Shedding light on the adult brain: a review of the clinical applications of near-infrared spectroscopy

Abstract

Near-infrared spectroscopy (NIRS) has potential as a non-invasive brain monitor in a wide range of clinical scenarios. In the last decade, there has been a rapid expansion of clinical experience using NIRS to monitor cerebral oxygenation, particularly in cardiac surgery, where there is some evidence that NIRS-guided brain protection protocols might lead to a reduction in peri-operative neurological complications. There are no data to support the wider application of NIRS to monitor cerebral oxygenation during routine anaesthesia and surgery, and its application in brain injury, where it might be expected to have a key monitoring role, is as yet undefined. Technological developments, including the introduction of broadband and time-resolved spectrometers that are capable of reliably measuring changes in oxidized cytochrome c oxidase, offer real potential for a single NIRS-based device to provide multi-site, regional monitoring of cerebral metabolic status as well as oxygenation and haemodynamics.

Event-related changes of the prefrontal cortex oxygen delivery and metabolism during driving measured by hyperspectral fNIRS

“…The total concentration of CCO in the short term is almost constant and it interconverts between reduced and oxidized states. The concentration changes of oxidized CCO (Δ[ox-CCO]) that can be monitored by NIRS represent changes in the CCO redox state and reflect the balance between cerebral oxygen delivery and utilization [4,5]. The brain cells have the highest mitochondrial density among all other body cells thus the concentration of CCO is significantly higher and easier to measure within brain tissue.…”

Modified Beer-Lambert law for blood flow

“…Diffuse optical techniques, such as near-infrared or diffuse optical spectroscopy (DOS, NIRS) and diffuse correlation spectroscopy (DCS), have been employed with remarkable success over the last two decades to probe hemodynamic processes in highly scattering tissues such as human brain, muscle and breast [1][2][3][4][5][6][7][8][9][10][11]. In total, this research has discovered new indicators of tissue function and health that are proving to be clinically relevant [6][7][8][9][10][11][12][13][14].…”

“…In total, this research has discovered new indicators of tissue function and health that are proving to be clinically relevant [6][7][8][9][10][11][12][13][14]. The most basic DOS/NIRS instrument measures diffuse reflectance from tissue as a function of input wavelength, and thereby derives the concentration of tissue chromophores and contrast agents, including oxyand deoxy-hemoglobin (HbO 2 , Hb), and changes thereof.…”

Optimal wavelength combinations for near-infrared spectroscopic monitoring of changes in brain tissue hemoglobin and cytochrome c oxidase concentrations

“…Wavelengthdependent optical attenuation signals can be resolved to extract information on biological chromophores that directly reflect the oxygenation, hemodynamic, and metabolic state of tissue site under investigation. Large penetration depth of infrared light allows for analysis of breast, muscle, and brain tissues, opening up the possibility of a wide range of clinical applications [1][2][3][4].…”