Diffuse correlation spectroscopy measurements of blood flow using 1064 nm light

Journal of Biomedical Optics, Год журнала: 2020, Номер 25(09)

Опубликована: Сен. 29, 2020

Significance: Diffuse correlation spectroscopy (DCS) is an established optical modality that enables noninvasive measurements of blood flow in deep tissue by quantifying the temporal light intensity fluctuations generated dynamic scattering moving red cells. Compared with near-infrared spectroscopy, DCS hampered a limited signal-to-noise ratio (SNR) due to need use small detection apertures preserve speckle contrast. However, technique and does not rely on hemoglobin contrast; thus, there are significant SNR advantages using longer wavelengths (>1000 nm) for measurement variety biophysical regulatory factors. Aim: We offer quantitative assessment benefits challenges operating at 1064 nm versus typical 765 850 wavelength through simulations experimental demonstrations. Approach: evaluate photon budget, depth sensitivity, detecting changes numerical simulations. discuss continuous wave (CW) time-domain (TD) hardware considerations operation. report proof-of-concept tissue-like phantoms healthy adult volunteers. Results: offers higher intrinsic sensitivity compared typically used range (765 increased counts slower autocorrelation decay. These explored demonstrated phantom vivo measurements. show first high-speed (cardiac pulsation-resolved), high-SNR large source–detector separation (3 cm) CW-DCS late gates (1 ns) TD-DCS. Conclusions: leap forward ability monitor could be especially useful increasing reliability cerebral monitoring adults.

Язык: Английский

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Fast and sensitive diffuse correlation spectroscopy with highly parallelized single photon detection

APL Photonics, Год журнала: 2021, Номер 6(2)

Опубликована: Фев. 1, 2021

Diffuse correlation spectroscopy (DCS) is a well-established method that measures rapid changes in scattered coherent light to identify blood flow and functional dynamics within tissue. While its sensitivity minute scatterer displacements leads number of unique advantages, conventional DCS systems become photon-limited when attempting probe deep into the tissue, which long measurement windows (∽1 sec). Here, we present high-sensitivity system with 1024 parallel detection channels integrated single-photon avalanche diode array demonstrate ability detect mm-scale perturbations up 1 cm tissue-like phantom at 33 Hz sampling rate. We also show this highly parallelized strategy can measure human pulse high fidelity behaviorally induced physiological variations from above prefrontal cortex. By greatly improving speed, opens new experiments for high-speed biological signal measurement.

Язык: Английский

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Functional interferometric diffusing wave spectroscopy of the human brain

Science Advances, Год журнала: 2021, Номер 7(20)

Опубликована: Май 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

Язык: Английский

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Validation of diffuse correlation spectroscopy measures of critical closing pressure against transcranial Doppler ultrasound in stroke patients

Journal of Biomedical Optics, Год журнала: 2021, Номер 26(03)

Опубликована: Март 27, 2021

Significance: Intracranial pressure (ICP), variability in perfusion, and resulting ischemia are leading causes of secondary brain injury patients treated the neurointensive care unit. Continuous, accurate monitoring cerebral blood flow (CBF) ICP guide intervention ultimately reduce morbidity mortality. Currently, only invasive tools used to monitor at high risk for intracranial hypertension. Aim: Diffuse correlation spectroscopy (DCS), a noninvasive near-infrared optical technique, is emerging as possible method continuous CBF critical closing (CrCP or zero-flow pressure), parameter directly related ICP. Approach: We optimized DCS hardware algorithms quantification CrCP. Toward its clinical translation, we validated estimates index (CBFi) CrCP ischemic stroke with respect simultaneously acquired transcranial Doppler ultrasound (TCD) velocity (CBFV) Results: found derived from TCD were highly linearly correlated (ipsilateral R2 = 0.77, p 9 × 10 − 7; contralateral 0.83, 7 8). weaker correlations between CBFi CBFV 0.25, 0.03; 0.48, 1 3) probably due different vasculature measured. Conclusion: Our results suggest valid alternative

Язык: Английский

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Model of dynamic speckle evolution for evaluating laser speckle contrast measurements of tissue dynamics

Biomedical Optics Express, Год журнала: 2022, Номер 13(12), С. 6533 - 6533

Опубликована: Ноя. 11, 2022

We introduce a dynamic speckle model (DSM) to simulate the temporal evolution of fully developed patterns arising from interference scattered light reemitted tissue. Using this numerical tool, performance laser contrast imaging (LSCI) or optical spectroscopy (SCOS) systems which quantify tissue dynamics using spatial with certain camera exposure time is evaluated. have investigated noise sources fundamental statistics due finite sampling as well those induced by experimental measurement conditions including shot noise, dark and read calibrated parameters an analytical initially in regime that quantifies SCOS number independent observables (NIO). Our analysis particularly focused on low photon flux relevant for human brain measurements, where impact can become significant. also validated experimentally novel fiber based (fb-SCOS) system sample. found signal-to-noise ratio (SNR) fb-SCOS measurements plateaus at time, marks dominates over noise. For fixed total there exists optimized if averaging utilized improve SNR. value, properties, speckle-to-pixel size (s/p) SNR maximized. work provides design principles any LSCI given detected properties instruments, will guide development high-quality, low-cost monitors blood flow functions.

Язык: Английский

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Complete head cerebral sensitivity mapping for diffuse correlation spectroscopy using subject-specific magnetic resonance imaging models

Biomedical Optics Express, Год журнала: 2022, Номер 13(3), С. 1131 - 1131

Опубликована: Янв. 21, 2022

We characterize cerebral sensitivity across the entire adult human head for diffuse correlation spectroscopy, an optical technique increasingly used bedside perfusion monitoring. Sixteen subject-specific magnetic resonance imaging-derived models were to identify high regions by running Monte Carlo light propagation simulations at over eight hundred uniformly distributed locations on head. Significant spatial variations in sensitivity, consistent subjects, found. also identified correlates of such differences suitable real-time assessment. These can be largely attributed changes extracerebral thickness and should taken into account optimize probe placement experimental settings.

Язык: Английский

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Measuring human cerebral blood flow and brain function with fiber-based speckle contrast optical spectroscopy system

Communications Biology, Год журнала: 2023, Номер 6(1)

Опубликована: Авг. 14, 2023

Abstract Cerebral blood flow (CBF) is crucial for brain health. Speckle contrast optical spectroscopy (SCOS) a technique that has been recently developed to measure CBF, but the use of SCOS human function at large source-detector separations with comparable or greater sensitivity cerebral rather than extracerebral not demonstrated. We describe fiber-based system capable measuring activation induced CBF changes 33 mm source detector using CMOS detectors. The implements pulsing strategy improve photon flux and uses data processing pipeline measurement accuracy. show outperforms current leading modality i.e. diffuse correlation (DCS), achieving more 10x SNR improvement similar financial cost. Fiber-based provides an alternative approach functional neuroimaging cognitive neuroscience health science applications.

Язык: Английский

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Comparing the performance potential of speckle contrast optical spectroscopy and diffuse correlation spectroscopy for cerebral blood flow monitoring using Monte Carlo simulations in realistic head geometries

Neurophotonics, Год журнала: 2024, Номер 11(01)

Опубликована: Янв. 27, 2024

SignificanceThe non-invasive measurement of cerebral blood flow based on diffuse optical techniques has seen increased interest as a research tool for perfusion monitoring in critical care and functional brain imaging. Diffuse correlation spectroscopy (DCS) speckle contrast (SCOS) are two such that measure complementary aspects the fluctuating intensity signal, with DCS quantifying temporal fluctuations signal SCOS spatial blurring pattern. With increasing use these techniques, thorough comparison would inform new adopters benefits each technique.AimWe systematically evaluate performance flow.ApproachMonte Carlo simulations dynamic light scattering an MRI-derived head model were performed. For both SCOS, estimates sensitivity to changes, coefficient variation measured flow, contrast-to-noise ratio calculated. By varying data collection between methods, we investigated different strategies, including altering number modes per detector, integration time/fitting time measurement, laser source delivery strategy.ResultsThrough across metrics simulated detectors having realistic noise properties, determine several guiding principles optimization report over range properties tissue geometries. We find outperforms terms ideal case here but note requires careful experimental calibrations ensure accurate measurements flow.ConclusionWe provide design by which development systems their flow.

Язык: Английский

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Effects of exercise training on calf muscle oxygen extraction and blood flow in patients with peripheral artery disease

Journal of Applied Physiology, Год журнала: 2017, Номер 123(6), С. 1599 - 1609

Опубликована: Окт. 5, 2017

We employed near-infrared optical techniques, diffuse correlation spectroscopy (DCS), and frequency-domain (FD-NIRS) to test the hypothesis that supervised exercise training increases skeletal muscle microvascular blood flow oxygen extraction in patients with peripheral artery disease (PAD) who experience claudication. PAD ( n = 64) were randomly assigned control groups. Patients group received 3 mo of training. Calf optically monitored before, during, after performance a graded treadmill protocol at baseline both Additionally, measurements ankle-brachial index (ABI) peak walking time (PWT) maximal claudication made during each patient visit. Supervised was found increase calf levels by 29% (13%, 50%) 8% (1%, 12%), respectively [ P < 0.001; median (25th percentile, 75th percentile)]. These improvements across population significantly higher than corresponding changes 0.004). Exercise also increased PWT 49% (18%, 101%) 0.01). However, within statistical error, ABI, resting extraction, recovery half-time for hemoglobin\myoglobin desaturation following cessation not altered The concurrent monitoring hybrid DCS/FD-NIRS instrument revealed enhanced oxidative metabolism physical activity from training, which could be an underlying mechanism observed improvement PWT. NEW & NOTEWORTHY report on noninvasive dynamics before/during/after tracked effects 3-mo improved ability activity.

Язык: Английский

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Noninvasive optical monitoring of critical closing pressure and arteriole compliance in human subjects

Journal of Cerebral Blood Flow & Metabolism, Год журнала: 2017, Номер 37(8), С. 2691 - 2705

Опубликована: Май 25, 2017

The critical closing pressure ( CrCP) of the cerebral circulation depends on both tissue intracranial and vasomotor tone. CrCP defines arterial blood ABP) at which flow approaches zero, their difference ABP - is an accurate estimate perfusion pressure. Here we demonstrate a novel non-invasive technique for continuous monitoring bedside. methodology combines optical diffuse correlation spectroscopy (DCS) measurements pulsatile in arterioles with concurrent data during cardiac cycle. Together, two waveforms permit calculation via two-compartment Windkessel model arterioles. Measurements by optics transcranial Doppler ultrasound (TCD) were carried out 18 healthy adults; they demonstrated good agreement (R = 0.66, slope 1.14 ± 0.23) means 11.1 5.0 13.0 7.5 mmHg, respectively. Additionally, potentially useful rarely measured arteriole compliance parameter was derived from phase between DCS waveforms. provide evidence that signals originate predominantly are well suited long-term assessment clinic.

Язык: Английский

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