Dark-field and directional dark-field on low-coherence x ray sources with random mask modulations: validation with SAXS anisotropy measurements.

Phase-contrast imaging, dark-field, and directional dark-field imaging are recent x ray imaging modalities that have been demonstrated to reveal different information and contrast from those provided by conventional x ray imaging. Access to these new types of images is currently limited because the acquisitions require coherent sources such as synchrotron radiation or complicated optical setups. This Letter demonstrates the possibility of efficiently performing phase-contrast, dark-field, and directional dark-field imaging on a low-coherence laboratory system equipped with a conventional x ray tube, using a simple, fast, and robust single-mask technique.

Synchrotron phase-contrast imaging applied to the anatomical study of the hand and its vascularization.

Microscopic anatomical study of the hand requires difficult or destructive dissection techniques for each anatomical structure. Synchrotron phase-contrast imaging (sPCI) allows us to study precisely, at a microscopic resolution and in a nondestructive approach, the soft tissues and bone structures within a single 3D image. Therefore, we aimed to assess the capacity of sPCI to study the arterial anatomy of the hand and digits in human cadavers for anatomical purposes. A non-injected hand from an embalmed body was imaged using sPCI at 21-µm pixel size. The vascularization and innervation of the hands were virtually reconstructed at 84-µm resolution, and the medial neurovascular bundle of the third digit at 21 µm. The thinner-most distal structures were observed and reported. The diameter and thickness of the vascular and neural structures were defined on 2D computed tomographic axial projections, and using a granulometry method coupled to the 3D reconstructions. The vascularization of the hand was visible from the radial and ulnar arteries to the distal digital transverse anastomoses. The thinnest structure observed was the anastomotic arterial network around the proper palmar digital nerve. The latter emerged from the proper palmar digital artery and vascularized the nerve around its whole length and circumference. The perineural arterioles individualizable at this resolution had a diameter of 66-309 µm. In conclusion, sPCI allows both the arterial and neural anatomy of the hand to be studied at the same time, as well as the anatomical interactions between both networks. It facilitates the study of structures that have different sizes, diameters, thickness, and histological origin with great precision, in a noninvasive way, and using a single technique.

Revealing metallic ink in Herculaneum papyri.

Writing on paper is essential to civilization, as Pliny the Elder remarks in his Natural History, when he describes the various types of papyri, the method of manufacturing them, and all that concerns writing materials in the mid-first century AD. For this reason, a rigorous scientific study of writing is of fundamental importance for the historical understanding of ancient societies. We show that metallic ink was used several centuries earlier than previously thought. In particular, we found strong evidence that lead was intentionally used in the ink of Herculaneum papyri and discuss the possible existence of ruled lines traced on the papyrus texture. In addition, the metallic concentrations found in these fragments deliver important information in view of optimizing future computed tomography (CT) experiments on still-unrolled Herculaneum scrolls to improve the readability of texts in the only surviving ancient Greco-Roman library.

Quantitative Assessment of Degenerative Cartilage and Subchondral Bony Lesions in a Preserved Cadaveric Knee: Propagation-Based Phase-Contrast CT Versus Conventional MRI and CT.

OBJECTIVE: The aim of this study was to quantitatively assess hyaline cartilage and subchondral bone conditions in a fully preserved cadaveric human knee joint using high-resolution x-ray propagation-based phase-contrast imaging (PBI) CT and to compare the performance of the new technique with conventional CT and MRI. MATERIALS AND METHODS: A cadaveric human knee was examined using an x-ray beam of 60 keV, a detector with a 90-mm2 FOV, and a pixel size of 46 × 46 µm2. PBI CT images were reconstructed with both the filtered back projection algorithm and the equally sloped tomography method. Conventional 3-T MRI and CT were also performed. Measurements of cartilage thickness, cartilage lesions, International Cartilage Repair Society scoring, and detection of subchondral bone changes were evaluated. Visual inspection of the specimen akin to arthroscopy was conducted and served as a standard of reference for lesion detection. RESULTS: Loss of cartilage height was visible on PBI CT and MRI. Quantification of cartilage thickness showed a strong correlation between the two modalities. Cartilage lesions appeared darker than the adjacent cartilage on PBI CT. PBI CT showed similar agreement to MRI for depicting cartilage substance defects or lesions compared with the visual inspection. The assessment of subchondral bone cysts showed moderate to strong agreement between PBI CT and CT. CONCLUSION: In contrast to the standard clinical methods of MRI and CT, PBI CT is able to simultaneously depict cartilage and bony changes at high resolution. Though still an experimental technique, PBI CT is a promising high-resolution imaging method to evaluate comprehensive changes of osteoarthritic disease in a clinical setting.

In vivo pink-beam imaging and fast alignment procedure for rat brain tumor radiation therapy.

A fast positioning method for brain tumor microbeam irradiations for preclinical studies at third-generation X-ray sources is described. The three-dimensional alignment of the animals relative to the X-ray beam was based on the X-ray tomography multi-slices after iodine infusion. This method used pink-beam imaging produced by the ID17 wiggler. A graphical user interface has been developed in order to define the irradiation parameters: field width, height, number of angles and X-ray dose. This study is the first reporting an image guided method for soft tissue synchrotron radiotherapy. It allowed microbeam radiation therapy irradiation fields to be reduced by a factor of ∼20 compared with previous studies. It permitted more targeted, more efficient brain tumor microbeam treatments and reduces normal brain toxicity of the radiation treatment.

Single-image phase retrieval using an edge illumination X-ray phase-contrast imaging setup.

A method is proposed which enables the retrieval of the thickness or of the projected electron density of a sample from a single input image acquired with an edge illumination phase-contrast imaging setup. The method assumes the case of a quasi-homogeneous sample, i.e. a sample with a constant ratio between the real and imaginary parts of its complex refractive index. Compared with current methods based on combining two edge illumination images acquired in different configurations of the setup, this new approach presents advantages in terms of simplicity of acquisition procedure and shorter data collection time, which are very important especially for applications such as computed tomography and dynamical imaging. Furthermore, the fact that phase information is directly extracted, instead of its derivative, can enable a simpler image interpretation and be beneficial for subsequent processing such as segmentation. The method is first theoretically derived and its conditions of applicability defined. Quantitative accuracy in the case of homogeneous objects as well as enhanced image quality for the imaging of complex biological samples are demonstrated through experiments at two synchrotron radiation facilities. The large range of applicability, the robustness against noise and the need for only one input image suggest a high potential for investigations in various research subjects.

High-resolution, low-dose phase contrast X-ray tomography for 3D diagnosis of human breast cancers.

Mammography is the primary imaging tool for screening and diagnosis of human breast cancers, but ~10-20% of palpable tumors are not detectable on mammograms and only about 40% of biopsied lesions are malignant. Here we report a high-resolution, low-dose phase contrast X-ray tomographic method for 3D diagnosis of human breast cancers. By combining phase contrast X-ray imaging with an image reconstruction method known as equally sloped tomography, we imaged a human breast in three dimensions and identified a malignant cancer with a pixel size of 92 µm and a radiation dose less than that of dual-view mammography. According to a blind evaluation by five independent radiologists, our method can reduce the radiation dose and acquisition time by ~74% relative to conventional phase contrast X-ray tomography, while maintaining high image resolution and image contrast. These results demonstrate that high-resolution 3D diagnostic imaging of human breast cancers can, in principle, be performed at clinical compatible doses.

Tomographic reconstruction of the refractive index with hard X-rays: an efficient method based on the gradient vector-field approach.

The refractive-index gradient vector field approach establishes a connection between a tomographic data set of differential phase contrast images and the distribution of the partial spatial derivatives of the refractive index in an object. The reconstruction of the refractive index in a plane requires the integration of its gradient field. This work shows how this integration can be efficiently performed by converting the problem to the Poisson equation, which can be accurately solved even in the case of noisy and large datasets. The performance of the suggested method is discussed and demonstrated experimentally by computing the refractive index distribution in both a simple plastic phantom and a complex biological sample. The quality of the reconstruction is evaluated through the direct comparison with other commonly used methods. To this end, the refractive index is retrieved from the same data set using also (1) the filtered backprojection algorithm for gradient projections, and (2) the regularized phase-retrieval procedure. Results show that the gradient vector field approach combined with the developed integration technique provides a very accurate depiction of the sample internal structure. Contrary to the two other techniques, the considered method does not require a preliminary phase-retrieval and can be implemented with any advanced computer tomography algorithm. In this work, analyzer-based phase contrast images are used for demonstration. Results, however, are generally valid and can be applied for processing differential phase-contrast tomographic data sets obtained with other phase-contrast imaging techniques.

An efficient numerical tool for dose deposition prediction applied to synchrotron medical imaging and radiation therapy.

Medical imaging and radiation therapy are widely used synchrotron-based techniques which have one thing in common: a significant dose delivery to typically biological samples. Among the ways to provide the experimenters with image guidance techniques indicating optimization strategies, Monte Carlo simulation has become the gold standard for accurately predicting radiation dose levels under specific irradiation conditions. A highly important hampering factor of this method is, however, its slow statistical convergence. A track length estimator (TLE) module has been coded and implemented for the first time in the open-source Monte Carlo code GATE/Geant4. Results obtained with the module and the procedures used to validate them are presented. A database of energy-absorption coefficients was also generated, which is used by the TLE calculations and is now also included in GATE/Geant4. The validation was carried out by comparing the TLE-simulated doses with experimental data in a synchrotron radiation computed tomography experiment. The TLE technique shows good agreement versus both experimental measurements and the results of a classical Monte Carlo simulation. Compared with the latter, it is possible to reach a pre-defined statistical uncertainty in about two to three orders of magnitude less time for complex geometries without loss of accuracy.

High-resolution synchrotron K-edge subtraction CT allows tracking and quantifying therapeutic cells and their scaffold in a rat model of focal cerebral injury and can serve as a reference for spectral photon counting CT.

Background: The objective of this study was to demonstrate that synchrotron K-edge subtraction tomography (SKES-CT) can simultaneously track therapeutic cells and their encapsulating carrier, in vivo, in a rat model of focal brain injury using a dual-contrast agent approach. The second objective was to determine if SKES-CT could be used as a reference method for spectral photon counting tomography (SPCCT). Methods: Phantoms containing different concentrations of gold and iodine nanoparticles (AuNPS/INPs) were imaged with SKES-CT and SPCCT to assess their performances. A pre-clinical study was performed in rats with focal cerebral injury which intracerebrally received AuNPs-labelled therapeutic cells encapsulated in a INPs-labelled scaffold. Animals were imaged in vivo with SKES-CT and back-to-back with SPCCT. Results: SKES-CT revealed to be reliable for quantification of gold and iodine, whether alone or mixed. In the preclinical model, SKES-CT showed that AuNPs remained at the site of cell injection, while INPs expanded within and/or along the lesion border, suggesting dissociation of both components in the first days post-administration. Compared to SKES-CT, SPCCT was able to correctly locate gold, but not completely located iodine. When SKES-CT was used as reference, SPCCT gold quantification appeared very accurate both in vitro and in vivo. Iodine quantification by SPCCT was also quite accurate, albeit less so than for gold. Conclusion: We here provide the proof-of-concept that SKES-CT is a novel method of choice for performing dual-contrast agent imaging in the context of brain regenerative therapy. SKES-CT may also serve as ground truth for emerging technologies such as multicolour clinical SPCCT.

Virtual histology of Alzheimer's disease: Biometal entrapment within amyloid-ß plaques allows for detection via X-ray phase-contrast imaging.

Amyloid-ß (Aß) plaques from Alzheimer's Disease (AD) can be visualized ex vivo in label-free brain samples using synchrotron X-ray phase-contrast tomography (XPCT). However, for XPCT to be useful as a screening method for amyloid pathology, it is essential to understand which factors drive the detection of Aß plaques. The current study was designed to test the hypothesis that Aß-related contrast in XPCT could be caused by Aß fibrils and/or by metals trapped in the plaques. Fibrillar and elemental compositions of Aß plaques were probed in brain samples from different types of AD patients and AD models to establish a relationship between XPCT contrast and Aß plaque characteristics. XPCT, micro-Fourier-Transform Infrared spectroscopy and micro-X-Ray Fluorescence spectroscopy were conducted on human samples (one genetic and one sporadic case) and on four transgenic rodent strains (mouse: APPPS1, ArcAß, J20; rat: TgF344). Aß plaques from the genetic AD patient were visible using XPCT, and had higher ß-sheet content and higher metal levels than those from the sporadic AD patient, which remained undetected by XPCT. Aß plaques in J20 mice and TgF344 rats appeared hyperdense on XPCT images, while they were hypodense with a hyperdense core in the case of APPPS1 and ArcAß mice. In all four transgenic strains, ß-sheet content was similar, while metal levels were highly variable: J20 (zinc and iron) and TgF344 (copper) strains showed greater metal accumulation than APPPS1 and ArcAß mice. Hence, a hyperdense contrast formation of Aß plaques in XPCT images was associated with biometal entrapment within plaques. STATEMENT OF SIGNIFICANCE: The role of metals in Alzheimer's disease (AD) has been a subject of continuous interest. It was already known that amyloid-ß plaques (Aß), the earliest hallmark of AD, tend to trap endogenous biometals like zinc, iron and copper. Here we show that this metal accumulation is the main reason why Aß plaques are detected with a new technique called X-ray phase contrast tomography (XPCT). XPCT enables to map the distribution of Aß plaques in the whole excised brain without labeling. In this work we describe a unique collection of four transgenic models of AD, together with a human sporadic and a rare genetic case of AD, thus exploring the full spectrum of amyloid contrast in XPCT.

Use of metal-based contrast agents for in vivo MR and CT imaging of phagocytic cells in neurological pathologies.

The activation of phagocytic cells is a hallmark of many neurological diseases. Imaging them in their 3-dimensional cerebral environment over time is crucial to better understand their role in disease pathogenesis and to monitor their potential therapeutic effects. Phagocytic cells have the ability to internalize metal-based contrast agents both in vitro and in vivo and can thus be tracked by magnetic resonance imaging (MRI) or computed tomography (CT). In this review article, we summarize the different labelling strategies, contrast agents, and in vivo imaging modalities that can be used to monitor cells with phagocytic activity in the central nervous system using MRI and CT, with a focus on clinical applications. Metal-based nanoparticle contrast agents such as gadolinium, gold and iron are ideal candidates for these applications as they have favourable magnetic and/or radiopaque properties and can be fine-tuned for optimal uptake by phagocytic cells. However, they also come with downsides due to their potential toxicity, especially in the brain where they might accumulate. We therefore conclude our review by discussing the pitfalls, safety and potential for clinical translation of these metal-based neuroimaging techniques. Early results in patients with neuropathologies such as multiple sclerosis, stroke, trauma, cerebral aneurysm and glioblastoma are promising. If the challenges represented by safety issues are overcome, phagocytic cells imaging will be a very valuable tool for studying and understanding the inflammatory response and evaluating treatments that aim at mitigating this response in patients with neurological diseases.

4D nanoimaging of early age cement hydration.

Despite a century of research, our understanding of cement dissolution and precipitation processes at early ages is very limited. This is due to the lack of methods that can image these processes with enough spatial resolution, contrast and field of view. Here, we adapt near-field ptychographic nanotomography to in situ visualise the hydration of commercial Portland cement in a record-thick capillary. At 19 h, porous C-S-H gel shell, thickness of 500 nm, covers every alite grain enclosing a water gap. The spatial dissolution rate of small alite grains in the acceleration period, ∼100 nm/h, is approximately four times faster than that of large alite grains in the deceleration stage, ∼25 nm/h. Etch-pit development has also been mapped out. This work is complemented by laboratory and synchrotron microtomographies, allowing to measure the particle size distributions with time. 4D nanoimaging will allow mechanistically study dissolution-precipitation processes including the roles of accelerators and superplasticizers.

A novel injectable radiopaque hydrogel with potent properties for multicolor CT imaging in the context of brain and cartilage regenerative therapy.

Cell therapy is promising to treat many conditions, including neurological and osteoarticular diseases. Encapsulation of cells within hydrogels facilitates cell delivery and can improve therapeutic effects. However, much work remains to be done to align treatment strategies with specific diseases. The development of imaging tools that enable monitoring cells and hydrogel independently is key to achieving this goal. Our objective herein is to longitudinally study an iodine-labeled hydrogel, incorporating gold-labeled stem cells, by bicolor CT imaging after in vivo injection in rodent brains or knees. To this aim, an injectable self-healing hyaluronic acid (HA) hydrogel with long-persistent radiopacity was formed by the covalent grafting of a clinical contrast agent on HA. The labeling conditions were tuned to achieve sufficient X-ray signal and to maintain the mechanical and self-healing properties as well as injectability of the original HA scaffold. The efficient delivery of both cells and hydrogel at the targeted sites was demonstrated by synchrotron K-edge subtraction-CT. The iodine labeling enabled to monitor the hydrogel biodistribution in vivo up to 3 days post-administration, which represents a technological first in the field of molecular CT imaging agents. This tool may foster the translation of combined cell-hydrogel therapies into the clinics.

Mouse Models of Osteoarthritis: A Summary of Models and Outcomes Assessment.

Osteoarthritis (OA) is a multidimensional health problem and a common chronic disease. It has a substantial impact on patient quality of life and is a common cause of pain and mobility issues in older adults. The functional limitations, lack of curative treatments, and cost to society all demonstrate the need for translational and clinical research. The use of OA models in mice is important for achieving a better understanding of the disease. Models with clinical relevance are needed to achieve 2 main goals: to assess the impact of the OA disease (pain and function) and to study the efficacy of potential treatments. However, few OA models include practical strategies for functional assessment of the mice. OA signs in mice incorporate complex interrelations between pain and dysfunction. The current review provides a comprehensive compilation of mouse models of OA and animal evaluations that include static and dynamic clinical assessment of the mice, merging evaluation of pain and function by using automatic and noninvasive techniques. These new techniques allow simultaneous recording of spontaneous activity from thousands of home cages and also monitor environment conditions. Technologies such as videography and computational approaches can also be used to improve pain assessment in rodents but these new tools must first be validated experimentally. An example of a new tool is the digital ventilated cage, which is an automated home-cage monitor that records spontaneous activity in the cages.

In Vitro Preparation of Actively Maturing Bovine Articular Cartilage Explants for X-Ray Phase Contrast Imaging.

Understanding the mechanisms that underpin post-natal maturation of articular cartilage is of crucial importance for designing the next generation of tissue engineering strategies and potentially repairing diseased or damaged cartilage. In general, postnatal maturation of the articular cartilage, which is a wholesale change in collagen structure and function of the tissue to accommodate growth of the organism, occurs over a timescale ranging from months to years. Conversely dissolution of the structural organization of the cartilage that also occurs over long timescales is the hallmark of tissue degeneration. Our ability to study these biological processes in detail have been enhanced by the findings that growth factors can induce precocious in vitro maturation of immature articular cartilage. The developmental and disease related changes that occur in the joint involve bone and cartilage and an ability to co-image these tissues would significantly increase our understanding of their intertwined roles. The simultaneous visualization of soft tissue, cartilage and bone changes is nowadays a challenge to overcome for conventional preclinical imaging modalities used for the joint disease follow-up. Three-dimensional X-ray Phase-Contrast Imaging methods (PCI) have been under perpetual developments for 20 years due to high performance for imaging low density objects and their ability to provide additional information compared to conventional X-ray imaging. In this protocol we detail the procedure used in our experiments from biopsy of the cartilage, generation of in vitro matured cartilage to data analysis of image collected using X-ray phase contrast imaging.

Brain virtual histology with X-ray phase-contrast tomography Part II:3D morphologies of amyloid-ß plaques in Alzheimer's disease models.

While numerous transgenic mouse strains have been produced to model the formation of amyloid-ß (Aß) plaques in the brain, efficient methods for whole-brain 3D analysis of Aß deposits have to be validated and standardized. Moreover, routine immunohistochemistry performed on brain slices precludes any shape analysis of Aß plaques, or require complex procedures for serial acquisition and reconstruction. The present study shows how in-line (propagation-based) X-ray phase-contrast tomography (XPCT) combined with ethanol-induced brain sample dehydration enables hippocampus-wide detection and morphometric analysis of Aß plaques. Performed in three distinct Alzheimer mouse strains, the proposed workflow identified differences in signal intensity and 3D shape parameters: 3xTg displayed a different type of Aß plaques, with a larger volume and area, greater elongation, flatness and mean breadth, and more intense average signal than J20 and APP/PS1. As a label-free non-destructive technique, XPCT can be combined with standard immunohistochemistry. XPCT virtual histology could thus become instrumental in quantifying the 3D spreading and the morphological impact of seeding when studying prion-like properties of Aß aggregates in animal models of Alzheimer's disease. This is Part II of a series of two articles reporting the value of in-line XPCT for virtual histology of the brain; Part I shows how in-line XPCT enables 3D myelin mapping in the whole rodent brain and in human autopsy brain tissue.

Brain virtual histology with X-ray phase-contrast tomography Part I: whole-brain myelin mapping in white-matter injury models.

White-matter injury leads to severe functional loss in many neurological diseases. Myelin staining on histological samples is the most common technique to investigate white-matter fibers. However, tissue processing and sectioning may affect the reliability of 3D volumetric assessments. The purpose of this study was to propose an approach that enables myelin fibers to be mapped in the whole rodent brain with microscopic resolution and without the need for strenuous staining. With this aim, we coupled in-line (propagation-based) X-ray phase-contrast tomography (XPCT) to ethanol-induced brain sample dehydration. We here provide the proof-of-concept that this approach enhances myelinated axons in rodent and human brain tissue. In addition, we demonstrated that white-matter injuries could be detected and quantified with this approach, using three animal models: ischemic stroke, premature birth and multiple sclerosis. Furthermore, in analogy to diffusion tensor imaging (DTI), we retrieved fiber directions and DTI-like diffusion metrics from our XPCT data to quantitatively characterize white-matter microstructure. Finally, we showed that this non-destructive approach was compatible with subsequent complementary brain sample analysis by conventional histology. In-line XPCT might thus become a novel gold-standard for investigating white-matter injury in the intact brain. This is Part I of a series of two articles reporting the value of in-line XPCT for virtual histology of the brain; Part II shows how in-line XPCT enables the whole-brain 3D morphometric analysis of amyloid- ß (A ß ) plaques.

Imaging of the angular-dependent coherent-scatter cross section with analyzer crystal: a Monte Carlo simulation.

A nontomography approach for the measurement of angular-dependent coherent-scatter cross section of x rays (E≃40-80 keV) is described. It is shown that an analyzer crystal, which is proposed to be used for the sampling of the cross section, simultaneously provides information about the location of the scattering volume inside the object. A numerical simulation demonstrates that this method can be applied for nondestructive analysis of an object's internal structure.

Calcified cartilage revealed in whole joint by X-ray phase contrast imaging.

Objective: X-ray Phase Contrast Imaging (PCI) is an emerging modality that will be in the next few years available in a wider range of preclinical set-ups. In this study, we compare this imaging technique with conventional preclinical modalities in an osteoarthritis mouse model. Method: Phase contrast technique was performed on 6 post-mortem, monoiodoacetate-induced osteoarthritis knees and 6 control knees. The mice knees were then imaged using magnetic resonance imaging and conventional micro computed tomography. Examples of imaging surrogate markers are reported: local distances within the articular space, cartilage surface roughness, calcified cartilage thickness, number, volume and locations of osteophytes. Results: Thanks to PCI, we can show in 3D calcified cartilage without contrast agent by a non-invasive technique. The phase contrast images reveal more details than conventional imaging techniques, especially at smaller scales, with for instance a higher number of micro-calcifications detected (57, 314 and 329 for MRI, conventional micro-CT and phase contrast imaging respectively). Calcified cartilage thickness was measured with a significant difference (p â€‹< â€‹0.01) between the control (23.4 â€‹± â€‹17.2 â€‹µm) and the osteoarthritis induced animal (46.9 â€‹± â€‹19.0 â€‹µm). Conclusions: X-ray phase contrast imaging outperforms the conventional imaging modalities for assessing the different tissue types (soft and hard). This new imaging modality seems to bring new relevant surrogate markers for following-up small animal models even for low-grade osteoarthritis.