Mapping human cerebral blood flow with high-density, multi-channel speckle contrast optical spectroscopy

Recently, speckle contrast optical spectroscopy (SCOS) enabled non-invasive, high signal-to-noise-ratio (SNR) human cerebral blood flow (CBF) measurements, relevant for both neuroscience and clinical monitoring of diseases with CBF dysregulation. Single channel SCOS measurements limit the information obtained to only one location on the head. In this work, we develop a multi-channel SCOS system to map spatial heterogeneity in CBF changes during human brain activation. Using a galvanometer, we temporally multiplexed a free-space laser to 7 source fibers positioned at different locations on the head. Diffuse light collected from the tissue is captured by fiber bundles projecting to 17 complementary metal-oxide semiconductor (CMOS) cameras, resulting in 50 source-detector channels measuring optical density (OD) and relative CBF changes covering an area of 7.6 cm by 6.6 cm on the head. We validated the spatial specificity and stability of the system using a liquid flow phantom. We then measured brain activity during a word-color Stroop task in 15 subjects and obtained brain activation maps. The average signal changes in the channel showing the largest activation were 1.7 × 10^-2 in $\text{ΔOD}$ and 6.6% in CBF.