Deep learning-based algorithms for low-dose CT imaging: A review.

The computed tomography (CT) technique is extensively employed as an imaging modality in clinical settings. The radiation dose of CT, however, is significantly high, thereby raising concerns regarding the potential radiation damage it may cause. The reduction of X-ray exposure dose in CT scanning may result in a significant decline in imaging quality, thereby elevating the risk of missed diagnosis and misdiagnosis. The reduction of CT radiation dose and acquisition of high-quality images to meet clinical diagnostic requirements have always been a critical research focus and challenge in the field of CT. Over the years, scholars have conducted extensive research on enhancing low-dose CT (LDCT) imaging algorithms, among which deep learning-based algorithms have demonstrated superior performance. In this review, we initially introduced the conventional algorithms for CT image reconstruction along with their respective advantages and disadvantages. Subsequently, we provided a detailed description of four aspects concerning the application of deep neural networks in LDCT imaging process: preprocessing in the projection domain, post-processing in the image domain, dual-domain processing imaging, and direct deep learning-based reconstruction (DLR). Furthermore, an analysis was conducted to evaluate the merits and demerits of each method. The commercial and clinical applications of the LDCT-DLR algorithm were also presented in an overview. Finally, we summarized the existing issues pertaining to LDCT-DLR and concluded the paper while outlining prospective trends for algorithmic advancement.

Direct investigations of the electrical conductivity of normal and cancer breast cells by conductive atomic force microscopy.

Breast cancer is one of the most commonly diagnosed malignant cancers that threatens the health of women severely. The pathogenesis has not been revealed exhaustively due to the complex mechanisms. Evidences suggest that electrical conductivity properties play critical roles in cellular functions and activities. But the roles of electrical conductivity in pathogenesis of breast cancer cells have not been studied clearly at the nanometer level yet. In the present work, the electrical conductivity and electron transport of two normal and one cancer breast cell lines were investigated and compared at nanometer spatial level and picoampere current level by Conductive Atomic Force Microscopy (CAFM). The cell bodies of normal and cancer breast cells show the typical capacitor behaviors with little conductivity capability for electricity. The capacitance of cell bodies of the cancer breast cells is less than the normal breast cells. The conductivity of the processes of normal and cancer breast cells has also been investigated. The processes of the normal breast cells also exhibit the capacitor behavior. While the processes of the breast cells are electrically conductive along micrometer length scales, and show the semiconductor like conductive characteristics with Schottky barrier of 0.8391 V. All these demonstrate that the electrical conductivity of the cancer breast cells is better than the normal breast cells. This work will be helpful in the further investigations of electrical conductivity of normal and cancer cells at nanometer level, and will also pave new way in the distinguishing the cancer cells and tissues from the normal cells and tissues.

Determination of Hepatic Iron Deposition in Drug-Induced Liver Fibrosis in Rats by Confocal Micro-XRF Spectrometry.

Liver fibrosis is the intermediate process and inevitable stage of the development of chronic liver disease into cirrhosis. Reducing the degree of liver fibrosis plays an extremely important role in treating chronic liver disease and preventing liver cirrhosis and liver cancer. The formation of liver fibrosis is affected by iron deposition to a certain extent, and excessive iron deposition further induces liver cirrhosis and liver cancer. Herein, confocal microbeam X-ray fluorescence (µ-XRF) was used to determine the intensity and biodistribution of iron deposition at different time points in the process of liver fibrosis induced by thioacetamide (TAA) in rats. To our best knowledge, this is the first study using confocal µ-XRF to analyze hepatic iron deposition in hepatic fibrosis. The results showed that there are minor and trace elements such as iron, potassium, and zinc in the liver of rats. Continuous injection of TAA solution resulted in increasing liver iron deposition over time. The intensity of iron deposition in liver tissue was also significantly reduced after bone mesenchymal stem cells (BMSCs) were injected. These findings indicated that confocal µ-XRF can be used as a nondestructive and quantitative method of evaluating hepatic iron deposition in hepatic fibrosis, and iron deposition may play an important role in the progression of hepatic fibrosis induced by TAA.

Correlation between the topologically close-packed structure and the deformation behavior of metallic Cu64.5Zr35.5.

The topologically close-packed (TCP) structural characteristics in a model metallic glass (MG) of Cu64.5Zr35.5 have been investigated by molecular dynamics simulations. A group of structural indicators based on the largest standard cluster (LaSC) have been correlated with the non-affine displacement (D2) of atoms, so as to reveal the hidden correlation between local structures and deformation behavior of Cu64.5Zr35.5 during compression. It was found that the 15 types of Top-10 LaSCs are all TCP-like ones, among which the most numerous icosahedron (Z12 and 1-Z12) decreases in population sharply and moderately during respectively the elastic and yield region of compression; while in the fluid-flow region, the number of all Top-10 LaSCs tends to be almost constant. Low-D2 atoms prefer to link with each other; while medium-D2 atoms act as transition structures between backbone areas and deformation areas. Most interestingly, the deformation response of TCP-like atoms is not only determined by its nearest neighbor characteristics, but also depends on the linkage with other atoms. In addition, icosahedral atoms with a higher degree of medium range five-fold symmetry (MRFFS) are more resistant to the stress-induced deformation. Therefore, the TCP characteristics, including its nearest neighbor feature and the inter-connection between TCP LaSCs, are closely related with the deformation behavior of atoms, especially the MRFFS (up to 5 layers) of icosahedral atoms. These findings shed new light on the understanding of the relationship between microstructure and deformation response of MGs, which will promote the development of deformation theory of MGs.

Studying the rhodopsin-like G protein-coupled receptors by atomic force microscopy.

Rhodopsin-like G protein-coupled receptors (GPCRs), widely distributed in microorganisms, invertebrates, and vertebrates, are the largest class in GPCRs, and are involved in many important physiological and pathological processes, including the photosensitivity, regulation of behavior and emotion, and so on. Atomic force microscopy (AFM) is a powerful and multifunctional toolkit in bionanotechnology, as it can image the morphology of membrane proteins at subnanometer spatial resolution and detect forces related with membrane proteins down to piconewton level by single-molecule force spectroscopy (SMFS) mode under physiological conditions. Herein, the achievements of AFM in the study of rhodopsin-like GPCRs, including observing the high-resolution topography and structural changes, revealing the interaction forces, binding kinetics, and mechanical properties (such as modulus), are reviewed and summarized. Finally, the challenges, outlook, and prospects of AFM in the study of rhodopsin-like GPCRs are discussed.

Energy-dispersive small-angle X-ray scattering with cone collimation using X-ray capillary optics.

Energy-dispersive small-angle X-ray scattering (ED-SAXS) with an innovative design of cone collimation based on an ellipsoidal single-bounce capillary (ESBC) and a polycapillary parallel X-ray lens (PPXRL) had been explored. Using this new cone collimation system, scattering angle 2θ has a theoretical minimum angle related to the mean half-opening angle of the hollow cone beam of 1.42 mrad, and with the usable X-ray energy ranging from 4 to 30 keV, the resulting observable scattering vector q is down to a minimum value of about 0.003 Å-1 (or a Bragg spacing of about 2100 Å). However, the absorption of lower energies by X-ray capillary optics, sample transmission, and detector response function limits the application range to lower energy. Cone collimation ED-SAXS experiments carried out on pure water, Lupolen, and in situ temperature-dependent measurement of diacetylenic acid/melamine micelle solid were presented at three different scattering angles 2θ of 0.18°, 0.70° and 1.18° to illustrate the new opportunities offered by this technique as well as its limitations. Also, a comparison has been made by replacing the PPXRL with a pinhole, and the result shows that cone collimation ED-SAXS based on ESBC with PPXRL was helpful in improving the signal-to-noise ratio (i.e., reducing the parasitic background scattering) than ESBC with a pinhole. The cone collimation instrument based on X-ray capillary optics could be considered as a promising tool to perform SAXS experiments, especially cone collimation ED-SAXS has potential application for the in situ temperature-dependent studying on the kinetics of phase transitions.

Authentication of vegetable oils by confocal X-ray scattering analysis with coherent/incoherent scattered X-rays.

This paper presents an alternative analytical method based on the Rayleigh to Compton scattering intensity ratio and effective atomic number for non-destructive identification of vegetable oils using confocal energy dispersive X-ray fluorescence and scattering spectrometry. A calibration curve for the Rayleigh to Compton scattering intensity ratio and effective atomic number was constructed on the basis of a reliable physical model for X-ray scattering. The content of light elements, which are "invisible" using X-ray fluorescence, can be calculated "by difference" from the calibration curve. In this work, we demonstrated the use of this proposed approach to identify complex organic matrices in different vegetable oils with high precision and accuracy.

Focal construct geometry for high intensity energy dispersive x-ray diffraction based on x-ray capillary optics.

We presented a focal construct geometry (FCG) method for high intensity energy dispersive X-ray diffraction by utilizing a home-made ellipsoidal single-bounce capillary (ESBC) and a polycapillary parallel X-ray lens (PPXRL). The ESBC was employed to focus the X-rays from a conventional laboratory source into a small focal spot and to produce an annular X-ray beam in the far-field. Additionally, diffracted polychromatic X-rays were confocally collected by the PPXRL attached to a stationary energy-resolved detector. Our FCG method based on ESBC and PPXRL had achieved relatively high intensity diffraction peaks and effectively narrowed the diffraction peak width which was helpful in improving the potential d-spacing resolution for material phase analysis.

[Application of Three Dimensional Confocal Micro X-Ray Fluorescence Technology Based on Polycapillary X-Ray Lens in Analysis of Rock and Mineral Samples].

Confocal three dimensional (3D) micro X-ray fluorescence (XRF) spectrometer based on a polycapillary focusing X-ray lens (PFXRL) in the excitation channel and a polycapillary parallel X-ray lens (PPXRL) in the detection channel was developed. The PFXRL and PPXRL were placed in a confocal configuration. This was helpful in improving the signal-to-noise ratio of the XRF spectra, and accordingly lowered the detection limitation of the XRF technology. The confocal configuration ensured that only the XRF signal from the confocal micro-volume overlapped by the output focal spot of the PFXRL and the input focal spot of the PPXRL could be detected by the detector. Therefore, the point-to-point information of XRF for samples could be obtained non-destructively by moving the sample located at the confocal position. The magnitude of the gain in power density of the PFXRL was 10(3). This let the low power conventional X-ray source be used in this confocal XRF, and, accordingly, decreased the requirement of high power X-ray source for the confocal XRF based on polycapillary X-ray optics. In this paper, we used the confocal 3D micro X-ray fluorescence spectrometer to non-destructively analyzed mineral samples and to carry out a 3D point-to-point elemental mapping scanning, which demonstrated the capabilities of confocal 3D micro XRF technology for non-destructive analysis elements composition and distribution for mineral samples. For one mineral sample, the experimental results showed that the area with high density of element of iron had high density of copper. To some extent, this reflected the growth mechanisms of the mineral sample. The confocal 3D micro XRF technology has potential applications in such fields like the analysis identification of ore, jade, lithoid utensils, "gamble stone" and lithoid flooring.

Application of confocal X-ray fluorescence micro-spectroscopy to the investigation of paint layers.

A confocal micro X-ray fluorescence (MXRF) spectrometer based on polycapillary X-ray optics was used for the identification of paint layers. The performance of the confocal MXRF was studied. Multilayered paint fragments of a car were analyzed nondestructively to demonstrate that this confocal MXRF instrument could be used in the discrimination of the various layers in multilayer paint systems.