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Publicações

2017

A diffusion-based connectivity map of the GPi for optimised stereotactic targeting in DBS

Autores
da Silva, NM; Ahmadi, SA; Tafula, SN; Silva Cunha, JPS; Botzel, K; Vollmar, C; Rozanski, VE;

Publicação
NEUROIMAGE

Abstract
Background: The GPi (globus pallidus internus) is an important target nucleus for Deep Brain Stimulation (DBS) in medically refractory movement disorders, in particular dystonia and Parkinson's disease. Beneficial clinical outcome critically depends on precise electrode localization. Recent evidence indicates that not only neurons, but also axonal fibre tracts contribute to promoting the clinical effect. Thus, stereotactic planning should, in the future, also take the individual course of fibre tracts into account. Objective: The aim of this project is to explore the GPi connectivity profile and provide a connectivity based parcellation of the GPi. Methods: Diffusion MRI sequences were performed in sixteen healthy, right-handed subjects. Connectivity-based parcellation of the GPi was performed applying two independent methods: 1) a hypothesis-driven, seed-to-target approach based on anatomic priors set as connectivity targets and 2) a purely data-driven approach based on k-means clustering of the GPi. Results: Applying the hypothesis-driven approach, we obtained five major parcellation clusters, displaying connectivity to the prefrontal cortex, the brainstem, the GPe (globus pallidus externus), the putamen and the thalamus. Parcellation clusters obtained by both methods were similar in their connectivity profile. With the data-driven approach, we obtained three major parcellation clusters. Inter individual variability was comparable with results obtained in thalamic parcellation. Conclusion: The three parcellation clusters obtained by the purely data-driven method might reflect GPi subdivision into a sensorimotor, associative and limbic portion. Clinical and physiological studies indicate greatest clinical DBS benefit for electrodes placed in the postero-ventro-lateral GPi, the region displaying connectivity to the thalamus in our study and generally attributed to the sensorimotor system. Clinical studies relating DBS electrode positions to our GPi connectivity map would be needed to complement our findings.

2017

Segmentation of the Rectus Abdominis Muscle Anterior Fascia for the Analysis of Deep Inferior Epigastric Perforators

Autores
Araujo, RJ; Oliveira, HP;

Publicação
PATTERN RECOGNITION AND IMAGE ANALYSIS (IBPRIA 2017)

Abstract
The segmentation of the anterior fascia of the rectus abdominis muscle is an important step towards the analysis of abdominal vasculature. It may advance Computer Aided Detection tools that support the activity of clinicians who study vessels for breast reconstruction using the Deep Inferior Epigastric Perforator flap. In this paper, we propose a two-fold methodology to detect the anterior fascia in Computerized Tomographic Angiography volumes. First, a slice-wise thresholding is applied and followed by a post-processing phase. Finally, an interpolation framework is used to obtain a final smooth fascia detection. We evaluated our method in 20 different volumes, by calculating the mean Euclidean distance to manual annotations, achieving subvoxel error.

2017

Optimal epidemic dissemination

Autores
Mercier, H; Hayez, L; Matos, M;

Publicação
CoRR

Abstract

2017

CAPACITY INVESTMENT ON ELECTRICITY MARKETS UNDER SUPPLY AND DEMAND UNCERTAINTY: AN OVERVIEW

Autores
Pinho, J; Resende, J; Soares, I;

Publicação
PROCEEDINGS OF THE 3RD INTERNATIONAL CONFERENCE ON ENERGY AND ENVIRONMENT (ICEE 2017)

Abstract
In the last decades, the weight of renewable energies sources (RES) in the electricity generation mix of most European countries has considerably increased. The implementation of these policies has been relying on different supporting schemes such as: the existence of a price premium for RES (feed-in tariffs); the assignment of priority access to renewable sources over conventional sources when entering the electricity network; and subsidizing investments in RE. While these incentives have certainly played a very important role in launching renewable energy production in Europe, more recently, both scholars and practitioners are claiming that RE generation should now be exposed to market incentives in order to promote economic efficiency. However, the inclusion of RE in the market may significantly affect equilibrium outcomes arising in electricity wholesale markets. Recent empirical studies, e.g. Puller (2007), point that the inclusion of RES in the market reduces average electricity prices at the cost of increasing price volatility (merit of order effect). Such outcomes can be explained by the intermittent nature of RES together with the asymmetry on generation marginal costs between RES and non-renewable energy sources (with the former being quite low for most of the available RES). However, the inclusion of RES in the wholesale electricity market may also yield strategic effects, as firms may strategically manipulate renewable energy production in order to have greater market power. In this paper, we provide an overview of the investment challenges following the introduction of market-based mechanisms for renewable production. The next step of this research project will be the development of a theoretical model, building on Milstein and Tishler (2011) in order to address the regulatory challenges related to capacity investment in a market with uncertain demand in which two firms offer two different electricity generation technologies, respectively using renewable and non-renewable energy sources. The renewable energy production is assumed to have an intermittent nature.

2017

Prediction of Breast Deformities: A Step Forward for Planning Aesthetic Results After Breast Surgery

Autores
Bessa, S; Zolfagharnasab, H; Pereira, E; Oliveira, HP;

Publicação
PATTERN RECOGNITION AND IMAGE ANALYSIS (IBPRIA 2017)

Abstract
The development of a three-dimensional (3D) planing tool for breast cancer surgery requires the existence of proper deformable models of the breast, with parameters that can be manipulated to obtain the desired shape. However, modelling breast is a challenging task due to the lack of physical landmarks that remain unchanged after deformation. In this paper, the fitting of a 3D point cloud of the breast to a parametric model suitable for surgery planning is investigated. Regression techniques were used to learn breast deformation functions from exemplar data, resulting in comprehensive models easy to manipulate by surgeons. New breast shapes are modelled by varying the type and degree of deformation of three common deformations: ptosis, turn and top-shape.

2017

Source code transformations and optimizations

Autores
Cardoso, JM; Coutinho, JGF; Diniz, PC;

Publicação
Embedded Computing for High Performance

Abstract

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