Abstract

Absolute concentrations of oxyhaemoglobin and deoxyhaemoglobin obtained using multi-wavelength measurements of time-resolved diffuse reflectance signals are presented. The aim was to test how accurately the concentration of oxy- and deoxyhemoglobin can be measured simultaneously at multiple wavelengths. The optical signals were collected using the system constructed by the author’s group^a, which records the distribution in time of flight of photons (DTOFs) simultaneously at 16 spectral channels ranging from 650 to 850 nm. The measurements were carried out on liquid phantoms containing intralipid solution, human blood and yeast in varying amounts. The oxygen saturation of blood covered a continuous range from 100 % to 0 % during 6 deoxygenation cycles. The estimated values of total haemoglobin (20.9, 35.7, 57.3, 45.7 μM) are close to the reference values obtained using a blood gas analyzer (21.3, 37.0, 57.3, 48.0 μM) and the estimated values of absolute concentrations of oxy-, deoxy- and total haemoglobin are similar to the values obtained using a commercial frequency-domain NIRS system (OxiplexTS^TM). The phantom measurements have shown the capability to measure the absolute concentrations of chromophores in a studied media using multi-wavelength, time-resolved NIRS technique. The excess number of spectral channels can potentially be used to resolve changes in oxidation state of cytochrome-c-oxidase enzyme.

© 2019 SPIE/OSA