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Fulltext Global health security and the health-security nexus: principles, politics and praxis

McCoy D, Roberts S, Daoudi S, Kennedy J

BMJ Glob Health, 2023 Sep;8(9).
PMID: 37748796 DOI: 10.1136/bmjgh-2023-013067

The past four decades have seen a steady rise of references to 'security' by health academics, policy-makers and practitioners, particularly in relation to threats posed by infectious disease pandemics. Yet, despite an increasingly dominant health security discourse, the many different ways in which health and security issues and actors intersect have remained largely unassessed and unpacked in current critical global health scholarship. This paper discusses the emerging and growing health-security nexus in the wake of COVID-19 and the international focus on global health security. In recognising the contested and fluid concept of health security, this paper presents two contrasting approaches to health security: neocolonial health security and universal health security. Building from this analysis, we present a novel heuristic that delineates the multiple intersections and entanglements between health and security actors and agendas to broaden our conceptualisation of global health security configurations and practices and to highlight the potential for harmful unintended consequences, the erosion of global health norms and values, and the risk of health actors being co-opted by the security sector.
Fulltext Quantitative CEST imaging of amide proton transfer in acute ischaemic stroke

Msayib Y, Harston GWJ, Tee YK, Sheerin F, Blockley NP, Okell TW, et al.

Neuroimage Clin, 2019;23:101833.
PMID: 31063943 DOI: 10.1016/j.nicl.2019.101833

BACKGROUND: Amide proton transfer (APT) imaging may help identify the ischaemic penumbra in stroke patients, the classical definition of which is a region of tissue around the ischaemic core that is hypoperfused and metabolically stressed. Given the potential of APT imaging to complement existing imaging techniques to provide clinically-relevant information, there is a need to develop analysis techniques that deliver a robust and repeatable APT metric. The challenge to accurate quantification of an APT metric has been the heterogeneous in-vivo environment of human tissue, which exhibits several confounding magnetisation transfer effects including spectrally-asymmetric nuclear Overhauser effects (NOEs). The recent literature has introduced various model-free and model-based approaches to analysis that seek to overcome these limitations.
OBJECTIVES: The objective of this work was to compare quantification techniques for CEST imaging that specifically separate APT and NOE effects for application in the clinical setting. Towards this end a methodological comparison of different CEST quantification techniques was undertaken in healthy subjects, and around clinical endpoints in a cohort of acute stroke patients.
METHODS: MRI data from 12 patients presenting with ischaemic stroke were retrospectively analysed. Six APT quantification techniques, comprising model-based and model-free techniques, were compared for repeatability and ability for APT to distinguish pathological tissue in acute stroke.
RESULTS: Robustness analysis of six quantification techniques indicated that the multi-pool model-based technique had the smallest contrast between grey and white matter (2%), whereas model-free techniques exhibited the highest contrast (>30%). Model-based techniques also exhibited the lowest spatial variability, of which 4-pool APTR∗ was by far the most uniform (10% coefficient of variation, CoV), followed by 3-pool analysis (20%). Four-pool analysis yielded the highest ischaemic core contrast-to-noise ratio (0.74). Four-pool modelling of APT effects was more repeatable (3.2% CoV) than 3-pool modelling (4.6% CoV), but this appears to come at the cost of reduced contrast between infarct growth tissue and normal tissue.
CONCLUSION: The multi-pool measures performed best across the analyses of repeatability, spatial variability, contrast-to-noise ratio, and grey matter-white matter contrast, and might therefore be more suitable for use in clinical imaging of acute stroke. Addition of a fourth pool that separates NOEs and semisolid effects appeared to be more biophysically accurate and provided better separation of the APT signal compared to the 3-pool equivalent, but this improvement appeared be accompanied by reduced contrast between infarct growth tissue and normal tissue.
Implantation and diabetes: analysis of 525 cases

Lim AS, Ang BC, Heng LK, Hart PM, Ngui MS, Chew P, et al.

Ann Acad Med Singap, 1989 Mar;18(2):174-7.
PMID: 2751233

This is a retrospective study of 525 posterior chamber implants in diabetics performed by A S M Lim and B C Ang of Singapore. The patients were reviewed by visiting ophthalmologists--J E Kennedy (Sydney), M Ngui (East Malaysia) and P M Hart (Belfast). This study did not show any significant difference in the complication of post-operative visual acuity between diabetics and non-diabetics. 95% obtained 6/12 vision or better when pre-existing disease was excluded. It also showed that posterior chamber implants can be inserted in eyes with maculopathy or proliferative retinopathy if laser treatment was effectively done before or after surgery.
Fulltext Identifying the ischaemic penumbra using pH-weighted magnetic resonance imaging

Harston GW, Tee YK, Blockley N, Okell TW, Thandeswaran S, Shaya G, et al.

Brain, 2015 Jan;138(Pt 1):36-42.
PMID: 25564491 DOI: 10.1093/brain/awu374

The original concept of the ischaemic penumbra suggested imaging of regional cerebral blood flow and metabolism would be required to identify tissue that may benefit from intervention. Amide proton transfer magnetic resonance imaging, a chemical exchange saturation transfer technique, has been used to derive cerebral intracellular pH in preclinical stroke models and has been proposed as a metabolic marker of ischaemic penumbra. In this proof of principle clinical study, we explored the potential of this pH-weighted magnetic resonance imaging technique at tissue-level. Detailed voxel-wise analysis was performed on data from a prospective cohort of 12 patients with acute ischaemic stroke. Voxels within ischaemic core had a more severe intracellular acidosis than hypoperfused tissue recruited to the final infarct (P < 0.0001), which in turn was more acidotic than hypoperfused tissue that survived (P < 0.0001). In addition, when confined to the grey matter perfusion deficit, intracellular pH (P < 0.0001), but not cerebral blood flow (P = 0.31), differed between tissue that infarcted and tissue that survived. Within the presenting apparent diffusion coefficient lesion, intracellular pH differed between tissue with early apparent diffusion lesion pseudonormalization and tissue with true radiographic recovery. These findings support the need for further investigation of pH-weighted imaging in patients with acute ischaemic stroke.