Noninvasive continuous optical monitoring of absolute cerebral blood flow in critically ill adults

He, Lian; Baker, Wesley B.; Milej, Daniel; Kavuri, Venkaiah C.; Mesquita, Rickson C.; Busch, David R.; Abramson, Kenneth; Jiang, Jane Yan; Diop, Mamadou; Lawrence, Keith St.; Amendolia, Olivia; Quattrone, Francis; Balu, Ramani; Kofke, W. Andrew; Yodh, Arjun G.

doi:10.1117/1.nph.5.4.045006

Cited by 42 publications

(28 citation statements)

References 77 publications

(114 reference statements)

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“…11,19 Accordingly, DCS is well-suited for continuous prolonged monitoring. [20][21][22]45 Herein, we investigated the effects of pressure on the DCS blood flow pulsatility signal These data were obtained on the right foreheads of 11 healthy adult volunteers at multiple probe pressures for each subject (i.e., N ¼ 60 probe pressures total; 1-min of DCS data acquired for each pressure, 2.1-cm source-detector separation). hBFIi o , P o , and PI o denote the subject's mean steady-state BFI, probe pressure, and PI measured at the baseline (initial) probe pressure.…”

Section: Discussionmentioning

confidence: 99%

“…DCS is well-suited for continuous monitoring and sensitive to localized microvasculature. 3,[19][20][21][22] To realize the full clinical potential of DCS pulsatility monitoring, however, a better understanding of confounding influences on the DCS pulsatility measurement is needed.…”

Section: Introductionmentioning

confidence: 99%

“…Previous work has shown that time-averaged steady-state DCS measurements of blood flow can be influenced by factors such as external probe pressure against the tissue, superficial tissue layers, and tissue optical properties. 20,[23][24][25][26] This pilot study examines the influence of external probe pressure on DCS measurements of blood flow pulsatility on the forearm and the forehead. The influence on pulsatility is further compared to the influence on steady-state blood flow measurements.…”

Section: Introductionmentioning

confidence: 99%

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Influence of probe pressure on the pulsatile diffuse correlation spectroscopy blood flow signal on the forearm and forehead regions

Wang

Gao

et al. 2019

Neurophoton.

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In a pilot study of 11 healthy adults (24 to 39 years, all male), we characterize the influence of external probe pressure on optical diffuse correlation spectroscopy (DCS) measurements of pulsatile blood flow obtained on the forearm and forehead. For external probe pressure control, a hand inflatable air balloon is inserted between the tissue and an elastic strap. The air balloon is sequentially inflated to achieve a wide range of external probe pressures between 20 and 250 mmHg on the forearm and forehead, which are measured with a flexible pressure sensor underneath the probe. At each probe pressure, the pulsatility index (PI) of arteriole blood flow on the forehead and forearm is measured with DCS (2.1-cm source-detector separation). We observe a strong correlation between probe pressure and PI on the forearm (R ¼ 0.66, p < 0.001), but not on the forehead (R ¼ −0.11, p ¼ 0.4). The forearm measurements demonstrate the sensitivity of the DCS PI to skeletal muscle tissue pressure, whereas the forehead measurements indicate that DCS PI measurements are not sensitive to scalp tissue pressure. Note, in contrast to pulsatility, the time-averaged DCS blood flow index on the forehead was significantly correlated with probe pressure (R ¼ −0.55, p < 0.001). This pilot data appears to support the initiation of more comprehensive clinical studies on DCS to detect trends in internal pressure in brain and skeletal muscle.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Influence of probe pressure on the pulsatile diffuse correlation spectroscopy blood flow signal on the forearm and forehead regions

Wang

Gao

et al. 2019

Neurophoton.

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“…The decay of the autocorrelation curve is fit with the solution of the correlation diffusion equation 4 to obtain an index of blood flow (BF i ) in units of cm 2 ∕s. Although the units of BF i are not the conventional units of ml∕ min ∕100 g tissue for perfusion, BF i has been shown to be reliably proportional to absolute flow, as demonstrated against "gold standards," such as arterial spin-labeled MRI, [8][9][10] fluorescent microspheres, 11 bolus tracking time-domain NIRS, 12,13 and phase-encoded velocity mapping MRI. 14 A significant limitation of both NIRS and DCS is the limited depth sensitivity, which is crucial when aiming to measure cerebral hemodynamics noninvasively in humans.…”

Section: Introductionmentioning

confidence: 99%

Diffuse correlation spectroscopy measurements of blood flow using 1064 nm light

et al. 2020

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

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“…Within certain contexts improvements to inter-subject variability; more reliable absolute chromophore concentration measurement and reduction in extracranial tissue (ECT) influence on parameters are critically important. Frequency domain [1][2], time domain [3], and contrast enhancement [4], represent just some of the avenues of research and system development at the forefront of this technology ( Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

The Valsalva maneuver: an indispensable physiological tool to differentiate intra versus extracranial near-infrared signal

Davies¹,

Yakoub²,

Su³

et al. 2020

Biomed. Opt. Express

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Developing near-infrared spectroscopy (NIRS) parameter recovery techniques to more specifically resolve brain physiology from that of the overlying tissue is an important part of improving the clinical utility of the technology. The Valsalva maneuver (VM) involves forced expiration against a closed glottis causing widespread venous congestion within the context of a fall in cardiac output. Due to the specific anatomical confines and metabolic demands of the brain we believe a properly executed VM has the ability to separate haemodynamic activity of brain tissue from that of the overlying scalp as observed by NIRS, and confirmed by functional magnetic resonance imaging (fMRI). Healthy individuals performed a series of standing maximum effort VMs under separate observation by frequency domain near-infrared spectroscopy (FD-NIRS) and fMRI. Nine individuals completed the clinical protocol (6 males, age 21-40). During the VMs, brain and extracranial tissue targeted signal were significantly different (opposite direction of change) in both fMRI and NIRS (p=0.00025 and 0.00115 respectively), with robust cross correlation of parameters between modalities. Four of these individuals performed further VMs after infiltrating 2% xylocaine/1:100,000 epinephrine (vasoconstrictor) into scalp tissue beneath the probes. No significant difference in the cerebrally derived parameters was observed. The maximum effort VM has the ability to separate NIRS observable physiology of the brain from the overlying extracranial tissue. Observations made by this FD cerebral NIRS device are comparable with fMRI in this context.

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Noninvasive continuous optical monitoring of absolute cerebral blood flow in critically ill adults

Cited by 42 publications

References 77 publications

Influence of probe pressure on the pulsatile diffuse correlation spectroscopy blood flow signal on the forearm and forehead regions

Influence of probe pressure on the pulsatile diffuse correlation spectroscopy blood flow signal on the forearm and forehead regions

Diffuse correlation spectroscopy measurements of blood flow using 1064 nm light

The Valsalva maneuver: an indispensable physiological tool to differentiate intra versus extracranial near-infrared signal

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