Functional interferometric diffusing wave spectroscopy of the human brain

Abstract

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

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

“… 2 To minimize these extracerebral contributions, several approaches have been proposed that typically fall into one of two categories: (1) hardware modifications or (2) improved analytical modeling. On the hardware side, developments include methods that enhance depth sensitivity, either through time domain 3 , 4 or interferometric approaches, 5 , 6 or by moving to the second optical window at 1064 nm. 7 While these approaches are exciting and will likely be the future of DCS, limitations related to detector speed, availability, and cost currently limit widespread adoption.…”

A Transparent Ultrasound Array for Real-Time Optical, Ultrasound, and Photoacoustic Imaging

“…Recently, intravascular PA (IVPA) is also being actively studied for mapping deep tissue atherosclerosis based on high optical absorption contrast of plaque lipids in the NIR-IIb (1.5 μm-1.7 μm) optical window [19][20][21][22][23]. Similarly, neuroscience studies also require high-resolution multiparametric hemodynamic information (cerebral blood flow, blood volume, and oxygen saturation) obtained from optical and photoacoustic imaging for mapping resting state brain connectivity [24][25][26], studying neuromodulation [27], neurovascular coupling [28][29][30], and neurodiseases [31][32][33]. For this purpose, recently functional ultrasound (fUS) imaging, which provides high resolution images of microvascular blood flow, has been integrated with hemoglobin absorption-based PA vascular imaging [34].…”

Transient motion classification through turbid volumes via parallelized single-photon detection and deep contrastive embedding

“…Recently developed highly parallelized DCS (PaDS) demonstrates that detecting multiple speckles across many optical sensor pixels results in significantly faster correlation sampling rate Johansson et al (2019); Liu et al (2021a);Sie et al (2020); Xu et al (2021b); Zhou et al (2021). Further, advances in contrastive representation learning Liu et al (2021b) facilitates the use of deep artificial neural networks to create an embedding space where similar inputs of unique sub-types are clustered together without any data labeling required.…”