An experimental approach to optimising refraction sensitivity for lab-based edge illumination phase contrast set-ups

Refraction sensitivity can be optimised for differential x-ray phase contrast (XPC) imaging methods by modifying the set-up. Often, modifications involve changing source/detector parameters, propagation distances, or the design of optical components, i.e. parameters that are not readily changed without non-trivial time investment, replacing components, or performing high-precision recalibrations. The edge illumination (EI) XPC method provides a method of optimising the refraction sensitivity, by exploiting micrometric translations of its periodic masks, that bypasses the constraints listed above. These translations can be performed on-the-fly and allow optimising the refraction signal for specific applications without making significant changes to the set-up. The method can prove advantageous for lab-based systems that make use of larger sources but with limited available set-up space. In this paper, we study how refraction sensitivity varies as a function of illuminated pixel fraction (IPF) under two commonly encountered experimental conditions: (1) at approximately constant detected counts, and (2) at equal exposure time. We compare the standard deviation in the background of reconstructed refraction images at different IPFs and find that refraction sensitivity is optimal at 25% IPF under both conditions. Finally, we demonstrate that refraction sensitivity affects the visibility of weakly refracting features on an insect leg. The results suggest that IPFs lower than 50% can actually be preferable, especially in the case where the statistics is kept constant, and provide experimental validation that phase sensitivity in EI is not fixed once the system parameters are defined

Effective modeling of high-energy laboratory-based x-ray phase contrast imaging utilizing absorption masks or gratings

Model refinements for the edge illumination x-ray phase contrast imaging method have been developed to improve simulation accuracy for high energy, polychromatic beams. High-energy x rays are desirable in imaging due to their penetrative power and, for biological samples, their lower dose deposition rate. Accurate models of such scenarios are required for designing appropriate imaging systems and to predict signal strength in complex settings such as clinical imaging or industrial quality assurance. When using optical components appropriate for high-energy x rays in a non-synchrotron setting, system performance was observed to deviate from that predicted by existing models. In this work, experimental data utilizing increasing thicknesses of a known filter material are used to illustrate the limitations of existing models and as validation for the new modeling features. Angular filtration of the cone beam was observed to be the most significant effect; however, specific features of the source and detector are also shown to affect system performance. We conclude by showing that a significantly improved agreement between experimental and simulated data is obtained with the refined model compared to previously existing ones

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

A qualitative study of patients and healthcare workers’ experiences and perceptions to inform a better understanding of gaps in care for pre-discharged tuberculosis patients in Cape Town, South Africa

Background Many people diagnosed with Mycobacterium tuberculosis (TB) in tertiary and district hospitals in South Africa do not arrive at their primary care clinic for continued care after they are discharged from the hospital. This loss to follow up is a major, ongoing problem for public health in South Africa, and contributes to drug-resistant TB strains. The objective of this paper was to explore patients’ experiences and perceptions of diagnosis and treatment before their discharge from hospital. We use a framework known as patient-centred care to illustrate how these patient narratives point to lapses in these principles within the hospital system, and to show how such lapses may contribute to loss to follow up and inconsistent TB care. Methods We employed a qualitative study using semi-structured interviews to investigate patient and healthcare workers’ experiences and perceptions of TB care in two Western Cape hospitals. We purposefully sampled 17 patients, 10 healthcare workers, and two key informant policy makers, all of whom had relevant experiences and insights. Data collection was done between October 2015 and February 2017. Data were analysed using Miles and Huberman’s qualitative analysis framework. Results Hospitals did not achieve patient-centred care. Newly diagnosed patients were provided with inadequate TB education, diseased-focused approaches were favoured over patient-focused approaches, and there was limited engagement with patients to understand their needs and feelings during the critical period between diagnosis and discharge. Consequently, some patients felt anxious prior to their discharge from hospital. Coupled with their overwhelming socio-economic barriers and complex family situations, some patients felt hopeless and powerless as they prepared for discharge. Finally, there was a lack of patient-provider partnership due to problems including healthcare workers’ time constraints and heavy workloads, which detracted from a focus on patients’ needs and feelings. Conclusions Improving the three intersecting elements of patient-centred care (health education, engaging with patients’ needs and feelings, and shared decision-making) has the potential to positively influence patients’ continuity of care for TB in South Africa. It would be helpful to also proactively address how patients plan to stay connected to care, on treatment, and supported, in light of their family situation or socio-economic circumstances. Detailed and unique pre-discharge counselling for each patient may be valuable in this regard

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

Signal of harm in morphine use in adults with acute pulmonary oedema: A rapid systematic review

Background. Heart failure affects nearly 65 million people globally, resulting in recurrent hospital admissions and substantial healthcare expenditure. The use of morphine in the management of acute pulmonary oedema remains controversial, with conflicting guidance and significant variation in practice. Synthesised evidence is needed to inform standard treatment guidelines and clinical practice. Objective. To determine whether morphine should be used in the treatment of acute pulmonary oedema (APE) in adults. Methods. A rapid review of systematic reviews of randomised controlled trials or observational studies, and then randomised controlled trials, was conducted searching three electronic databases (PubMed, Embase, Cochrane Library) and one clinical trial registry on 12 February 2022. We used a prespecified protocol following Cochrane rapid review methods and aligned to the National Standard Treatment Guidelines and Essential Medicines List methodology. We first considered relevant high-quality systematic reviews of randomised controlled trials or observational studies, then (if required) randomised controlled trials to inform time-sensitive or urgent evidence requests, clinical practice, policy, or standard treatment guidelines. Results. We identified four systematic reviews of observational studies. The two most relevant, up-to-date, and highest-quality reviews were used to inform evidence for critical outcomes. Morphine may increase in-hospital mortality (odds ratio (OR) 1.78; 95% confidence interval (CI) 1.01 - 3.13; low certainty of evidence; six observational studies, n=151 735 participants), resulting in 15 more per 1 000 hospital deaths, ranging from 0 to 40 more hospital deaths. Morphine may result in a large increase in invasive mechanical ventilation (OR 2.72; 95% CI 1.09 - 6.80; low certainty of evidence; four observational studies, n=167 847 participants), resulting in 45 more per 1 000 ventilations, ranging from 2 more to 136 more. Adverse events and hospital length of stay were not measured across reviews or trials. Conclusion. Based on the most recent, relevant and best-available quality evidence, morphine use in adults with APE may increase in-hospital and all-cause mortality and may result in a large increase in the need for invasive mechanical ventilation compared to not using morphine. Recommending against the use of morphine in pulmonary oedema may improve patient outcomes. Disinvesting in morphine for this indication may result in cost savings, noting the possible accrued benefits of fewer patients requiring invasive ventilation and management of morphine-related side-effects

Replacing the detector mask with a structured scintillator in edge-illumination x-ray phase contrast imaging

We present a proof-of-concept edge illumination x-ray phase contrast system where the detector mask has been replaced by an indirect conversion detector in which sensitive and insensitive regions have been obtained by “patterning” the scintillator. This was achieved by creating a free-standing grid with period and aperture size matching that of a typical detector mask and filling the apertures with gadolinium oxysulfide. Images of various samples were collected with both the modified and the original edge illumination systems based on the use of two masks to characterize the performances of this detector design. We found that, despite the proof-of-concept nature of this attempt resulting in a structured detector with suboptimal performance, it allows effective separation of the attenuation and refraction channels through phase retrieval and the visualization of hard-to-detect features such as cartilage through the latter channel, thus demonstrating that the proposed approach holds the potential to lead to improved stability since it will use a single optical element facilitating the design of rotating phase contrast systems or the retrofitting of conventional x-ray systems

Organisational Culture and Mask-Wearing Practices for Tuberculosis Infection Prevention and Control among Health Care Workers in Primary Care Facilities in the Western Cape, South Africa: A Qualitative Study

Background: Although many healthcare workers (HCWs) are aware of the protective role that mask-wearing has in reducing transmission of tuberculosis (TB) and other airborne diseases, studies on infection prevention and control (IPC) for TB in South Africa indicate that mask-wearing is often poorly implemented. Mask-wearing practices are influenced by aspects of the environment and organisational culture within which HCWs work. Methods: We draw on 23 interviews and four focus group discussions conducted with 44 HCWs in six primary care facilities in the Western Cape Province of South Africa. Three key dimensions of organisational culture were used to guide a thematic analysis of HCWs’ perceptions of masks and mask-wearing practices in the context of TB infection prevention and control. Results: First, HCW accounts address both the physical experience of wearing masks, as well as how mask-wearing is perceived in social interactions, reflecting visual manifestations of organisational culture in clinics. Second, HCWs expressed shared ways of thinking in their normalisation of TB as an inevitable risk that is inherent to their work and their localization of TB risk in specific areas of the clinic. Third, deeper assumptions about mask-wearing as an individual choice rather than a collective responsibility were embedded in power and accountability relationships among HCWs and clinic managers. These features of organisational culture are underpinned by broader systemic shortcomings, including limited availability of masks, poorly enforced protocols, and a general lack of role modelling around mask-wearing. HCW mask-wearing was thus shaped not only by individual knowledge and motivation but also by the embodied social dimensions of mask-wearing, the perceptions that TB risk was normal and localizable, and a shared underlying tendency to assume that mask-wearing, ultimately, was a matter of individual choice and responsibility. Conclusions: Organisational culture has an important, and under-researched, impact on HCW mask-wearing and other PPE and IPC practices. Consistent mask-wearing might become a more routine feature of IPC in health facilities if facility managers more actively promote engagement with TB-IPC guidelines and develop a sense of collective involvement and ownership of TB-IPC in facilities

Waiting times, patient flow, and occupancy density in South African primary health care clinics: implications for infection prevention and control

AbstractBackgroundTransmission of respiratory pathogens, such as Mycobacterium tuberculosis and severe acute respiratory syndrome coronavirus 2, is more likely during close, prolonged contact and when sharing a poorly ventilated space. In clinics in KwaZulu-Natal (KZN) and Western Cape (WC), South Africa, we estimated clinic visit duration, time spent indoors and outdoors, and occupancy density of waiting rooms.MethodsWe used unique barcodes to track attendees’ movements in 11 clinics in two provinces, multiple imputation to estimate missing arrival and departure times, and mixed-effects linear regression to examine associations with visit duration.Results2,903 attendees were included. Median visit duration was 2 hours 36 minutes (interquartile range [IQR] 01:36–3:43). Longer mean visit times were associated with being female (13.5 minutes longer than males; p&lt;0.001) and attending with a baby (18.8 minutes longer than those without; p&lt;0.01), and shorter mean times with later arrival (14.9 minutes shorter per hour after 0700; p&lt;0.001) and attendance for tuberculosis or ante/postnatal care (24.8 and 32.6 minutes shorter, respectively, than HIV/acute care; p&lt;0.01).Overall, attendees spent more of their time indoors (median 95.6% [IQR 46–100]) than outdoors (2.5% [IQR 0–35]). Attendees at clinics with outdoor waiting areas spent a greater proportion (median 13.7% [IQR 1– 75]) of their time outdoors.In two clinics in KZN (no appointment system), occupancy densities of ∼2.0 persons/m2 were observed in smaller waiting rooms during busy periods. In one clinic in WC (appointment system), occupancy density did not exceed 1.0 persons/m2 despite higher overall attendance.ConclusionsLonger waiting times were associated with early arrival, being female, and attending with a young child. Attendees generally waited where they were asked to. Regular estimation of occupancy density (as patient flow proxy) may help staff assess for risk of infection transmission and guide intervention to reduce time spent in risky spaces.</jats:sec

Estimating waiting times, patient flow, and waiting room occupancy density as part of tuberculosis infection prevention and control research in South African primary health care clinics

From PLOS via Jisc Publications RouterHistory: received 2021-09-01, collection 2022, accepted 2022-06-13, epub 2022-07-20Publication status: PublishedFunder: Economic and Social Research Council; funder-id: http://dx.doi.org/10.13039/501100000269; Grant(s): ES/P008011/1Funder: The Bloomsbury SET; Grant(s): CCF17-7779Transmission of respiratory pathogens, such as Mycobacterium tuberculosis and severe acute respiratory syndrome coronavirus 2, is more likely during close, prolonged contact and when sharing a poorly ventilated space. Reducing overcrowding of health facilities is a recognised infection prevention and control (IPC) strategy; reliable estimates of waiting times and ‘patient flow’ would help guide implementation. As part of the Umoya omuhle study, we aimed to estimate clinic visit duration, time spent indoors versus outdoors, and occupancy density of waiting rooms in clinics in KwaZulu-Natal (KZN) and Western Cape (WC), South Africa. We used unique barcodes to track attendees’ movements in 11 clinics, multiple imputation to estimate missing arrival and departure times, and mixed-effects linear regression to examine associations with visit duration. 2,903 attendees were included. Median visit duration was 2 hours 36 minutes (interquartile range [IQR] 01:36–3:43). Longer mean visit times were associated with being female (13.5 minutes longer than males; p<0.001) and attending with a baby (18.8 minutes longer than those without; p<0.01), and shorter mean times with later arrival (14.9 minutes shorter per hour after 0700; p<0.001). Overall, attendees spent more of their time indoors (median 95.6% [IQR 46–100]) than outdoors (2.5% [IQR 0–35]). Attendees at clinics with outdoor waiting areas spent a greater proportion (median 13.7% [IQR 1–75]) of their time outdoors. In two clinics in KZN (no appointment system), occupancy densities of ~2.0 persons/m2 were observed in smaller waiting rooms during busy periods. In one clinic in WC (appointment system, larger waiting areas), occupancy density did not exceed 1.0 persons/m2 despite higher overall attendance. In this study, longer waiting times were associated with early arrival, being female, and attending with a young child. Occupancy of waiting rooms varied substantially between rooms and over the clinic day. Light-touch estimation of occupancy density may help guide interventions to improve patient flow