Influence of oversimplifying the head anatomy on cerebral blood flow measurements with diffuse correlation spectroscopy

Neurophotonics, Год журнала: 2023, Номер 10(01)

Опубликована: Март 30, 2023

SignificanceDiffuse correlation spectroscopy (DCS) is an emerging optical modality for non-invasive assessment of index regional cerebral blood flow. By the nature this noninvasive measurement, light must pass through extracerebral layers (i.e., skull, scalp, and spinal fluid) before detection at tissue surface. To minimize contribution these to measured signal, analytical model has been developed that treats head as a series three parallel infinitely extending slabs (mimicking brain). The three-layer shown provide significant improvement in flow estimation over typically used bulk homogenous medium. However, still gross oversimplification geometry ignores curvature, presence cerebrospinal fluid (CSF), heterogeneity layer thickness.AimDetermine influence oversimplifying on estimated with model.ApproachData were simulated Monte Carlo four-layer slab medium sphere isolate CSF respectively. Additionally, simulations performed magnetic resonance imaging (MRI) templates spanning wide-range ages. Simulated data fit both CBF. Finally, mitigate errors potential CBF due difficulty defining thickness, we investigated approach identify equivalent, "optimized" thickness via pressure modulation.ResultsBoth curvature failing account lead effect relative changes minimal. Further, found was underestimated all MRI-templates, although magnitude underestimations highly influenced by small variations source detector optode positioning. optimized obtained from modulation did not improve accuracy CBF, it significantly CBF.ConclusionsIn sum, findings suggest holds promise improving flow; however, estimations absolute should be viewed caution given difficult appreciable sources error, such CSF.

Язык: Английский

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Assessing the Sensitivity of Multi-Distance Hyperspectral NIRS to Changes in the Oxidation State of Cytochrome C Oxidase in the Brain

Metabolites, Год журнала: 2022, Номер 12(9), С. 817 - 817

Опубликована: Авг. 31, 2022

Near-infrared spectroscopy (NIRS) measurements of tissue oxygen saturation (StO2) are frequently used during vascular and cardiac surgeries as a non-invasive means assessing brain health; however, signal contamination from extracerebral tissues remains concern. As an alternative, hyperspectral (hs)NIRS can be to measure changes in the oxidation state cytochrome c oxidase (ΔoxCCO), which provides greater sensitivity given its higher mitochondrial concentration versus scalp. The purpose this study was evaluate depth oxCCO occurring components. assessment conducted using multi-distance hsNIRS (source-detector separations = 1 3 cm), metabolic were compared StO2. Ten participants monitored in-house system combining diffuse correlation (DCS). Data acquired carotid compression (CC) reduce blood flow hypercapnia increase flow. Reducing by CC resulted significant decrease measured at rSD cm but not cm. In contrast, StO2 found both distances. Hypercapnia caused increases cm, Extracerebral elevated after hypercapnia, significantly reduced applying regression analysis. This demonstrated that less sensitive signals than

Язык: Английский

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Pulsatile microvascular cerebral blood flow waveforms change with intracranial compliance and age

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

Опубликована: Янв. 20, 2024

SignificanceDiffuse correlation spectroscopy (DCS) is an optical method to measure relative changes in cerebral blood flow (rCBF) the microvasculature. Each heartbeat generates a pulsatile signal with distinct morphological features that we hypothesized be related intracranial compliance (ICC).AimWe aim study how three of rCBF waveforms: augmentation index (AIx), pulsatility index, and area under curve, change respect ICC. We describe ICC as combination vascular extravascular compliance.ApproachSince patients Chiari malformations (CM) (n=30) have been shown altered compliance, compare morphology waveforms CM age-matched healthy control (n=30).ResultsAIx measured supine position was significantly less compared controls (p<0.05). Since physiologic aging also leads vessel stiffness intravascular evaluate waveform age find AIx feature strongly correlated (Rhealthy subjects=−0.63, Rpreoperative patient=−0.70, Rpostoperative patients=−0.62, p<0.01).ConclusionsThese results suggest microvasculature using DCS may

Язык: Английский

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

Journal of Biomedical Optics, Год журнала: 2024, Номер 29(01)

Опубликована: Янв. 24, 2024

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

Язык: Английский

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Fast Multi-Distance Time-Domain NIRS and DCS System for Clinical Applications

Sensors, Год журнала: 2024, Номер 24(22), С. 7375 - 7375

Опубликована: Ноя. 19, 2024

We have designed and built an improved system for combined Time-Domain Near-Infrared Spectroscopy (TD NIRS) Diffuse Correlation (DCS) measurements. The features two independent channels, enabling TD NIRS DCS acquisition at short long source-detector distances to enhance depth sensitivity in layered tissues. Moreover, the device can operate fast rates (up 50 Hz) monitor hemodynamic oscillations biological An OEM (Original Equipment Manufacturer) enables stable robust of photon distribution time-of-flight. For signals, use a time tagger software correlator allows us flexibility post-processing. A user-friendly GUI controls data online analysis. present results characterization on calibrated tissue phantoms according standardized protocols performance assessment devices. In-vivo measurements during rest vascular occlusions are also reported validate real settings.

Язык: Английский

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