Real-time X-ray imaging of mouse cerebral microvessels in vivo using a pixel temporal averaging method

Using digital pathology to analyze the murine cerebrovasculature

Research on the cerebrovasculature may provide insights into brain health and disease. Immunohistochemical staining is one way to visualize blood vessels, and digital pathology has the potential to revolutionize the measurement of blood vessel parameters. These tools provide opportunities for translational mouse model research. However, mouse brain tissue presents a formidable set of technical challenges, including potentially high background staining and cross-reactivity of endogenous IgG. Formalin-fixed paraffin-embedded (FFPE) and fixed frozen sections, both of which are widely used, may require different methods. In this study, we optimized blood vessel staining in mouse brain tissue, testing both FFPE and frozen fixed sections. A panel of immunohistochemical blood vessel markers were tested (including CD31, CD34, collagen IV, DP71, and VWF), to evaluate their suitability for digital pathological analysis. Collagen IV provided the best immunostaining results in both FFPE and frozen fixed murine brain sections, with highly-specific staining of large and small blood vessels and low background staining. Subsequent analysis of collagen IV-stained sections showed region and sex-specific differences in vessel density and vessel wall thickness. We conclude that digital pathology provides a useful tool for relatively unbiased analysis of the murine cerebrovasculature, provided proper protein markers are used.

Dynamic X-ray speckle-tracking imaging with high-accuracy phase retrieval based on deep learning

Speckle-tracking X-ray imaging is an attractive candidate for dynamic X-ray imaging owing to its flexible setup and simultaneous yields of phase, transmission and scattering images. However, traditional speckle-tracking imaging methods suffer from phase distortion at locations with abrupt changes in density, which is always the case for real samples, limiting the applications of the speckle-tracking X-ray imaging method. In this paper, we report a deep-learning based method which can achieve dynamic X-ray speckle-tracking imaging with high-accuracy phase retrieval. The calibration results of a phantom show that the profile of the retrieved phase is highly consistent with the theoretical one. Experiments of polyurethane foaming demonstrated that the proposed method revealed the evolution of the complicated microstructure of the bubbles accurately. The proposed method is a promising solution for dynamic X-ray imaging with high-accuracy phase retrieval, and has extensive applications in metrology and quantitative analysis of dynamics in material science, physics, chemistry and biomedicine.

Large-view x-ray imaging for medical applications using the world's only vertically polarized synchrotron radiation beam and a single asymmetric Si crystal

Objective.X-ray microangiography provides detailed information on the internal structure and function of a biological subject. Its ability to evaluate the microvasculature of small animals is useful for acquiring basic and clinical medical knowledge. The following three conditions are necessary to attain detailed knowledge of biological functions: (1) high temporal resolution with sufficient x-ray intensity, (2) high spatial resolution, and (3) a wide field of view. Because synchrotron radiation microangiography systems provide high sapatial resolution and high temporal resolution as a result of their high x-ray intensity, such systems have been developed at various synchrotron radiation facilities, starting with the photon factory, leading to numerous medical discoveries. However, the three aforementioned functions are incompatible with the use of synchrotron radiation because the x-ray intensity decreases when a wide field of view is obtained. To overcome these problems, we developed a new x-ray optical system for microangiography in rats using synchrotron radiation x-rays.Approach.Instead of using monochromatic synchrotron radiation x-rays with a conventional double-crystal monochromator, we used white synchrotron radiation x-rays and an asymmetric Si crystal to simultaneously monochromatize the beam and widen the field of view.Main results.The intensity profile and spatial resolution of the x-ray images were then evaluated. The proposed x-ray optics increased the x-ray intensity and beam width by factors of 1.3 and 2.7, respectively, compared with those of conventional monochromatic x-rays. In addition,in vivostudies on microangiography in rats were performed to confirm that the images had sufficient intensity, spatial resolution, and field of view. One of a series of images taken at 50 ms frame-1was shown as an example.Significance.This x-ray optics provides sufficient x-ray intensity, high spatial resolution, and a wide field of view. This technique is expected providing new insights into the evaluation of the vascular system.

Evaluation of high intensity synchrotron radiation x-ray imaging using Si crystals with lapped surface at 33.3 keV

In x-ray imaging methods, such as synchrotron radiation microangiography, the x-ray intensity has become more important in recent years for real-time dynamic observations to evaluate temporal changes in samples. Many synchrotron radiation facilities use x-rays monochromated by diffraction from perfect Si crystals to improve the spatial resolution of x-ray images and obtain detailed information about a sample. In this paper, monochromatic synchrotron x-ray images were acquired using Si crystals lapped with abrasives to enhance the x-ray intensity using white synchrotron radiation x-rays for observing dynamic changes in samples. The x-ray intensity, spatial resolution, and contrast noise ratio (CNR) in the acquired x-ray images were quantitatively evaluated using a state-of-the-art high-spatial-resolution detector. The x-ray intensity was substantially increased by a factor of ∼8 when a lapped Si crystal was used. When the lapped Si crystal was used, the spatial resolution of x-ray images in the diffraction-plane direction was ∼70% lower than when an etched Si crystal was used at a spatial resolution of 10 lp/mm. By contrast, the CNR in x-ray images, which is important for observing the interior of a sample, increased threefold when a contrast agent containing iodine at a concentration of 38 wt. % was used. It was confirmed that the combination of white synchrotron radiation x-rays and a lapped crystal produces an intense monochromatic x-ray, providing an important evaluation for the use of optics for each research purpose.