Abstract
Frequency domain near infrared spectroscopy (FD-NIRS) and diffuse correlation spectroscopy (DCS) have emerged as synergistic techniques for the non-invasive assessment of tissue health. Combining FD-NIRS oximetry with DCS measures of blood flow, the tissue oxygen metabolic rate can be quantified, a parameter more closely linked to underlying physiology and pathology than either NIRS or DCS estimates alone. Here we describe the first commercially available integrated instrument, called the "MetaOx", designed to enable simultaneous FD-NIRS and DCS measurements at rates of 10 + Hz, and offering real-time data evaluation. We show simultaneously acquired characterization data demonstrating performance equivalent to individual devices and sample in vivo measurements of pulsation resolved blood flow, forearm occlusion hemodynamic changes and muscle oxygen metabolic rate monitoring during stationary bike exercise.
Highlights
Diffuse optical methods that rely on the deep penetration of near infrared light in biological tissues have emerged as useful non-invasive tools to monitor tissue physiology
The design of the Frequency domain near infrared spectroscopy (FD-NIRS) component was based on previous frequency domain spectrometers developed by ISS Inc., with several improvements aimed at optimal performance
Compared to previous devices used in NIRS-diffuse correlation spectroscopy (DCS) studies, we demonstrate for the first time an integrated instrument that enables simultaneous operation of the two optical sub-systems, and brings them under a unified user interface that provides real-time display of the raw data, as well as derived parameters, such as total hemoglobin concentration, hemoglobin oxygen saturation and DCS blood flow index
Summary
Diffuse optical methods that rely on the deep penetration of near infrared light in biological tissues have emerged as useful non-invasive tools to monitor tissue physiology. By combining oximetry and flow measures, the tissue oxygen metabolic rate (MRO2) can be quantified, a parameter closely linked to underlying physiology and pathological states [2,21] This measure is of particular importance when applied to the brain (cerebral MRO2, i.e. CMRO2) given the strong dependence of this organ on aerobic metabolism [28]. Combining NIRS and DCS technologies into a single instrument capable of taking both measurements in parallel, with a unified user interface could benefit the further development of this research field Such integration requires solving issues of interference between the two laser sources and the respective detection systems, as well as the synchronization of the measurements. We report demonstrative data from simultaneous measurements during a forearm arterial occlusion protocol on healthy volunteers, pulsation resolved blood flow monitoring on the forehead, and muscle oxygen metabolism rate monitoring during exercise on a stationary bike
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