943 research outputs found
An Interpretable Machine Vision Approach to Human Activity Recognition using Photoplethysmograph Sensor Data
The current gold standard for human activity recognition (HAR) is based on
the use of cameras. However, the poor scalability of camera systems renders
them impractical in pursuit of the goal of wider adoption of HAR in mobile
computing contexts. Consequently, researchers instead rely on wearable sensors
and in particular inertial sensors. A particularly prevalent wearable is the
smart watch which due to its integrated inertial and optical sensing
capabilities holds great potential for realising better HAR in a non-obtrusive
way. This paper seeks to simplify the wearable approach to HAR through
determining if the wrist-mounted optical sensor alone typically found in a
smartwatch or similar device can be used as a useful source of data for
activity recognition. The approach has the potential to eliminate the need for
the inertial sensing element which would in turn reduce the cost of and
complexity of smartwatches and fitness trackers. This could potentially
commoditise the hardware requirements for HAR while retaining the functionality
of both heart rate monitoring and activity capture all from a single optical
sensor. Our approach relies on the adoption of machine vision for activity
recognition based on suitably scaled plots of the optical signals. We take this
approach so as to produce classifications that are easily explainable and
interpretable by non-technical users. More specifically, images of
photoplethysmography signal time series are used to retrain the penultimate
layer of a convolutional neural network which has initially been trained on the
ImageNet database. We then use the 2048 dimensional features from the
penultimate layer as input to a support vector machine. Results from the
experiment yielded an average classification accuracy of 92.3%. This result
outperforms that of an optical and inertial sensor combined (78%) and
illustrates the capability of HAR systems using...Comment: 26th AIAI Irish Conference on Artificial Intelligence and Cognitive
Scienc
A Review of Deep Learning Methods for Photoplethysmography Data
Photoplethysmography (PPG) is a highly promising device due to its advantages
in portability, user-friendly operation, and non-invasive capabilities to
measure a wide range of physiological information. Recent advancements in deep
learning have demonstrated remarkable outcomes by leveraging PPG signals for
tasks related to personal health management and other multifaceted
applications. In this review, we systematically reviewed papers that applied
deep learning models to process PPG data between January 1st of 2017 and July
31st of 2023 from Google Scholar, PubMed and Dimensions. Each paper is analyzed
from three key perspectives: tasks, models, and data. We finally extracted 193
papers where different deep learning frameworks were used to process PPG
signals. Based on the tasks addressed in these papers, we categorized them into
two major groups: medical-related, and non-medical-related. The medical-related
tasks were further divided into seven subgroups, including blood pressure
analysis, cardiovascular monitoring and diagnosis, sleep health, mental health,
respiratory monitoring and analysis, blood glucose analysis, as well as others.
The non-medical-related tasks were divided into four subgroups, which encompass
signal processing, biometric identification, electrocardiogram reconstruction,
and human activity recognition. In conclusion, significant progress has been
made in the field of using deep learning methods to process PPG data recently.
This allows for a more thorough exploration and utilization of the information
contained in PPG signals. However, challenges remain, such as limited quantity
and quality of publicly available databases, a lack of effective validation in
real-world scenarios, and concerns about the interpretability, scalability, and
complexity of deep learning models. Moreover, there are still emerging research
areas that require further investigation
A machine vision approach to human activity recognition using photoplethysmograph sensor data
Human activity recognition (HAR) is an active area of research concerned with the classification of human motion. Cameras are the gold standard used in this area, but they are proven to have scalability and privacy issues. HAR studies have also been conducted with wearable devices consisting of inertial sensors. Perhaps the most common wearable, smart watches, comprising of inertial and optical sensors, allow for scalable, non-obtrusive studies. We are seeking to simplify this wearable approach further by determining if wrist-mounted optical sensing, usually used for heart rate determination, can also provide useful data for relevant activity recognition. If successful, this could eliminate the need for the inertial sensor, and so simplify the technological requirements in wearable HAR. We adopt a machine vision approach for activity recognition based on plots of the optical signals so as to produce classifications that are easily explainable and interpretable by non-technical users. Specifically, time-series images of photoplethysmography signals are used to retrain the penultimate layer of a pretrained convolutional neural network leveraging the concept of transfer learning. Our results demonstrate an average accuracy of 75.8%. This illustrates the feasibility of implementing an optical sensor-only solution for a coarse activity and heart rate monitoring system. Implementing an optical sensor only in the design of these wearables leads to a trade off in classification performance, but in turn, grants the potential to simplify the overall design of activity monitoring and classification systems in the future
Photoplethysmography based atrial fibrillation detection: an updated review from July 2019
Atrial fibrillation (AF) is a prevalent cardiac arrhythmia associated with
significant health ramifications, including an elevated susceptibility to
ischemic stroke, heart disease, and heightened mortality. Photoplethysmography
(PPG) has emerged as a promising technology for continuous AF monitoring for
its cost-effectiveness and widespread integration into wearable devices. Our
team previously conducted an exhaustive review on PPG-based AF detection before
June 2019. However, since then, more advanced technologies have emerged in this
field. This paper offers a comprehensive review of the latest advancements in
PPG-based AF detection, utilizing digital health and artificial intelligence
(AI) solutions, within the timeframe spanning from July 2019 to December 2022.
Through extensive exploration of scientific databases, we have identified 59
pertinent studies. Our comprehensive review encompasses an in-depth assessment
of the statistical methodologies, traditional machine learning techniques, and
deep learning approaches employed in these studies. In addition, we address the
challenges encountered in the domain of PPG-based AF detection. Furthermore, we
maintain a dedicated website to curate the latest research in this area, with
regular updates on a regular basis
Learned Kernels for Interpretable and Efficient PPG Signal Quality Assessment and Artifact Segmentation
Photoplethysmography (PPG) provides a low-cost, non-invasive method to
continuously monitor various cardiovascular parameters. PPG signals are
generated by wearable devices and frequently contain large artifacts caused by
external factors, such as motion of the human subject. In order to ensure
robust and accurate extraction of physiological parameters, corrupted areas of
the signal need to be identified and handled appropriately. Previous
methodology relied either on handcrafted feature detectors or signal metrics
which yield sub-optimal performance, or relied on machine learning techniques
such as deep neural networks (DNN) which lack interpretability and are
computationally and memory intensive. In this work, we present a novel method
to learn a small set of interpretable convolutional kernels that has
performance similar to -- and often better than -- the state-of-the-art DNN
approach with several orders of magnitude fewer parameters. This work allows
for efficient, robust, and interpretable signal quality assessment and artifact
segmentation on low-power devices.Comment: 16 pages, 6 figure
BayesBeat: A Bayesian Deep Learning Approach for Atrial Fibrillation Detection from Noisy Photoplethysmography Data
The increasing popularity of smartwatches as affordable and longitudinal
monitoring devices enables us to capture photoplethysmography (PPG) sensor data
for detecting Atrial Fibrillation (AF) in real-time. A significant challenge in
AF detection from PPG signals comes from the inherent noise in the smartwatch
PPG signals. In this paper, we propose a novel deep learning based approach,
BayesBeat that leverages the power of Bayesian deep learning to accurately
infer AF risks from noisy PPG signals, and at the same time provide the
uncertainty estimate of the prediction. Bayesbeat is efficient, robust,
flexible, and highly scalable which makes it particularly suitable for
deployment in commercially available wearable devices. Extensive experiments on
a recently published large dataset reveal that our proposed method BayesBeat
substantially outperforms the existing state-of-the-art methods.Comment: 8 pages, 5 figure
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