390 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
Camera-Based Heart Rate Extraction in Noisy Environments
Remote photoplethysmography (rPPG) is a non-invasive technique that benefits from video to measure vital signs such as the heart rate (HR). In rPPG estimation, noise can introduce artifacts that distort rPPG signal and jeopardize accurate HR measurement. Considering that most rPPG studies occurred in lab-controlled environments, the issue of noise in realistic conditions remains open.
This thesis aims to examine the challenges of noise in rPPG estimation in realistic scenarios, specifically investigating the effect of noise arising from illumination variation and motion artifacts on the predicted rPPG HR. To mitigate the impact of noise, a modular rPPG measurement framework, comprising data preprocessing, region of interest, signal extraction, preparation, processing, and HR extraction is developed. The proposed pipeline is tested on the LGI-PPGI-Face-Video-Database public dataset, hosting four different candidates and real-life scenarios. In the RoI module, raw rPPG signals were extracted from the dataset using three machine learning-based face detectors, namely Haarcascade, Dlib, and MediaPipe, in parallel. Subsequently, the collected signals underwent preprocessing, independent component analysis, denoising, and frequency domain conversion for peak detection.
Overall, the Dlib face detector leads to the most successful HR for the majority of scenarios. In 50% of all scenarios and candidates, the average predicted HR for Dlib is either in line or very close to the average reference HR. The extracted HRs from the Haarcascade and MediaPipe architectures make up 31.25% and 18.75% of plausible results, respectively. The analysis highlighted the importance of fixated facial landmarks in collecting quality raw data and reducing noise
Spatio-temporal analysis of blood perfusion by imaging photoplethysmography
Imaging photoplethysmography (iPPG) has attracted much attention over the last years. The vast majority of works focuses on methods to reliably extract the heart rate from videos. Only a few works addressed iPPGs ability to exploit spatio-temporal perfusion pattern to derive further diagnostic statements.
This work directs at the spatio-temporal analysis of blood perfusion from videos. We present a novel algorithm that bases on the two-dimensional representation of the blood pulsation (perfusion map). The basic idea behind the proposed algorithm consists of a pairwise estimation of time delays between photoplethysmographic signals of spatially separated regions. The probabilistic approach yields a parameter denoted as perfusion speed. We compare the perfusion speed versus two parameters, which assess the strength of blood pulsation (perfusion strength and signal to noise ratio).
Preliminary results using video data with different physiological stimuli (cold pressure test, cold face test) show that all measures are in fluenced by those stimuli (some of them with statistical certainty). The perfusion speed turned out to be more sensitive than the other measures in some cases. However, our results also show that the intraindividual stability and interindividual comparability of all used measures remain critical points.
This work proves the general feasibility of employing the perfusion speed as novel iPPG quantity. Future studies will address open points like the handling of ballistocardiographic effects and will try to deepen the understanding of the predominant physiological mechanisms and their relation to the algorithmic performance
Respiratory Rate Estimation from Face Videos
Vital signs, such as heart rate (HR), heart rate variability (HRV),
respiratory rate (RR), are important indicators for a person's health. Vital
signs are traditionally measured with contact sensors, and may be inconvenient
and cause discomfort during continuous monitoring. Commercial cameras are
promising contact-free sensors, and remote photoplethysmography (rPPG) have
been studied to remotely monitor heart rate from face videos. For remote RR
measurement, most prior art was based on small periodical motions of chest
regions caused by breathing cycles, which are vulnerable to subjects' voluntary
movements. This paper explores remote RR measurement based on rPPG obtained
from face videos. The paper employs motion compensation, two-phase temporal
filtering, and signal pruning to capture signals with high quality. The
experimental results demonstrate that the proposed framework can obtain
accurate RR results and can provide HR, HRV and RR measurement synergistically
in one framework
Analisis Photoplethysmography Jarak Jauh dalam berbagai Kondisi Pencahayaan
Photoplethysmography (PPG) konvensional untuk mengukur kecepatan jantung memiliki keterbatasan tersendiri, salah satunya yaitu diperlukannya kontak langsung dengan bagian tubuh pasien. rPPG (remote-Photoplethysmography) dapat digunakan untuk melakukan pemantauan jantung dari seorang pasien berbasis citra. Sama halnya dengan sistem lain yang berbasis kamera, algoritma rPPG sangat bergantung pada kondisi pencahayaan. Oleh karena itu diperlukan suatu studi analisis yang mengindahkan aspek tentang pengaruh kondisi dan arah cahaya terhadap subjek yang diamati terhadap hasil estimasi laju denyut jantung dengan algoritma rPPG. Pada penelitian ini diimplementasikan algoritma rPPG dengan Short-Time Fourier Transform (STFT) untuk memperkirakan laju detak jantung dalam berbagai kondisi cahaya. Hasil yang diperoleh merupakan analisa spektral dari perubahan frame video pada area dahi terhadap perubahan waktu dari model input warna Green-Channel dan HSV (Hue, Saturation, Value). Perbandingan dengan pengukuran ground truth pada pencahayaan 260 lux, 19 lux, dan 11 lux, estimasi laju detak jantung yang didapatkan dari input Green Channel menghasilkan persentase error rata-rata 0,038, 0,118, dan 0,229, dimana hasil persentase rata-rata error ini lebih rendah dari masukan HSV, yaitu 0,095, 0,212, dan 0,24
An intelligent information forwarder for healthcare big data systems with distributed wearable sensors
© 2016 IEEE. An increasing number of the elderly population wish to live an independent lifestyle, rather than rely on intrusive care programmes. A big data solution is presented using wearable sensors capable of carrying out continuous monitoring of the elderly, alerting the relevant caregivers when necessary and forwarding pertinent information to a big data system for analysis. A challenge for such a solution is the development of context-awareness through the multidimensional, dynamic and nonlinear sensor readings that have a weak correlation with observable human behaviours and health conditions. To address this challenge, a wearable sensor system with an intelligent data forwarder is discussed in this paper. The forwarder adopts a Hidden Markov Model for human behaviour recognition. Locality sensitive hashing is proposed as an efficient mechanism to learn sensor patterns. A prototype solution is implemented to monitor health conditions of dispersed users. It is shown that the intelligent forwarders can provide the remote sensors with context-awareness. They transmit only important information to the big data server for analytics when certain behaviours happen and avoid overwhelming communication and data storage. The system functions unobtrusively, whilst giving the users peace of mind in the knowledge that their safety is being monitored and analysed
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