Open-source FlexNIRS: A low-cost, wireless and wearable cerebral health tracker

Wearable Wireless Functional Near-Infrared Spectroscopy System for Cognitive Activity Monitoring

From learning environments to battlefields to marketing teams, the desire to measure cognition and cognitive fatigue in real time has been a grand challenge in optimizing human performance. Near-infrared spectroscopy (NIRS) is an effective optical technique for measuring changes in subdermal hemodynamics, and it has been championed as a more practical method for monitoring brain function compared to MRI. This study reports on an innovative functional NIRS (fNIRS) sensor that integrates the entire system into a compact and wearable device, enabling long-term monitoring of patients. The device provides unrestricted mobility to the user with a Bluetooth connection for settings configuration and data transmission. A connected device, such as a smartphone or laptop equipped with the appropriate interface software, collects raw data, then stores and generates real-time analyses. Tests confirm the sensor is sensitive to oxy- and deoxy-hemoglobin changes on the forehead region, which indicate neuronal activity and provide information for brain activity monitoring studies.

Creating anatomically-derived, standardized, customizable, and three-dimensional printable head caps for functional neuroimaging

Significance

Consistent and accurate probe placement is a crucial step towards enhancing the reproducibility of longitudinal and group-based functional neuroimaging studies. While the selection of headgear is central to these efforts, there does not currently exist a standardized design that can accommodate diverse probe configurations and experimental procedures.

Aim

We aim to provide the community with an open-source software pipeline for conveniently creating low-cost, 3-D printable neuroimaging head caps with anatomically significant landmarks integrated into the structure of the cap.

Approach

We utilize our advanced 3-D head mesh generation toolbox and 10-20 head landmark calculations to quickly convert a subject's anatomical scan or an atlas into a 3-D printable head cap model. The 3-D modeling environment of the open-source Blender platform permits advanced mesh processing features to customize the cap. The design process is streamlined into a Blender add-on named "NeuroCaptain".

Results

Using the intuitive user interface, we create various head cap models using brain atlases, and share those with the community. The resulting mesh-based head cap designs are readily 3-D printable using off-the-shelf printers and filaments while accurately preserving the head topology and landmarks.

Conclusions

The methods developed in this work result in a widely accessible tool for community members to design, customize and fabricate caps that incorporate anatomically derived landmarks. This not only permits personalized head cap designs to achieve improved accuracy, but also offers an open platform for the community to propose standardizable head caps to facilitate multi-centered data collection and sharing.

Cross-wavelength calibrating method for real-time imaging of tissue optical properties using frequency-domain diffuse optical spectroscopy

Frequency-domain diffuse optical spectroscopy (FD-DOS) is a powerful non-invasive technique for assessing tissue optical properties, with applications ranging from basic research to clinical diagnosis. In this study, we introduce and validate a novel approach termed the cross-wavelength calibrating (CWC) method within the framework of TrackDOSI, a real-time FD-DOS imaging system for tissue characterization. The CWC method aims to mitigate the effects of changing optical coupling and motion artifacts encountered during probe scanning, thus enhancing the accuracy and reliability of optical property measurements. Notably, the CWC method also allows for a simpler geometry with fewer sources than traditional self-calibrating (SC) methods, reducing instrumental complexity and cost while maintaining robustness in estimating optical properties. We first validate the CWC method on solid silicone phantoms, demonstrating strong agreement with the gold standard SC method with an error of -10% and 1% for absorption and reduced scattering coefficients, respectively. Furthermore, experiments on phantom and human tissue reveal the CWC approach's ability to suppress motion artifacts and optical coupling variations, thereby improving measurement repeatability, signal fidelity, and artifact correction in dynamic imaging scenarios. Our findings underscore the potential of the CWC method to enhance the clinical utility of DOSI techniques by enabling real-time artifact correction and improving the accuracy of tissue optical property measurements.

Measuring pulsatile cortical blood flow and volume during carotid endarterectomy

Carotid endarterectomy (CEA) involves removal of plaque in the carotid artery to reduce the risk of stroke and improve cerebral perfusion. This study aimed to investigate the utility of assessing pulsatile blood volume and flow during CEA. Using a combined near-infrared spectroscopy/diffuse correlation spectroscopy instrument, pulsatile hemodynamics were assessed in 12 patients undergoing CEA. Alterations to pulsatile amplitude, pulse transit time, and beat morphology were observed in measurements ipsilateral to the surgical side. The additional information provided through analysis of pulsatile hemodynamic signals has the potential to enable the discovery of non-invasive biomarkers related to cortical perfusion.

Multi-wavelength multi-distance diffuse correlation spectroscopy system for assessment of premature infants' cerebral hemodynamics

Infants born at an extremely low gestational age (ELGA, < 29 weeks) are at an increased risk of intraventricular hemorrhage (IVH), and there is a need for standalone, safe, easy-to-use tools for monitoring cerebral hemodynamics. We have built a multi-wavelength multi-distance diffuse correlation spectroscopy device (MW-MD-DCS), which utilizes time-multiplexed, long-coherence lasers at 785, 808, and 853 nm, to simultaneously quantify the index of cerebral blood flow (CBFi) and the hemoglobin oxygen saturation (SO2). We show characterization data on liquid phantoms and demonstrate the system performance on the forearm of healthy adults, as well as clinical data obtained on two preterm infants.

Resting-State Cerebral Hemodynamics is Associated With Problem Behaviors in Pediatric Sleep-Disordered Breathing

OBJECTIVE

Untreated sleep-disordered breathing (SDB) is associated with problem behaviors in children. The neurological basis for this relationship is unknown. We used functional near-infrared spectroscopy (fNIRS) to assess the relationship between cerebral hemodynamics of the frontal lobe of the brain and problem behaviors in children with SDB.

STUDY DESIGN

Cross-sectional.

SETTING

Urban tertiary care academic children's hospital and affiliated sleep center.

METHODS

We enrolled children with SDB aged 5 to 16 years old referred for polysomnography. We measured fNIRS-derived cerebral hemodynamics within the frontal lobe during polysomnography. We assessed parent-reported problem behaviors using the Behavioral Response Inventory of Executive Function Second Edition (BRIEF-2). We compared the relationships between (i) the instability in cerebral perfusion in the frontal lobe measured fNIRS, (ii) SDB severity using apnea-hypopnea index (AHI), and (iii) BRIEF-2 clinical scales using Pearson correlation (r). A p < .05 was considered significant.

RESULTS

A total of 54 children were included. The average age was 7.8 (95% confidence interval, 7.0-8.7) years; 26 (48%) were boys and 25 (46%) were Black. The mean AHI was 9.9 (5.7-14.1). There is a statistically significant inverse relationship between the coefficient of variation of perfusion in the frontal lobe and BRIEF-2 clinical scales (range of r = 0.24-0.49, range of p = .076 to <.001). The correlations between AHI and BRIEF-2 scales were not statistically significant.

CONCLUSION

These results provide preliminary evidence for fNIRS as a child-friendly biomarker for the assessment of adverse outcomes of SDB.

Wearable, high-density fNIRS and diffuse optical tomography technologies: a perspective

Recent progress in optoelectronics has made wearable and high-density functional near-infrared spectroscopy (fNIRS) and diffuse optical tomography (DOT) technologies possible for the first time. These technologies have the potential to open new fields of real-world neuroscience by enabling functional neuroimaging of the human cortex at a resolution comparable to fMRI in almost any environment and population. In this perspective article, we provide a brief overview of the history and the current status of wearable high-density fNIRS and DOT approaches, discuss the greatest ongoing challenges, and provide our thoughts on the future of this remarkable technology.