Phase-contrast x-ray imaging (PCI) is an innovative method that is sensitive to the refraction of the x-rays in matter. PCI is particularly adapted to visualize weakly absorbing details like those often encountered in biology and medicine. In past years, PCI has become one of the most used imaging methods in laboratory and preclinical studies: its unique characteristics allow high contrast 3D visualization of thick and complex samples even at high spatial resolution. Applications have covered a wide range of pathologies and organs, and are more and more often performed in vivo. Several techniques are now available to exploit and visualize the phase-contrast: propagation- and analyzer-based, crystal and grating interferometry and non-interferometric methods like the coded aperture. In this review, covering the last five years, we will give an overview of the main theoretical and experimental developments and of the important steps performed towards the clinical implementation of PCI.

http://iopscience.iop.org/article/10.1088/0031-9155/58/1/R1/pdf

X-ray phase-contrast imaging: from pre-clinical applications towards clinics

Screening for breast cancer.

http://xrm.phys.northwestern.edu/research/pdf_papers/2007/withers_mater_today_2007.pdf

X-ray nanotomography

Summary We demonstrate compact full-field soft X-ray transmission microscopy with sub 60-nm resolution operating at λ= 2.48 nm. The microscope is based on a 100-Hz regenerative liquid-nitrogen-jet laser-plasma source in combination with a condenser zone plate and a micro-zone plate objective for highresolution imaging onto a 2048 × 2048 pixel CCD detector. The sample holder is mounted in a helium atmosphere and allows imaging of both dry and wet specimens. The microscope design enables fast sample switching and the sample can be prealigned using a visible-light microscope. High-quality images can be acquired with exposure times of less than 5 min. We demonstrate the performance of the microscope using both dry and wet samples.

/pdf/high-resolution-compact-x-ray-microscopy-36d2mk7155.pdf

High-resolution compact x-ray microscopy

Spectral computed tomography (CT) is a promising technique with the potential for improving lesion detection, tissue characterization, and material decomposition. In this paper, we are interested in kVp switching-based spectral CT that alternates distinct kVp X-ray transmissions during gantry rotation. This system can acquire multiple X-ray energy transmissions without additional radiation dose. However, only sparse views are generated for each spectral measurement; and the spectra themselves are limited in number. To address these limitations, we propose a penalized maximum likelihood method using spectral patch-based low-rank penalty, which exploits the self-similarity of patches that are collected at the same position in spectral images. The main advantage is that the relatively small number of materials within each patch allows us to employ the low-rank penalty that is less sensitive to intensity changes while preserving edge directions. In our optimization formulation, the cost function consists of the Poisson log-likelihood for X-ray transmission and the nonconvex patch-based low-rank penalty. Since the original cost function is difficult to minimize directly, we propose an optimization method using separable quadratic surrogate and concave convex procedure algorithms for the log-likelihood and penalty terms, which results in an alternating minimization that provides a computational advantage because each subproblem can be solved independently. We performed computer simulations and a real experiment using a kVp switching-based spectral CT with sparse-view measurements, and compared the proposed method with conventional algorithms. We confirmed that the proposed method improves spectral images both qualitatively and quantitatively. Furthermore, our GPU implementation significantly reduces the computational cost.

Sparse-View Spectral CT Reconstruction Using Spectral Patch-Based Low-Rank Penalty

In this paper, the development of compact transmission soft x-ray microscopy (XM) with sub-50 nm spatial resolution for biomedical applications is described. The compact transmission soft x-ray microscope operates at lambda = 2.88 nm (430 eV) and is based on a tabletop regenerative x-ray source in combination with a tandem ellipsoidal condenser mirror for sample illumination, an objective micro zone plate and a thinned back-illuminated charge coupled device to record an x-ray image. The new, compact x-ray microscope system requires the fabrication of proper x-ray optical devices in order to obtain high-quality images. For an application-oriented microscope, the alignment procedure is fully automated via computer control through a graphic user interface. In imaging studies using our compact XM system, a gold mesh image was obtained with 45 nm resolution at x580 magnification and 1 min exposure. Images of a biological sample (Coscinodiscus oculoides) were recorded.

/pdf/compact-soft-x-ray-transmission-microscopy-with-sub-50-nm-53kpot0933.pdf

Compact soft x-ray transmission microscopy with sub-50 nm spatial resolution.

Disclosed herein are an X-ray imaging apparatus and a method for controlling the same. The X-ray imaging apparatus includes an X-ray generator configured to radiate first-energy X-rays toward an object, an X-ray detector configured to detect the first-energy X-rays which propagate through the object, an image processor configured to generate a first object image which correspond to the detected first-energy X-rays and to estimate a second object image which corresponds to second-energy X-rays based on the generated first object image, and a controller configured to control the image processor to repeatedly estimate the second object image by controlling the X-ray generator to repeatedly radiate the first-energy X-rays toward the object.

X-ray imaging apparatus and method of controlling the same

The X-ray imaging apparatus to form a phase contrast image includes an X-ray source that generates X-rays to emit the X-rays to an object; an X-ray detector configured to detect X-rays having passed through the object to acquire phase contrast image signals on a per energy band basis; and a quantitative data acquirer configured to calculate approximate quantitative data of two or more constituent substances of the object using a relation between the phase contrast image signals on the per energy band basis and quantitative data of the constituent substances, and estimate quantitative data of the constituent substances by iteratively applying a regularization function to the approximate quantitative data.

X-ray imaging apparatus and control method for the same

This article presents a novel six degrees-of-freedom nanopositioning stage having a low-profile shape. The six degrees-of-freedom motion is achieved in a parallel configuration comprising four crab-leg flexure guide mechanisms and eight electromagnetic actuators. The crab-leg flexure can be engineered to exhibit similar stiffness levels in all the directions. The noncontact direct-drive nature of the electromagnetic actuators and the symmetric layout simplify the kinematics and result in considerably low coupling between the motion axes. For design optimization, we derived an analytical model that described the static and dynamic performances of the proposed stage using the matrix method. Then, we fabricated the stage with a stroke of 0.5 mm in the translational directions and 5 mrad in the rotational directions. The stage measured 250 mm × 250 mm × 57.4 mm. In an open-loop operation, the six-axis motions exhibited linear and repeatable performances. The maximum parasitic error was less than 1.8% of full scale. The tracking errors for the closed-loop control of the 5 Hz sinusoidal trajectory were less than 222 nm and 4.2  μ rad. The temperature elevation was 5.8 °C after 3 h using half of the entire power consumption. The stage was utilized for developing an autofocusing system in dynamic scanning using an optical microscope.

Six Degrees-of-Freedom Direct-Driven Nanopositioning Stage Using Crab-Leg Flexures

Disclosed herein are an X-ray detection panel, an X-ray image generating module, an X-ray imaging apparatus, and a method of generating an X-ray image The X-ray imaging apparatus includes an X-ray generator configured to emit X-rays; an X-ray detection panel comprising a plurality of pixel groups, each pixel group configured to detect X-rays having an energy band and to convert the detected X-rays into electrical signals; and an image processor configured to acquire readout data from the electrical signals of at least one of the plurality of pixel groups, to calculate estimated data, and to generate an X-ray image by combining the readout data and the estimated data

Sung Hoon Kang

Papers

Compact soft x-ray transmission microscopy with sub-50 nm spatial resolution.

X-ray imaging apparatus and method of controlling the same

X-ray imaging apparatus and control method for the same

Six Degrees-of-Freedom Direct-Driven Nanopositioning Stage Using Crab-Leg Flexures

Method and apparatus of generating X-ray image