cerebral perfusion measurement accuracy, it requires precise knowledge of the properties of superficial layers. To address this challenge, we demonstrate a method for quantifying superficial blood flow dynamics and thickness using three-channel DCS measurements. The approach was validated via simulation and layered phantom experiments. Results demonstrated that an accurate superficial-layer blood flow index can be obtained by adjusting photon count rates at short separations. In turn, this enabled estimation of the superficial-layer thickness and the lower-layer blood flow index from DCS data acquired at two long source-detector separations.