Optical coherence tomography angiography (OCTA) offers unparalleled capabilities for non-invasive detection of vessels. However, the lack of accurate models for light-tissue interaction in OCTA jeopardizes the development of the techniques to further extract quantitative information from the measurements. In this manuscript, we propose a Monte Carlo (MC)-based simulation method to precisely describe the signal formation of OCTA based on the fundamental theory of light-tissue interactions. A dynamic particle-fixed model is developed to depict the spatial-temporal behaviors of the tissue phantom: the particles are initialized and fixed in specific locations with wavelength-dependent scattering cross-sections and are allowed to travel over time. We then employ a full-spectrum MC engine to faithfully simulate the formation of OCT and OCTA images. A simulation on a vessel-mimicking phantom demonstrated that speckle characteristics in OCT as well as decorrelation maps in OCTA could be successfully reproduced. We further illustrate the usefulness of our method on the quantitative OCTA by extending it to simulate the gradual saturation of decorrelation in OCTA-based velocimetry. We believe our method will serve as a valuable tool for studying OCTA theory and inspire better solutions and metrics for non-invasive flow velocity measurement.
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http://dx.doi.org/10.1364/BOE.540916 | DOI Listing |
Struct Dyn
January 2025
Center for Free-Electron Laser Science CFEL, Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany.
Sub-ångström spatial resolution of electron density coupled with sub-femtosecond to few-femtosecond temporal resolution is required to directly observe the dynamics of the electronic structure of a molecule after photoinitiation or some other ultrafast perturbation, such as by soft X-rays. Meeting this challenge, pushing the field of quantum crystallography to attosecond timescales, would bring insights into how the electronic and nuclear degrees of freedom couple, enable the study of quantum coherences involved in molecular dynamics, and ultimately enable these dynamics to be controlled. Here, we propose to reach this realm by employing convergent-beam x-ray crystallography with high-power attosecond pulses from a hard-x-ray free-electron laser.
View Article and Find Full Text PDFCureus
December 2024
Ophthalmology Department, University of Kansas School of Medicine, Kansas City, USA.
Background: An idiopathic macular hole (IMH) is a foveal opening in the neurosensory retina caused by perifoveal vitreomacular traction and detachment. IMH prevalence varies considerably across populations, highlighting a need for further investigation, especially in underrepresented groups such as Hispanics.
Methods: This retrospective, descriptive, cross-sectional study analyzed IMH prevalence in a Hispanic population over four years.
Biomed Opt Express
January 2025
Department of Biomedical Engineering, University of Illinois Chicago, Chicago, IL 60607, USA.
The choroid, a critical vascular layer beneath the retina, is essential for maintaining retinal function and monitoring chorioretinal disorders. Existing imaging methods, such as indocyanine green angiography (ICGA) and optical coherence tomography (OCT), face significant limitations, including contrast agent requirements, restricted field of view (FOV), and high costs, limiting accessibility. To address these challenges, we developed a nonmydriatic, contrast agent-free fundus camera utilizing transcranial near-infrared (NIR) illumination.
View Article and Find Full Text PDFBiomed Opt Express
January 2025
Department of Robotics, University of Michigan, USA.
Conventional scanned optical coherence tomography (OCT) suffers from the frame rate/resolution tradeoff, whereby increasing image resolution leads to decreases in the maximum achievable frame rate. To overcome this limitation, we propose two variants of machine learning (ML)-based adaptive scanning approaches: one using a ConvLSTM-based sequential prediction model and another leveraging a temporal attention unit (TAU)-based parallel prediction model for scene dynamics prediction. These models are integrated with a kinodynamic path planner based on the clustered traveling salesperson problem to create two versions of ML-based adaptive scanning pipelines.
View Article and Find Full Text PDFBiomed Opt Express
January 2025
Department of Electronic Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
Optical coherence tomography angiography (OCTA) offers unparalleled capabilities for non-invasive detection of vessels. However, the lack of accurate models for light-tissue interaction in OCTA jeopardizes the development of the techniques to further extract quantitative information from the measurements. In this manuscript, we propose a Monte Carlo (MC)-based simulation method to precisely describe the signal formation of OCTA based on the fundamental theory of light-tissue interactions.
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