Métodos de segmentação para modelação 3D do ouvido a partir de imagens

O objectivo principal deste artigo centra-se na apresentação de métodos de segmentação de imagem adequados para a construção de modelos geométricos 3D das estruturas do ouvido a partir de imagens médicas de Tomografia Computorizada (TC), sendo discutidas as vantagens e desvantagens de cada um. Os métodos são classificados de acordo com as técnicas utilizadas; nomeadamente, em métodos de thresholding, de clustering e de modelos deformáveis. Neste artigo, são também apresentados e discutidos resultados experimentais de segmentação das estruturas do ouvido em imagens de TC

3D models of pelvic floor muscles developed by manual segmentation to FEM

The female pelvic floor is an understudied region of the body from the biomechanical perspective. MRI has been used in the diagnostic evaluation of the pelvic floor dysfunctions. Static images show their morphology while dynamic images show the functional changes that occur on straining and contraction of the pelvic floor. In the present work, MR images contribute to generate 3D solids of pelvic floor muscles through manual segmentation. To study the biomechanical behavior of pelvic floor muscles the Finite Element Method (FEM) would be applied to these 3D solids, contributing to analyze this complex musculature structure. The purpose of this study was to reconstruct tridimensional pelvic floor muscle by manual segmentation and apply FEM. The manual segmentation was made within commercial software. MR images were acquired from the subject supine position, using a 3.0 T system. Field view of the exam was 25×25 cm, 2 mm thick with no gap. The images were acquired in DICOM format, and later converted jpeg format. Twenty consecutive images obtained in the axial plane for each woman were used to construct a 3D model from each of the 8 women. From this 3D reconstruction made through splines in each image, changes in the pubovisceral muscle (a part from the pelvic floor muscles) from the pubis to coccyx were edited. All the pubovisceral muscles edited were exported in step format to the FE analyses software ABAQUS. Finite element meshes were generated for each woman pubovisceral muscle. According to literature soft tissues properties, FE analyses were established to better understand pelvic floor muscles biomechanics. Manual segmentation of the pelvic floor muscles tissues generated very realistic completely different volumetric solids for each woman. It is a very sluggish technique and the nonlinear shape of the pelvic floor makes difficult the utilization of other automatic segmentation

Top quark forward-backward asymmetry in R-parity violating supersymmetry

The interaction of bottom squark-mediated top quark pair production, occurring in the R-parity violating minimal supersymmetric standard model (MSSM), is proposed as an explanation of the anomalously large $t\bar{t}$ forward-backward asymmetry (FBA) observed at the Tevatron. We find that this model can give a good fit to top quark data, both the inclusive and invariant mass-dependent asymmetries, while remaining consistent (at the 2-$\sigma$ level) with the total and differential production cross-sections. The scenario is challenged by strong constraints from atomic parity violation (APV), but we point out an extra diagram for the effective down quark-Z vertex, involving the same coupling constant as required for the FBA, which tends to weaken the APV constraint, and which can nullify it for reasonable values of the top squark masses and mixing angle. Large contributions to flavor-changing neutral currents can be avoided if only the third generation of sparticles is light.Comment: 24 pages, 7 figures. v3: included LHC top production cross section data; model still consistent at 2 sigma leve

An initial psychometric evaluation and exploratory cross-sectional study of the Body Checking Questionnaire among Brazilian women

Body checking is considered an expression of an excessive preoccupation with appearance. The first aim of this study was to evaluate the psychometric properties of a Brazilian Portuguese version of the Body Checking Questionnaire (BCQ). Additionally, we wanted to examine the questionnaire’s associations with body avoidance behaviour, body mass index, dietary habits, and the intensity, frequency, and length of physical exercise. Finally, we also examined the differences between the total BCQ score and the individual BCQ factor scores. Differences between active and sedentary persons and between non-dieters and those on weight-loss diets were also analyzed. For the psychometric study, 546 female public university students from four different courses were surveyed. Two minor samples of university students and eating disorders women were also recruited. In the second part of the study, 403 women were recruited from weight-loss programs, gyms, and a university. All participants were verbally invited to participate in the research and voluntarily took part. Confirmatory factor analysis showed a good fit to the original model of the Brazilian BCQ that retained all 23 items. Satisfactory evidence of construct validity and internal consistency were also generated through analysis of factor loadings, t-values, Cronbach’s alpha, and construct reliability tests. The results also showed associations among body checking and body avoidance, body satisfaction, social anxiety, body mass index, and the frequency and intensity of physical exercise. Significant differences were found between non-dieters and weight-loss dieters for all BCQ factors and the total BCQ score. For physically active and sedentary persons, a significant difference was only observed for idiosyncratic checking behaviour. In conclusion, the BCQ appears to be a valid and reliable scale for Brazilian research, and the associations and differences found in this study suggest that women at gyms and especially in weight-loss programs should be targeted for future body checking studies

Analysis of ground reaction force and electromyographic activity of the gastrocnemius muscle during double support

O documento em anexo encontra-se na versão post-print (versão corrigida pelo editor).Purpose: Mechanisms associated with energy expenditure during gait have been extensively researched and studied. According to the double-inverted pendulum model energy expenditure is higher during double support, as lower limbs need to work to redirect the centre of mass velocity. This study looks into how the ground reaction force (GRF) of one limb affects the muscle activity required by the medial gastrocnemius (MG) of the contralateral limb during step-to-step transition. Methods: Thirty-five subjects were monitored as to the MG electromyographic activity (EMGa) of one limb and the GRF of the contralateral limb during double support. Results: After determination of the Pearson correlation coefficient (r), a moderate correlation was observed between the MG EMGa of the dominant leg and the vertical (Fz) and anteroposterior (Fy) components of GRF of the non-dominant leg (r=0.797, p<0.0001; r=-0.807, p<0.0001) and a weak and moderate correlation was observed between the MG EMGa of the non-dominant leg and the Fz and Fy of the dominant leg, respectively (r=0.442, p=0.018; r=-0.684 p<0.0001). Conclusions: The results obtained suggest that during double support, GRF is associated with the EMGa of the contralateral MG and that there is an increased dependence between the GRF of the non-dominant leg and the EMGa of the dominant MG

Hunting for the high-affinity state of G-protein coupled receptors with agonist tracers:Theoretical and practical considerations for positron emission tomography (PET) imaging

The concept of the high-affinity state postulates that a certain subset of G-protein-coupled receptors is primarily responsible for receptor signaling in the living brain. Assessing the abundance of this subset is thus potentially highly relevant for studies concerning the responses of neurotransmission to pharmacological or physiological stimuli, and the dysregulation of neurotransmission in neurological or psychiatric disorders. The high-affinity state is preferentially recognized by agonists in vitro. For this reason, agonist tracers have been developed as tools for the non-invasive imaging of the high-affinity state with positron emission tomography (PET). This review provides an overview of agonist tracers that have been developed for PET imaging of the brain, and the experimental paradigms that have been developed for the estimation of the relative abundance of receptors configured in the high-affinity state. Agonist tracers appear to be more sensitive to endogenous neurotransmitter challenge than antagonists, as was originally expected. However, other expectations regarding agonist tracers have not been fulfilled. Potential reasons for difficulties in detecting the high-affinity state in vivo are discussed