2016
Autores
Ramos, J; Kockelkorn, TTJP; Ramos, I; Ramos, R; Grutters, J; Viergever, MA; van Ginneken, B; Campilho, A;
Publicação
IEEE JOURNAL OF BIOMEDICAL AND HEALTH INFORMATICS
Abstract
Content-based image retrieval (CBIR) is a search technology that could aid medical diagnosis by retrieving and presenting earlier reported cases that are related to the one being diagnosed. To retrieve relevant cases, CBIR systems depend on supervised learning to map low-level image contents to high-level diagnostic concepts. However, the annotation by medical doctors for training and evaluation purposes is a difficult and time-consuming task, which restricts the supervised learning phase to specific CBIR problems of well-defined clinical applications. This paper proposes a new technique that automatically learns the similarity between the several exams from textual distances extracted from radiology reports, thereby successfully reducing the number of annotations needed. Our method first infers the relation between patients by using information retrieval techniques to determine the textual distances between patient radiology reports. These distances are subsequently used to supervise a metric learning algorithm, that transforms the image space accordingly to textual distances. CBIR systems with different image descriptions and different levels of medical annotations were evaluated, with and without supervision from textual distances, using a database of computer tomography scans of patients with interstitial lung diseases. The proposed method consistently improves CBIR mean average precision, with improvements that can reach 38%, and more marked gains for small annotation sets. Given the overall availability of radiology reports in picture archiving and communication systems, the proposed approach can be broadly applied to CBIR systems in different medical problems, and may facilitate the introduction of CBIR in clinical practice.
2016
Autores
Cordeiro, M; Sarmento, RP; Gama, J;
Publicação
SOCIAL NETWORK ANALYSIS AND MINING
Abstract
The amount and the variety of data generated by today's online social and telecommunication network services are changing the way researchers analyze social networks. Facing fast evolving networks with millions of nodes and edges are, among other factors, its main challenge. Community detection algorithms in these conditions have also to be updated or improved. Previous state-of-the-art algorithms based on the modularity optimization (i.e. Louvain algorithm), provide fast, efficient and robust community detection on large static networks. Nonetheless, due to the high computing complexity of these algorithms, the use of batch techniques in dynamic networks requires to perform network community detection for the whole network in each one of the evolution steps. This fact reveals to be computationally expensive and unstable in terms of tracking of communities. Our contribution is a novel technique that maintains the community structure always up-to-date following the addition or removal of nodes and edges. The proposed algorithm performs a local modularity optimization that maximizes the modularity gain function only for those communities where the editing of nodes and edges was performed, keeping the rest of the network unchanged. The effectiveness of our algorithm is demonstrated with the comparison to other state-of-the-art community detection algorithms with respect to Newman's Modularity, Modularity with Split Penalty, Modularity Density, number of detected communities and running time.
2016
Autores
Bitencort, B; Moraes, R; Portugal, P; Vasques, F;
Publicação
2016 IEEE 14TH INTERNATIONAL CONFERENCE ON INDUSTRIAL INFORMATICS (INDIN)
Abstract
The LLDN (Low Latency Deterministic Network) mode is a IEEE 802.15.4e amendment specifically designed for industrial applications requiring low latency and low loss rate. It is based on a static TDMA scheme composed of fixed-size slots. One of its limitations regards the support of messages with different sizes and different periodicities. In this paper, a slot allocation scheme is proposed, enabling the support of heterogeneous message streams. The rationale is to compute a suitable timeslot size to communication devices, enabling adaptive control of the superframe without changing the LLDN standard. This paper shows that it is possible to accommodate heterogeneous message streams while maintaining low cycle times when transmitting messages with variable payload.
2016
Autores
Abreu, MH; Abreu, PH; Afonso, N; Pereira, D; Henrique, R; Lopes, C;
Publicação
INTERNATIONAL JOURNAL OF CANCER
Abstract
Male breast cancer (MBC) patients seem to have inferior survival compared to female (FBC) ones, which is not fully explained by usual prognostic factors. Recurrence analysis could show differences in relapse patterns and/or in patients' approaches that justify these outcomes. Retrospective analysis of MBC patients treated in a cancer center between 1990 and 2014, looking for relapse. For each patient, three matched FBC patients were selected by: diagnosis' year, age (within 5 years), stage and tumors' type (only luminal-like were considered). Differences between cohorts were assessed by chi(2) test and hierarchical clustering was performed to define subgroups according to relapse local. Survival curves were calculated by Kaplan-Meier and compared using log-rank test. Statistical significance was defined as p < 0.05. Groups were balanced according to age, histological grade, stage, expression of hormonal receptors and adjuvant treatments. Median time to recurrence was equivalent, p = 0.72, with the majority of patients presented with distant metastases, p = 0.69, with more lung involvement in male, p =0.003. Male patients were more often proposed to symptomatic treatment (21.1% vs. 4.4%, p = 0.02). Overall and from recurrence survivals were poorer for male, median: 5 years [95% confidence interval (CI): 4.1-5.9 years] and 1 year (95% CI: 0-2.1 years) vs. 10 years (95% CI: 7.8-12.2 years) and 2 years (95% CI: 1.6-2.4 years), p < 0.001 and p = 0.004, respectively, and this tendency remained in the five cluster subgroups, that identified five patterns of relapse, p = 0.003. MBC patients had the worst survival, even after controlling important factors, namely the local of relapse. Palliative systemic treatment had favorable impact in prognosis and its frequently avoidance in male could justify the outcomes differences.
2016
Autores
Almeida, V; Gama, J;
Publicação
PROCEEDINGS OF THE 9TH INTERNATIONAL CONFERENCE ON COMPUTER RECOGNITION SYSTEMS, CORES 2015
Abstract
In this paper we propose a new methodology for evaluating prediction intervals (PIs). Typically, PIs are evaluated with reference to confidence values. However, other metrics should be considered, since high values are associated to too wide intervals that convey little information and are of no use for decision-making. We propose to compare the error distribution (predictions out of the interval) and the maximum mean absolute error (MAE) allowed by the confidence limits. Along this paper PIs based on neural networks for short-term load forecast are compared using two different strategies: (1) dual perturb and combine (DPC) algorithm and (2) conformal prediction. We demonstrated that depending on the real scenario (e.g., time of day) different algorithms perform better. The main contribution is the identification of high uncertainty levels in forecast that can guide the decision-makers to avoid the selection of risky actions under uncertain conditions. Small errors mean that decisions can be made more confidently with less chance of confronting a future unexpected condition.
2016
Autores
Alves, R; Souto, T; Escudeiro, P; Escudeiro, N;
Publicação
SERIOUS GAMES, INTERACTION, AND SIMULATION, SGAMES 2015
Abstract
One of the major challenges for healthcare professionals in the XXI century is the increasing number of elderly in the world population. It is clearly important to find ways to stimulate cognitively this population, helping them to develop strategies and maintaining independency in their daily life activities. Conventional cognitive stimulation is time consuming task often causing discomfort in patients. Computer based tools may be used to perform cognitive stimulation and improve transferability in a setting that does not increase anxiety in individuals. This paper aims to present a pilot study of automatic platforms to enhance the cognitive process for older adults in order to promote an active aging.
The access to the final selection minute is only available to applicants.
Please check the confirmation e-mail of your application to obtain the access code.