Evaluation of Haemoglobin and Cytochrome Responses During Forearm Ischaemia Using Multi-wavelength Time Domain NIRS

Abstract

We demonstrate the ability of a 16-wavelength time domain near-infrared spectroscopy system to monitor changes in oxy- and deoxy haemoglobin ([HbO2] [HHb]) and the oxidation of cytochrome-c-oxidase ([oxCCO]), during forearm ischaemia. We tested two methods to retrieve the concentration changes. The first uses the measured changes in light attenuation and the modified Beer-Lambert law, and the second uses the absorption and scattering estimated by the measured time-point spread function. The system is able to retrieve the concentration changes with both methods, giving similar results. At the end of forearm ischaemia (t = 5 min), we measured an increase in [HHb] of 16.77 ± 2.52 and 16.37 ± 2.33 μMol, and a decrease in [HbO2] of −6.12 ± 1.62 and −5.57 ± 2.02 μMol for method 1 and 2, respectively. At that same time, the changes in [oxCCO] were −0.36 ± 0.33 and −1.40 ± 1.20 μMol, for method 1 and 2, respectively. These small changes in [oxCCO], despite a huge change in haemoglobin, demonstrate the absence of crosstalk and are comparable to previous measurements using broadband NIRS.

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

“…During the recovery, we observe the typical hyperaemia peak before the return to baseline. Moreover, the amplitudes match the one already reported in the literature [40,41].…”

“…Here we used the method described in Section 2.E to calculate the concentration changes in HbO 2 and [HHb]. The measured path length was 6.7 cm at 800 nm, corresponding to a differential pathlength factor of 3.35, which is in accordance with the literature [39,40].…”

“…Dunne and colleagues have reported a multispectral system that can acquire up to 16 wavelengths with an acquisition time compatible with functional studies. Indeed, that system has been designed to be able to measure the absolute concentration of [oxCCO] in the brain [40,60,61]. Those systems demonstrate that the use of the spectral information, coupled with the TR information, can be a great asset whether for fine tissue characterization or for the detection of supplementary contrasts.…”

“…The source detector distance is 2 cm for every channel. It covers the dorsolateral prefontal cortex (DLPFC), which is involved in arithmetic tasks [40]. The measurement was performed, like the cuff occlusion, in two steps.…”

MAESTROS: A Multiwavelength Time-Domain NIRS System to Monitor Changes in Oxygenation and Oxidation State of Cytochrome-C-Oxidase

“…Preliminary system description has been provided by Dunne and colleagues [41] , and Lange and colleagues [42] . In the present work, Section II will describe the instrument in depth, both in terms of the hardware and software.…”