1,137 research outputs found
A Comparative Evaluation of Heart Rate Estimation Methods using Face Videos
This paper presents a comparative evaluation of methods for remote heart rate
estimation using face videos, i.e., given a video sequence of the face as
input, methods to process it to obtain a robust estimation of the subjects
heart rate at each moment. Four alternatives from the literature are tested,
three based in hand crafted approaches and one based on deep learning. The
methods are compared using RGB videos from the COHFACE database. Experiments
show that the learning-based method achieves much better accuracy than the hand
crafted ones. The low error rate achieved by the learning based model makes
possible its application in real scenarios, e.g. in medical or sports
environments.Comment: Accepted in "IEEE International Workshop on Medical Computing
(MediComp) 2020
Cardiovascular assessment by imaging photoplethysmography – a review
AbstractOver the last few years, the contactless acquisition of cardiovascular parameters using cameras has gained immense attention. The technique provides an optical means to acquire cardiovascular information in a very convenient way. This review provides an overview on the technique’s background and current realizations. Besides giving detailed information on the most widespread application of the technique, namely the contactless acquisition of heart rate, we outline further concepts and we critically discuss the current state.</jats:p
Remote Assessment of the Cardiovascular Function Using Camera-Based Photoplethysmography
Camera-based photoplethysmography (cbPPG) is a novel measurement technique that allows the continuous monitoring of vital signs by using common video cameras. In the last decade, the technology has attracted a lot of attention as it is easy to set up, operates remotely, and offers new diagnostic opportunities. Despite the growing interest, cbPPG is not completely established yet and is still primarily the object of research. There are a variety of reasons for this lack of development including that reliable and autonomous hardware setups are missing, that robust processing algorithms are needed, that application fields are still limited, and that it is not completely understood which physiological factors impact the captured signal. In this thesis, these issues will be addressed.
A new and innovative measuring system for cbPPG was developed. In the course of three large studies conducted in clinical and non-clinical environments, the system’s great flexibility, autonomy, user-friendliness, and integrability could be successfully proven.
Furthermore, it was investigated what value optical polarization filtration adds to cbPPG. The results show that a perpendicular filter setting can significantly enhance the signal quality. In addition, the performed analyses were used to draw conclusions about the origin of cbPPG signals: Blood volume changes are most likely the defining element for the signal's modulation.
Besides the hardware-related topics, the software topic was addressed. A new method for the selection of regions of interest (ROIs) in cbPPG videos was developed. Choosing valid ROIs is one of the most important steps in the processing chain of cbPPG software. The new method has the advantage of being fully automated, more independent, and universally applicable. Moreover, it suppresses ballistocardiographic artifacts by utilizing a level-set-based approach. The suitability of the ROI selection method was demonstrated on a large and challenging data set.
In the last part of the work, a potentially new application field for cbPPG was explored. It was investigated how cbPPG can be used to assess autonomic reactions of the nervous system at the cutaneous vasculature. The results show that changes in the vasomotor tone, i.e. vasodilation and vasoconstriction, reflect
in the pulsation strength of cbPPG signals. These characteristics also shed more light on the origin problem. Similar to the polarization analyses, they support the classic blood volume theory.
In conclusion, this thesis tackles relevant issues regarding the application of cbPPG. The proposed solutions pave the way for cbPPG to become an established and widely accepted technology
Remote Bio-Sensing: Open Source Benchmark Framework for Fair Evaluation of rPPG
Remote Photoplethysmography (rPPG) is a technology that utilizes the light
absorption properties of hemoglobin, captured via camera, to analyze and
measure blood volume pulse (BVP). By analyzing the measured BVP, various
physiological signals such as heart rate, stress levels, and blood pressure can
be derived, enabling applications such as the early prediction of
cardiovascular diseases. rPPG is a rapidly evolving field as it allows the
measurement of vital signals using camera-equipped devices without the need for
additional devices such as blood pressure monitors or pulse oximeters, and
without the assistance of medical experts. Despite extensive efforts and
advances in this field, serious challenges remain, including issues related to
skin color, camera characteristics, ambient lighting, and other sources of
noise, which degrade performance accuracy. We argue that fair and evaluable
benchmarking is urgently required to overcome these challenges and make any
meaningful progress from both academic and commercial perspectives. In most
existing work, models are trained, tested, and validated only on limited
datasets. Worse still, some studies lack available code or reproducibility,
making it difficult to fairly evaluate and compare performance. Therefore, the
purpose of this study is to provide a benchmarking framework to evaluate
various rPPG techniques across a wide range of datasets for fair evaluation and
comparison, including both conventional non-deep neural network (non-DNN) and
deep neural network (DNN) methods. GitHub URL:
https://github.com/remotebiosensing/rppg.Comment: 19 pages, 10 figure
A high speed Tri-Vision system for automotive applications
Purpose: Cameras are excellent ways of non-invasively monitoring the interior and exterior of vehicles. In particular, high speed stereovision and multivision systems are important for transport applications such as driver eye tracking or collision avoidance. This paper addresses the synchronisation problem which arises when multivision camera systems are used to capture the high speed motion common in such applications.
Methods: An experimental, high-speed tri-vision camera system intended for real-time driver eye-blink and saccade measurement was designed, developed, implemented and tested using prototype, ultra-high dynamic range, automotive-grade image sensors specifically developed by E2V (formerly Atmel) Grenoble SA as part of the European FP6 project – sensation (advanced sensor development for attention stress, vigilance and sleep/wakefulness monitoring).
Results : The developed system can sustain frame rates of 59.8 Hz at the full stereovision resolution of 1280 × 480 but this can reach 750 Hz when a 10 k pixel Region of Interest (ROI) is used, with a maximum global shutter speed of 1/48000 s and a shutter efficiency of 99.7%. The data can be reliably transmitted uncompressed over standard copper Camera-Link® cables over 5 metres. The synchronisation error between the left and right stereo images is less than 100 ps and this has been verified both electrically and optically. Synchronisation is automatically established at boot-up and maintained during resolution changes. A third camera in the set can be configured independently. The dynamic range of the 10bit sensors exceeds 123 dB with a spectral sensitivity extending well into the infra-red range.
Conclusion: The system was subjected to a comprehensive testing protocol, which confirms that the salient requirements for the driver monitoring application are adequately met and in some respects, exceeded. The synchronisation technique presented may also benefit several other automotive stereovision applications including near and far-field obstacle detection and collision avoidance, road condition monitoring and others.Partially funded by the EU FP6 through the IST-507231 SENSATION project.peer-reviewe
mEBAL: A Multimodal Database for Eye Blink Detection and Attention Level Estimation
This work presents mEBAL, a multimodal database for eye blink detection and
attention level estimation. The eye blink frequency is related to the cognitive
activity and automatic detectors of eye blinks have been proposed for many
tasks including attention level estimation, analysis of neuro-degenerative
diseases, deception recognition, drive fatigue detection, or face
anti-spoofing. However, most existing databases and algorithms in this area are
limited to experiments involving only a few hundred samples and individual
sensors like face cameras. The proposed mEBAL improves previous databases in
terms of acquisition sensors and samples. In particular, three different
sensors are simultaneously considered: Near Infrared (NIR) and RGB cameras to
capture the face gestures and an Electroencephalography (EEG) band to capture
the cognitive activity of the user and blinking events. Regarding the size of
mEBAL, it comprises 6,000 samples and the corresponding attention level from 38
different students while conducting a number of e-learning tasks of varying
difficulty. In addition to presenting mEBAL, we also include preliminary
experiments on: i) eye blink detection using Convolutional Neural Networks
(CNN) with the facial images, and ii) attention level estimation of the
students based on their eye blink frequency
Remote heart rate monitoring - Assessment of the Facereader rPPg by Noldus
Remote photoplethysmography (rPPG) allows contactless monitoring of human cardiac activity through a video camera. In this study, we assessed the accuracy and precision for heart rate measurements of the only consumer product available on the market, namely the Facereader™ rPPG by Noldus, with respect to a gold standard electrocardiograph. Twenty-four healthy participants were asked to sit in front of a computer screen and alternate two periods of rest with two stress tests (i.e. Go/No-Go task), while their heart rate was simultaneously acquired for 20 minutes using the ECG criterion measure and the Facereader™ rPPG. Results show that the Facereader™ rPPG tends to overestimate lower heart rates and underestimate higher heart rates compared to the ECG. The Facereader™ rPPG revealed a mean bias of 9.8 bpm, the 95% limits of agreement (LoA) ranged from almost -30 up to +50 bpm. These results suggest that whilst the rPPG Facereader™ technology has potential for contactless heart rate monitoring, its predictions are inaccurate for higher heart rates, with unacceptable precision across the entire range, rendering its estimates unreliable for monitoring individuals
Innovative IoT Solutions and Wearable Sensing Systems for Monitoring Human Biophysical Parameters: A Review
none3noDigital and information technologies are heavily pervading several aspects of human activities, improving our life quality. Health systems are undergoing a real technological revolution, radically changing how medical services are provided, thanks to the wide employment of the Internet of Things (IoT) platforms supporting advanced monitoring services and intelligent inferring systems.
This paper reports, at first, a comprehensive overview of innovative sensing systems for monitoring
biophysical and psychophysical parameters, all suitable for integration with wearable or portable
accessories. Wearable devices represent a headstone on which the IoT-based healthcare platforms
are based, providing capillary and real-time monitoring of patient’s conditions. Besides, a survey of
modern architectures and supported services by IoT platforms for health monitoring is presented,
providing useful insights for developing future healthcare systems. All considered architectures
employ wearable devices to gather patient parameters and share them with a cloud platform where
they are processed to provide real-time feedback. The reported discussion highlights the structural
differences between the discussed frameworks, from the point of view of network configuration, data
management strategy, feedback modality, etc.Article Number: 1660openRoberto De Fazio; Massimo De Vittorio; Paolo ViscontiDE FAZIO, Roberto; DE VITTORIO, Massimo; Visconti, Paol
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