A review on time domain diffuse optics: principles and applications on human biological tissues

Deleted Journal, Journal Year: 2025, Volume and Issue: unknown

Published: April 9, 2025

Abstract The term diffusive media refers to all the for which photon diffusion equation provides an accurate description of light propagation. Indeed, this is case a plethora natural media, such as biological tissues and agricultural products, when illuminated by red near-infrared light. Diffuse Optics (DO) branch that studies how absorption scattering phenomena affect propagation in media. In review paper, we present introduction time domain (TD) DO, specific implementation DO employs picosecond pulses, fast sensitive photodetectors timing electronics record distribution time-of-flight (or path lengths) By interpreting TD signals with physical model provided theory, it possible estimate properties medium can be related physiological pathological conditions. We focus on principles building blocks instrumentation, applications targeting human (such brain, breast, muscle, others).

Language: Английский

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Influence of Tissue Curvature on the Absolute Quantification in Frequency-Domain Diffuse Optical Spectroscopy

Spectroscopy Journal, Journal Year: 2025, Volume and Issue: 3(2), P. 14 - 14

Published: April 13, 2025

Accurate estimation of optical properties and hemodynamic parameters is critical for advancing frequency-domain diffuse spectroscopy (FD-DOS) techniques in clinical neuroscience. However, conventional FD-DOS models often assume planar air–tissue interfaces, introducing errors anatomically curved regions such as the forehead or infant heads. This study evaluates impact incorporating tissue curvature into forward analysis. Using simulations phantoms, we demonstrate that reduce absorption coefficient from 20% to less than 10% high-curvature scenarios. Within curvatures tested, even minor mismatches resulted significantly lower those observed approximations (p < 0.001). In low-curvature regions, yielded comparable (<5% both cases). When applied human data, our proposed model increased hemoglobin concentration estimates by 10–15% compared standard semi-infinite models, closer physiological expectations. Overall, these results quantitatively accounting improves accuracy property estimation. We propose a numerical framework achieves this fast reliable manner, robust tool research applications complex regions.

Language: Английский

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Minimum spectral resolution for continuous-wave hyperspectral near-infrared tissue spectroscopy

Journal of Biomedical Optics, Journal Year: 2025, Volume and Issue: 30(04)

Published: April 24, 2025

Continuous-wave hyperspectral near-infrared spectroscopy (h-NIRS) is a reliable and cost-effective technique for noninvasive monitoring of tissue blood content oxygenation at the point-of-care; however, most h-NIRS devices are based on expensive custom-built spectrometers. For widespread adoption, low-cost, miniature, off-the-shelf spectrometers needed. To guide development such spectrometers, standard spectral resolution must first be defined. We aim to identify minimum needed accurately measure oxy- deoxy-hemoglobin (HbO Hb) concentrations in tissue. measurements were acquired from fully oxygenated deoxygenated blood-lipid phantoms 13 resolutions. Data other levels simulated using NIRFAST. HbO Hb estimated each compared with ground truth hemoglobin concentration. The concentration was high accuracy resolutions up 10 nm, whereas estimates more variable. both chromophores, estimation gradually decreased beyond nm. Spectral nm can used without compromising estimating oxygenation.

Language: Английский

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Accuracy of diffuse correlation spectroscopy measurements of cerebral blood flow when using a three-layer analytical model

Biomedical Optics Express, Journal Year: 2021, Volume and Issue: 12(11), P. 7149 - 7149

Published: Oct. 20, 2021

Diffuse correlation spectroscopy (DCS) is a non-invasive optical technology for the assessment of an index cerebral blood flow (CBFi). Analytical methods that model head as three-layered medium (i.e., scalp, skull, brain) are becoming more commonly used to minimize contribution extracerebral layers measured DCS signal in adult studies. However, these models rely on priori knowledge layer properties and thicknesses. Errors values can lead errors estimation CBFi, although magnitude this influence has not been rigorously characterized. Herein, we investigate accuracy measuring with three-layer when or thicknesses present. Through series silico experiments, demonstrate CBFi highly sensitive brain skull scalp Relative changes less but influenced by thickness. Thus, using model, accurate thickness required reliable results.

Language: Английский

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Interferometric diffusing wave spectroscopy imaging with an electronically variable time-of-flight filter

Optica, Journal Year: 2022, Volume and Issue: 10(1), P. 42 - 42

Published: Nov. 14, 2022

Diffuse optics (DO) is a light-based technique used to study the human brain, but it suffers from low brain specificity. Interferometric diffuse (iDO) promises improve quantitative accuracy and depth specificity of DO, particularly, coherent light fluctuations (CLFs) arising blood flow. iDO techniques have alternatively achieved either time-of-flight (TOF) discrimination or highly parallel detection, not both at once. Here, we break this barrier with single instrument. Specifically, show that rapid tuning temporally laser during sensor integration time increases effective linewidth seen by interferometer. Using concept create continuously variable user-specified TOF filter, demonstrate solution canonical problem measuring optical properties. Then, deep reduce scalp sensitivity CLFs 2.7 times 1 cm source-collector separation. With unique combination desirable features, i.e., TOF-discrimination, spatial localization, CLF perform multiparametric imaging intensities via forehead.

Language: Английский

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Non-invasive diffuse optical monitoring of cerebral physiology in an adult swine-model of impact traumatic brain injury

Biomedical Optics Express, Journal Year: 2023, Volume and Issue: 14(6), P. 2432 - 2432

Published: April 13, 2023

In this study, we used diffuse optics to address the need for non-invasive, continuous monitoring of cerebral physiology following traumatic brain injury (TBI). We combined frequency-domain and broadband optical spectroscopy with correlation monitor oxygen metabolism, blood volume, water content in an established adult swine-model impact TBI. Cerebral was monitored before after TBI (up 14 days post injury). Overall, our results suggest that non-invasive can assess physiologic impairments post-TBI, including initial reduction development hemorrhage/hematoma, swelling.

Language: Английский

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Optical Detection of Intracranial Pressure and Perfusion Changes in Neonates With Hydrocephalus

The Journal of Pediatrics, Journal Year: 2021, Volume and Issue: 236, P. 54 - 61.e1

Published: May 15, 2021

To demonstrate that a novel noninvasive index of intracranial pressure (ICP) derived from diffuse optics-based techniques is associated with hypertension.We compared and invasive ICP measurements in infants hydrocephalus. Infants born term preterm were eligible for inclusion if clinically determined to require cerebrospinal fluid (CSF) diversion. Ventricular size was assessed preoperatively via ultrasound measurement the fronto-occipital (FOR) frontotemporal (FTHR) horn ratios. Invasive obtained at time surgical intervention manometer. Intracranial hypertension defined as ≥15 mmHg. Diffuse optical cerebral perfusion, oxygen extraction, performed preoperatively, intraoperatively, postoperatively. Optical measures measurements, their change values after CSF diversion obtained.We included 39 infants, 23 hypertension. No group difference ventricular found by FOR (P = .93) or FTHR .76). had significantly higher .02) extraction fraction (OEF) .01) without Increased blood flow .005) improved OEF < .001) observed only hypertension.Noninvasive (including index) The findings suggest impaired perfusion independent size. Hemodynamic evidence benefits seen Noninvasive hold promise aiding assessment timing.

Language: Английский

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Influence of source–detector separation on diffuse correlation spectroscopy measurements of cerebral blood flow with a multilayered analytical model

Neurophotonics, Journal Year: 2022, Volume and Issue: 9(03)

Published: July 1, 2022

Significance: Diffuse correlation spectroscopy (DCS) is an emerging noninvasive optical technology for bedside monitoring of cerebral blood flow. However, extracerebral hemodynamics can significantly influence DCS estimations perfusion. Advanced analytical models be used to remove the contribution hemodynamics; however, these are highly sensitive measurement noise. There a need empirical determination optimal source-detector separation(s) (SDS) that improves accuracy and reduces sensitivity noise in estimation flow with models. Aim: To determine SDS on solution uniqueness, accuracy, inaccuracies model parameters when using three-layer estimate DCS. Approach: We performed series silico simulations samples spanning wide range physiologically-relevant layer properties, thicknesses, Data were simulated at ranging from 0.5 3.0 cm diffusion equation (with without added) slab Monte Carlo simulations. quantified inverse model. Results: Two required ensure unique index (CBFi). Combinations 0.5/1.0/1.5 2.5 provide choice balancing depth penetration signal-to-noise ratio minimize error CBFi across varying dynamics. Conclusions: These results suggest critical minimizing estimated analyze data.

Language: Английский

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Using depth-enhanced diffuse correlation spectroscopy and near-infrared spectroscopy to isolate cerebral hemodynamics during transient hypotension

Neurophotonics, Journal Year: 2023, Volume and Issue: 10(02)

Published: June 5, 2023

Combining diffuse correlation spectroscopy (DCS) and near-infrared (NIRS) permits simultaneous monitoring of multiple cerebral hemodynamic parameters related to autoregulation; however, interpreting these optical measurements can be confounded by signal contamination from extracerebral tissue.We aimed evaluate in NIRS/DCS data acquired during transient hypotension assess suitable means separating scalp brain signals.A hybrid time-resolved NIRS/multidistance DCS system was used simultaneously acquire oxygenation blood flow orthostatic induced rapid-onset lower body negative pressure (LBNP) nine young, healthy adults. Changes microvascular were verified against changes middle artery velocity (MCAv) measured transcranial Doppler ultrasound.LBNP significantly decreased arterial (-18%±14%), (>30%), tissue (all p≤0.04 versus baseline). However, implementing depth-sensitive techniques for both NIRS indicated that LBNP did not alter relative their baseline values p≥0.14). In agreement, there no significant reduction MCAv (8%±16%; p=0.09).Transient caused larger the compared brain. We demonstrate importance accounting within measures hemodynamics physiological paradigms designed test autoregulation.

Language: Английский

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Optimizing a two-layer method for hybrid diffuse correlation spectroscopy and frequency-domain diffuse optical spectroscopy cerebral measurements in adults

Neurophotonics, Journal Year: 2023, Volume and Issue: 10(02)

Published: May 23, 2023

SignificanceThe sensitivity to extracerebral tissues is a well-known confounder of diffuse optics. Two-layer (2L) head models can separate cerebral signals from artifacts, but they also carry the risk crosstalk between fitting parameters.AimWe aim implement constrained 2L model for hybrid correlation spectroscopy (DCS) and frequency-domain optical (FD-DOS) data characterize errors in blood flow tissue absorption with proposed model.ApproachThe algorithm uses analytical solution cylinder an priori layer thickness fit multidistance FD-DOS (0.8 4 cm) DCS 2.5 data, assuming homogeneous reduced scattering. We characterized algorithm's accuracy simulated noise generated using slab realistic adult geometries vitro phantom data.ResultsOur recovered index 6.3 [2.8, 13.2]% 34 [30, 42]% (median absolute percent error [interquartile range]) geometries, respectively. Corresponding coefficient were 5.0 [3.0, 7.9]% 4.6 [2.4, 7.2]% 8 [5, 12]% our experiment. Our results minimally sensitive second-layer scattering changes robust cross-talk parameters.ConclusionsIn adults, promises improve FD-DOS/DCS compared conventional semi-infinite approach.

Language: Английский

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