Abstract
Photoplethysmographic imaging is an optical solution for non-contact cardiovascular monitoring from a distance. This camera-based technology enables physiological monitoring in situations where contact-based devices may be problematic or infeasible, such as ambulatory, sleep, and multi-individual monitoring. However, automatically extracting the blood pulse waveform signal is challenging due to the unknown mixture of relevant (pulsatile) and irrelevant pixels in the scene. Here, we propose a signal fusion framework, FusionPPG, for extracting a blood pulse waveform signal with strong temporal fidelity from a scene without requiring anatomical priors. The extraction problem is posed as a Bayesian least squares fusion problem, and solved using a novel probabilistic pulsatility model that incorporates both physiologically derived spectral and spatial waveform priors to identify pulsatility characteristics in the scene. Evaluation was performed on a 24-participant sample with various ages (9-60 years) and body compositions (fat% 30.0 ± 7.9, muscle% 40.4 ± 5.3, BMI 25.5 ± 5.2 kg·m-2). Experimental results show stronger matching to the ground-truth blood pulse waveform signal compared to the FaceMeanPPG (p < 0.001) and DistancePPG (p < 0.001) methods. Heart rates predicted using FusionPPG correlated strongly with ground truth measurements (r2 = 0.9952). A cardiac arrhythmia was visually identified in FusionPPG's waveform via temporal analysis.
Highlights
Photoplethysmography (PPG) is a safe and inexpensive cardiovascular monitoring technology [1]
Data were collected across 24 participants of varying age (9–60 years, (μ±σ) = 28.7±12.4) and body compositions
To capture deep tissue penetration using NIR wavelengths, and to minimize the effects of visible environmental illumination, an 850–1000 nm optical bandpass filter was mounted in front of the camera lens
Summary
Photoplethysmography (PPG) is a safe and inexpensive cardiovascular monitoring technology [1]. PPG is monitored via a contact probe that operates in either transmittance or reflectance mode, where the source and detector are placed on opposite or the same side of the tissue, respectively. This conventional type of monitoring provides hemodynamic information only for a single point, and is an impractical measurement tool in settings such as ambulatory and multi-individual monitoring. Recent studies have focused on developing and validating photoplethysmographic imaging (PPGI) systems [2] These systems substitute contact-based detectors with a camera and use non-contact illumination sources, enabling non-contact cardiovascular monitoring from a distance [3]. The pulsatile nature of the blood pulse waveform is not fully understood [3, 12]
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