Clinical Brain Monitoring with Time Domain NIRS: A Review and Future Perspectives

Frédéric Lange,Ilias Tachtsidis

doi:10.3390/app9081612

Frédéric Lange, Ilias Tachtsidis

Open Access

https://doi.org/10.3390/app9081612

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Journal: Applied sciences	Publication Date: Apr 18, 2019
Citations: 88	License type: CC BY 4.0

Affiliation: University College London

Abstract

Near-infrared spectroscopy (NIRS) is an optical technique that can measure brain tissue oxygenation and haemodynamics in real-time and at the patient bedside allowing medical doctors to access important physiological information. However, despite this, the use of NIRS in a clinical environment is hindered due to limitations, such as poor reproducibility, lack of depth sensitivity and poor brain-specificity. Time domain NIRS (or TD-NIRS) can resolve these issues and offer detailed information of the optical properties of the tissue, allowing better physiological information to be retrieved. This is achieved at the cost of increased instrument complexity, operation complexity and price. In this review, we focus on brain monitoring clinical applications of TD-NIRS. A total of 52 publications were identified, spanning the fields of neonatal imaging, stroke assessment, traumatic brain injury (TBI) assessment, brain death assessment, psychiatry, peroperative care, neuronal disorders assessment and communication with patient with locked-in syndrome. In all the publications, the advantages of the TD-NIRS measurement to (1) extract absolute values of haemoglobin concentration and tissue oxygen saturation, (2) assess the reduced scattering coefficient, and (3) separate between extra-cerebral and cerebral tissues, are highlighted; and emphasize the utility of TD-NIRS in a clinical context. In the last sections of this review, we explore the recent developments of TD-NIRS, in terms of instrumentation and methodologies that might impact and broaden its use in the hospital.

Highlights

Over the last two decades, the near-infrared spectroscopy (NIRS) field has gained lots of attention as more and more instruments are used in patients within the hospitals [1]
We have summarized the clinical application of time domain (TD)-NIRS and reported its use (1) in the neonatology unit to follow neonates with various conditions, (2) in the ICU to monitor stroke or traumatic brain injury (TBI) patients, or to communicate with patients with locked-in syndrome, (3) in the operating room to follow brain oxygenation during surgery, and (4) in more “standard” neuroscience environments for studies focusing on patients with psychiatric disorders
The present review shows that current generation of TD-NIRS can be used in a clinical environment on patients with different pathologies

Summary

Introduction

Over the last two decades, the near-infrared spectroscopy (NIRS) field has gained lots of attention as more and more instruments are used in patients within the hospitals [1]. NIRS relies on the fact that light, in the range of 600 to 1000 nm, can penetrate deep into the biological tissue, because in that wavelength range absorption is low, and scattering is the dominant interaction process. Each absorber, called chromophore, has a specific absorption or extinction coefficient [2]. It is possible to quantify the contribution of each chromophore and to resolve its concentration in the tissue. One of the main chromophores in tissue that is oxygen dependent is haemoglobin; NIRS can quantify the in vivo concentrations of oxygenated (HbO2 ) and deoxygenated (HHb) haemoglobin and monitor tissue oxygenation non-invasively, and in real-time.

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