We propose a novel and accessible approach for fabricating thin phantoms with controllable absorption properties in terms of magnitude, spectral shape, and spatial distribution. The method involves a standard laser printer to print on thin polyurethane films emulating optical properties of biological tissue. We characterize the thin phantoms in terms of optical properties, thickness, microscopic structure, and reproducibility of the printing process. We argue that these thin phantoms hold potential for a wide range of biomedical applications and will discuss their potential application in transcutaneous bilirubinometry performance studies.
Quantification of total hemoglobin concentrations [tHb] is imperative to determine blood-related diseases such as anemia. In this work, we validate [tHb] estimates by visible-light spectroscopic optical coherence tomography (vis-sOCT) with the gold standard, intravenous blood sample analysis from a commercial avoximeter. We recruited a group of 27 volunteers and retrieved [tHb] with vis-sOCT data from the microcirculation in the skin of the left posterior forearm. Expected [tHb] were obtained from blood sample analysis by a commercial analyzer. We compare the [tHb] estimated by vis-sOCT with the expected [tHb]. Additionally, the effect of multiple factors of influence such as gender, skin tone, and epidermal thickness is investigated.
Thrombus formation is a physiological response to damage in a blood vessel. Monitoring thrombus formation is challenging, due to the limited imaging options available to analyze flowing blood. In this work, we use a visible-light optical coherence tomography (vis-OCT) system to monitor the dynamic process of the formation of thrombi in a microfluidic blood vessel-on-chip (VoC) device. Inside the VoC, thrombi form in a monolayered channel of endothelial cells perfused by human whole blood. We show that the correlation of the vis-OCT signal can be utilized as a marker for thrombus formation and can track and quantify its growth over time. We validate our results with fluorescence microscopic imaging of fibrin and platelets.
In this work, we developed a methodology to non-invasively quantify total hemoglobin [tHb] concentrations in the microcirculation of the skin with visible-light spectroscopic optical coherence tomography (vis-sOCT). Our approach is based on the spatial distribution of [tHb] inside a vis-sOCT scan. Local [tHb] are retrieved by analyzing the optical density at each point of the tomogram. We show that the [tHb] distribution map, termed hemogram, presents blood vessel distributions comparable to that of optical coherence tomography angiography. In addition, we obtain a clinically useful measurement of the average [tHb] by analyzing the [tHb] across the hemogram. For a healthy volunteer, this average [tHb] of 11.62 g/dL falls within the expected clinical range and is consistent between eight independent measurement locations on the skin with a standard deviation of 0.88 g/dL.
We present a novel processing technique to retrieve total haemoglobin concentrations with spectroscopic optical coherence tomography data based on numerical optimization of the optical density. We validated our method with ex-vivo human whole blood.
We present a mathematical model for the generation of vortex-beams by using a square profile amplitude fork diffraction grating with arbitrary topological charge. The mathematical framework of aberrations in the forked-shape diffraction grating is analysed, and the resulting diffracted pattern is simulated. Three cases of desired distortions (aberrations) in the diffraction grating are considered, obtaining phase modulation from the amplitude grating. Experimental optical vortices are generated by using a transmission spatial light modulator, which is used as a dynamic diffraction grating, allowing us to aberrate it. We show the effect of aberrations in the experimental diffracted vortex-beams and compare it with the numerical simulation.
A cylindrical matrix device with a circular release area with inhomogeneous diffusivity was analyzed using a Laplace transform–based method, using Bromwich integral and residue theorem. The two-dimensional model represented a pharmaceutical agent uniformly distributed in a polymeric matrix with a diffusivity spatially modulated, surrounded by an impermeable layer. The pharmaceutical agent could be transferred only through a small hole centered at the top surface of the cylinder. A closed-form solution was obtained in terms of Bessel functions with the aim to help study the effects of design parameters and geometries on the cumulative amount of pharmaceutical agent released. The cumulative flux of pharmaceutical agent increased with the mass transfer and diffusion coefficients and decreased with any increment in the device’s length and variations of the diffusivity coefficients. The delivery rate was described by an effective time constant calculated from Laplace transforms and using Bessel functions and their zeros. Reducing the orifice diameter or fabricating a longer system would delay transport of the medication. Simplified expressions for the release profile and the time constant were derived for special design cases.
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