Assessing extracerebral signal contamination in optical measurements of cerebral blood flow and oxygenation

Milej, Daniel; Rajaram, Ajay; Abdalmalak, Androu; Khalid, Mahro; Shahid, Marwan; Kewin, Matthew; Lawrence, Keith St.

doi:10.1117/12.2527150

Cited by 3 publications

(6 citation statements)

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“…Another potential source of error with optical neuromonitoring methods is the effect of scalp contamination. The influence of the scalp is considerably less in infants compared with adults, and within this study its effects were mitigated using appropriate source-detector distances for B-NIRS (SDD = 3 cm) and DCS (SDD = 2 cm) [54]. An additional source of signal contamination unique to hydrocephalus is possible light loss in the enlarged ventricle as the cortical mantle becomes increasingly thin.…”

Section: Discussionmentioning

confidence: 95%

Perfusion and Metabolic Neuromonitoring during Ventricular Taps in Infants with Post-Hemorrhagic Ventricular Dilatation

et al. 2020

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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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Section: Discussionmentioning

confidence: 95%

Perfusion and Metabolic Neuromonitoring during Ventricular Taps in Infants with Post-Hemorrhagic Ventricular Dilatation

et al. 2020

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“…In the simulations, the true optical pathlength was known; however, in the two-layer phantom experiments, the optical pathlength was estimated using the water peak in the second derivative of the CW reflectance data and corrected with the time-point-specific spectral shape of the TR pathlength. Since the TR pathlength was obtained using mean TOF, which is susceptible to surface contamination, 27 , 28 it is unlikely that the spectral shape of the TR pathlength changed as much as the spectral shape of the CW pathlength with oxygenation changes in the bottom layer. By not fully accounting for the changes in pathlength with changes in absorption, changes in chromophore concentrations may be underestimated in the CW analysis as a result of cross talk with the pathlength 13 , 82 .…”

Section: Discussionmentioning

confidence: 99%

“…As anticipated, the CW approach performed the worst when estimating ΔHb and ΔoxCCO in the bottom layer from the surface of the two-layer phantoms, substantially underestimating the changes in chromophore concentrations. This was anticipated given that the probes were placed atop a 10 mm thick static surface layer and previous studies have shown that the CW-NIRS signal in the adult head is dominated by ECL contributions 27 – 29 Since the concentrations changed only in the bottom layer while the top layer remained static, it was expected that CW would underestimate the changes in the bottom layer due to contamination by the top layer (partial volume effect) 72 .…”

Section: Discussionmentioning

confidence: 99%

“…Several studies have demonstrated that oxCCO can be monitored in piglets and neonates using CW systems; 5 , 7 , 24 however, extending the technique to adults has been hampered by contamination of brain-related signals by the thick adult extracerebral layers (ECL; scalp and skull) 6 , 25 , 26 . In adults, substantial light absorption and scattering occur in these surface layers, limiting light penetration into deeper tissues and reducing sensitivity to the brain 27 – 29 Multi-distance measurements have been proposed to account for the ECL contribution to the NIRS signal, 25 , 26 , 30 , 31 wherein the signal from a short source–detector distance is regressed from a long source–detector distance measurement.…”

Section: Introductionmentioning

confidence: 99%

“… 6 , 25 , 26 In adults, substantial light absorption and scattering occur in these surface layers, limiting light penetration into deeper tissues and reducing sensitivity to the brain. 27 – 29 Multi-distance measurements have been proposed to account for the ECL contribution to the NIRS signal, 25 , 26 , 30 , 31 wherein the signal from a short source–detector distance is regressed from a long source–detector distance measurement. However, this approach assumes that the ECL contribution to both signals is similar, which may not be the case due to local variations in scalp hemodynamics.…”

Section: Introductionmentioning

confidence: 99%

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HyperTRCSS: A hyperspectral time-resolved compressive sensing spectrometer for depth-sensitive monitoring of cytochrome-c-oxidase and blood oxygenation

Li,

Ioussoufovitch,

Diop

2024

J. Biomed. Opt.

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Hyperspectral time-resolved (TR) near-infrared spectroscopy offers the potential to monitor cytochrome-c-oxidase (oxCCO) and blood oxygenation in the adult brain with minimal scalp/skull contamination. We introduce a hyperspectral TR spectrometer that uses compressive sensing to minimize acquisition time without compromising spectral range or resolution and demonstrate oxCCO and blood oxygenation monitoring in deep tissue.Aim: Develop a hyperspectral TR compressive sensing spectrometer and use it to monitor oxCCO and blood oxygenation in deep tissue.Approach: Homogeneous tissue-mimicking phantom experiments were conducted to confirm the spectrometer's sensitivity to oxCCO and blood oxygenation. Twolayer phantoms were used to evaluate the spectrometer's sensitivity to oxCCO and blood oxygenation in the bottom layer through a 10 mm thick static top layer. Results:The spectrometer was sensitive to oxCCO and blood oxygenation changes in the bottom layer of the two-layer phantoms, as confirmed by concomitant measurements acquired directly from the bottom layer. Measures of oxCCO and blood oxygenation by the spectrometer were highly correlated with "gold standard" measures in the homogeneous and two-layer phantom experiments. Conclusions:The results show that the hyperspectral TR compressive sensing spectrometer is sensitive to changes in oxCCO and blood oxygenation in deep tissue through a thick static top layer.

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Assessing Time-Resolved fNIRS for Brain-Computer Interface Applications of Mental Communication

et al. 2020

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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.

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Assessing extracerebral signal contamination in optical measurements of cerebral blood flow and oxygenation

Cited by 3 publications

References 8 publications

Perfusion and Metabolic Neuromonitoring during Ventricular Taps in Infants with Post-Hemorrhagic Ventricular Dilatation

Perfusion and Metabolic Neuromonitoring during Ventricular Taps in Infants with Post-Hemorrhagic Ventricular Dilatation

HyperTRCSS: A hyperspectral time-resolved compressive sensing spectrometer for depth-sensitive monitoring of cytochrome-c-oxidase and blood oxygenation

Assessing Time-Resolved fNIRS for Brain-Computer Interface Applications of Mental Communication

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