SignificanceCerebral blood flow (CBF) and cerebral blood volume (CBV) are key metrics for regional cerebrovascular monitoring. Simultaneous, non-invasive measurement of CBF and CBV at different brain locations would advance cerebrovascular monitoring and pave the way for brain injury detection as current brain injury diagnostic methods are often constrained by high costs, limited sensitivity, and reliance on subjective symptom reporting.AimWe aim to develop a multi-channel non-invasive optical system for measuring CBF and CBV at different regions of the brain simultaneously with a cost-effective, reliable, and scalable system capable of detecting potential differences in CBF and CBV across different regions of the brain.ApproachThe system is based on speckle contrast optical spectroscopy and consists of laser diodes and board cameras, which have been both tested and investigated for safe use on the human head. Apart from the universal serial bus connection for the camera, the entire system, including its battery power source, is integrated into a wearable headband and is powered by 9-V batteries.ResultsThe temporal dynamics of both CBF and CBV in a cohort of five healthy subjects were synchronized and exhibited similar cardiac period waveforms across all six channels. The potential use of our six-channel system for detecting the physiological sequelae of brain injury was explored in two subjects, one with moderate and one with significant structural brain damage, where the six-point CBF and CBV measurements were referenced to structural magnetic resonance imaging (MRI) scans.ConclusionsWe pave the way for a viable multi-point optical instrument for measuring CBF and CBV. Its cost-effectiveness allows for baseline metrics to be established prior to injury in populations at risk for brain injury.
SignificanceIn the realm of cerebrovascular monitoring, primary metrics typically include blood pressure, which influences cerebral blood flow (CBF) and is contingent upon vessel radius. Measuring CBF noninvasively poses a persistent challenge, primarily attributed to the difficulty of accessing and obtaining signal from the brain.AimOur study aims to introduce a compact speckle contrast optical spectroscopy device for noninvasive CBF measurements at long source-to-detector distances, offering cost-effectiveness, and scalability while tracking blood flow (BF) with remarkable sensitivity and temporal resolution.ApproachThe wearable sensor module consists solely of a laser diode and a board camera. It can be easily placed on a subject’s head to measure BF at a sampling rate of 80 Hz.ResultsCompared to the single-fiber-based version, the proposed device achieved a signal gain of about 70 times, showed superior stability, reproducibility, and signal-to-noise ratio for measuring BF at long source-to-detector distances. The device can be distributed in multiple configurations around the head.ConclusionsGiven its cost-effectiveness, scalability, and simplicity, this laser-centric tool offers significant potential in advancing noninvasive cerebral monitoring technologies.
Diffusing Wave Spectroscopy (DWS) employs non-invasive techniques to study dynamic behaviors within scattering mediums. This involves detecting speckle light patterns from the moving media and gauging speckle decorrelation time for dynamic quantification. A specific form of DWS is Speckle Visibility Spectroscopy (SVS), which employs spatial ensembles by utilizing a high-pixel-count cameras to capture multiple speckles in a single frame. To further increase SNR at low signal level, one combines interferometric techniques with SVS to form interferometric SVS (iSVS).
In this talk, I will present the benefits and constraints associated with the utilization of interferometric detection (iSVS) over direct detection (SVS). Surprisingly, we found that iSVS does not always outperform SVS, but it does emerge as the prevailing choice in most cases.
Measuring blood flow on the head is an indirect yet crucial way to access or quantify brain activity non-invasively, useful for diagnosing traumatic brain injuries by looking at the changes of blood flow. However, measuring the cerebral blood flow (CBF) remains challenging, principally due to the ability to reach and collect signal from the brain. In this talk, I will present our efforts in building an affordable, compact, and portable laser device for real-time Cerebral Blood Flow (CBF) monitoring. Our technique draws upon the speckle visibility spectroscopy technique, using the spatial ensemble of the speckle field to evaluate blood flow dynamics.
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