Imaging Of Structures Research Articles

Optimising 4D imaging of fast-oscillating structures using X-ray microtomography with retrospective gating

Imaging the internal architecture of fast-vibrating structures at micrometer scale and kilohertz frequencies poses great challenges for numerous applications, including the study of biological oscillators, mechanical testing of materials, and process engineering. Over the past decade, X-ray microtomography with retrospective gating has shown very promising advances in meeting these challenges. However, breakthroughs are still expected in acquisition and reconstruction procedures to keep improving the spatiotemporal resolution, and study the mechanics of fast-vibrating multiscale structures. Thereby, this works aims to improve this imaging technique by minimising streaking and motion blur artefacts through the optimisation of experimental parameters. For that purpose, we have coupled a numerical approach relying on tomography simulation with vibrating particles with known and ideal 3D geometry (micro-spheres or fibres) with experimental campaigns. These were carried out on soft composites, imaged in synchrotron X-ray beamlines while oscillating up to 400 Hz, thanks to a custom-developed vibromechanical device. This approach yields homogeneous angular sampling of projections and gives reliable predictions of image quality degradation due to motion blur. By overcoming several technical and scientific barriers limiting the feasibility and reproducibility of such investigations, we provide guidelines to enhance gated-CT 4D imaging for the analysis of heterogeneous, high-frequency oscillating materials.

Deep learning permits imaging of multiple structures with the same fluorophores

Fluorescence microscopy, which employs fluorescent tags to label and observe cellular structures and their dynamics, is a powerful tool for life sciences. However, due to the spectral overlap between different dyes, a limited number of structures can be separately labeled and imaged for live-cell applications. In addition, the conventional sequential channel imaging procedure is quite time consuming, as it needs to switch either different lasers or filters. Here, we propose a novel double-structure network (DBSN) that consists of multiple connected models, which can extract six distinct subcellular structures from three raw images with only two separate fluorescent labels. DBSN combines the intensity-balance model to compensate for uneven fluorescent labels for different structures and the structure-separation model to extract multiple different structures with the same fluorescent labels. Therefore, DBSN breaks the bottleneck of the existing technologies and holds immense potential applications in the field of cell biology.

Applying the Atomic Force Microscopy Technique in Medical Sciences-A Narrative Review.

Penetrating deep into the cells of the human body in real time has become increasingly possible with the implementation of modern technologies in medicine. Atomic force microscopy (AFM) enables the effective live imaging of cellular and molecular structures of biological samples (such as cells surfaces, components of biological membranes, cell nuclei, actin networks, proteins, and DNA) and provides three-dimensional surface visualization (in X-, Y-, and Z-planes). Furthermore, the AFM technique enables the study of the mechanical, electrical, and magnetic properties of cells and cell organelles and the measurements of interaction forces between biomolecules. The technique has found wide application in cancer research. With the use of AFM, it is not only possible to differentiate between healthy and cancerous cells, but also to distinguish between the stages of cancerous conditions. For many years, AFM has been an important tool for the study of neurodegenerative diseases associated with the deposition of peptide amyloid plaques. In recent years, a significant amount of research has been conducted on the application of AFM in the evaluation of connective tissue cell mechanics. This review aims to provide the spectrum of the most important applications of the AFM technique in medicine to date.

Improved tools for live imaging of F-actin structures in yeast.

For over 20 years, the most effective probe for live imaging of yeast actin cables has been Abp140-GFP. Here, we report that endogenously-tagged Abp140-GFP poorly decorates actin patches and cables in the bud compartment of yeast cells, while robustly decorating these structures in the mother cell. Using mutagenesis, we found that asymmetric decoration by Abp140 requires F-actin binding. By expressing integrated Bni1-Bnr1 and Bnr1-Bni1 chimeras, we demonstrate that asymmetric cable decoration by Abp140 also does not depend on which formin assembles the cables in each compartment. In contrast, the short actin-binding fragment of Abp140 (known as "Lifeact"), fused to 1x or 3xmNeonGreen and expressed from the endogenous ABP140 promoter, uniformly decorates patches and cables in both compartments. Further, this probe dramatically improves live imaging detection of cables (and patches) without altering their in vivo dynamics or cell growth. Improved detection allows us to visualize cables growing inward from the cell cortex and dynamically interacting with the vacuole. This probe also robustly decorates the cytokinetic actomyosin ring. Because Lifeact-3xmNeon expressed at relatively low levels provides intense labeling of cellular F-actin structures, this tool may improve live imaging in other organisms where higher levels of Lifeact expression are detrimental.

The use of Intracardiac Echocardiography in Catheter Ablation of Atrial Fibrillation.

Intracardiac echocardiography (ICE) provides real-time, fluoroless imaging of cardiac structures, allowing optimal catheter positioning and energy delivery during ablation procedures. This review summarizes the use of ICE in catheter ablation of atrial fibrillation (AF). Growing evidence suggests that the use of ICE improves procedural safety and facilitates radiofrequency and cryoballoon AF ablation. ICE-guided catheter ablation is associated with reduced procedural duration and fluoroscopy use. Recent studies have examined the role of ICE in guiding novel ablation techniques, such as pulsed field ablation. Finally, the use of ICE allows for early detection and timely management of potentially serious procedural complications. Intracardiac echocardiography offers significant advantages during AF ablation procedures and its use should be encouraged to improve procedural safety and efficacy.

Image-domain least-squares imaging in an elastic vertically transversely isotropic medium: Multiparameter point-spread function deconvolution

By solving a linear inverse problem, least-squares migration (LSM) can provide higher-precision images of complex subsurface structures than traditional adjoint-operator-based migration. LSM can be conducted in the data domain and the image domain (IDLSM). IDLSM in acoustic media has been extensively studied, commonly using single-parameter point-spread function (PSF) deconvolution. For high-accuracy imaging of complex media, we develop an image-domain elastic least-squares imaging method using multiparameter PSF deconvolution for vertically transversely isotropic (VTI) media. The multiparameter PSFs, including P-P, P-S, S-P, and S-S components, are calculated on a sparse grid using elastic VTI wave equation Born modeling and migration. The traditional migration result is then decomposed into individual local results, each corresponding to the size of a single PSF, through unit partitioning. Finally, a set of filters is derived from four elastic VTI PSF components to approximate the Hessian inverse, which are subsequently assembled to reconstruct an entire deconvolved image. The numerical experiments confirm that our method can significantly decrease multiparameter crosstalk artifacts and improve spatial resolution and amplitude fidelity.

Gravity and magnetism of southern Africa in relation to Craton structures and belts

The general tectonic structural architecture of southern Africa is an ensemble comprised of Kalahari Craton, a vast range of mosaics of the best-preserved geological Belts, and exposed crustal blocks. In the region, demarcation of geological boundaries, tracing of magnetic and gravitational bodies, and detrending lineaments are essential to understanding the structural limits. The study presents the prevalent gravitational and magnetic investigation of major geological Belts, enhancing edges of Cratons, and evaluation of surface invariants to improve the geological understanding and evaluate the correlation of structures with the general structural tectonic framework. The utilized filter methods in the gravity maps are the Directional derivatives along x, y, and z-directions, the Modulus tensor, the Total horizontal derivative, and the Tilt angle techniques.The phase-based filters used in the magnetic section include the Total horizontal derivative, Analytical signal, Tilt angle method, Tilt of total horizontal derivative, Theta method, Horizontal tilt angle method, Enhanced tilt filter, and Enhanced total derivative of the tilt angle. The Directional derivatives of the gravity field and the Modulus of the gravity gradient tensor demarcate the boundaries of geological structures. The Total horizontal derivative method gives an immediate and easy-to-read image of the linear structures and fault systems. The signal cluster on the Analytical signal and Tilt angle maps delineate the boundaries of causative geological sources. The Theta map is comparable with the enhanced total derivative of the tilt angle. The Tilt of the total horizontal derivative, Theta map, and Enhanced tilt filter accentuate the traces of magnetic bodies, including the Cratons. The study finds regional lineaments surrounding the Cratons and concentrated along the geological Belts. The approach of using joint elegant filters is effective and increases the certainty of the interpretation.

Organelle-Targeting Polymer Dots Exhibiting Thermally Activated Delayed Fluorescence for Subcellular Imaging.

Selective imaging of specific subcellular structures provides valuable information about the cellular microenvironment. Materials exhibiting thermally activated delayed fluorescence (TADF) are rapidly emerging as metal-free probes with long-lived emission for intracellular time-gated imaging applications. Polymers incorporating TADF emitters can self-assemble into luminescent nanoparticles, termed polymer dots (Pdots), and this strategy enables them to circumvent the limitations of commercial organelle trackers and small molecule TADF emitters. In this study, diblock copolymers comprised of a hydrophilic block containing organelle-targeting monomers and a hydrophobic TADF-active block were synthesized by ring-opening metathesis polymerization (ROMP). Oxanorbornene-based monomers incorporating morpholine and triphenylphosphonium groups for lysosome and mitochondria targeting, respectively, were also synthesized. ROMP by sequential addition yielded well-defined diblock copolymers with dispersities <1.28. To analyze the effect of tuning the hydrophilic corona on cellular viability and uptake, we prepared Pdots with poly(ethylene glycol) (PEG) and bis-guanidinium (BGN) coronas, resulting in limited and efficient cellular uptake, respectively. Red-emissive Pdots with BGN-based coronas and organelle-targeting functionality were obtained with quantum yields up to 12% in water under air. Colocalization analysis confirmed that lysosome and mitochondria labeling in live HeLa cells was accomplished within 2 h of incubation, affording Pearson's correlation coefficients of 0.37 and 0.70, respectively. The potential application of these Pdots for time-resolved imaging is highlighted by a proof of concept using time-gated spectroscopy, which effectively separates the delayed emission of the TADF Pdots from the background autofluorescence of biological serum.

Accuracy of Cone-beam Computed Tomography in diagnosing root canal configuration: a literature review

Objectives: This review article aims to describe the accuracy of cone-beam computed tomography (CBCT) in diagnosing root canal configuration. Review: This study is a literature review consisting of English articles about the accuracy of cone-beam computed tomography in diagnosing root canal configuration, published in 2013 – 2023. The article search databases used were Pubmed and Science Direct with the keyword “(cone-beam computed tomography[MeSH Terms]) AND (configuration, root canal[MeSH Terms]).” The selected articles were screened by checking the publication year, duplicating articles, reading the titles and abstracts, and the entire article's contents. The total search results for articles based on keywords obtained were 205 and only seven were included. In order to successfully perform root canal treatment, thorough knowledge of the root canal configuration is essential. Cone-beam computed tomography (CBCT) can improve our understanding of root canal configuration. The development of CBCT has brought to light the disadvantages of conventional radiography, which include the compression of three-dimensional anatomy, geometric distortion, and anatomical noise. Conclusion: Radiology is essential in treatment planning, disease monitoring, and assessmen t of treatment outcomes. The development of cone-beam computed tomography (CBCT) offers three-dimensional accuracy with a reasonable cost, no geometric distortion and anatomical noise, and the ability to create cross-sectional images, revolutionizing the imaging of dentomaxillofacial structures. This imaging system has been shown to overcome some of the limitations of conventional radiography.

(Invited) Understanding Environmental Effects on Carbon Nanotube Fluorescence for Biomedicine

Semiconducting single-walled carbon nanotubes (SWCNTs) transduce subtle changes in the microenvironment via modulation of their near-infrared fluorescence with potential applications in sensing and imaging. Controlled liquid filling in an endohedral volume of SWCNTs modifies the optical properties of SWCNTs. However, the effects of endohedral solvent dielectric on the nanotube fluorescence and their structure property relationship for biomedical applications are largely unexplored. In this talk, we discuss the environmental effects on SWCNT fluorescence to improve the spectral response of SWCNT-based imaging and sensing agents. We analyze a large dataset of hyperspectral single-tube images of diverse SWCNT structures with controlled endohedral filling. We investigate the correlations between SWCNT structure and molecular descriptors of filled molecules to explain spectral homogeneity at a single tube level as well as at an ensemble.

Quadrant darkfield (QDF) for label-free imaging of intracellular puncta.

Measuring changes in cellular structure and organelles is crucial for understanding disease progression and cellular responses to treatments. A label-free imaging method can aid in advancing biomedical research and therapeutic strategies. This study introduces a computational darkfield imaging approach named quadrant darkfield (QDF) to separate smaller cellular features from large structures, enabling label-free imaging of cell organelles and structures in living cells. Using a programmable LED array as illumination source, we vary the direction of illumination to encode additional information about the feature size within cells. This is possible due to the varying level of directional scattering produced by features based on their sizes relative to the wavelength of light used. QDF successfully resolved small cellular features without interference from larger structures. QDF signal is more consistent during cell shape changes than traditional darkfield. QDF signals correlate with flow cytometry side scatter measurements, effectively differentiating cells by organelle content. QDF imaging enhances the study of subcellular structures in living cells, offering improved quantification of organelle content compared to darkfield without labels. This method can be simultaneously performed with other techniques such as quantitative phase imaging to generate a multidimensional picture of living cells in real-time.

Nanoscale volumetric fluorescence imaging via photochemical sectioning.

Optical nanoscopy of intact biological specimens has been transformed by recent advancements in hydrogel-based tissue clearing and expansion, enabling the imaging of cellular and subcellular structures with molecular contrast. However, existing high-resolution fluorescence microscopes have limited imaging depth, which prevents the study of whole-mount specimens without physical sectioning. To address this challenge, we developed "photochemical sectioning," a spatially precise, light-based sample sectioning process. By combining photochemical sectioning with volumetric lattice light-sheet imaging and petabyte-scale computation, we imaged and reconstructed axons and myelination sheaths across entire mouse olfactory bulbs at nanoscale resolution. An olfactory-bulb-wide analysis of myelinated and unmyelinated axons revealed distinctive patterns of axon degeneration and de-/dysmyelination in the neurodegenerative mouse, highlighting the potential for peta- to exabyte-scale super-resolution studies using this approach.

Three New Species and a New Record of the Lichen Genus Peltula (Peltulaceae) from Helan Mountain in China.

In this study, a systematic taxonomic analysis was carried out on the lichen genus Peltula, collected from Helan Mountain in China; three new species (Peltula helanense, P. overlappine, and P. reticulata) and a new record (P. crispatula (Nyl.) Egea) for China were identified. Four species were identified by morph-anatomical, chemical, and phylogenetic analyses by combining two gene loci (ITS and LSU). Peltula helanense is with tiny individual thalli up to 1mm, attached by creamy-white cylindrical rhizoids and apothecia filling the whole squamule. Peltula overlappine is characterized by thallus squamulose forming rosette-shaped patches and squamules with distinctive thickened margins. Peltula reticulata is characterized by brownish brown thallus and squamules with densely reticulate upper surface. P. crispatula is characterized by irregular squamules attached to a tuft of hyphae. The four species are described in detail, compared, and discussed with similar species, and images of morpho-anatomical structures of the four species are also provided. Moreover, a key to the species of Peltula from Helan Mountain is provided. The results enrich the data of the genus Peltula and also indicate that the rich diversity of lichen species in Helan Mountain is worthy of in-depth study.

3D-measurement of particles and particulate assemblies - A review of the paradigm shift in describing anisotropic particles

The goal of seeking advanced solutions to the descriptions of particle shape, packing and tomographic measurement were key areas promoted by Professor Reg Davies. In this paper we review and reflect on the revolution that has taken place over the last 30 years in our ability to describe and measure particle shape going beyond simple shape factors to their real morphologies of complex particles and particulate assemblies. The paper presents a comprehensive review of how shape has been described and some critical analyses in the form of extended tabulations. We show how digital approaches to particle descriptions can be used to predict the properties of particles and assemblies and their use in simulations of particle processing. We note the current status and prospects for the continued development of microtomographic systems to enable the measurement of particle shape in 3D and also the 3D imaging of complex particulate structures to enable property and processing predictions. Examples of these developments and critical appraisal of their utility will be given.

Orthodox Church Architecture of the Kuban Settlements of the Late 18th – First Half of the 19th Century

A retrospective analysis of the history of the architecture of Orthodox churches in Kuban from the end of the 18th to the first half of the 19th century was carried out on specific objects of religious architecture. The historical approach allows us to consider these objects as unique elements of the architectural and urban heritage of the period under study. The special value of Orthodox churches in the concept of forming a holistic environment of urban and rural settlements is indicated. The main means of artistic expression based on volumetric planning techniques, with the help of which the compositional image of the temple is created, are noted. The presented illustrative material graphically displays the scientific content, executed on certain visual images of religious architecture structures and visually complements the text material. Great importance is given to the current issues of integrity and sustainable balance of modern buildings and structures with previously erected religious architecture objects and monuments of historical and cultural heritage.

EIT probe based intraoperative tissue inspection for minimally invasive surgery

Abstract Electrical impedance tomography (EIT) has become an integral component in the repertoire of medical imaging techniques, particularly due to its non-invasive nature and real-time imaging capabilities. Despite its potential, the application of EIT in minimally invasive surgery (MIS) has been hindered by a lack of specialized electrode probes. Existing designs often compromise between invasiveness and spatial sensitivity: probes small enough for MIS often fail to provide detailed imaging, while those offering greater sensitivity are impractically large for use through a surgical trocar. Addressing this challenge, our study presents a breakthrough in EIT probe design. The open electrode probe we have developed features a line of 16 electrodes, thoughtfully arrayed to balance the spatial demands of MIS with the need for precise imaging. Employing an advanced EIT reconstruction algorithm, our probe not only captures images that reflect the electrical characteristics of the tissues but also ensures the homogeneity of the test material is accurately represented. The versatility of our probe is demonstrated by its capacity to generate high-resolution images of subsurface anatomical structures, a feature particularly valuable during MIS where direct visual access is limited. Surgeons can rely on intraoperative EIT imaging to inform their navigation of complex anatomical landscapes, enhancing both the safety and efficacy of their procedures. Through rigorous experimental validation using ex vivo tissue phantoms, we have established the probe’s proficiency. The experiments confirmed the system’s high sensitivity and precision, particularly in the critical tasks of subsurface tissue detection and surgical margin delineation. These capabilities manifest the potential of our probe to revolutionize the field of surgical imaging, providing a previously unattainable level of detail and assurance in MIS procedures.

Adaptive contour-tracking to aid wide-field swept-source optical coherence tomography imaging of large objects with uneven surface topology.

High-speed and wide-field optical coherence tomography (OCT) imaging is increasingly essential for clinical applications yet faces challenges due to its inherent sensitivity roll-off and limited depth of focus, particularly when imaging samples with significant variations in surface contour. Here, we propose one innovative solution of adaptive contour tracking and scanning methods to address these challenges. The strategy integrates an electrically tunable lens and adjustable optical delay line control with real-time surface contour information, enabling dynamic optimization of imaging protocols. It rapidly pre-scans the sample surface to acquire a comprehensive contour map. Using this map, it generates a tailored scanning protocol by partitioning the entire system ranging distance into depth-resolved segments determined by the optical Raleigh length of the objective lens, ensuring optimal imaging at each segment. Employing short-range imaging mode along the sample contour minimizes data storage and post-processing requirements, while adaptive adjustment of focal length and reference optical delay line maintains high imaging quality throughout. Experimental demonstrations show the effectiveness of the adaptive contour tracking OCT in maintaining high contrast and signal-to-noise ratio across the entire field of view, even in samples with significantly uneven surface curvatures. Notably, this approach achieves these results with reduced data volume compared to traditional OCT methods. This advancement holds promise for enhancing OCT imaging in clinical settings, particularly in applications requiring rapid, wide-field imaging of tissue structures and blood flow.

Advancing cellular insights: Super-resolution STORM imaging of cytoskeletal structures in human stem and cancer cells

Fluorescence microscopy is an important tool for cell biology and cancer research. Present-day approach of implementing advanced optical microscopy methods combined with immunofluorescence labelling of specific proteins in cells is now able to deliver optical super-resolution up to ∼25 nm. Here we perform super-resolved imaging using standard immunostaining protocol combined with easy stochastic optical reconstruction microscopy (easySTORM) to observe structural differences of two cytoskeleton elements, actin and tubulin in three different cell types namely human bone marrow-derived mesenchymal stem cells (MSCs), human glioblastoma (U87MG) and breast cancer (MDAMB-231) cells. The average width of the actin bundle obtained from STORM images of stem cells is observed to be larger than the same for U87MG and MDAMB-231 cells. No significant difference is however noticed in the width of the tubulin within the same cells. We also study the functional effect on the 2D migration potential of MDAMB-231 cells silenced for NICD1 and β-catenin. Although similar migration speed is observed for cells with the above two conditions compared to their control cells, easySTORM images show that widths of the actin in MDAMB-231 cells in β-catenin silenced is significantly lower than the same in control cells. Such minute differences however are not observable in widefield images. The outcome of our easySTORM investigation should benefit the researchers carrying out detailed investigations of the cellular structure and potential therapeutic applications.

Human gender estimation from CT images of skull using deep feature selection and feature fusion

This research endeavors to prognosticate gender by harnessing the potential of skull computed tomography (CT) images, given the seminal role of gender identification in the realm of identification. The study encompasses a corpus of CT images of cranial structures derived from 218 male and 203 female subjects, constituting a total cohort of 421 individuals within the age bracket of 25 to 65 years. Employing deep learning, a prominent subset of machine learning algorithms, the study deploys convolutional neural network (CNN) models to excavate profound attributes inherent in the skull CT images. In pursuit of the research objective, the focal methodology involves the exclusive application of deep learning algorithms to image datasets, culminating in an accuracy rate of 96.4%. The gender estimation process exhibits a precision of 96.1% for male individuals and 96.8% for female individuals. The precision performance varies across different selections of feature numbers, namely 100, 300, and 500, alongside 1000 features without feature selection. The respective precision rates for these selections are recorded as 95.0%, 95.5%, 96.2%, and 96.4%. It is notable that gender estimation via visual radiography mitigates the discrepancy in measurements between experts, concurrently yielding an expedited estimation rate. Predicated on the empirical findings of this investigation, it is inferred that the efficacy of the CNN model, the configurational intricacies of the classifier, and the judicious selection of features collectively constitute pivotal determinants in shaping the performance attributes of the proposed methodology.

Adaptive optical third-harmonic generation microscopy for in vivo imaging of tissues.

Third-harmonic generation microscopy is a powerful label-free nonlinear imaging technique, providing essential information about structural characteristics of cells and tissues without requiring external labelling agents. In this work, we integrated a recently developed compact adaptive optics module into a third-harmonic generation microscope, to measure and correct for optical aberrations in complex tissues. Taking advantage of the high sensitivity of the third-harmonic generation process to material interfaces and thin membranes, along with the 1,300-nm excitation wavelength used here, our adaptive optical third-harmonic generation microscope enabled high-resolution in vivo imaging within highly scattering biological model systems. Examples include imaging of myelinated axons and vascular structures within the mouse spinal cord and deep cortical layers of the mouse brain, along with imaging of key anatomical features in the roots of the model plant Brachypodium distachyon. In all instances, aberration correction led to enhancements in image quality.