Avaliação da influência dos formatos DICOM e JPEG na reprodutibilidade de pontos cefalométricos em Telerradiografia digital em Norma Frontal

A imagem digital no formato DICOM requer grande espaço para armazenamento, dificultando o arquivamento e transmissão da imagem via internet, sendo necessária, muitas vezes, a compressão das imagens por meio de formatos de arquivo como o JPEG. O objetivo neste estudo foi avaliar a influência dos formatos DICOM e JPEG, nos Fatores de Qualidade 100, 80 e 60, na reprodutibilidade intra e interexaminador na marcação de pontos cefalométricos em Telerradiografias digitais em Norma Frontal. A amostra consistiu de 120 imagens digitais de Telerradiografias em Norma Frontal, obtidas de 30 indivíduos. As 30 imagens originais, em formato DICOM, posteriormente, foram convertidas para o formato JPEG, nos Fatores de Qualidade 100, 80 e 60. Após cegar e randomizar a amostra, três ortodontistas calibrados marcaram os 18 pontos cefalométricos em cada imagem utilizando um programa de cefalometria computadorizada, que registra as medidas dos pontos cefalométricos em um sistema de coordenadas cartesianas X e Y. Nos resultados, os testes estatísticos de correlações intraclasses e análise de variância (ANOVA) apresentaram concordância de reprodutibilidade dos pontos cefalométricos em Telerradiografias digitais em Norma Frontal, tanto intra como interexaminador, com exceção dos pontos ZL, ZR, AZ, JR, NC, CN na coordenada Y e A6 na coordenada X, independentemente dos formatos de arquivo. Em conclusão, os formatos de arquivo DICOM e JPEG, nos Fatores de Qualidade 100, 80 e 60, não afetaram a reprodutibilidade intra e interexaminador na marcação dos pontos cefalométricos.(AU)

Quantitative differences in beta/A4 protein subtypes in the parahippocampal gyrus and frontal cortex in Alzheimer's disease

The density of diffuse, primitive and classic beta/A4 protein deposits was estimated in sulci and gyri in the frontal cortex and parahippocampal gyrus (PHG) in 8 cases of Alzheimer's disease. Total beta/A4 deposit density was similar in the frontal cortex and PHG but the ratio of primitive and classic deposits to the total was greater in the PHG compared with the frontal cortex. Total beta/A4 deposit density was greater in the depths of the sulci, but the proportions of the various beta/A4 subtypes were similar in sulci and gyri. Hence, increased density of primitive and classic deposits in the PHG could reflect enhanced conversion of diffuse to mature deposits whereas increased density of mature beta/A4 subtypes in sulci versus gyri may reflect increased beta/A4 deposition in the sulci.

Developments in contact lens measurement:a comparative study of industry standard geometric inspection and optical coherence tomography

Purpose: The aim of this study was to compare a developmental optical coherence tomography (OCT) based contact lens inspection instrument to a widely used geometric inspection instrument (Optimec JCF), to establish the capability of a market focused OCT system. Methods: Measurements of 27 soft spherical contact lenses were made using the Optimec JCF and a new OCT based instrument, the Optimec is830. Twelve of the lenses analysed were specially commissioned from a traditional hydrogel (Contamac GM Advance 49%) and 12 from a silicone hydrogel (Contamac Definitive 65), each set with a range of back optic zone radius (BOZR) and centre thickness (CT) values. Three commercial lenses were also measured; CooperVision MyDay (Stenfilcon A) in −10D, −3D and +6D powers. Two measurements of BOZR, CT and total diameter were made for each lens in temperature controlled saline on both instruments. Results: The results showed that the is830 and JCF measurements were comparable, but that the is830 had a better repeatability coefficient for BOZR (0.065 mm compared to 0.151 mm) and CT (0.008 mm compared to 0.027 mm). Both instruments had similar results for total diameter (0.041 mm compared to 0.044 mm). Conclusions: The OCT based instrument assessed in this study is able to match and improve on the JCF instrument for the measurement of total diameter, back optic zone radius and centre thickness for soft contact lenses in temperature controlled saline.

Modelling frontal discontinuities in wind fields

A Bayesian procedure for the retrieval of wind vectors over the ocean using satellite borne scatterometers requires realistic prior near-surface wind field models over the oceans. We have implemented carefully chosen vector Gaussian Process models; however in some cases these models are too smooth to reproduce real atmospheric features, such as fronts. At the scale of the scatterometer observations, fronts appear as discontinuities in wind direction. Due to the nature of the retrieval problem a simple discontinuity model is not feasible, and hence we have developed a constrained discontinuity vector Gaussian Process model which ensures realistic fronts. We describe the generative model and show how to compute the data likelihood given the model. We show the results of inference using the model with Markov Chain Monte Carlo methods on both synthetic and real data.

Attentional changes in pre-stimulus oscillatory activity within early visual cortex are predictive of human visual performance

Physiological and neuroimaging studies provide evidence to suggest that attentional mechanisms operating within the fronto-parietal network may exert top–down control on early visual areas, priming them for forthcoming sensory events. The believed consequence of such priming is enhanced task performance. Using the technique of magnetoencephalography (MEG), we investigated this possibility by examining whether attention-driven changes in cortical activity are correlated with performance on a line-orientation judgment task. We observed that, approximately 200 ms after a covert attentional shift towards the impending visual stimulus, the level of phase-resetting (transient neural coherence) within the calcarine significantly increased for 2–10 Hz activity. This was followed by a suppression of alpha activity (near 10 Hz) which persisted until the onset of the stimulus. The levels of phase-resetting, alpha suppression and subsequent behavioral performance varied between subjects in a systematic fashion. The magnitudes of phase-resetting and alpha-band power were negatively correlated, with high levels of coherence associated with high levels of performance. We propose that top–down attentional control mechanisms exert their initial effects within the calcarine through a phase-resetting within the 2–10 Hz band, which in turn triggers a suppression of alpha activity, priming early visual areas for incoming information and enhancing behavioral performance.

Laminar distribution of the pathological changes in frontal and temporal cortex in 8 patients with progressive supranuclear palsy

OBJECTIVE: To determine the laminar distribution of the pathological changes in the cerebral cortex in progressive supranuclear palsy (PSP). METHOD: The distribution of the abnormally enlarged neurons (EN), surviving neurons, neurofibrillary tangles (NFT), glial inclusions (GI), tufted astrocytes (TA), and neuritic plaques (NP) were studied across the cortex in tau immunolabeled sections of frontal and temporal cortex in 8 cases of PSP. RESULTS: The distribution of the NFT was highly variable with no consistent pattern of laminar distribution. The GI were distributed either in the lower laminae or uniformly across the cortex. Surviving neurons exhibited either a density peak in the upper laminae or a bimodal distribution was present with density peaks in the upper and lower laminae. The EN and glial cell nuclei were distributed primarily in the lower cortical laminae. There were positive correlations between the densities of the EN and glial cell nuclei and negative correlations between the surviving neurons and glial cells. No correlations were present between the densities of the NFT and GI. CONCLUSION: Cortical pathology in PSP predominantly affects the lower laminae but may spread to affect the upper laminae in some cases. The NFT and GI may have different laminar distributions and gliosis occurs concurrently with neuronal enlargement.

Multiple system atrophy: laminar distribution of the pathological changes in frontal and temporal neocortex--a study in ten patients

OBJECTIVE: To determine the distribution of the pathological changes in the neocortex in multiple-system atrophy (MSA). METHOD: The vertical distribution of the abnormal neurons (neurons with enlarged or atrophic perikarya), surviving neurons, glial cytoplasmic inclusions (GCI) and neuronal cytoplasmic inclusions (NI) were studied in alpha-synuclein-stained material of frontal and temporal cortex in ten cases of MSA. RESULTS: Abnormal neurons exhibited two common patterns of distribution, viz., density was either maximal in the upper cortex or a bimodal distribution was present with a density peak in the upper and lower cortex. The NI were either located in the lower cortex or were more uniformly distributed down the cortical profile. The distribution of the GCI varied considerably between gyri and cases. The density of the glial cell nuclei was maximal in the lower cortex in the majority of gyri. In a number of gyri, there was a positive correlation between the vertical densities of the abnormal neurons, the total number of surviving neurons, and the glial cell nuclei. The vertical densities of the GCI were not correlated with those of the surviving neurons or glial cells but the GCI and NI were positively correlated in a small number of gyri. CONCLUSION: The data suggest that there is significant degeneration of the frontal and temporal lobes in MSA, the lower laminae being affected more significantly than the upper laminae. Cortical degeneration in MSA is likely to be secondary to pathological changes occurring within subcortical areas.

Graphical modelling for brain connectivity via partial coherence

Spectral and coherence methodologies are ubiquitous for the analysis of multiple time series. Partial coherence analysis may be used to try to determine graphical models for brain functional connectivity. The outcome of such an analysis may be considerably influenced by factors such as the degree of spectral smoothing, line and interference removal, matrix inversion stabilization and the suppression of effects caused by side-lobe leakage, the combination of results from different epochs and people, and multiple hypothesis testing. This paper examines each of these steps in turn and provides a possible path which produces relatively ‘clean’ connectivity plots. In particular we show how spectral matrix diagonal up-weighting can simultaneously stabilize spectral matrix inversion and reduce effects caused by side-lobe leakage, and use the stepdown multiple hypothesis test procedure to help formulate an interaction strength.

Sense of coherence and diabetes:a prospective occupational cohort

Background: Sense of coherence (SOC) is an individual characteristic related to a positive life orientation leading to effective coping. A weak SOC has been associated with indicators of general morbidity and mortality. However, the relationship between SOC and diabetes has not been studied in prospective design. The present study prospectively examined the relationship between a weak SOC and the incidence of diabetes. Methods: The relationship between a weak SOC and the incidence of diabetes was investigated among 5827 Finnish male employees aged 18–65 at baseline (1986). SOC was measured by questionnaire survey at baseline. Data on prescription diabetes drugs from 1987 to 2004 were obtained from the Drug Imbursement Register held by the Social Insurance Institution. Results: During the follow-up, 313 cases of diabetes were recorded. A weak SOC was associated with a 46% higher risk of diabetes in participants who had been =<50 years of age on entry into the study. This association was independent of age, education, marital status, psychological distress, self-rated health, smoking status, binge drinking and physical activity. No similar association was observed in older employees. Conclusion: The results suggest that besides focusing on well-known risk factors for diabetes, strengthening SOC in employees of =<50 years of age can also play a role in attempts to tackle increasing rates of diabetes.