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Neurons in an animal body form a highly complex and spatially organized 3D structure, which can be characterized by neuronal networks or circuits. Currently, the most common method of studying the 3D structure of neuron networks is by using a confocal fluorescence microscope, which requires fluorescence tagging with either transient membrane dyes or after fixation of the cells. Therefore, studies on neurons are often limited to samples that are chemically treated and/or dead.
WDT presents a solution for imaging live neuron networks with a high spatial and temporal resolution, because it is a 3D imaging method that is label-free and non-invasive. Using this method, a mouse or rat hippocampal neuron culture and a mouse dorsal root ganglion (DRG) neuron culture have been imaged in order to see the extension of processes between the cells in 3D. Furthermore, the tomogram is compared with a confocal fluorescence image in order to investigate the 3D structure at synapses.
By contrast, commercial projectors provide a high power output that is comparable to the halogen lamps while allowing for great flexibility in patterning the illumination. In addition to their high brightness, the illumination can be patterned to have arbitrary spatial and spectral distributions. Therefore, commercial projectors can be adopted as a flexible light source to an optical microscope by careful alignment to the existing optical path.
In this study, we employed a commercial projector source to a quantitative phase imaging system called spatial light interference microscopy (SLIM), which is an outside module for an existing phase contrast (PC) microscope. By replacing the ring illumination of PC with a ring-shaped pattern projected onto the condenser plane, we were able to recover the same result as the original SLIM. Furthermore, the ring illumination is replaced with multiple dots aligned along the same ring to minimize the overlap between the scattered and unscattered fields. This new method minimizes the halo artifact of the imaging system, which allows for a halo-free high-resolution quantitative phase microscopy system.
To meet these challenges, we present our new Quantitative Phase Imaging pipeline, with improved instrument performance, friendly user interface and robust data processing features, enabling us to acquire and catalog clinical datasets hundreds of gigapixels in size.
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This course aims to help researchers join the exciting and quickly emerging field of biomedical QPI. Quantifying cell-induced shifts in the optical path-lengths permits nanometer scale measurements of structures and motions in a non-contact, non-invasive manner. We will explain the basic principles and applications of QPI.
In the first part of the course – Methods - we will cover the main approaches to QPI, including phase-shifting, off-axis, common-path, and white-light methods, together with their figures of merit. A practical guide to designing and implementing instrumentation for QPI, along with image processing techniques will be presented.
The second part of the course – Applications – will review recent advances in biomedical applications of QPI. We will cover basic applications published in the recent literature on cell structure, dynamics and light scattering, as well as clinical applications such as blood testing and tissue diagnosis.
This course aims to familiarize optics researchers with the power of the Fourier transform and its application in all branches of linear optics. We will cover concepts of field propagation in both time and space and employ useful properties of the Fourier transform to gain understanding into physical phenomena and simplify our calculations. The first part of the course will be dedicated to describing the Fourier transform in 1D, 2D, and 3D, along with its most important properties, relevant to optical signals. The second part will be focused on applying the Fourier transform to solving optical problems of practical interest, as follows. 1D: pulse propagation in dispersive media, plane wave propagation in space; 2D: light diffraction on arbitrary apertures, imaging of two-dimensional objects, spatial and temporal coherence, holography; 3D: light scattering under the Born approximation and tomographic reconstructions.
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