870 resultados para Semi-supervised segmentation
Resumo:
Application of semi-distributed hydrological models to large, heterogeneous watersheds deals with several problems. On one hand, the spatial and temporal variability in catchment features should be adequately represented in the model parameterization, while maintaining the model complexity in an acceptable level to take advantage of state-of-the-art calibration techniques. On the other hand, model complexity enhances uncertainty in adjusted model parameter values, therefore increasing uncertainty in the water routing across the watershed. This is critical for water quality applications, where not only streamflow, but also a reliable estimation of the surface versus subsurface contributions to the runoff is needed. In this study, we show how a regularized inversion procedure combined with a multiobjective function calibration strategy successfully solves the parameterization of a complex application of a water quality-oriented hydrological model. The final value of several optimized parameters showed significant and consistentdifferences across geological and landscape features. Although the number of optimized parameters was significantly increased by the spatial and temporal discretization of adjustable parameters, the uncertainty in water routing results remained at reasonable values. In addition, a stepwise numerical analysis showed that the effects on calibration performance due to inclusion of different data types in the objective function could be inextricably linked. Thus caution should be taken when adding or removing data from an aggregated objective function.
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Conjunctival nevi are lesions observed commonly occasionnally and can be found later in a life. Such a lesion was observed on the conjunctival semilunar fold in a 76-year-old female patient. It was oval in shape, pigmented, and was mainly visible when the affected eye was in abduction. As no accurate anterior clinical history was available, surgical resection was performed. Hitopathological study disclosed a subepithelial nevus, which was completely resected. Regular follow-up was recommended, as is usual after surgical resection of a conjunctival pigmented tumor.
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We present MBIS (Multivariate Bayesian Image Segmentation tool), a clustering tool based on the mixture of multivariate normal distributions model. MBIS supports multichannel bias field correction based on a B-spline model. A second methodological novelty is the inclusion of graph-cuts optimization for the stationary anisotropic hidden Markov random field model. Along with MBIS, we release an evaluation framework that contains three different experiments on multi-site data. We first validate the accuracy of segmentation and the estimated bias field for each channel. MBIS outperforms a widely used segmentation tool in a cross-comparison evaluation. The second experiment demonstrates the robustness of results on atlas-free segmentation of two image sets from scan-rescan protocols on 21 healthy subjects. Multivariate segmentation is more replicable than the monospectral counterpart on T1-weighted images. Finally, we provide a third experiment to illustrate how MBIS can be used in a large-scale study of tissue volume change with increasing age in 584 healthy subjects. This last result is meaningful as multivariate segmentation performs robustly without the need for prior knowledge.
Resumo:
BACKGROUND: Supervised injection services (SISs) have been developed to promote safer drug injection practices, enhance health-related behaviors among people who inject drugs (PWID), and connect PWID with external health and social services. Nevertheless, SISs have also been accused of fostering drug use and drug trafficking. AIMS: To systematically collect and synthesize the currently available evidence regarding SIS-induced benefits and harm. METHODS: A systematic review was performed via the PubMed, Web of Science, and ScienceDirect databases using the keyword algorithm [("supervised" or "safer") and ("injection" or "injecting" or "shooting" or "consumption") and ("facility" or "facilities" or "room" or "gallery" or "centre" or "site")]. RESULTS: Seventy-five relevant articles were found. All studies converged to find that SISs were efficacious in attracting the most marginalized PWID, promoting safer injection conditions, enhancing access to primary health care, and reducing the overdose frequency. SISs were not found to increase drug injecting, drug trafficking or crime in the surrounding environments. SISs were found to be associated with reduced levels of public drug injections and dropped syringes. Of the articles, 85% originated from Vancouver or Sydney. CONCLUSION: SISs have largely fulfilled their initial objectives without enhancing drug use or drug trafficking. Almost all of the studies found in this review were performed in Canada or Australia, whereas the majority of SISs are located in Europe. The implementation of new SISs in places with high rates of injection drug use and associated harms appears to be supported by evidence.
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This paper presents automated segmentation of structuresin the Head and Neck (H\&N) region, using an activecontour-based joint registration and segmentation model.A new atlas selection strategy is also used. Segmentationis performed based on the dense deformation fieldcomputed from the registration of selected structures inthe atlas image that have distinct boundaries, onto thepatient's image. This approach results in robustsegmentation of the structures of interest, even in thepresence of tumors, or anatomical differences between theatlas and the patient image. For each patient, an atlasimage is selected from the available atlas-database,based on the similarity metric value, computed afterperforming an affine registration between each image inthe atlas-database and the patient's image. Unlike manyof the previous approaches in the literature, thesimilarity metric is not computed over the entire imageregion; rather, it is computed only in the regions ofsoft tissue structures to be segmented. Qualitative andquantitative evaluation of the results is presented.
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O estudo teve como objetivo avaliar um modelo físico do sistema de cria de bovinos para as áreas mais secas do Semi-Árido brasileiro, associando a pastagem natural com pastos cultivados tolerantes à seca. A caatinga foi pastejada no período verde, e o capim buffel no restante do ano. A suplementação com leucena ocorreu no período seco, sob pastejo direto e feno no cocho. Parâmetros de desempenho, monitorados de novembro de 1991 a outubro de 1995, mostraram uma taxa média de parição da ordem de 72,8% ao ano e taxas de mortalidade praticamente nulas. O peso vivo médio dos bezerros aos 205 dias de idade foi de 153,4 kg e a produ- ção de bezerros desmamados foi de 109,5 kg/matriz exposta/ano e de 25,5 kg/hectare/ano. Os resultados são considerados bastante expressivos, considerando-se que mais da metade da área era ocupada com pastagens nativas de caatinga e que a oferta de leucena foi limitada pela ocorrência de uma forte estiagem.
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In recent grammars and dictionaries also (`therefore, so, well¿) continues to be preferably presented as an adverb with a conclusive-consecutive connective function that essentially corresponds to its use in formal written German. Its function as a modal particle is documented, however, since the beginnings of what is known as Partikelforschung, though not all its uses have been systematically investigated contrasting oral and written German, either in mode or concept. In this article we analyse the uses of also in semi-informal oral interactions on the basis of empirical data (from a subsample of the VARCOM corpus). Specifically, we will analyse the presence and frequency of also at the beginning of a sentence or sequence, the functions it serves as a logical-semantic connector or discourse and interaction marker and the interrelations between these functions, in order to contrast these results with the description of also provided by current reference works.
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Foi realizado um experimento para avaliar a influência da suplementação alimentar na produção de leite de cabras da raça Anglo-nubiana, durante a época chuvosa, na região semi-árida do Nordeste brasileiro. Vinte e quatro cabras foram mantidas em pastagem nativa rebaixada, distribuídas ao acaso, por tipo de parto e produção de leite, em três níveis de suplementação: N0 - sem suplementação, N1 -150 g de concentrado/animal/dia e N2 - 300 g de concentrado/animal/dia. Não houve diferença significativa (p>0,05) entre os níveis de suplementação. A produção de leite foi descrita por uma regressão múltipla em função do período de lactação em semana. A interação semana x níveis de suplementação foi significativa (p<0,01). Os resultados revelam que a suplementação com concentrado, na dose de 300 g/animal/dia, foi a melhor opção para se produzir leite com cabras Anglo-nubianas, durante a época chuvosa.
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In this paper, we present the segmentation of the headand neck lymph node regions using a new active contourbased atlas registration model. We propose to segment thelymph node regions without directly including them in theatlas registration process; instead, they are segmentedusing the dense deformation field computed from theregistration of the atlas structures with distinctboundaries. This approach results in robust and accuratesegmentation of the lymph node regions even in thepresence of significant anatomical variations between theatlas-image and the patient's image to be segmented. Wealso present a quantitative evaluation of lymph noderegions segmentation using various statistical as well asgeometrical metrics: sensitivity, specificity, dicesimilarity coefficient and Hausdorff distance. Acomparison of the proposed method with two other state ofthe art methods is presented. The robustness of theproposed method to the atlas selection, in segmenting thelymph node regions, is also evaluated.
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For radiotherapy treatment planning of retinoblastoma inchildhood, Computed Tomography (CT) represents thestandard method for tumor volume delineation, despitesome inherent limitations. CT scan is very useful inproviding information on physical density for dosecalculation and morphological volumetric information butpresents a low sensitivity in assessing the tumorviability. On the other hand, 3D ultrasound (US) allows ahigh accurate definition of the tumor volume thanks toits high spatial resolution but it is not currentlyintegrated in the treatment planning but used only fordiagnosis and follow-up. Our ultimate goal is anautomatic segmentation of gross tumor volume (GTV) in the3D US, the segmentation of the organs at risk (OAR) inthe CT and the registration of both. In this paper, wepresent some preliminary results in this direction. Wepresent 3D active contour-based segmentation of the eyeball and the lens in CT images; the presented approachincorporates the prior knowledge of the anatomy by usinga 3D geometrical eye model. The automated segmentationresults are validated by comparing with manualsegmentations. Then, for the fusion of 3D CT and USimages, we present two approaches: (i) landmark-basedtransformation, and (ii) object-based transformation thatmakes use of eye ball contour information on CT and USimages.
Resumo:
Realizou-se um experimento, usando solo álico da Zona da Mata e do Semi-Árido do Estado de Pernambuco, com o objetivo de avaliar o efeito da calagem (0, 3 e 6 t ha-1) e da inoculação das estirpes de rizóbio: NFB 539, NFB 577 e NFB 578, previamente selecionadas para sabiá (Mimosa caesalpiniaefolia) em meio de cultura ácido. Adicionaram-se tratamentos sem inoculação, sem e com adição de N mineral (100 kg ha-1), para fins comparativos. O experimento seguiu o esquema fatorial 2x3x5, no delineamento em blocos ao acaso, com quatro repetições. As plantas foram colhidas 110 dias após a emergência (DAE). A inoculação de rizóbio, em todos os níveis de calagem, mostrou efeito significativo nos parâmetros avaliados. No nível de 3 t ha-1 não houve efeito da calagem, porém a adição de 6 t ha-1 de calcário reduziu o peso de matéria seca, o N total na parte aérea, a nodulação e a atividade da nitrogenase. O baixo pH e Al3+ do solo não prejudicou a fixação do N2, e o crescimento das plantas que receberam o inóculo. Portanto, torna-se desnecessária a calagem no cultivo de sabiá em solos ácidos, quando usadas estirpes selecionadas visando à resistência a acidez.
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O crescimento de Eucalyptus é favorecido por fungos ectomicorrízicos (FECM). De ocorrência comum nas plantações florestais, os FECM diferem, entretanto, em infectividade e eficiência. O objetivo deste estudo foi testar a compatibilidade e a eficiência do inoculante ectomicorrízico produzido por fermentação semi-sólida, em relação a Eucalyptus dunnii Maiden. Neste sentido, o inoculante de Pisolithus sp., produzido por fermentação semi-sólida em vermiculita-solução nutritiva, foi aplicado ao substrato turfa-vermiculita (30:70, v/v) nas concentrações de 0, 1, 3, 5 e 10% (v/v) que foi semeado com E. dunnii, e mantido em casa de vegetação. A inoculação proporcionou colonização radicular e aumento da matéria seca da parte aérea e do conteúdo de P em razão da concentração do inoculante. O peso da matéria seca das plantas com 1% de inoculante não diferiu do peso das testemunhas. A 3% e 5%, a matéria seca aumentou 62%. O maior valor foi obtido com 10% de inoculante, onde o peso das plantas foi 73% superior ao das testemunhas, e o teor de P, 130%. Resultados semelhantes foram obtidos em relação à raiz. Altura e diâmetro foram positivamente afetados pela inoculação, mas não a relação raiz/parte aérea. As doses mais eficientes de inoculante foram aquelas de 3% ou superiores. Este método de produção deverá ser testado com outros FECM, e sua eficiência, avaliada em viveiro e no campo.
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We propose to evaluate automatic three-dimensional gray-value rigid registration (RR) methods for prostate localization on cone-beam computed tomography (CBCT) scans. In total, 103 CBCT scans of 9 prostate patients have been analyzed. Each one was registered to the planning CT scan using different methods: (a) global RR, (b) pelvis bone structure RR, (c) bone RR refined by local soft-tissue RR using the CT clinical target volume (CTV) expanded with a 1, 3, 5, 8, 10, 12, 15 or 20-mm margin. To evaluate results, a radiation oncologist was asked to manually delineate the CTV on the CBCT scans. The Dice coefficients between each automatic CBCT segmentation - derived from the transformation of the manual CT segmentation - and the manual CBCT segmentation were calculated. Global or bone CT/CBCT RR has been shown to yield insufficient results in average. Local RR with an 8-mm margin around the CTV after bone RR was found to be the best candidate for systematically significantly improving prostate localization.