Comparing signal intensity and refraction sensitivity of double and single mask edge illumination lab-based x-ray phase contrast imaging set-ups

Double mask edge illumination (DM-EI) set-ups can detect differential phase and attenuation information from a sample. However, analytical separation of the two signals often requires acquiring two frames with inverted differential phase contrast signals. Typically, between these two acquisitions, the first mask is moved to create a different illumination condition. This can lead to potential errors which adversely affect the data collected. In this paper, we implement a single mask EI laboratory set-up that allows for a single shot retrieval of the differential phase and attenuation images, without the need for a high resolution detector or high magnification. As well as simplifying mask alignment, the advantages of the proposed set-up can be exploited in one of two ways: either the total acquisition time can be halved with respect to the DM-EI set-up or, for the same acquisition time, twice the statistics can be collected. In this latter configuration, the signal-to-noise ratio and contrast in the mixed intensity images, and the angular sensitivity of the two set-ups were compared. We also show that the angular sensitivity of the single mask set-up can be well approximated from its illumination curve, which has been modelled as a convolution between the source spatial distribution at the detector plane, the pre-sample mask and the detector point spread function (PSF). A polychromatic wave optics simulation was developed on these bases and benchmarked against experimental data. It can also be used to predict the angular sensitivity and contrast of any set-up as a function of detector PSF

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

A laboratory based edge-Illumination x-ray phase-contrast imaging setup with two-directional sensitivity

We report on a preliminary laboratory based x-ray phase-contrast imaging system capable of achieving two directional phase sensitivity thanks to the use of L-shaped apertures. We show that in addition to apparent absorption, two-directional differential phase images of an object can be quantitatively retrieved by using only three input images. We also verify that knowledge of the phase derivatives along both directions allows for straightforward phase integration with no streak artefacts, a known problem common to all differential phase techniques. In addition, an analytical method for 2-directional dark field retrieval is proposed and experimentally demonstrated

Simple and robust synchrotron and laboratory solutions for high-resolution multimodal X-ray phase-based imaging

Edge illumination X-ray phase contrast imaging techniques are capable of quantitative retrieval of differential phase, absorption and X-ray scattering. We have recently developed a series of approaches enabling high-resolution implementations, both using synchrotron radiation and laboratory-based set-ups. Three-dimensional reconstruction of absorption, phase and dark-field can be achieved with a simple rotation of the sample. All these approaches share a common trait which consists in the use of an absorber that shapes the radiation field, in order to make the phase modulations introduced by the sample detectable. This enables a well-defined and high-contrast structuring of the radiation field as well as an accurate modelling of the effects that are related to the simultaneous use of a wide range of energies. Moreover, it can also be adapted for use with detectors featuring large pixel sizes, which could be desirable when a high detection efficiency is important

Barriers and facilitators of tuberculosis infection prevention and control in low- and middle-income countries from the perspective of healthcare workers: A systematic review.

Tuberculosis remains a leading cause of death worldwide. Transmission is the dominant mechanism sustaining the multidrug-resistant tuberculosis epidemic. Tuberculosis infection prevention and control (TBIPC) guidelines for healthcare facilities are poorly implemented. This systematic review aimed to explore the barriers and facilitators of implementation of TBIPC guidelines in low- and middle-income countries from the perspective of healthcare workers. Two separate reviewers carried out an electronic database search to select qualitative and quantitative studies exploring healthcare workers attitudes towards TBIPC. Eligible studies underwent thematic synthesis. Derived themes were further organised into a macro-, meso- and micro-level framework, which allows us to analyse barriers at different levels of the healthcare system. We found that most studies focused on assessing implementation within facilities in accordance with the hierarchy of TBIPC measures-administrative, environmental and respiratory protection controls. TBIPC implementation was over-estimated by self-report compared with what researchers observed within facilities, indicating a knowledge-action gap. Macro-level barriers included the lack of coordination of integrated HIV/tuberculosis care, in the context of an expanding antiretroviral therapy programme and hence increasing opportunity for nosocomial acquisition of tuberculosis; a lack of funding; and ineffective occupational health policies, such as poor systems for screening for tuberculosis amongst healthcare workers. Meso-level barriers included little staff training to implement programmes, and managers not understanding policy sufficiently to translate it into an IPC programme. Most studies reported micro-level barriers including the impact of stigma, work culture, lack of perception of risk, poor supply and use of respirators and difficulty sensitising patients to the need for IPC. Existing literature on healthcare workers' attitudes to TBIPC focusses on collecting data about poor implementation at facility level. In order to bridge the knowledge-action gap, we need to understand how best to implement policy, taking account of the context

‘It has become everybody’s business and nobody’s business’: Policy actor perspectives on the implementation of TB infection prevention and control (IPC) policies in South African public sector primary care health facilities

Karina Kielmann - ORCID: 0000-0001-5519-1658 https://orcid.org/0000-0001-5519-1658South Africa is increasingly offering screening, diagnosis and treatment of tuberculosis (TB), and especially drug-resistant TB, at the primary care level. Nosocomial transmission of TB within primary health facilities is a growing concern in South Africa, and globally. We explore here how TB infection prevention and control (IPC) policies, historically focused on hospitals, are being implemented within primary care facilities. We spoke to 15 policy actors using in-depth interviews about barriers to effective TB-IPC and opportunities for improving implementation. We identified four drivers of poor policy implementation: fragmentation of institutional responsibility and accountability for TB-IPC; struggles by TB-IPC advocates to frame TB-IPC as an urgent and addressable policy problem; barriers to policy innovation from both a lack of evidence as well as a policy environment dependent on ‘new’ evidence to justify new policy; and the impact of professional medical cultures on the accurate recognition of and response to TB risks. Participants also identified examples of TB-IPC innovation and described conditions necessary for these successes. TB-IPC is a long-standing, complex health systems challenge. As important as downstream practices like mask-wearing and ventilation are, sustained, effective TB-IPC ultimately requires that we better address the upstream barriers to TB-IPC policy formulation and implementation.The support of the Economic and Social Research Council (IK) is gratefully acknowledged. The project is partly funded by the Antimicrobial Resistance Cross Council Initiative supported by the seven research councils in partnership with other funders including support from the GCRF. Grant reference: ES/P008011/1https://doi.org/10.1080/17441692.2020.183993216pubpub1

Review of Remediation Solutions for Acid Mine Drainage Using the Modified Hill Framework

This paper reviews the Acid Mine Drainage (AMD) remediation potential and operational costs of twelve existing AMD remediation methods against Class 0 and Class I AMD geochemical characteristics as defined in the Modified Hill Framework. Of the twelve remediation options reviewed in this study, eleven required additional process steps either for further treatment to achieve the discharge limits or for the safe management of hazardous waste by-products. Chemical desalination showed the greatest potential with high quality treated water and operational costs between USD 0.25 and USD 0.75 per cubic meter treated. The management of the toxic metal and sulphide by-products remains a key challenge that requires further research for sustainable mine water remediation. Further development of end-to-end methods suitable for Class 0 AMD with economical operational costs is recommended in order to effectively address the ongoing environmental challenges posed by AMD globally

Design model of a novel cooling condensation type atmospheric water generator for coastal rural South Africa

Abstract: In many of South Africa’s rural communities, rivers and rain water storage tanks are the main source for domestic water supply and agricultural use. However, from 2015 to date South Africa has faced severe water shortages due to the worst droughts the country has experienced in over 23 years. The droughts have led to the reduction in flow volumes of some rivers and domestic rain water storage tanks being rendered mostly empty. This greatly endangered the livelihoods of many rural communities in South Africa. This study investigates the implementation of an affordable cooling condensation type Atmospheric Water Generator (AWG) solution for coastal rural households as a supplementary water source in the event of water crisis. The eastern coastal region of KwaZulu-Natal (KZN), situated between the towns of Amanzimtoti and St. Lucia, was chosen as the case study location due to the favourable climate conditions for the implementation of AWG technology as well as the large number of surrounding rural communities that have been affected by the on-going draughts..

The effect of a variable focal spot size on the contrast channels retrieved in edge illumination x-ray phase contrast imaging

Multi-modal X-ray imaging allows the extraction of phase and dark-field (or “Ultra-small Angle Scatter”) images alongside conventional attenuation ones. Recently, scan-based systems using conventional sources that can simultaneously output the above three images on relatively large-size objects have been developed by various groups. One limitation is the need for some degree of spatial coherence, achieved either through the use of microfocal sources, or by placing an absorption grating in front of an extended source. Both these solutions limit the amount of flux available for imaging, with the latter also leading to a more complex setup with additional alignment requirements. Edge-illumination partly overcomes this as it was proven to work with focal spots of up to 100 micron. While high-flux, 100 micron focal spot sources do exist, their comparatively large footprint and high cost can be obstacles to widespread translation. A simple solution consists in placing a single slit in front of a large focal spot source. We used a tunable slit to study the system performance at various effective focal spot sizes, by extracting transmission, phase and dark-field images of the same specimens for a range of slit widths. We show that consistent, repeatable results are obtained for varying X-ray statistics and effective focal spot sizes. As the slit width is increased, the expected reduction in the raw differential phase peaks is observed, compensated for in the retrieval process by a broadened sensitivity function. This leads to the same values being correctly retrieved, but with a slightly larger error bar i.e. a reduction in phase sensitivity. Concurrently, a slight increase in the dark-field signal is also observed