KEYWORDS: In vivo imaging, Cerebral blood flow, Signal to noise ratio, Single mode fibers, Autocorrelation, Ultrafast phenomena, Scattered light, Prefrontal cortex, Interferometry, Cameras
Optical methods can provide noninvasive approach for continuous cerebral blood flow (CBF) monitoring in humans in vivo. Diffuse correlation spectroscopy (DCS) is an established modality for qualitative CBF monitoring. DCS decodes the CBF from an analysis of the temporal correlations of the light scattered by the tissue. This, however, requires ultra-fast, generating vast amount of data to be processed. Instead of rapidly sensing temporal correlations, we can decode sample dynamics by quantifying speckle contrast, which is inversely proportional to the blood flow. Here, we analyze such an approach in the continuous-wave parallel interferometric near-infrared spectroscopy (CW-πNIRS)
In this study we demonstrated the effectiveness of dynamic light scattering (DLS) in enhancing the resolution of optical coherence tomography (OCT) images of static samples. By carefully analyzing the movement of particles within the sample, utilizing the autocorrelation function of the backscattered light and performing averaging of OCT images captured at different time points, we were able to effectively suppress spatial coherence and achieve improved transverse resolution in the images. Additionally, this technique holds the potential for providing valuable insights into the internal movements of biological samples, such as blood flow. To validate our method, we conducted experiments using an OCT system and introduced scatterers exhibiting random Brownian motion. The enhanced spatial resolution was clearly demonstrated through the visualization of cross-sections of bars and the analysis of B-scans. Our findings pave the way for further advancements in OCT imaging techniques and offer promising applications in the study of static biological samples.
Optical Coherence Tomography (OCT) is a well-established modality for structural and functional imaging of the biological samples. Conventional scanning OCT combines the low temporal coherence with confocal gating to reject multiply scattered light. However, OCT uses a spatially coherent light source, and thus, is susceptible to speckle noise, which reduces the transverse resolution. We use dynamic light scattering to improve the transverse resolution. The dynamic scattering particles induce speckles, that change over time due to particle displacement. By incoherently averaging OCT images acquired under different particle distributions, we effectively suppress the spatial coherence and improve transverse image resolution.
KEYWORDS: Near infrared spectroscopy, Interferometry, In vivo imaging, Blood circulation, Brain, Absorption, Signal processing, Cerebral blood flow, Cameras, Tissues
Interferometric near-infrared spectroscopy (iNIRS) noninvasively measures the optical and dynamical properties of the human brain in vivo. However, iNIRS uses single-mode fibers, which reduces the detected light throughput. Here, we demonstrate the parallel interferometric near-infrared spectroscopy (πNIRS) to overcome this limitation. In πNIRS we use multi-mode fibers for light collection and a high-speed, two-dimensional camera for light detection. With more than 8000 parallel channels, we can sense the cerebral blood flow and absorption changes with only 2-10 msec integration time (~100-500x faster than conventional iNIRS). This capability enabled us to monitor prefrontal cortex activation in humans in vivo.
KEYWORDS: Near infrared spectroscopy, Interferometry, Blood circulation, Brain, Tissue optics, Tissues, System integration, Spectroscopy, Single mode fibers, Signal detection
We developed and applied parallel interferometric near-infrared spectroscopy (πNIRS) to noninvasively monitor pulsatile blood flow deep into the human tissue in vivo. With the unique capability of accessing complex information (amplitude and phase) about the sample with more than 1000 parallel channels, we can sense blood flow with only 20 ms integration time, making the πNIRS one of the fastest and comprehensive diffuse optical method.
Optical coherence tomography (OCT) is a well-established modality for structural and functional imaging of the biological samples. Conventional scanning OCT combines the low temporal coherence with confocal gating to reject multiply scattered light. However, OCT uses a spatially coherent light source, and thus, is susceptible to speckle noise, which reduces the transverse resolution. We use dynamic light scattering to improve the transverse resolution. The dynamic scattering particles induce speckles, that change over time due to particle displacement. By incoherently averaging OCT images acquired under different particle distributions, we effectively suppress the spatial coherence and improve transverse image resolution.
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