Measuring human cerebral blood flow and brain function with fiber-based speckle contrast optical spectroscopy system

Cerebral blood flow (CBF) is an important indicator of brain health and function. Diffuse correlation spectroscopy (DCS) is an optical technique that enables non-invasive and continuous bedside monitoring of human CBF. However, traditional DCS consisting of a few channels has relatively low signal-to-noise ratio (SNR), preventing measurements at long source detector separations (SDS) with increased sensitivity to cerebral rather than extracerebral blood flow. Here we developed a fiber-based speckle contrast optical spectroscopy (SCOS) system and the corresponding data analysis pipeline to measure CBF variations. We show that SCOS outperforms traditional DCS by more than an order of magnitude in SNR with comparable financial cost. We also demonstrated human brain function measurements during a cognitive task at an SDS of 33 mm. This technology will establish the foundation for devices that use spatial speckle statistics to non-invasively monitor human CBF, leading to a new functional neuroimaging approach for cognitive neuroscience.