Simultaneous Optical Measurement of Hemoglobin, Cerebral Blood Flow, and Cytochrome-C-Oxidase Changes Via Wavelength Time-Multiplexed Speckle Sensing

Monitoring cytochrome-c oxidase (CCO) alongside changes in hemoglobin (Hb) concentration and cerebral blood flow (CBF) offers significant advantages for assessing metabolic activity non-invasively in real time. In this study, we present a five-wavelength laser system synchronized with CMOS cameras, enabling simultaneous measurements of functional near-infrared spectroscopy (fNIRS), CCO and speckle contrast optical spectroscopy (SCOS) changes. We first validated the performance of our time-multiplexed laser system by comparing it with a five-LED setup and a broadband system in phantom measurements, demonstrating strong correlations across all modalities. Subsequently, we applied our system in human studies to capture concurrent hemodynamic and metabolic responses, including variations induced by cardiac and breath holding in CCO, Hb, and CBF.