False positives and false negatives in functional near-infrared spectroscopy: issues, challenges, and the way forward

Neurophotonics, Journal Year: 2016, Volume and Issue: 3(3), P. 031405 - 031405

Published: March 9, 2016

We highlight a significant problem that needs to be considered and addressed when performing functional near-infrared spectroscopy (fNIRS) studies, namely the possibility of inadvertently measuring fNIRS hemodynamic responses are not due neurovascular coupling. These can misinterpreted as brain activity, i.e., “false positives” (errors caused by wrongly assigning detected response activity), or mask negatives” observed in presence activity). Here, we summarize possible physiological origins these issues suggest ways avoid remove them.

Language: Английский

---

Optical imaging and spectroscopy for the study of the human brain: status report

Neurophotonics, Journal Year: 2022, Volume and Issue: 9(S2)

Published: Aug. 30, 2022

This report is the second part of a comprehensive two-part series aimed at reviewing an extensive and diverse toolkit novel methods to explore brain health function. While first focused on neurophotonic tools mostly applicable animal studies, here, we highlight optical spectroscopy imaging relevant noninvasive human studies. We outline current state-of-the-art technologies software advances, most recent impact these neuroscience clinical applications, identify areas where innovation needed, provide outlook for future directions.

Language: Английский

---

Fast blood flow monitoring in deep tissues with real-time software correlators

Biomedical Optics Express, Journal Year: 2016, Volume and Issue: 7(3), P. 776 - 776

Published: Feb. 3, 2016

We introduce, validate and demonstrate a new software correlator for high-speed measurement of blood flow in deep tissues based on diffuse correlation spectroscopy (DCS).The scheme employs standard PC-based data acquisition boards to measure temporal intensity autocorrelation functions continuously at 50 -100 Hz, the fastest measurements reported with DCS date.The streams, obtained vivo typical source-detector separations 2.5 cm, easily resolve pulsatile heart-beat fluctuations which were previously considered be noise.We employ device separate tissue from absorption/scattering dynamics thereby show that origin signal is primarily flow, we monitor cerebral autoregulation healthy volunteers more accurately than traditional instrumentation as result increased rates.Finally, characterize signal-to-noise ratio identify count rate averaging parameters needed optimal performance.

Language: Английский

---

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

Applied Sciences, Journal Year: 2019, Volume and Issue: 9(8), P. 1612 - 1612

Published: April 18, 2019

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

Language: Английский

---

Continuous non-invasive optical monitoring of cerebral blood flow and oxidative metabolism after acute brain injury

Journal of Cerebral Blood Flow & Metabolism, Journal Year: 2019, Volume and Issue: 39(8), P. 1469 - 1485

Published: May 14, 2019

Rapid detection of ischemic conditions at the bedside can improve treatment acute brain injury. In this observational study 11 critically ill brain-injured adults, we employed a monitoring approach that interleaves time-resolved near-infrared spectroscopy (TR-NIRS) measurements cerebral oxygen saturation and extraction fraction (OEF) with diffuse correlation (DCS) measurement blood flow (CBF). Using approach, demonstrate clinical promise non-invasive, continuous optical changes in CBF metabolic rate (CMRO 2 ). addition, CMRO measures were compared to invasive tissue tension (PbtO ), thermal diffusion flowmetry CBF, microdialysis obtained concurrently. The information successfully distinguished between ischemic, hypermetabolic, hyperemic arose spontaneously during patient care. Moreover, pressor-induced mean arterial pressure enabled assessment autoregulation. total, findings suggest hybrid non-invasive neurometabolic monitor (NNOM) facilitate adverse physiological injured patients are otherwise difficult measure conventional techniques.

Language: Английский

---

Diffuse correlation spectroscopy: current status and future outlook

Neurophotonics, Journal Year: 2023, Volume and Issue: 10(01)

Published: Jan. 24, 2023

Diffuse correlation spectroscopy (DCS) has emerged as a versatile, noninvasive method for deep tissue perfusion assessment using near-infrared light. A broad class of applications is being pursued in neuromonitoring and beyond. However, technical limitations the technology originally implemented remain barriers to wider adoption. wide variety approaches improve measurement performance reduce cost are explored; these include interferometric methods, camera-based multispeckle detection, long path photon selection improved depth sensitivity. We review here current status DCS summarize future development directions challenges that on widespread

Language: Английский

---

Clinical applications of near-infrared diffuse correlation spectroscopy and tomography for tissue blood flow monitoring and imaging

Physiological Measurement, Journal Year: 2017, Volume and Issue: 38(4), P. R1 - R26

Published: Feb. 15, 2017

Blood flow is one such available observable promoting a wealth of physiological insight both individually and in combination with other metrics.Near-infrared diffuse correlation spectroscopy (DCS) and, to lesser extent, tomography (DCT), have increasingly received interest over the past decade as noninvasive methods for tissue blood measurements imaging. DCS/DCT offers several attractive features measurements/imaging noninvasiveness, portability, high temporal resolution, relatively large penetration depth (up centimeters).This review first introduces basic principle instrumentation DCS/DCT, followed by presenting clinical application examples diagnosis therapeutic monitoring diseases variety organs/tissues including brain, skeletal muscle, tumor.Clinical study results demonstrate technical versatility providing important information disease intervention monitoring.

Language: Английский

---

Time domain diffuse correlation spectroscopy with a high coherence pulsed source: in vivo and phantom results

Biomedical Optics Express, Journal Year: 2017, Volume and Issue: 8(11), P. 5311 - 5311

Published: Oct. 27, 2017

Diffuse correlation spectroscopy (DCS), combined with time-resolved reflectance (TRS) or frequency domain spectroscopy, aims at path length (i.e.depth) resolved, non-invasive and simultaneous assessment of tissue composition blood flow.However, while TRS provides a resolved data, the standard DCS does not.Recently, time experiment showed measurements for improved quantification respect to classical DCS, but was limited phantoms small animal studies.Here, we demonstrate in vivo studies on adult forehead arm.We achieve by means an actively modelocked Ti:Sapphire laser that allows high coherence pulses, thus enabling adequate signal-tonoise ratio relatively fast (~1 s) temporal resolution.This work paves way translation this approach practical use.

Language: Английский

---

Direct assessment of extracerebral signal contamination on optical measurements of cerebral blood flow, oxygenation, and metabolism

Neurophotonics, Journal Year: 2020, Volume and Issue: 7(04)

Published: Oct. 7, 2020

Significance: Near-infrared spectroscopy (NIRS) combined with diffuse correlation (DCS) provides a noninvasive approach for monitoring cerebral blood flow (CBF), oxygenation, and oxygen metabolism. However, these methods are vulnerable to signal contamination from the scalp. Our work evaluated of reducing impact this using time-resolved (TR) NIRS multidistance (MD) DCS. Aim: The magnitude scalp was by measuring flow, metabolic responses global hemodynamic challenge. Contamination assessed collecting data without impeding flow. Approach: Experiments involved healthy participants. A pneumatic tourniquet used cause ischemia, as confirmed contrast-enhanced NIRS, computerized gas system generate hypercapnic Results: Comparing acquired demonstrated that TR-NIRS technique could reduce contributions in signals up 4 times (rSD = 3 cm) 6 cm). Similarly, brain be separated analyzing MD DCS multilayer model. Using techniques, there no change metabolism during hypercapnia, expected, despite large increases CBF oxygenation. Conclusion: NIRS/DCS can accurately monitor appropriate enhancement depth sensitivity, highlighting potential techniques neuromonitoring.

Language: Английский

---

Functional interferometric diffusing wave spectroscopy of the human brain

Science Advances, Journal Year: 2021, Volume and Issue: 7(20)

Published: May 12, 2021

Cerebral blood flow (CBF) is essential for brain function, and CBF-related signals can inform us about activity. Yet currently, high-end medical instrumentation needed to perform a CBF measurement in adult humans. Here, we describe functional interferometric diffusing wave spectroscopy (fiDWS), which introduces collects near-infrared light via the scalp, using inexpensive detector arrays rapidly monitor coherent fluctuations that encode index (BFI), surrogate CBF. Compared other optical approaches, fiDWS measures BFI faster deeper while also providing continuous absorption signals. Achieving clear pulsatile waveforms at source-collector separations of 3.5 cm, confirm BFI, not absorption, shows graded hypercapnic response consistent with human cerebrovascular physiology, has better contrast-to-noise ratio than during activation. By high-throughput measurements low cost, will expand access

Language: Английский

---