This paper presents a novel approach of generating synthetic Photoplethysmogram (PPG) data using a physical model of the cardiovascular system to improve classifier performance with a combination of synthetic and real data. The physical model is an in-silico cardiac computational model, consisting of a four-chambered heart with electrophysiology, hemodynamic, and blood pressure auto-regulation functionality. Starting with a small number of measured PPG data, the cardiac model is used to synthesize healthy as well as PPG time-series pertaining to coronary artery disease (CAD) by varying pathophysiological parameters. A Variational Autoencoder (VAE) structure is proposed to derive a statistical feature space for CAD classification. Results are presented in two perspectives namely, (i) using artificially reduced real disease data and (ii) using all the real disease data. In both cases, by augmenting with the synthetic data for training, the performance (sensitivity, specificity) of the classifier changes from (i) (0.65, 1) to (1, 0.9) and (ii) (1, 0.95) to (1, 1). The proposed hybrid approach of combining physical modelling and statistical feature space selection generates realistic PPG data with pathophysiological interpretation and can outperform a baseline Generative Adversarial Network (GAN) architecture with a relatively small amount of real data for training. This proposed method could aid as a substitution technique for handling the problem of bulk data required for training machine learning algorithms for cardiac health-care applications.

Freezing of Gait (FoG) is a paroxysmal and devitalizing symptom associated with Parkinson’s disease (PD). Episodes of FoG impedes gait and augments fall propensity, often leading to serious fall-injury. In this paper, we present a method for online detection of FoG using a wearable motion sensor. The novelty lies in utilizing the Empirical Wavelet Transform for signal denoising and incorporating the two new features to ameliorate the accuracy of the algorithm. Fundamentally, we have focused on a patient-independent model and leveraged a single ankle sensor which makes it a more feasible approach in terms of usability. Our model is evaluated on Daphnet dataset and achieved the average Sensitivity of.95 and Specificity of.70 with only a single sensor, demonstrating its immense potential.

Synthetic data generation has recently emerged as a substitution technique for handling the problem of bulk data needed in training machine learning algorithms. Healthcare, primarily cardiovascular domain is a major area where synthetic physiological data can be used improve accuracy of machine learning algorithm. This paper presents a novel approach of generating synthetic Photoplethysmogram (PPG) data using statistical explosion. Synthetic data is subsequently used to classify Coronary Artery Disease (CAD) using a two stage cascaded classifier. Proposed classifier along with synthetic data removes class bias and provides better accuracy compared to state of art. The proposed data generation and cascaded classifier is generic enough to be used to improve machine learning algorithm on any time series signal.

MOTIVATION: The identification of sub-populations of patients with similar characteristics, called patient subtyping, is important for realizing the goals of precision medicine. Accurate subtyping is crucial for tailoring therapeutic strategies that can potentially lead to reduced mortality and morbidity. Model-based clustering, such as Gaussian mixture models, provides a principled and interpretable methodology that is widely used to identify subtypes. However, they impose identical marginal distributions on each variable; such assumptions restrict their modeling flexibility and deteriorates clustering performance. RESULTS: In this paper, we use the statistical framework of copulas to decouple the modeling of marginals from the dependencies between them. Current copula-based methods cannot scale to high dimensions due to challenges in parameter inference. We develop HD-GMCM, that addresses these challenges and, to our knowledge, is the first copula-based clustering method that can fit high-dimensional data. Our experiments on real high-dimensional gene-expression and clinical datasets show that HD-GMCM outperforms state-of-the-art model-based clustering methods, by virtue of modeling non-Gaussian data and being robust to outliers through the use of Gaussian mixture copulas. We present a case study on lung cancer data from TCGA. Clusters obtained from HD-GMCM can be interpreted based on the dependencies they model, that offers a new way of characterizing subtypes. Empirically, such modeling not only uncovers latent structure that leads to better clustering but also meaningful clinical subtypes in terms of survival rates of patients. AVAILABILITY AND IMPLEMENTATION: An implementation of HD-GMCM in R is available at: https://bitbucket.org/cdal/hdgmcm/. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

In this paper we propose a novel process flow of a low-cost, non-invasive screening system for identifying Coronary Artery Disease (CAD) patients using a two-stage classification approach. A statistical rule engine is designed based on patient demography and medical history which is applied at the first stage of the proposed classification system. The misclassification error at this stage is reduced at the second stage based on numerical features extracted from multiple cardiovascular signals. Two sets of features are extracted from phonocardiogram (PCG) and photoplethysmogram (PPG) signals, collected from each subject for creating two independent Support Vector Machine (SVM) classifiers. Outcomes of the two classifiers are fused at the decision level for final prediction at second stage based on absolute distance of the test data-point from its respective SVM hyperplane. Results show that the proposed approach achieves sensitivity of 0.92 and specificity of 0.90 in classifying CAD patients on a hospital dataset of 99 subjects including CAD and non-CAD patients.

In this paper we propose a feature extraction algorithm for classifying Coronary Artery Disease (CAD) patients from Photoplethysmogram (PPG) signals. Several domain-independent features, representing inherent properties of a time series are explored in our study. These are combined with Heart Rate Variability (HRV) and other popularly used morphological PPG features. A statistical feature selection algorithm, based on Maximal Information Coefficient (MIC) is applied on MIMIC II dataset for ranking and choosing the optimum features. A second hospital dataset of different patient demography is used for performance evaluation. Results show that, Support Vector Machine (SVM) classifier, designed using the selected features yields average sensitivity and specificity of more than 0.8 in identifying CAD patients and also outperforms two recent prior art approaches when applied on the test dataset.

Determining mortality risk is important for critical decisions in Intensive Care Units (ICU). The need for machine learning models that provide accurate patient-specific prediction of mortality is well recognized. We present a new algorithm for ICU mortality prediction that is designed to address the problem of imbalance, which occurs, in the context of binary classification, when one of the two classes is significantly under--represented in the data. We take a fundamentally new approach in exploiting the class imbalance through a feature transformation such that the transformed features are easier to classify. Hypothesis testing is used for classification with a test statistic that follows the distribution of the difference of two chi-squared random variables, for which there are no analytic expressions and we derive an accurate approximation. Experiments on a benchmark dataset of 4000 ICU patients show that our algorithm surpasses the best competing methods for mortality prediction.

Binary classification based methods are commonly used for designing predictive models in healthcare. A common problem in many healthcare datasets is that of imbalance, where there are far more observations in one class than the other during training. In such conditions, most classifiers do not have good predictive accuracy with respect to the under-represented class. We design a new similarity-based classifier to learn from imbalanced datasets, wherein input features are transformed using similarity with respect to a chosen subset of training points. We empirically demonstrate the superiority of our algorithm over state-of-the-art methods for imbalanced data classification in real and synthetic datasets. We also illustrate the application of our classifier in predicting Acute Respiratory Failure (ARF), a critical complication in Intensive Care Units (ICU), using semi-structured text contained in nursing notes recorded during a patient's ICU stay. Our experiments, on more than 800 patient records show that using our new classifier to learn from text- based features can effectively be used to predict ARF and, potentially, other complications in ICUs.

Crowd workers exhibit varying work patterns, expertise, and quality leading to wide variability in the performance of crowdsourcing platforms. The onus of choosing a suitable platform to post tasks is mostly with the requester, often leading to poor guarantees and unmet requirements due to the dynamism in performance of crowd platforms. Towards this end, we demonstrate CrowdUtility, a statistical modelling based tool for evaluating multiple crowdsourcing platforms and recommending a platform that best suits the requirements of the requester. CrowdUtility uses an online Multi-Armed Bandit framework, to schedule tasks while optimizing platform performance. We demonstrate an end-to end system starting from requirements specification, to platform recommendation, to real-time monitoring.

We propose an online scheduling algorithm for posting crowdsourcing tasks which maximizes a novel metric called task viewership. This metric is computed using stochastic model based on coverage process and it measures the likelihood that a task is viewed by multiple crowd workers, which is correlated to the likelihood that it will be selected and completed.

A rank clustering system, CloudRank, is proposed that takes into account cloud user preference data to characterize cloud user behaviour and also identify (an initially unknown set of) groups of users with similar behaviour in an unsupervised manner. The user groups are determined based on fitting mixture models on the cloud user preference observations. A preference can be anything that a system designer would like to include to characterize high-level user requirements such as demands on performance, cost, security, availability, etc. CloudRank can be useful for: (i) cloud providers to target their service offerings according to the user groups (i.e. customer segments) through appropriate customization of services pertaining to the user groups typical requirements; (ii) recommendation systems or a marketplace (that enables inter-operability among different providers) to determine which offerings best suit certain user groups; and (iii) prediction of any new users behaviour based on their preference information. Results on realistic feedbacks from internal cloud service providers show an average of 80% accuracy of the proposed unsupervised technique. When compared with a supervised technique, i.e. when the number of user groups are known beforehand, the error is within 15%, thus making it a promising technique for realistic deployments, particularly when there is no prior knowledge regarding the clusters.