Contact-Free Measurement of Cardiac Pulse Based on the Analysis of Thermal Imagery

• Published in: IEEE transactions on biomedical engineering Vol. 54; no. 8; pp. 1418 - 1426
• Main Authors: Garbey, Marc, Sun, Nanfei, Merla, Arcangelo, Pavlidis, Ioannis
• Format: Journal Article
• Language: English
• Published: United States IEEE 01.08.2007; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Adaptive filtering; Algorithms; Anthropometry; Biomedical engineering; Blood flow; cardiac pulse; Computer Simulation; Contact; Data mining; Diagnosis, Computer-Assisted - methods; Electrocardiography - methods; fast Fourier transform (FFT); Fast Fourier transforms; Feet; Fourier transforms; Frequency modulation; Heart Rate - physiology; Humans; Image analysis; medical imaging; Models, Biological; Modulation; Pulse measurements; Pulse modulation; Reproducibility of Results; Sensitivity and Specificity; Skin Temperature - physiology; Temperature sensors; Thermal imaging; Thermography - methods; Transducers
• ISSN: 0018-9294; 1558-2531
• DOI: 10.1109/TBME.2007.891930

We have developed a novel method to measure human cardiac pulse at a distance. It is based on the information contained in the thermal signal emitted from major superficial vessels. This signal is acquired through a highly sensitive thermal imaging system. Temperature on the vessel is modulated by pulsative blood flow. To compute the frequency of modulation (pulse), we extract a line-based region along the vessel. Then, we apply fast Fourier transform (FFT) to individual points along this line of interest to capitalize on the pulse's thermal propagation effect. Finally, we use an adaptive estimation function on the average FFT outcome to quantify the pulse. We have carried out experiments on a data set of 34 subjects and compared the pulse computed from our thermal signal analysis method to concomitant ground-truth measurements obtained through a standard contact sensor (piezo-electric transducer). The performance of the new method ranges from 88.52% to 90.33% depending on the clarity of the vessel's thermal imprint. To the best of our knowledge, it is the first time that cardiac pulse has been measured several feet away from a subject with passive means.