Diffuse optics (DO) has been widely used for physiological monitoring for over 40 years [1]. Near-infrared spectroscopy (NIRS) is a well-known DO technique that measures changes in light attenuation due to changes in tissue chromophore concentrations. While NIRS instruments based on continuous waves (CW) have primarily been used to monitor muscle and brain oxygenation changes, recent methodological advancements have increased the accuracy and robustness of NIRS measurements and enabled the monitoring of metabolism and the development of new biomarkers. These advances have pushed the use of NIRS, and more generally DO, in the clinic.
During my presentation, I will showcase the work I have been conducting at the University College London (UCL) to advance the capabilities of DO and extend its use in various fields, such as neuroscience, physiological research, and particularly in a clinical environment.
Indeed, our group, led by Prof. Tachtsidis, is focused on developing optical methodologies to measure brain oxygenation and metabolism. To do so, our primary focus has been on the development of broadband NIRS infrared spectroscopy, an extension of the standard NIRS technique that uses hundreds of wavelengths to acquire more information about the brain. This technique allows us to monitor, on top of the traditional oxygenation parameters monitored with NIRS, the concentration changes in cytochrome-c-oxidase (oxCCO), which is a marker of metabolism. We have shown that monitoring both oxygenation and metabolic changes concurrently could have significant impact for clinical monitoring [2].
Secondly, I will show more recent work that has focused on combining diffuse correlation spectroscopy (DCS) with our broadband NIRS device to further extend the capacities of the system, in an instrument called FLORENCE [3]. Indeed, DCS is an established optical modality that enables non-invasive measurements of blood flow in deep tissue by quantifying the temporal light intensity fluctuations generated by dynamic scattering of moving red blood cells. Thus, the addition of DCS gives us access to blood flow information, enabling us to extract information about the cerebral metabolic rate of oxygen (CMRO2). I will show the benefits of accessing all of this information in a clinical context.
Finally, I will briefly talk about the most advanced instrument that we have been developing, called MAESTROS, which is based on time-domain NIRS (TD-NIRS) and measures the arrival time of photons [4]. This is the most advanced form of NIRS and can unlock new possibilities. It is notably the best technique to enhance the depth sensitivity of NIRS measurements, enabling us to overcome the most significant issue with NIRS, i.e., superficial tissue contamination [5]. I will show an example of a clinical use of this system, together with the new possibilities that it offers.
In conclusion, my talk will provide an overview of the work done at UCL to advance the state-of-the-art of DO and promote its usefulness and adoption in a clinical context.