X-ray phase-contrast imaging (XPCI) overcomes the problem of low contrast between different soft tissues achieved in conventional x-ray imaging by introducing x-ray phase as an additional contrast mechanism. This work describes a compact x-ray light source (CXLS) and compares, via simulations, the high quality XPCI results that can be produced from this source to those produced using a microfocus x-ray source. The simulation framework is first validated using an image acquired with a microfocus-source, propagation-based XPCI (PB-XPCI) system. The phase contrast for a water sphere simulating a simple cyst submersed in muscle is evaluated and the evolution of PB-XPCI signal as the object to detector distance is increased is demonstrated. The proposed design of a PB-XPCI system using the CXLS is described and simulated images of a coronary artery compared between CXLS and microfocus source PB-XPCI systems. To generate images with similar noise levels, a microfocus source would require a 3000 times longer exposure than would the CXLS. We conclude that CXLS technology has the potential to provide high-quality XPCI in a medical environment using extremely short exposure times relative to microfocus source approaches.
We implement differential interference contrast (DIC) microscopy using high-speed synthetic aperture imaging that expands the passband of coherent imaging by a factor of 2.2. For an aperture synthesized coherent image, we apply for the numerical post-processing and obtain a high-contrast DIC image for arbitrary shearing direction and bias retardation. In addition, we obtain images at different depths without a scanning objective lens by numerically propagating the acquired coherent images. Our method achieves high-resolution and high-contrast 3-D DIC imaging of live biological cells. The proposed method will be useful for monitoring 3-D dynamics of intracellular particles.
Self-referenced quantitative phase microscopy (SrQPM) is reported, wherein quantitative phase imaging is achieved
through the interference of the sample wave with a reflected version of itself. The off-axis interference between the two
beams generates a spatially modulated hologram that is analyzed to quantify the sample's amplitude and phase profile.
SrQPM requires approximately one-half of the object field of view to be empty and optically flat, which serves as a reference for the other half of the field of view containing the sample.
We propose a method based on wavefront shaping for enhancing the backscattered light detected from any location in a
sample medium, using low-coherence interferometry. The lateral phase profile of the light incident upon the sample is
controlled using a spatial light modulator (SLM). In this manner, we apply an orthogonal set of phase masks to the
illumination (input) and measure the backscattered signal response (output). These measurements permit us to determine
the linear transformation between the input complex-amplitude modulation profile and the output time-resolved signal.
Thus, we can determine the appropriate SLM write pattern for maximizing the detected signal for a given optical time
delay (in the sample arm). In this manuscript, we are interested in the degree to which maximizing this signal also
permits us to localize the three-dimensional sample region from which the backscattered signal is derived.
Tomographic phase microscopy measures the 3-D refractive index distribution of cells and tissues by combining the information from a series of angle-dependent interferometric phase images. In the original device, the frame rate was limited to 0.1 frames per second (fps) by the technique used to acquire phase images, preventing measurements of moving or rapidly changing samples. We describe an improved tomographic phase microscope in which phase images are acquired via a spatial fringe pattern demodulation method, enabling a full tomogram acquisition rate of 30 fps. In addition, in this system the refractive index is calculated by a diffraction tomography algorithm that accounts for the effects of diffraction in the 3-D reconstruction. We use the instrument to quantitatively monitor rapid changes in refractive index within defined subregions of cells due to exposure to acetic acid or changes in medium osmolarity.
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