A coded-aperture technique allowing x-ray phase contrast imaging with conventional sources

Phase contrast imaging (PCI) solves the basic limitation of x-ray imaging, i.e., poor image contrast resulting from small absorption differences. Up to now, it has been mostly limited to synchrotron radiation facilities, due to the stringent requirements on the x-ray source and detectors, and only one technique was shown to provide PCI images with conventional sources but with limits in practical implementation. The authors propose a different approach, based on coded apertures, which provides high PCI signals with conventional sources and detectors and imposes practically no applicability limits. They expect this method to cast the basis of a widespread diffusion of PCI. (C) 2007 American Institute of Physics

A multi-layer edge-on single photon counting silicon microstrip detector for innovative techniques in diagnostic radiology

A three-layer detector prototype, obtained by stacking three edge-on single photon counting silicon microstrip detectors, has been developed and widely tested. This was done in the framework of the Synchrotron Radiation for Medical Physics/Frontier Radiology (SYRMEP/FRONTRAD) collaboration activities, whose aim is to improve the quality of mammographic examinations operating both on the source and on the detector side. The active surface of the device has been fully characterized making use of an edge-scanning technique and of a well-collimated laminar synchrotron radiation beam. The obtained data (interlayer distances, channel correspondence, etc.) have then been used to combine information coming from each detector layer, without causing any loss in spatial and contrast resolution of the device. Contrast and spatial resolution have also been separately evaluated for each detector layer. Moreover, imaging techniques (phase contrast, refraction, and scatter imaging), resulting in an increased visibility of low absorbing details, have been implemented, and their effectiveness has been tested on a biological sample. Finally, the possibility of simultaneously acquiring different kind of images with the different detector layers is discussed. This would result in maximizing the information extracted from the sample, while at the same time the high absorption efficiency of the detector device would allow a low dose delivery

Evaluation of a compact multi-contrast and multi-resolution X-ray phase contrast edge illumination system for small animal imaging

PURPOSE: In this work the performance of a compact multi-resolution and multi-contrast X-ray phase system based on edge illumination is investigated. It has been designed for small animal imaging and with a limited footprint for ease of deployment in laboratories. METHODS: The presented edge illumination system is based on a compact microfocus tungsten X-ray source combined with a at panel detector. The source has a maximum output of 10 W when the minimum spot size of about 15 µm is used. The system has an overall length of 70 cm. A new double sample mask design, obtained by arranging both skipped and non-skipped configurations on the same structure, provides dual resolution capability. To test the system, we carried out CT scans of a plastic phantom with different source settings using both single-image and multi-image acquisition schemes at different spatial resolutions. In addition, CT scans of an ex-vivo mouse specimen were acquired at the best identified working conditions to demonstrate the application of the presented system to small animal imaging. RESULTS: We found this system delivers good image quality, allowing for an efficient material separation and improving detail visibility in small animals thanks to the higher signal-to-noise ratio (SNR) of phase contrast with respect to conventional attenuation contrast. The system offers high versatility in terms of spatial resolution thanks to the double sample mask design integrated into a single scanner. The availability of both multi and single image acquisition schemes coupled with their dedicated retrieval algorithms, allows different working modes which can be selected based on user preference. Multi-image acquisition provides quantitative separation of the real and imaginary part of the refractive index, however it requires a long scanning time. On the other hand, the single image approach delivers the best material separation and image quality at all the investigated source settings with a shorter scanning time but at the cost of quantitativeness. Finally, we also observed that the single image approach combined with a high-power X-ray source may result in a fast acquisition protocol compatible with in-vivo imaging

Optimal design of steel exoskeleton for the retrofitting of RC buildings via genetic algorithm

In recent decades, steel exoskeletons have gathered significant attention as a seismic retrofitting technique for existing structures. The design methods proposed so far are focused on the identification of the system's overall parameters through simplified models. Although these methodologies provide helpful guidance at the preliminary design stage, they do not consider aspects such as the distribution of the exoskeletons and sizing of their components. To overcome these limitations, an optimization process based on the Genetic Algorithm is proposed in this paper to identify the optimal exoskeleton number and spatial arrangement, and to determine the optimal size of their constituent elements. The algorithm aims to minimize the weight of the retrofit solution while keeping the whole existing structure in the elastic field and ensuring the structural verification of the exoskeleton's elements. The analyses have been conducted using a finite-element code with an Open Application Programming Interface, which allows the models to be handled through automatic routines. The proposed optimization tool has been applied to several case studies, considering two different layouts for the exoskeletons. Finally, the effectiveness of the retrofit method has been demonstrated, and the proposed optimization tool has been able to significantly reduce the weight and cost of the intervention

Patterns of cervical and masticatory impairment in subgroups of people with temporomandibular disorders–an explorative approach based on factor analysis

Objectives: To identify clinical patterns of impairment affecting the cervical spine and masticatory systems in different subcategories of temporomandibular disorder (TMD) by an explorative data-driven approach. Methods: For this observational study, 144 subjects were subdivided according to Research Diagnostic Criteria for TMDs into: Healthy controls, temporomandibular joint (TMJ) signs without symptoms, TMJ affected, temporomandibular muscles affected, or TMJ and muscles affected. Factor analysis and linear regression were applied to cervical spine and masticatory data to identify and characterize clinical patterns in subgroups. Results: Factor analysis identified five clinical dimensions, which explained 59% of all variance: Mechanosensitivity, cervical movement, cervical and masticatory dysfunction, jaw movement, and upper cervical movement. Regression analysis identified different clinical dimensions in each TMD subgroup. Conclusion: Distinct clinical patterns of cervical spine and masticatory function were found among subgroups of TMD, which has clinical implications for therapeutic management

The Intertwined Successional Development of the Lamb Gut Microbiota And Immune System (Poster)

Gastrointestinal tract (GIT) microbes play critical roles in host nutrition, health and immunological development. For adult ruminants, GIT-dwelling microbes provide ~70% of daily energy requirements. The GIT also houses 70 % of the animal’s immune system in the form of the Gut-associated Lymphatic Tissue (GALT), which houses 80% of all plasma cells and depends on microbial stimulation for maturation. Because nutrition and disease are two major factors in the economic sustainability of livestock production, our group set out to characterize the successional development of GIT microbiota and immune activity. Blood and GIT samples were collected from lambs immediately at birth through one-year of age, and from the dam’s vagina, mouth, and rectum at parturition. Blood samples were profiled for serum titers of IgM, IgA and IgG, while microbiota were profiled in GIT samples by 16S rRNA gene sequencing. Lamb GIT microbiota initially resembled the dam’s vaginal microbiota but following exposure to the dam, became rapidly more similar to the dam’s teat. GIT samples eventually formed stable climax communities similar to the dams around 180 days of age. This corresponded to the peak serum titers for each immunoglobin, which, aside from a peak in IgG at birth (likely colostral transfer), had gradually increased prior to this time. Immunoglobins peaked and then return to a sub peak level between 180 and 365 days. These results indicate dam vaginal microbiota have a short-lived impact on the neonatal microbiota, with the GIT microbiota going through a dynamic successional development to 180 d when immune function appears to peak

Laboratory implementation of edge illumination X-ray phase-contrast imaging with energy-resolved detectors

Edge illumination (EI) X-ray phase-contrast imaging (XPCI) has potential for applications in different fields of research, including materials science, non-destructive industrial testing, small-animal imaging, and medical imaging. One of its main advantages is the compatibility with laboratory equipment, in particular with conventional non-microfocal sources, which makes its exploitation in normal research laboratories possible. In this work, we demonstrate that the signal in laboratory implementations of EI can be correctly described with the use of the simplified geometrical optics. Besides enabling the derivation of simple expressions for the sensitivity and spatial resolution of a given EI setup, this model also highlights the EI’s achromaticity. With the aim of improving image quality, as well as to take advantage of the fact that all energies in the spectrum contribute to the image contrast, we carried out EI acquisitions using a photon-counting energy-resolved detector. The obtained results demonstrate that this approach has great potential for future laboratory implementations of EI. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Paragenesis and mineral chemistry of alabandite (MnS) from the Ag-rich Santo Toribio epithermal deposit

The Miocene, epithermal, Ag-rich polymetallic Santo Toribio deposit is hosted by the volcanics of the Quiruvilva-Pierina subbelt, Northern Peru, which also comprises the world-class, high sulphidation Pierina deposit. The Ag-rich, alabandite-bearing veins of the Santo Toribio deposit formed during two major stages. The early stage is characterized by deposition of arsenopyrite, pyrite, quartz, Mnsphalerite, stannite, alabandite and minor miargyrite. Sphalerite associated with this stage is exceptionally enriched in Mn (up to 14.5 wt.%) and alabandite is optically and mineralogically zoned. Its brown zones have greater Fe+Sb and smaller Mn contents than the green zones and Fe+Sb replaces Mn in its structure. During this early stage, f S 2 must have been high to allow the stabilization of alabandite relative to rhodochrosite. In the second stage, the physicochemical conditions changed and the CO 2 /S ratio increased, causing dissolution of alabandite and the deposition of abundant rhodochrosite and a second generation of arsenopyrite, pyrite and quartz, sphalerite with chalcopyrite inclusions, mirargyrite, ramdohrite, and finally stibnite. This polymetallic ore probably formed due to an abrupt decrease in H + and/or Cl À concentration caused by boiling or dilution of the high-salinity hydrothermal fluids and constitutes an example of ''intermediate sulfidation-state'' epithermal deposits

Methotrexate and Cyclosporine Treatments Modify the Activities of Dipeptidyl Peptidase IV and Prolyl Oligopeptidase in Murine Macrophages

Analysis of the effects of cyclosporine A (25–28 mgkg−1) and/or methotrexate (0.1 mgkg−1) treatments on dipeptidyl peptidase IV (DPPIV) and prolyl oligopeptidase (POP) activities and on algesic response in two distinct status of murine macrophages (Mφs) was undertaken. In resident Mφs, DPPIV and POP were affected by neither individual nor combined treatments. In thioglycolate-elicited Mφs, methotrexate increased DPPIV (99–110%) and POP (60%), while cyclosporine inhibited POP (21%). Combined treatment with both drugs promoted a rise (51–84%) of both enzyme activities. Only cyclosporine decreased (42%) the tolerance to algesic stimulus. Methotrexate was revealed to exert prevalent action over that of cyclosporine on proinflammatory Mφ POP. The opposite effects of methotrexate and cyclosporine on POP activity might influence the availability of the nociceptive mediators bradykinin and substance P in proinflammatory Mφs. The exacerbated response to thermally induced algesia observed in cyclosporine-treated animals could be related to upregulation of those mediators