The discriminative bilateral filter: An enhanced denoising filter for electron microscopy data

Advances in three-dimensional (313) electron microscopy (EM) and image processing are providing considerable improvements in the resolution of subcellular volumes, macromolecular assemblies and individual proteins. However, the recovery of high-frequency information from biological samples is hindered by specimen sensitivity to beam damage. Low dose electron cryo-microscopy conditions afford reduced beam damage but typically yield images with reduced contrast and low signal-to-noise ratios (SNRs). Here, we describe the properties of a new discriminative bilateral (DBL) filter that is based upon the bilateral filter implementation of Jiang et al. (Jiang, W., Baker, M.L., Wu, Q., Bajaj, C., Chin, W., 2003. Applications of a bilateral denoising filter in biological electron microscopy. J. Struc. Biol. 128, 82-97.). In contrast to the latter, the DBL filter can distinguish between object edges and high-frequency noise pixels through the use of an additional photometric exclusion function. As a result, high frequency noise pixels are smoothed, yet object edge detail is preserved. In the present study, we show that the DBL filter effectively reduces noise in low SNR single particle data as well as cellular tomograms of stained plastic sections. The properties of the DBL filter are discussed in terms of its usefulness for single particle analysis and for pre-processing cellular tomograms ahead of image segmentation. (c) 2006 Elsevier Inc. All rights reserved.

Relationship between myocardial perfusion and dysfunction in diabetic cardiomyopathy: A study of quantitative contrast echocardiography and strain rate imaging

Objective: To use quantitative myocardial contrast echocardiography (MCE) and strain rate imaging (SRI) to assess the role of microvascular disease in subclinical diabetic cardiomyopathy. Methods: Stress MCE and SRI were performed in 48 patients (22 with type II diabetes mellitus (DM) and 26 controls), all with normal left ventricular systolic function and no obstructive coronary disease by quantitative coronary angiography. Real-time MCE was acquired in three apical views at rest and after combined dipyridamole-exercise stress. Myocardial blood flow (MBF) was quantified in the 10 mid- and apical cardiac segments at rest and after stress. Resting peak systolic strain rate (SR) and peak systolic strain (epsilon) were calculated in the same 10 myocardial segments. Results: The DM and control groups were matched for age, sex and other risk factors, including hypertension. The DM group had higher body mass index and left ventricular mass index. Quantitative SRI analysis was possible in all patients and quantitative MCE in 46 (96%). The mean e, SR and MBF reserve were all significantly lower in the DM group than in controls, with diabetes the only independent predictor of each parameter. No correlation was seen between MBF and SR (r = -0.01, p = 0.54) or between MBF and epsilon ( r = -0.20, p = 0.20). Conclusions: Quantitative MCE shows that patients with diabetes but no evidence of obstructive coronary artery disease have impaired MBF reserve, but abnormal transmural flow and subclinical longitudinal myocardial dysfunction are not related.

Free radical reactions in atherosclerosis; An EPR spectrometry study

The copper catalysed oxidation of homocysteine has been studied by electron paramagnetic resonance (EPR) spectroscopy and spin trapping techniques to determine the nature of free radical species formed under varying experimental conditions. Three radicals; thiyl, alkyl and hydroxyl were detected with hydroxyl being predominant. A reaction mechanism is proposed involving Fenton chemistry. Inclusion of catalase to test for intermediate generation of hydrogen peroxide showed a marked reduction in amount of hydroxyl radical generated. In contrast, the addition of superoxide dismutase showed no significant effect on the level of hydroxyl radical formed. Enhanced radical formation was observed at higher levels of oxygen, an effect which has consequences for differential oxygen levels in arterial and venous systems. Implications are drawn for a higher incidence of atherosclerotic plaque formation in arteries versus veins. © 2006 - IOS Press and the authors. All rights reserved.

Induced gamma activity in primary visual cortex is related to luminance and not color contrast: an MEG study

Gamma activity in the visual cortex has been reported in numerous EEG studies of coherent and illusory figures. A dominant theme of many such findings has been that temporal synchronization in the gamma band in response to these identifiable percepts is related to perceptual binding of the common features of the stimulus. In two recent studies using magnetoencephalography (MEG) and the beamformer analysis technique, we have shown that the magnitude of induced gamma activity in visual cortex is dependent upon independent stimulus features such as spatial frequency and contrast. In particular, we showed that induced gamma activity is maximal in response to gratings of 3 cycles per degree (3 cpd) of high luminance contrast. In this work, we set out to examine stimulus contrast further by using isoluminant red/green gratings that possess color but not luminance contrast using the same cohort of subjects. We found no induced gamma activity in V1 or visual cortex in response to the isoluminant gratings in these subjects who had previously shown strong induced gamma activity in V1 for luminance contrast gratings.

Enhanced diabetes care to patients of south Asian ethnic origin (the United Kingdom Asian Diabetes Study):a cluster randomised controlled trial

Background - Delivery of high-quality, evidence-based health care to deprived sectors of the community is a major goal for society. We investigated the effectiveness of a culturally sensitive, enhanced care package in UK general practices for improvement of cardiovascular risk factors in patients of south Asian origin with type 2 diabetes. Methods - In this cluster randomised controlled trial, 21 inner-city practices in the UK were assigned by simple randomisation to intervention (enhanced care including additional time with practice nurse and support from a link worker and diabetes-specialist nurse [nine practices; n=868]) or control (standard care [12 practices; n=618]) groups. All adult patients of south Asian origin with type 2 diabetes were eligible. Prescribing algorithms with clearly defined targets were provided for all practices. Primary outcomes were changes in blood pressure, total cholesterol, and glycaemic control (haemoglobin A1c) after 2 years. Analysis was by intention to treat. This trial is registered, number ISRCTN 38297969. Findings - We recorded significant differences between treatment groups in diastolic blood pressure (1·91 [95% CI -2·88 to -0·94] mm?Hg, p=0·0001) and mean arterial pressure (1·36 [-2·49 to -0·23] mm?Hg, p=0·0180), after adjustment for confounders and clustering. We noted no significant differences between groups for total cholesterol (0·03 [-0·04 to 0·11] mmol/L), systolic blood pressure (-0·33 [-2·41 to 1·75] mm?Hg), or HbA1c (-0·15% [-0·33 to 0·03]). Economic analysis suggests that the nurse-led intervention was not cost effective (incremental cost-effectiveness ratio £28?933 per QALY gained). Across the whole study population over the 2 years of the trial, systolic blood pressure, diastolic blood pressure, and cholesterol decreased significantly by 4·9 (95% CI 4·0–5·9) mm?Hg, 3·8 (3·2–4·4) mm?Hg, and 0·45 (0·40–0·51) mmol/L, respectively, and we recorded a small and non-significant increase for haemoglobin A1c (0·04% [-0·04 to 0·13]), p=0·290). Interpretation - We recorded additional, although small, benefits from our culturally tailored care package that were greater than the secular changes achieved in the UK in recent years. Stricter targets in general practice and further measures to motivate patients are needed to achieve best possible health-care outcomes in south Asian patients with diabetes. Funding - Pfizer, Sanofi-Aventis, Servier Laboratories UK, Merck Sharp & Dohme/Schering-Plough, Takeda UK, Roche, Merck Pharma, Daiichi-Sankyo UK, Boehringer Ingelheim, Eli Lilly, Novo Nordisk, Bristol-Myers Squibb, Solvay Health Care, and Assurance Medical Society UK.

Enhanced text spacing improves reading performance in individuals with macular disease

The search by many investigators for a solution to the reading problems encountered by individuals with no central vision has been long and, to date, not very fruitful. Most textual manipulations, including font size, have led to only modest gains in reading speed. Previous work on spatial integrative properties of peripheral retina suggests that 'visual crowding' may be a major factor contributing to inefficient reading. Crowding refers to the fact that juxtaposed targets viewed eccentrically may be difficult to identify. The purpose of this study was to assess the combined effects of line spacing and word spacing on the ability of individuals with age-related macular degeneration (ARMD) to read short passages of text that were printed with either high (87.5%) or low contrast (17.5%) letters. Low contrast text was used to avoid potential ceiling effects and to mimic a possible reduction in letter contrast with light scatter from media opacities. For both low and high contrast text, the fastest reading speeds we measured were for passages of text with double line and double word spacing. In comparison with standard single spacing, double word/line spacing increased reading speed by approximately 26% with high contrast text (p < 0.001), and by 46% with low contrast text (p < 0.001). In addition, double line/word spacing more than halved the number of reading errors obtained with single spaced text. We compare our results with previous reading studies on ARMD patients, and conclude that crowding is detrimental to reading and that its effects can be reduced with enhanced text spacing. Spacing is particularly important when the contrast of the text is reduced, as may occur with intraocular light scatter or poor viewing conditions. We recommend that macular disease patients should employ double line spacing and double-character word spacing to maximize their reading efficiency. © 2013 Blackmore-Wright et al.

Microbial phylogenetic and functional responses within acidified wastewater communities exhibiting enhanced phosphate uptake

Acid stimulated accumulation of insoluble phosphorus within microbial cells is highly beneficial to wastewater treatment but remains largely unexplored. Using single cell analyses and next generation sequencing, the response of active polyphosphate accumulating microbial communities under conditions of enhanced phosphorus uptake under both acidic and aerobic conditions was characterised. Phosphorus accumulation activities were highest under acidic conditions (pH 5.5 > 8.5), where a significant positive effect on bioaccumulation was observed at pH 5.5 when compared to pH 8.5. In contrast to the Betaproteobacteria and Actinobacteria dominated enhanced biological phosphorus removal process, the functionally active polyP accumulators at pH 5.5 belonged to the Gammaproteobacteria, with key accumulators identified as members of the families Aeromonadaceae and Enterobacteriaceae. This study demonstrated a significant enrichment of key polyphosphate kinase and exopolyphosphatase genes within the community metagenome after acidification, concomitant with an increase in P accumulation kinetics.

Assessment of the performance of an enhanced planar processing algorithm for whole-body bone scintigraphy : a phantom study

A cintigrafia óssea de corpo inteiro representa um dos exames imagiológicos mais frequentes realizados em medicina nuclear. Para além de outras aplicações, este procedimento é capaz de fornecer o diagnóstico de metástases ósseas. Em doentes oncológicos, a presença de metástases ósseas representa um forte indicador prognóstico da longevidade do doente. Para além disso, a presença ou ausência de metástases ósseas irá influenciar o planeamento do tratamento, requerendo para isso uma interpretação precisa dos resultados imagiológicos. Problema: Tendo em conta que a metastização óssea é considerada uma complicação severa relacionada com aumento da morbilidade e diminuição de sobrevivência dos doentes, o conceito de patient care torna-se ainda mais imperativo nestas situações. Assim, devem ser implementadas as melhores práticas imagiológicas de forma a obter o melhor resultado possível do procedimento efetuado, associado ao desconforto mínimo do doente. Uma técnica provável para atingir este objetivo no caso específico da cintigrafia óssea de corpo inteiro é a redução do tempo de aquisição, contudo, as imagens obtidas por si só teriam qualidade de tal forma reduzida que os resultados poderiam ser enviesados. Atualmente, surgiram novas técnicas, nomeadamente relativas a processamento de imagem, através das quais é possível gerar imagens cintigráficas com contagem reduzida de qualidade comparável àquela obtida com o protocolo considerado como standard. Ainda assim, alguns desses métodos continuam associados a algumas incertezas, particularmente no que respeita a sustentação da confiança diagnóstica após a modificação dos protocolos de rotina. Objetivos: O presente trabalho pretende avaliar a performance do algoritmo Pixon para processamento de imagem por meio de um estudo com fantoma. O objetivo será comparar a qualidade de imagem e a detetabilidade fornecidas por imagens não processadas com aquelas submetidas à referida técnica de processamento. Para além disso, pretende-se também avaliar o efeito deste algoritmo na redução do tempo de aquisição. De forma a atingir este objetivo, irá ser feita uma comparação entre as imagens obtidas com o protocolo standard e aquelas adquiridas usando protocolos mais rápidos, posteriormente submetidas ao método de processamento referido. Material e Métodos: Esta investigação for realizada no departamento de Radiologia e Medicina Nuclear do Radboud University Nijmegen Medical Centre, situado na Holanda. Foi utilizado um fantoma cilíndrico contendo um conjunto de seis esferas de diferentes tamanhos, adequado à técnica de imagem planar. O fantoma foi preparado com diferentes rácios de atividade entre as esferas e o background (4:1, 8:1, 17:1, 22:1, 32:1 e 71:1). Posteriormente, para cada teste experimental, o fantoma foi submetido a vários protocolos de aquisição de imagem, nomeadamente com diferentes velocidades de aquisição: 8 cm/min, 12 cm/min, 16 cm/min e 20 cm/min. Todas as imagens foram adquiridas na mesma câmara gama - e.cam Signature Dual Detector System (Siemens Medical Solutions USA, Inc.) - utilizando os mesmos parâmetros técnicos de aquisição, à exceção da velocidade. Foram adquiridas 24 imagens, todas elas submetidas a pós-processamento com recurso a um software da Siemens (Siemens Medical Solutions USA, Inc.) que inclui a ferramenta necessária ao processamento de imagens cintigráficas de corpo inteiro. Os parâmetros de reconstrução utilizados foram os mesmos para cada série de imagens, estando estabelecidos em modo automático. A análise da informação recolhida foi realizada com recurso a uma avaliação objetiva (utilizando parâmetros físicos de qualidade de imagem) e outra subjetiva (através de dois observadores). A análise estatística foi efetuada recorrendo ao software SPSS versão 22 para Windows. Resultados: Através da análise subjetiva de cada rácio de atividade foi demonstrado que, no geral, a detetabilidade das esferas aumentou após as imagens serem processadas. A concordância entre observadores para a distribuição desta análise foi substancial, tanto para imagens não processadas como imagens processadas. Foi igualmente demonstrado que os parâmetros físicos de qualidade de imagem progrediram depois de o algoritmo de processamento ter sido aplicado. Para além disso, observou-se ao comparar as imagens standard (adquiridas com 8 cm/min) e aquelas processadas e adquiridas com protocolos mais rápidos que: imagens adquiridas com uma velocidade de aquisição de 12 cm/min podem fornecer resultados melhorados, com parâmetros de qualidade de imagem e detetabilidade superiores; imagens adquiridas com uma velocidade de 16 cm/min fornecem resultados comparáveis aos standard, com valores aproximados de qualidade de imagem e detetabilidade; e imagens adquiridas com uma velocidade de 20 cm/min resultam em valores diminuídos de qualidade de imagem, bem como redução a nível da detetabilidade. Discussão: Os resultados obtidos foram igualmente estabelecidos por meio de um estudo clínico numa investigação independente, no mesmo departamento. Foram incluídos cinquenta e um doentes referidos com carcinomas da mama e da próstata, com o objetivo de estudar o impacto desta técnica na prática clínica. Os doentes foram, assim, submetidos ao protocolo standard e posteriormente a uma aquisição adicional com uma velocidade de aquisição de 16 cm/min. Depois de as imagens terem sido cegamente avaliadas por três médicos especialistas, concluiu-se que a qualidade de imagem bem como a detetabilidade entre imagens era comparável, corroborando os resultados desta investigação. Conclusão: Com o objetivo de reduzir o tempo de aquisição aplicando um algoritmo de processamento de imagem, foi demonstrado que o protocolo com 16 cm/min de velocidade de aquisição será o limite para o aumento dessa mesma velocidade. Após processar a informação, este protocolo fornece os resultados mais equivalentes àqueles obtidos com o protocolo standard. Tendo em conta que esta técnica foi estabelecida com sucesso na prática clínica, pode-se concluir que, pelo menos em doentes referidos com carcinomas da mama e da próstata, o tempo de aquisição pode ser reduzido para metade, duplicando a velocidade de aquisição de 8 para 16 cm/min.

Contrast sensitivity evaluation with filter contact lenses in patients with retinitis pigmentosa: a pilot study

Purpose: the aim of this pilot study was to test whether retinitis pigmentosa patients would benefit from filter contact lenses as an effective optical aid against glare and photophobia. Methods: fifteen subjects with retinitis pigmentosa were enrolled in this study. All of them were evaluated with filter soft contact lenses (MaxSight), filter glasses (CPF 527) and without filters (control). All patients were assessed for the three aid conditions by means of best corrected visual acuity (BCVA), contrast sensitivity (without glare and with central and peripheral glare)(CSV-1000) and a specific subjective questionnaire about quality of vision. Results: BCVA was slightly better with filters than without filter but the differences were not statistically significant. Contrast sensitivity without glare improved significantly with the contact lenses (p<0.05). The central glare had significant differences for the frequencies of 3 cpd and 18 cpd between the contact lens filter and the control group (p=0.021 and p=0.044, respectively). For the peripheral glare contrast sensitivity improved with contact lens versus control group for highest frequencies, 12 and 18 cpd (p<0.001 and p=0.045, respectively). According to the questionnaire the contact lens filter gave them more visual comfort than the glasses filter under the scenarios of indoors glare, outdoors activities and indoors comfort. Conclusion: the filter contact lenses seem to be a good option to improve the quality of vision of patients with retinitis pigmentosa.

A study of the role of a technology-enhanced learning implementation group in mediating an institutional VLE minimum standards policy

Recent years have seen a focus on responding to student expectations in higher education. As a result, a number of technology-enhanced learning (TEL) policies have stipulated a requirement for a minimum virtual learning environment (VLE) standard to provide a consistent student experience. This paper offers insight into an under-researched area of such a VLE standard policy development using a case study of one university. With reference to the implementation staircase model, this study takes cue from the view that an institutional VLE template can affect lower levels directly, sidestepping the chain in the implementation staircase. The Group's activity whose remit is to design and develop a VLE template, therefore, becomes significant. The study, drawing on activity theory, explores the mediating role of such a Group. Factors of success and sources of tension are analysed to understand the interaction between the individuals and the collective agency of Group members. The paper identifies implications to practice for similar TEL development projects. Success factors identified demonstrated the importance of good project management principles, establishing clear rules and division of labour for TEL development groups. One key finding is that Group members are needed to draw on both different and shared mediating artefacts, supporting the conclusion that the nature of the group's composition and the situated expertise of its members are crucial for project success. The paper's theoretical contribution is an enhanced representation of a TEL policy implementation staircase.