A line-field scanning Fourier-domain optical coherence tomography (OCT) system (LF-FDOCT) that makes high-resolution and large-dynamic-range imaging possible was demonstrated. Unlike the conventional flying-spot OCT system, the x-axis parallel imaging (one B-scan) has a coherent imaging mode. A theoretical simulation of parallel interference imaging was derived, and the anisotropic resolution along two orthogonal directions was achieved. Validated by experimental results, the spatial resolutions along the x and y axis directions were 2.46 and 2.19 μm, and the theoretical resolutions were 1.8 and 1.34 μm, respectively. The field of view (FOV) in the lateral direction was 900 μm ( x ) × 850 μm ( y ) , and the axial resolution and FOV in the experiment were 2.5 and 700 μm, respectively. The maximal axial sensitivity was measured to be 90.5 dB when the sample was a specula. The en face of tomato and the cross-section of multilayer glass were demonstrated based on the LF-FDOCT system. The three-dimensional image of adherend sample including gels and microelectrodes was realized, proving the LF-FDOCT system had the capability of high resolution and high-dynamic-range imaging.
We present methods based on Optical Coherence Tomography to quantify longitudinal changes in murine cortical vasculature. To demonstrate our methods, we tracked age-related changes in vascular structure and function of 3xTg Alzheimer’s disease (AD) and age-matched wild-type (WT) mice over the course of 7 months. In total, we measured 27 longitudinal parameters related to the morphology, topology, and function of the cortical vasculature across all scales: large pial vessels, penetrating vessels, and capillaries. Ten of these parameters showed different time-courses between AD and WT mice, with significant alterations preceding the onset of cognitive decline.
We report optical coherence tomography (OCT) imaging of localized fast optical signals (FOS) arising from whisker stimulation in awake mice. The activated voxels were identified by fitting the OCT intensity signal time course with a response function over a time scale of a few hundred milliseconds after the whisker stimulation. The significantly activated voxels were shown to be localized to the expected brain region for whisker stimulation. The ability to detect functional stimulation-evoked, depth resolved FOS with intrinsic contrast from the cortex provides a new tool for neural activity studies.
KEYWORDS: Optical coherence tomography, 3D image processing, Stereoscopy, Tissue optics, 3D metrology, Luminescence, Diffusion, 3D displays, Tissues, Cancer
The recent development of 3D tissue spheroids aims to address current limitations with traditional 2D cell cultures in various studies, including cancer drug screening and environmental toxin testing. In these studies, measurements of cellular viability are commonly utilized to assess the effects of drug or toxins. Existing methods include live/dead assays, colorimetric assays, fluorescence calcium imaging, and immunohistochemistry. However, those methods involve the addition of histological stains, fluorescent proteins, or other labels to the sample; some methods also require sample fixation. Fixation-based methods preclude the possibility of longitudinal study of viability, and confocal fluorescence imaging-based methods suffer from insufficient delivery of labels near the center of 3D spheroids. Here, we demonstrate the use of label-free optical coherence tomography (OCT) for quantitative cellular viability imaging of 3D tissue spheroids. OCT intensity and decorrelation signals acquired from neurospheroids exhibited changes correlated with cellular viability as manipulated with ethanol. Interestingly, when we repeated the imaging while cells gradually became less viable, the intensity and decorrelation signals exhibited different time courses, suggesting that they may represent different cellular processes in cell death. More quantitative measurements of viability using dynamic light scattering optical coherence microscopy (DLS-OCM) will be also presented. DLS-OCM enables us to obtain 3D maps of the diffusion coefficient, and we found that the diffusion coefficient of intra-cellular motility correlated with cellular viability manipulated by changes in temperature and pH. Finally, applications of these novel methods to human-cell 3D spheroids will be discussed.
Dynamic Light Scattering-Optical Coherence Tomography (DLS-OCT) takes the advantages of using DLS to measure particle flow and diffusion within an OCT resolution-constrained 3D volume, enabling the simultaneous measurements of absolute RBC velocity and diffusion coefficient with high spatial resolution. In this work, we applied DLS-OCT to measure both RBC velocity and the shear-induced diffusion coefficient within penetrating venules of the somatosensory cortex of anesthetized mice. Blood flow laminar profile measurements indicate a blunted laminar flow profile, and the degree of blunting decreases with increasing vessel diameter. The measured shear-induced diffusion coefficient was proportional to the flow shear rate with a magnitude of ~ 0.1 to 0.5 × 10-6 mm2 . These results provide important experimental support for the recent theoretical explanation for why DCS is dominantly sensitive to RBC diffusive motion.
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