Brain-computer interfaces (BCIs) are becoming increasingly popular as a tool to improve the quality of life of patients with disabilities. Recently, time-resolved functional nearinfrared spectroscopy (TR-fNIRS) based BCIs are gaining traction because of their enhanced depth sensitivity leading to lower signal contamination from the extracerebral layers. This study presents the first account of TR-fNIRS based BCI for "mental communication" on healthy participants. Twenty-one (21) participants were recruited and were repeatedly asked a series of questions where they were instructed to imagine playing tennis for "yes" and to stay relaxed for "no." The change in the mean timeof-flight of photons was used to calculate the change in concentrations of oxy-and deoxyhemoglobin since it provides a good compromise between depth sensitivity and signal-to-noise ratio. Features were extracted from the average oxyhemoglobin signals to classify them as "yes" or "no" responses. Linear-discriminant analysis (LDA) and support vector machine (SVM) classifiers were used to classify the responses using the leave-one-out cross-validation method. The overall accuracies achieved for all participants were 75% and 76%, using LDA and SVM, respectively. The results also reveal that there is no significant difference in accuracy between questions. In addition, physiological parameters [heart rate (HR) and mean arterial pressure (MAP)] were recorded on seven of the 21 participants during motor imagery (MI) and rest to investigate changes in these parameters between conditions. No significant difference in these parameters was found between conditions. These findings suggest that TR-fNIRS could be suitable as a BCI for patients with brain injuries.

During cardiac surgery with cardiopulmonary bypass (CPB), adequate maintenance of cerebral blood flow (CBF) is vital in preventing postoperative neurological injury – i.e. stroke, delirium, cognitive impairment. Reductions in CBF large enough to impact cerebral energy metabolism can lead to tissue damage and subsequent brain injury. Current methods for neuromonitoring during surgery are limited. This study presents the clinical translation of a hybrid optical neuromonitor for continuous intraoperative monitoring of cerebral perfusion and metabolism in ten patients undergoing non-emergent cardiac surgery with non-pulsatile CPB. The optical system combines broadband near-infrared spectroscopy (B-NIRS) to measure changes in the oxidation state of cytochrome c oxidase (oxCCO) – a direct marker of cellular energy metabolism – and diffuse correlation spectroscopy (DCS) to provide an index of cerebral blood flow (CBFi). As the heart was arrested and the CPB-pump started, increases in CBFi (88.5 ± 125.7%) and significant decreases in oxCCO (−0.5 ± 0.2 µM) were observed; no changes were noted during transitions off CPB. Fifteen hypoperfusion events, defined as large and sustained reductions in CPB-pump flow rate, were identified across all patients and resulted in significant decreases in perfusion and metabolism when mean arterial pressure dropped to 30 mmHg or below. The maximum reduction in cerebral blood flow preceded the corresponding metabolic reduction by 18.2 ± 15.0 s. Optical neuromonitoring provides a safe and non-invasive approach for assessing intraoperative perfusion and metabolism and has potential in guiding patient management to prevent adverse clinical outcomes.

Post-hemorrhagic ventricular dilatation (PHVD) is characterized by a build-up of cerebral spinal fluid (CSF) in the ventricles, which increases intracranial pressure and compresses brain tissue. Clinical interventions (i.e., ventricular taps, VT) work to mitigate these complications through CSF drainage; however, the timing of these procedures remains imprecise. This study presents Neonatal NeuroMonitor (NNeMo), a portable optical device that combines broadband near-infrared spectroscopy (B-NIRS) and diffuse correlation spectroscopy (DCS) to provide simultaneous assessments of cerebral blood flow (CBF), tissue saturation (StO2), and the oxidation state of cytochrome c oxidase (oxCCO). In this study, NNeMo was used to monitor cerebral hemodynamics and metabolism in PHVD patients selected for a VT. Across multiple VTs in four patients, no significant changes were found in any of the three parameters: CBF increased by 14.6 ± 37.6% (p = 0.09), StO2 by 1.9 ± 4.9% (p = 0.2), and oxCCO by 0.4 ± 0.6 µM (p = 0.09). However, removing outliers resulted in significant, but small, increases in CBF (6.0 ± 7.7%) and oxCCO (0.1 ± 0.1 µM). The results of this study demonstrate NNeMo’s ability to provide safe, non-invasive measurements of cerebral perfusion and metabolism for neuromonitoring applications in the neonatal intensive care unit.

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Introduction The microcirculation is the primary facilitator of oxygen delivery in tissue, and dysfunction in the microvasculature is often the first indication of a disease state. The microcirculation can be studied using a variety of methods, both invasive and non‐invasive. Two non‐invasive optical methods are near infrared spectroscopy (NIRS) and diffuse correlation spectroscopy (DCS). NIRS is sensitive to changes in tissue hemoglobin concentration and oxygen, while DCS is sensitive to changes in blood flow. However, neither method can directly visualize changes on a capillary by capillary basis. Intravital Video Microscopy (IVVM) allows us to do so, but is an invasive technique that requires surgery to expose the microcirculation. By using IVVM we can compare a direct visualization of the microvasculature to the signal received by NIRS/DCS in an equivalent microvascular bed. In addition, we can compare the NIRS/DCS signal from the skeletal muscle to the signal from the brain, allowing us to simultaneously monitor change in these two organs in response to disease progression or in response to stimulus. Methods Data is collected from Sprague Dawley rats (n=4) using both a dual wavelength Olympus inverted microscope (with 2 Rolera XR cameras and a beam splitter) and an in‐house NIRS/DCS device. Rats are anaesthetized and have their right extensor digitorum longus (EDL) muscle, found in the hind limb, exposed and reflected over the objective. Probes for the NIRS/DCS device are located on the left hind limb and the top of the skull. IVVM is used to collect microvascular velocity, hematocrit, and oxygen saturation from the right EDL, and NIRS/DCS will be used to collect microvascular hematocrit, oxygen saturation, and blood flow data from the left hind limb and the brain. Microvascular blood flow and oxygen saturation data from the left and right hind limbs will be compared, then the NIRS/DCS‐gathered data from the left hind limb will be compared to NIRS/DCS‐gathered data from the brain. Discussion This study will be the first to make a direct comparison between NIRS/DCS and IVVM measurements of the microcirculation, and will provide insight into the sensitivity of NIRS/DCS and its ability to accurately monitor the microvasculature. In addition, this study will be the first to make a direct comparison between skeletomuscular and cerebral NIRS/DCS measurements. Future work includes using this approach to determine the differences in effect of a phenylephrine bolus or an inspired oxygen challenge on these two microvascular beds. Further studies will determine whether disease progression occurs on the same timeline in the brain as it does in skeletal muscle. Support or Funding Information NSERC Discovery Grant to C.G. Ellis.

A major concern with preterm birth is the risk of neurodevelopmental disability. Poor cerebral circulation leading to periods of hypoxia is believed to play a significant role in the etiology of preterm brain injury, with the first three days of life considered the period when the brain is most vulnerable. This study focused on monitoring cerebral perfusion and metabolism during the first 72 h after birth in preterm infants weighing less than 1500 g. Brain monitoring was performed by combining hyperspectral near-infrared spectroscopy to assess oxygen saturation and the oxidation state of cytochrome c oxidase (oxCCO), with diffuse correlation spectroscopy to monitor cerebral blood flow (CBF). In seven of eight patients, oxCCO remained independent of CBF, indicating adequate oxygen delivery despite any fluctuations in cerebral hemodynamics. In the remaining infant, a significant correlation between CBF and oxCCO was found during the monitoring periods on days 1 and 3. This infant also had the lowest baseline CBF, suggesting the impact of CBF instabilities on metabolism depends on the level of blood supply to the brain. In summary, this study demonstrated for the first time how continuous perfusion and metabolic monitoring can be achieved, opening the possibility to investigate if CBF/oxCCO monitoring could help identify preterm infants at risk of brain injury.

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