Automatic discrimination between safe and unsafe swallowing using a reputation-based classifier

<p>Abstract</p> <p>Background</p> <p>Swallowing accelerometry has been suggested as a potential non-invasive tool for bedside dysphagia screening. Various vibratory signal features and complementary measurement modalities have been put forth in the literature for the potential discrimination between safe and unsafe swallowing. To date, automatic classification of swallowing accelerometry has exclusively involved a single-axis of vibration although a second axis is known to contain additional information about the nature of the swallow. Furthermore, the only published attempt at automatic classification in adult patients has been based on a small sample of swallowing vibrations.</p> <p>Methods</p> <p>In this paper, a large corpus of dual-axis accelerometric signals were collected from 30 older adults (aged 65.47 ± 13.4 years, 15 male) referred to videofluoroscopic examination on the suspicion of dysphagia. We invoked a reputation-based classifier combination to automatically categorize the dual-axis accelerometric signals into safe and unsafe swallows, as labeled via videofluoroscopic review. From these participants, a total of 224 swallowing samples were obtained, 164 of which were labeled as unsafe swallows (swallows where the bolus entered the airway) and 60 as safe swallows. Three separate support vector machine (SVM) classifiers and eight different features were selected for classification.</p> <p>Results</p> <p>With selected time, frequency and information theoretic features, the reputation-based algorithm distinguished between safe and unsafe swallowing with promising accuracy (80.48 ± 5.0%), high sensitivity (97.1 ± 2%) and modest specificity (64 ± 8.8%). Interpretation of the most discriminatory features revealed that in general, unsafe swallows had lower mean vibration amplitude and faster autocorrelation decay, suggestive of decreased hyoid excursion and compromised coordination, respectively. Further, owing to its performance-based weighting of component classifiers, the static reputation-based algorithm outperformed the democratic majority voting algorithm on this clinical data set.</p> <p>Conclusion</p> <p>Given its computational efficiency and high sensitivity, reputation-based classification of dual-axis accelerometry ought to be considered in future developments of a point-of-care swallow assessment where clinical informatics are desired.</p

A radial basis classifier for the automatic detection of aspiration in children with dysphagia

BACKGROUND: Silent aspiration or the inhalation of foodstuffs without overt physiological signs presents a serious health issue for children with dysphagia. To date, there are no reliable means of detecting aspiration in the home or community. An assistive technology that performs in these environments could inform caregivers of adverse events and potentially reduce the morbidity and anxiety of the feeding experience for the child and caregiver, respectively. This paper proposes a classifier for automatic classification of aspiration and swallow vibration signals non-invasively recorded on the neck of children with dysphagia. METHODS: Vibration signals associated with safe swallows and aspirations, both identified via videofluoroscopy, were collected from over 100 children with neurologically-based dysphagia using a single-axis accelerometer. Five potentially discriminatory mathematical features were extracted from the accelerometry signals. All possible combinations of the five features were investigated in the design of radial basis function classifiers. Performance of different classifiers was compared and the best feature sets were identified. RESULTS: Optimal feature combinations for two, three and four features resulted in statistically comparable adjusted accuracies with a radial basis classifier. In particular, the feature pairing of dispersion ratio and normality achieved an adjusted accuracy of 79.8 ± 7.3%, a sensitivity of 79.4 ± 11.7% and specificity of 80.3 ± 12.8% for aspiration detection. Addition of a third feature, namely energy, increased adjusted accuracy to 81.3 ± 8.5% but the change was not statistically significant. A closer look at normality and dispersion ratio features suggest leptokurticity and the frequency and magnitude of atypical values as distinguishing characteristics between swallows and aspirations. The achieved accuracies are 30% higher than those reported for bedside cervical auscultation. CONCLUSION: The proposed aspiration classification algorithm provides promising accuracy for aspiration detection in children. The classifier is conducive to hardware implementation as a non-invasive, portable "aspirometer". Future research should focus on further enhancement of accuracy rates by considering other signal features, classifier methods, or an augmented variety of training samples. The present study is an important first step towards the eventual development of wearable intelligent intervention systems for the diagnosis and management of aspiration

Gene Expression Based Leukemia Sub-Classification Using Committee Neural Networks

Analysis of gene expression data provides an objective and efficient technique for sub-classification of leukemia. The purpose of the present study was to design a committee neural networks based classification systems to subcategorize leukemia gene expression data. In the study, a binary classification system was considered to differentiate acute lymphoblastic leukemia from acute myeloid leukemia. A ternary classification system which classifies leukemia expression data into three subclasses including B-cell acute lymphoblastic leukemia, T-cell acute lymphoblastic leukemia and acute myeloid leukemia was also developed. In each classification system gene expression profiles of leukemia patients were first subjected to a sequence of simple preprocessing steps. This resulted in filtering out approximately 95 percent of the non-informative genes. The remaining 5 percent of the informative genes were used to train a set of artificial neural networks with different parameters and architectures. The networks that gave the best results during initial testing were recruited into a committee. The committee decision was by majority voting. The committee neural network system was later evaluated using data not used in training. The binary classification system classified microarray gene expression profiles into two categories with 100 percent accuracy and the ternary system correctly predicted the three subclasses of leukemia in over 97 percent of the cases

Facial expression (mood) recognition from facial images using committee neural networks

<p>Abstract</p> <p>Background</p> <p>Facial expressions are important in facilitating human communication and interactions. Also, they are used as an important tool in behavioural studies and in medical rehabilitation. Facial image based mood detection techniques may provide a fast and practical approach for non-invasive mood detection. The purpose of the present study was to develop an intelligent system for facial image based expression classification using committee neural networks.</p> <p>Methods</p> <p>Several facial parameters were extracted from a facial image and were used to train several generalized and specialized neural networks. Based on initial testing, the best performing generalized and specialized neural networks were recruited into decision making committees which formed an integrated committee neural network system. The integrated committee neural network system was then evaluated using data obtained from subjects not used in training or in initial testing.</p> <p>Results and conclusion</p> <p>The system correctly identified the correct facial expression in 255 of the 282 images (90.43% of the cases), from 62 subjects not used in training or in initial testing. Committee neural networks offer a potential tool for image based mood detection.</p

Effects of liquid stimuli on dual-axis swallowing accelerometry signals in a healthy population

<p>Abstract</p> <p>Background</p> <p>Dual-axis swallowing accelerometry has recently been proposed as a tool for non-invasive analysis of swallowing function. Although swallowing is known to be physiologically modifiable by the type of food or liquid (i.e., stimuli), the effects of stimuli on dual-axis accelerometry signals have never been thoroughly investigated. Thus, the objective of this study was to investigate stimulus effects on dual-axis accelerometry signal characteristics. Signals were acquired from 17 healthy participants while swallowing 4 different stimuli: water, nectar-thick and honey-thick apple juices, and a thin-liquid barium suspension. Two swallowing tasks were examined: discrete and sequential. A variety of features were extracted in the time and time-frequency domains after swallow segmentation and pre-processing. A separate Friedman test was conducted for each feature and for each swallowing task.</p> <p>Results</p> <p>Significant main stimulus effects were found on 6 out of 30 features for the discrete task and on 5 out of 30 features for the sequential task. Analysis of the features with significant stimulus effects suggested that the changes in the signals revealed slower and more pronounced swallowing patterns with increasing bolus viscosity.</p> <p>Conclusions</p> <p>We conclude that stimulus type does affect specific characteristics of dual-axis swallowing accelerometry signals, suggesting that associated clinical screening protocols may need to be stimulus specific.</p

A Method for Removal of Low Frequency Components Associated with Head Movements from Dual-Axis Swallowing Accelerometry Signals

Head movements can greatly affect swallowing accelerometry signals. In this paper, we implement a spline-based approach to remove low frequency components associated with these motions. Our approach was tested using both synthetic and real data. Synthetic signals were used to perform a comparative analysis of the spline-based approach with other similar techniques. Real data, obtained data from 408 healthy participants during various swallowing tasks, was used to analyze the processing accuracy with and without the spline-based head motions removal scheme. Specifically, we analyzed the segmentation accuracy and the effects of the scheme on statistical properties of these signals, as measured by the scaling analysis. The results of the numerical analysis showed that the spline-based technique achieves a superior performance in comparison to other existing techniques. Additionally, when applied to real data, we improved the accuracy of the segmentation process by achieving a 27% drop in the number of false negatives and a 30% drop in the number of false positives. Furthermore, the anthropometric trends in the statistical properties of these signals remained unaltered as shown by the scaling analysis, but the strength of statistical persistence was significantly reduced. These results clearly indicate that any future medical devices based on swallowing accelerometry signals should remove head motions from these signals in order to increase segmentation accuracy

Neural network committees for finger joint angle estimation from surface EMG signals

<p>Abstract</p> <p>Background</p> <p>In virtual reality (VR) systems, the user's finger and hand positions are sensed and used to control the virtual environments. Direct biocontrol of VR environments using surface electromyography (SEMG) signals may be more synergistic and unconstraining to the user. The purpose of the present investigation was to develop a technique to predict the finger joint angle from the surface EMG measurements of the extensor muscle using neural network models.</p> <p>Methodology</p> <p>SEMG together with the actual joint angle measurements were obtained while the subject was performing flexion-extension rotation of the index finger at three speeds. Several neural networks were trained to predict the joint angle from the parameters extracted from the SEMG signals. The best networks were selected to form six committees. The neural network committees were evaluated using data from new subjects.</p> <p>Results</p> <p>There was hysteresis in the measured SMEG signals during the flexion-extension cycle. However, neural network committees were able to predict the joint angle with reasonable accuracy. RMS errors ranged from 0.085 ± 0.036 for fast speed finger-extension to 0.147 ± 0.026 for slow speed finger extension, and from 0.098 ± 0.023 for the fast speed finger flexion to 0.163 ± 0.054 for slow speed finger flexion.</p> <p>Conclusion</p> <p>Although hysteresis was observed in the measured SEMG signals, the committees of neural networks were able to predict the finger joint angle from SEMG signals.</p

Previsão e geração de sinais EMG de Parkison com redes neurais

Orientador: Esther Luna ColombiniDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de ComputaçãoResumo: A doença de Parkinson é uma desordem neurodegenerativa que afeta aproximadamente 2% da população mundial acima de 60 anos (7-10 milhões de pessoas), e é caracterizada por sintomas como tremor em repouso e em movimento, que podem causar graves restrições na vida dos pacientes e também estão associados a sintomas não motores como dificuldade para dormir, depressão e fadiga. Apenas no Brasil, existem mais de 200.000 pessoas diagnosticadas com doença de Parkinson, número que pode duplicar até 2030 devido ao envelhecimento da população brasileira. Neste contexto, o desenvolvimento de novos tratamentos e formas de assistência que possam melhorar a qualidade de vida e a autonomia de pacientes é extremamente importante. Neste trabalho, são propostas novas técnicas baseadas em Redes Neurais para a previsão e geração de sinais de eletromiografia (EMG) do tremor em pacientes, para o suporte ao desenvolvimento de novos dispositivos e técnicas para assistência a pacientes. Primeiro, comparamos diferentes modelos de Redes Neuras, utilizando perceptron multicamadas (MLP) e redes neurais recorrentes (RNN) para a previsão dos sinais EMG de doença de Parkinson, antecipando os padrões de tremor em repouso. Os resultados experimentais indicam que os modelos propostos adaptam-se aos padrões específicos de cada paciente, gerando previsões acuradas para os sinais puros ou envelopes EMG. Segundo, são propostos duas novas técnicas para aumento de dados baseadas em redes adversárias generativas convolucionais profundas (DCGANs) e transferência de estilo (ST) para aumentar sinais EMG, cujos resultados mostram que os modelos propostos conseguem adaptar-se aos diferentes formatos, frequências e amplitudes de tremor, simulando os padrões específicos de cada paciente e estendendo as bases de dados existentes para diferentes protocolos de movimento. Ambos resultados sugerem que o emprego de redes neurais na geração e previsão de sinais biológicos complexos como sinais EMG pode ser bem-sucedido, permitindo o uso de tais modelos para a extensão dos dados de pacientes e para geração de sinais de tremor que auxiliem no desenvolvimento e validação de novas técnicas de supressão de tremor em pacientesAbstract: Parkinson¿s Disease (PD) is a neurodegenerative disorder that affects approximately 2% of the world¿s population over 60 years old (7-10 million people). It is characterized by symptoms like resting and action tremors, which cause severe impairments to the patient¿s life and may also cause non-motor symptoms such as difficulty to sleep, depression, and fatigue. Only in Brazil, there are more than 200,000 people with PD, a number that might double by 2030 due to the aging of the population. In such a context, developing new treatments and assistance techniques that can improve PD patient¿s life quality and autonomy are extremely important. In this work, we propose novel methods based on Neural Networks (NN) for predicting and generating patient-specific PD electromyography (EMG) tremor signals, to support the development of new assisting devices and techniques. First, we compare different NN models, using the multi-layer perceptron (MLPs) and recurrent neural network (RNN) for predicting PD EMG signals, to anticipate resting tremor patterns. The experimental results indicate that the proposed models can adapt to the patient¿s specific tremor patterns and provide reasonable predictions for both EMG envelopes and EMG raw signals. Next, we propose two new data augmentation approaches based on Deep Convolutional Generative Adversarial Networks (DCGANs) and Style Transfer (ST) for augmenting EMG signals. Results show that the proposed models can adapt to different shapes, frequencies, and amplitudes of tremor, simulating each patient¿s specific tremor patterns and extending them to different sets of movement protocols. All results suggest that Neural Networks can successfully be used for predicting and generating complex biological signals like EMG, allowing these models to be used for extending patients¿ datasets and generating tremor signals. These new data could help to validate treatment approaches on different movement scenarios, contributing to the development of new techniques for tremor suppression on patientsMestradoCiência da ComputaçãoMestre em Ciência da Computaçã