Multi-channel multi-distance broadband near-infrared spectroscopy system to measure the spatial response of cellular oxygen metabolism and tissue oxygenation

Abstract

We present a multi-channel, multi-distance broadband near-infrared spectroscopy (NIRS) system with the capability of measuring changes in haemoglobin concentrations (Δ[HbO2], Δ[HHb]), oxidation state of cytochrome-c-oxidase (Δ[oxCCO]) and tissue oxygen saturation (TOI) in the adult human brain. The main components of the instrument are two customized spectrographs and two light sources. Each spectrograph is lens-based to improve light throughput, has a grating enhanced to optimise reflection in the near-infrared (NIR) spectral region and uses a front illuminated cooled CCD camera (−70° C) with a square chip dimension of 12.3 x 12.3 mm (512 x 512 pixels). Each light source uses a 50W halogen bulb with a gold plated mirror to increase the intensity of the NIR light. Each light source was connected to a custom-built bifurcated fibre bundle to create two source fibre bundles (3.2 mm diameter each). Each spectrograph received light input from another custom-built fibre bundle comprised of six individual bundles (one with 0.6 mm diameter and the other five with 1.5 mm diameter). All fibre bundles were fixed on a 3D printed optode holder (two light sources x two fibre bundles each = four probes; and two spectrographs x six fibre bundles each = 12 probes) that allowed 24 multi-distance channels across the forehead (six channels at 20 mm, three channels at 30 mm and 15 channels at 35 mm) and six TOI measurements. We demonstrated the use of the system in a cohort of nine healthy adult volunteers during prefrontal cortex functional activation using the Stroop task. We have observed functional responses identified as significant increase in Δ[HbO2], decrease in Δ[HHb] and increase in Δ[oxCCO] in five channels (out of 12), that overlay the left and right dorsolateral prefrontal cortices. There was no observable TOI functional response and we have shown small variations in TOI across different sites within the same subject and within the same site across subjects.

Quantification of the severity of hypoxic-ischemic brain injury in a neonatal preclinical model using measurements of cytochrome-c-oxidase from a miniature broadband-near-infrared spectroscopy system

“…16,17 Use of the full nearinfrared (NIR) spectrum from 780 to 900 nm obtained by bNIRS has enabled precise measurement of tissue changes in [oxCCO] in animals, neonates, and adults. [18][19][20][21][22][23][24][25][26][27][28][29][30] Cooper et al 31 described the integration of an in-house built bNIRS system with 31 P-MRS to investigate HI in newborn pigs and discussed the physiological/biochemical relationships of these measurements. They reported that the measurement of Δ½oxCCO correlates with changes in energy metabolism measured by 31 P-MRS during HI and early recovery after reperfusion and oxygenation.…”

Broadband time-resolved multi-channel functional near-infrared spectroscopy system to monitor in vivo physiological changes of human brain activity

“…fNIRS can monitor the changes in the redox state of CCO using the oxidized minus reduced CCO spectra to obtain a measurement of changes in the concentration of oxidized CCO ([oxCCO]). Thus, this biomarker could be very interesting because it provides another and complementary way to evaluate neural activity [54].…”

A Mini-Review on Functional Near-Infrared Spectroscopy (fNIRS): Where Do We Stand, and Where Should We Go?

“…New developments in fNIRS technology will further allow for the monitoring, at least on newborns, of the cytochrome-c-oxidase redox state (CCO), which is also a metabolic marker of oxidative metabolism [111]. The hyperspectral CW NIR technique is currently used by some research groups to monitor in vivo human brain metabolism via measurements of the concentration changes in O 2 Hb, HHb and the oxidation state of CCO to achieve the quantification of cerebral metabolic activation in different situations from functional stimulation to response during oxygen-dependent conditions [23,24]. An increase of the CCO signal, typically corresponding to an increment in cerebral metabolism, was found, for instance, during the functional activation induced by simulated driving [23], the Stroop task [24] or working memory tasks [112].…”

“…The hyperspectral CW NIR technique is currently used by some research groups to monitor in vivo human brain metabolism via measurements of the concentration changes in O 2 Hb, HHb and the oxidation state of CCO to achieve the quantification of cerebral metabolic activation in different situations from functional stimulation to response during oxygen-dependent conditions [23,24]. An increase of the CCO signal, typically corresponding to an increment in cerebral metabolism, was found, for instance, during the functional activation induced by simulated driving [23], the Stroop task [24] or working memory tasks [112]. Unlike the hemodynamic changes that are strongly affected by scalp blood flow changes, the changes in the CCO signal more specifically reflect the brain cortex activation.…”