Heart Beat Characterization from Ballistocardiogram Signals using Extended Functions of Multiple Instances

A multiple instance learning (MIL) method, extended Function of Multiple Instances ($e$FUMI), is applied to ballistocardiogram (BCG) signals produced by a hydraulic bed sensor. The goal of this approach is to learn a personalized heartbeat "concept" for an individual. This heartbeat concept is a prototype (or "signature") that characterizes the heartbeat pattern for an individual in ballistocardiogram data. The $e$FUMI method models the problem of learning a heartbeat concept from a BCG signal as a MIL problem. This approach elegantly addresses the uncertainty inherent in a BCG signal e. g., misalignment between training data and ground truth, mis-collection of heartbeat by some transducers, etc. Given a BCG training signal coupled with a ground truth signal (e.g., a pulse finger sensor), training "bags" labeled with only binary labels denoting if a training bag contains a heartbeat signal or not can be generated. Then, using these bags, $e$FUMI learns a personalized concept of heartbeat for a subject as well as several non-heartbeat background concepts. After learning the heartbeat concept, heartbeat detection and heart rate estimation can be applied to test data. Experimental results show that the estimated heartbeat concept found by $e$FUMI is more representative and a more discriminative prototype of the heartbeat signals than those found by comparison MIL methods in the literature.Comment: IEEE EMBC 2016, pp. 1-

A temporal analysis system for early detection of health changes

Abstract from public.pdf.To make it possible for elders to live independently at home and yet get help from health care providers when small changes in health conditions take place, smart home technologies are developed to enhance safety and monitor health conditions via noninvasive sensors and other devices. To better analyze the wealth of the activity information from various kinds of sensors to locate trends that correspond states of wellbeing, this thesis proposes a new system to build adaptive models for detecting health changes based on temporal analysis, including outlier detection, customization and adaption to new changes. Our hope is that by using more sophisticated temporal analysis method we can capture more predictive alerts and more customized alerts that can help us detect more meaningful health changes before they become big problems. Since we cannot have full access to all the embedded sensor data from TigerPlace at the moment, the system is tested using synthetic datasets which simulate gradual changes, sudden changes, changes of baseline health condition and system noise that might happen in the real-world data. Based on the experiments on the synthetic datasets, the system is proved to have the ability to adapt to gradual changes, find anomalies and spawn a new component for the GMM when there is an emerging new normal pattern. The system achieves our goals when tested on the synthetic datasets over extended period of time. We hope that by using the system in Tiger Place, it will help by detecting health changes before real health issue happens

Data-driven methods for analyzing ballistocardiograms in longitudinal cardiovascular monitoring

Cardiovascular disease (CVD) is the leading cause of death in the US; about 48% of American adults have one or more types of CVD. The importance of continuous monitoring of the older population, for early detection of changes in health conditions, has been shown in the literature, as the key to a successful clinical intervention. We have been investigating environmentally-embedded in-home networks of non-invasive sensing modalities. This dissertation concentrates on the signal processing techniques required for the robust extraction of morphological features from the ballistocardiographs (BCG), and machine learning approaches to utilize these features in non-invasive monitoring of cardiovascular conditions. At first, enhancements in the time domain detection of the cardiac cycle are addressed due to its importance in the estimation of heart rate variability (HRV) and sleep stages. The proposed enhancements in the energy-based algorithm for BCG beat detection have shown at least 50% improvement in the root mean square error (RMSE) of the beat to beat heart rate estimations compared to the reference estimations from the electrocardiogram (ECG) R to R intervals. These results are still subject to some errors, primarily due to the contamination of noise and motion artifacts caused by floor vibration, unconstrained subject movements, or even the respiratory activities. Aging, diseases, breathing, and sleep disorders can also affect the quality of estimation as they slightly modify the morphology of the BCG waveform.Includes bibliographical reference